Microbes in Human Welfare - Class 12 Biology - Chapter 8 - Notes, NCERT Solutions & Extra Questions
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Extra Questions - Microbes in Human Welfare | NCERT | Biology | Class 12
Match the following:
Column I | Column II |
---|---|
a. Ernst Mayr | 1. Discovered viroids |
b. Whittaker | 2. Contagium vivum fluidum |
c. Beijerinck | 3. Proposed Five Kingdom Classification |
d. Diener | 4. Darwin of 20th century |
(A) a-4, b-3, c-2, d-1 (B) a-3, b-4, c-2, d-1 (C) a-2, b-3, c-4, d-1 (D) a-1, b-2, c-3, d-4
The correct match is:
(A) a-4, b-3, c-2, d-1
Detailing the Matches:
Ernst Mayr is famously known as the "Darwin of the 20th century" due to his work expanding on Darwin’s theory of natural selection. He proposed the biological species concept, which played a pivotal role in evolutionary biology.
R.H. Whittaker introduced the Five Kingdom Classification system, a fundamental framework in biology that categorizes all life into five distinct kingdoms.
Beijerinck made a significant discovery in virology when he described an infectious agent from tobacco plants (affected by tobacco mosaic virus) as "contagium vivum fluidum" translating to "living infectious fluid." This concept was crucial in the understanding of viruses.
Diener is renowned for the discovery of viroids, which are infectious particles composed of a single-strand RNA without a protein coat, making them one of the smallest infectious agents.
Therefore, Option (A) is the correct answer, adhering to the historical and scientific contributions of each figure as mentioned.
What are the uses of antibiotics and vitamin $B_{12}$?
Antibiotics: Antibiotics are chemical substances derived from organisms such as fungi and bacteria, effectively used to kill or inhibit the growth of harmful pathogens, thereby treating various infectious diseases.
Vitamin $B_{12}$: Vitamin $B_{12}$, often produced through biotechnological methods, is primarily used to treat pernicious anemia, a condition that prevents the body from making enough healthy red blood cells.
In which of the following kingdoms are diatoms placed?
A Plantae
B Fungi
C Animalia
D Protista
The correct option is D Protista.
Diatoms are classified under the kingdom Protista because they are unicellular and eukaryotic organisms.
From the options given below, identify the gene responsible for nitrogen fixation.
A. Nif
B. Nitrogenase
C. Leg-hemoglobin
D. None of the above
The correct answer is A. Nif.
The nif genes are responsible for encoding enzymes that facilitate the fixation of atmospheric nitrogen. Essential to this process is the nitrogenase complex, a critical enzyme system encoded by the nif genes, which converts atmospheric nitrogen into ammonia. This conversion is crucial as ammonia can be readily utilized by plants.
While Leg-hemoglobin, a pink pigment found in the root nodules of leguminous plants, plays a significant role in nitrogen fixation by acting as an oxygen scavenger to maintain anaerobic conditions favorable for the nitrogenase enzyme, it does not encode the enzymes itself. Hence, the direct gene responsible for nitrogen fixation from the given options is Nif.
Which antibiotic inhibits the interaction between tRNA and mRNA during bacterial protein synthesis?
A) Erythromycin
B) Neomycin
C) Streptomycin
D) Tetracycline
The correct answer is B) Neomycin.
Neomycin is known to inhibit the interaction between tRNA and mRNA during bacterial protein synthesis. This action disrupts the protein synthesis process which is crucial for bacterial growth and multiplication.
Name the microorganisms which fix nitrogen gas of the air into compounds of nitrogen.
Rhizobium is a type of bacteria that converts nitrogen gas from the atmosphere into nitrogen compounds that plants can use.
A nitrogen-fixing microbe associated with Azolla in a rice field is:
A. Frankia
B. Tolypothrix
C. Spirulina
D. Anabaena
The correct answer is D. Anabaena
Anabaena is a nitrogen-fixing cyanobacterium known for its symbiotic relationship with Azolla, commonly found in rice fields.
Which is not true for nitrogenase enzyme in root nodules in legumes?
A) Associated with Rhizobium
B) Site of reduction of $\mathrm{N}{2}$ into $\mathrm{NH}{3}$
C) It is a Mo-Fe protein
D) Resistant to $\mathrm{O}_{2}$ concentration
The correct option is D) Resistant to $\mathrm{O}_{2}$ concentration.
Rhizobium is a type of nitrogen-fixing bacterium found in the root nodules of legumes. These nodules contain crucial biochemical components, including enzymes like nitrogenase and leghaemoglobin. Nitrogenase is known as a Mo-Fe protein and plays a pivotal role in catalyzing the conversion of atmospheric nitrogen ($\mathrm{N}_2$) into ammonia ($\mathrm{NH}_3$). An important characteristic of nitrogenase is that it is highly sensitive to molecular oxygen; it requires an anaerobic environment to function effectively. To counter the damaging effects of oxygen within the root nodules, an oxygen-scavenger called leghaemoglobin is present to protect the nitrogenase enzyme from oxygen exposure.
If you remove the fimbriae from the bacterial cell, which of the following would you expect to happen?
A) The bacteria could no longer swim.
B) The bacteria would not adhere to the host tissue.
C) Transportation of molecules across the membrane would stop.
D) The shape of bacteria would change.
The correct answer is B) The bacteria would not adhere to the host tissue.
Fimbriae are hair-like structures found in abundance in many bacteria. Their primary function is to assist the bacteria in adhering to solid surfaces or host tissues. Thus, if you remove the fimbriae from a bacterial cell, the cell’s ability to attach to these surfaces or tissues would be compromised.
Consider the following statements:
Nitrification is done by Nitrosomonas bacteria.
Denitrification is the process of conversion of nitrogen into nitrates.
Select the correct code:
A) Only 1
B) Only 2
C) Both 1 and 2
D) None of the above
The correct option is A) Only 1
Statement 1:Nitrification is indeed a process where ammonia is converted into nitrites or nitrates. This is facilitated by bacteria such as Nitrosomonas, which convert ammonia to nitrites, and Nitrobacter, which convert nitrites to nitrates.
Statement 2:This statement is incorrect as it mischaracterizes denitrification. Denitrification is actually the process where nitrates are reduced to gaseous nitrogen, not the conversion of nitrogen into nitrates. This reversal of nitrogen fixation is accomplished by denitrifying bacteria, which thrive in oxygen-depleted environments near water tables.
In summary, statement 1 is accurate while statement 2 is not, hence the correct choice is A) Only 1.
Match column I with column II and select the correct option from the codes given below.
Column I | Column II |
---|---|
A. Commensalism | (ii) One benefited, other unaffected |
B. Parasitism | (iv) One benefited, other harmed |
C. Mutualism | (iii) Both are benefited |
D. Amensalism | (i) One inhibited, other unaffected |
B. A -(iii), B -(iv), C -(ii), D -(i)
C. A -(ii), B -(iv), C -(iii), D -(i)
D. A -(ii), B -(iv), C -(i), D -(iii)
The correct answer is C: A -(ii), B -(iv), C -(iii), D -(i)
Commensalism: One organism is benefited, while the other is unaffected. Match to (ii).
Parasitism: One organism is benefited at the expense of another which is harmed. Match to (iv).
Mutualism: Both organisms are benefited. Match to (iii).
Amensalism: One organism is inhibited or unaffected by the presence of another, which itself is unaffected. Match to (i).
Explain the significance of root nodules in leguminous plants.
Significance of Root Nodules in Leguminous Plants:
Root nodules are structures formed on the roots of leguminous plants that house nitrogen-fixing bacteria such as Rhizobium.
These nodules are prominent in environments where nitrogen is limited.
Common examples of leguminous plants include beans, clover, and peas.
There exists a symbiotic relationship in the root nodules, where both the plant and the bacteria benefit. The plant provides carbohydrates to the bacteria, and in return, the bacteria fix atmospheric nitrogen.
Farmers utilize this trait by growing leguminous plants to improve the nitrogen content of the soil through these nodules, enhancing the nutrient quality for future crops.
In these nodules, atmospheric nitrogen ($N_2$) is converted into ammonia ($NH_3$), which the plants then use to synthesize amino acids, nucleotides, and other vital compounds such as vitamins and hormones. These are crucial for plant growth and development.
The ability for legumes to fix nitrogen naturally reduces the need for artificial nitrogen fertilizers, making legumes extremely beneficial in agricultural practices.
Rhizobium helps in the conversion of atmospheric nitrogen into ammonia.
A) True
B) False
The correct answer is A) True.
Rhizobium bacteria engage in a process known as nitrogen fixation, where they convert atmospheric nitrogen into ammonia, a form usable by plants. This interaction typically occurs in the root nodules of leguminous plants like peas and lentils.
During this symbiotic relationship, Rhizobium bacteria reside within the roots of the host plant. The plant provides nutrients and shelter to the bacteria, and in return, it receives ammonia, which is crucial for its growth. This mutual benefit defines the symbiosis between the plant and Rhizobium.
Which of the following acts as a biofertilizer?
A. Nostoc
B. Rhizobium
C. Mycorrhiza
D. All of the above
The correct answer is D. All of the above.
Nostoc, Rhizobium, and Mycorrhiza are all examples of biofertilizers. Each of these organisms contributes to plant growth by enhancing nutrient availability in the soil, thus acting as biofertilizers.
In our body, which organ is responsible for the conversion of ammonia into urea?
A. Kidney
B. Lungs
C. Liver
D. Heart
The correct answer to the question "In our body, which organ is responsible for the conversion of ammonia into urea?" is:
C. Liver
To explain further, within our body, it is the liver that plays a crucial role in converting toxic substances like ammonia into a less toxic compound, urea. This conversion takes place through a series of biochemical reactions known as the Ornithine cycle or the Urea cycle.
Here's a simplified breakdown of the process:
Ammonia (NH₃), which is highly toxic, combines with carbon dioxide (CO₂) in liver cells.
Through the reactions in the Ornithine cycle, these substances are ultimately transformed into urea (NH₂-CO-NH₂), a less toxic compound.
The urea produced is then released into the blood, travels to the kidneys, and is filtered out of the blood to be excreted in urine.
This conversion is essential as ammonia is more toxic and needs to be converted to urea, which is less harmful and can be safely transported in the bloodstream to the kidneys for excretion. Thus, organs such as the kidneys, lungs, and heart do not engage in converting ammonia to urea; rather, they have different functions, with the liver solely responsible for this specific conversion.
Lacteal present in the villi of the small intestine:
A. Help to absorb fatty acids and glycerol
B. Secrete enzymes for digestion
C. Secrete hormones
D. Help to absorb proteins
Lacteals are specialized structures located in the villi of the small intestine. These villi are essentially finger-like projections or folds that significantly increase the surface area of the small intestine, which is pivotal for nutrient absorption.
Inside each villus, aside from numerous blood capillaries, there is a central lymphatic vessel known as a lacteal. The primary function of lacteals is quite specific; they are responsible for the absorption of fatty acids and glycerol. These components are key products of fat digestion and are too large to be absorbed directly into the blood capillaries. Instead, they are taken into the lymphatic system via the lacteals.
Given the options:
A. Help to absorb fatty acids and glycerol
B. Secrete enzymes for digestion
C. Secrete hormones
D. Help to absorb proteins
The correct answer is A - Lacteals help to absorb fatty acids and glycerol, facilitating the transport of these fat digestion products from the intestinal lumen into the lymphatic system, ultimately entering the blood circulation to be utilized by the body. Thus, lacteals play a crucial role in the absorption and handling of dietary fats.
An exception to cell theory is: A) Bacteria B) Virus C) Algae D) All
The given question is to identify an exception to the cell theory. Cell theory primarily states that:
All living organisms are composed of cells.
The cell is the basic unit of life.
All cells arise from pre-existing cells.
Option Analysis:
A) Bacteria: These are unicellular organisms and do conform to the cell theory as they consist of a single cell. Hence, they are not an exception.
C) Algae: Algae can be either unicellular or multicellular but regardless, they are made up of cells. Therefore, algae also adhere to the cell theory and are not an exception.
D) All: Not all options listed are exceptions to the cell theory based on the described characteristics of bacteria and algae.
On the other hand:
B) Virus: Viruses provide the correct answer. They are unique as they do not consist of cells. Viruses exist in a sort of twilight state where they display characteristics of both life and non-life. When outside a host, they are considered abiotic (non-living), and only when inside a host organism do they exhibit life-like behavior using the host's cellular machinery. However, inherently, they are not made up of cells, thus making them an exception to the cell theory.
Conclusion:The correct option that signifies an exception to the cell theory is:
B) Virus
Viruses are considered exceptions because they do not consist of cells, a fundamental criterion stated in cell theory. Therefore, option B is the correct answer.
Bacteria "eaters" are:
A) Virus
B) Bacteria
C) Fungi
D) Algae.
The question pertains to identifying organisms that feed on bacteria, sometimes referred to as "bacteria eaters." Here are considerations for each option provided:
Algae: These organisms are autotrophs, which means they produce their food through photosynthesis and do not consume other organisms.
Fungi: Fungi are primarily saprophytes, thriving on decomposing and dead material rather than preying on living bacteria.
Bacteria: Typically, one bacterium does not consume another bacterium.
Virus: This is the correct answer as some viruses, known as bacteriophages, specialize in infecting and multiplying within bacteria. These viruses have a protein coat and contain genetic material, which they inject into bacterial cells to replicate, eventually leading to the bacteria's destruction.
Hence, the answer to the question of what organisms eat bacteria is: A) Virus
Abundance of coliform bacteria in a water body is indicative of pollution from:
A) petroleum refinery. B) metal smelter. C) fertilizer factory. D) domestic sewage.
The high presence of coliform bacteria in a water body is a significant indicator of pollution primarily due to domestic sewage. The reason this particular type of bacteria serves as a pollution indicator is because it is predominantly found in human feces.
When examining potential sources of these bacteria, such as petroleum refineries, metal smelters, and fertilizer factories, none typically feature human fecal contamination. On the other hand, domestic sewage often contains human waste, which leads to the presence of coliform bacteria when introduced into bodies of water.
This presence is concerning because it potentially increases pollution levels in the water and poses health risks. Water from such sources may be used for drinking after treatment, but inadequate treatment might not effectively eliminate these bacteria, leading to diseases like nausea, vomiting, and diarrhea.
Coliform bacteria contamination is one reason why chlorination is often used in water treatment processes. Chlorine can effectively kill these bacteria, ensuring the safety of tap water.
Therefore, the correct answer is D) domestic sewage.
Cow has a special stomach as compared to that of a lion in order to:
A. absorb food in a better manner. B. digest cellulose present in the food. C. assimilate food in a better way. D. absorb a large amount of water.
The special stomach of a cow compared to that of a lion is primarily designed to address the unique dietary needs specific to herbivores. Cows predominantly eat cellulose-rich plant materials which require special digestive mechanisms.
Lions, being carnivores, consume meats that predominantly lack cellulose. Therefore, their digestive system is not equipped to handle cellulose digestion.
The key functionality of the cow's stomach is its ability to digest cellulose present in their plant-based diet. This is facilitated by a specialized digestive system, including a multi-chambered stomach with regions like the rumen, which harbors microbes that assist in breaking down cellulose into glucose. This process provides essential nutrients and energy necessary for the cow’s survival.
In the context of the choices provided:
The cow's capacity to better absorb or assimilate food or to absorb a large amount of water, while important, are not the primary reasons for its specialized stomach.
Thus, the correct answer to why cows have a special stomach as compared to that of a lion is:
B. digest cellulose present in the food.
In the symbiotic relationship between a bacterium and a root of a legume, the bacteria provide $N_{2}$, and the plant roots provide carbon. The bacteria provide $\mathrm{NH}{4}$, and the roots provide carbon. The roots provide $\mathrm{NH}{4}$, and bacteria provide carbon. Bacteria provide $\mathrm{N}{2}$, and the roots provide $\mathrm{NH}{4}$.
In the symbiotic relationship between the bacteria and the roots of a legume, the key components exchanged are nitrogen and carbon. The bacteria have the capability to fix atmospheric nitrogen, transforming it into a form that the plant can use. Specifically, the bacteria convert the nitrogen ($N_2$) into ammonia ($\mathrm{NH}_4$), which is usable by the plant for its nutritional needs.
In return, the plant roots provide organic carbon compounds to the bacteria. These carbon compounds are essential for the bacteria as they use them as a food source. This mutual exchange benefits both parties; the plant receives nitrogen in a usable form, and the bacteria obtain necessary carbon, enabling both to thrive.
Given the options:
Bacteria provide $N_{2}$, and the plant roots provide carbon.
Bacteria provide $\mathrm{NH}_{4}$, and the roots provide carbon.
The roots provide $\mathrm{NH}_{4}$, and bacteria provide carbon.
Bacteria provide $\mathrm{N}{2}$, and the roots provide $\mathrm{NH}{4}$.
The correct answer is option 2 where bacteria provide $\mathrm{NH}_4$ (ammonia) and the roots provide carbon. This is the core of the symbiotic relationship, with bacteria fixing nitrogen and the plant providing organic carbon.
At every 20 minutes, one bacterium divides into two. How many bacteria will be produced after two hours if one starts with 10 bacteria?
A) $2^{5} \times 10$
B) $2^{5} \times 10^{5}$
C) $2^{6} \times 10$
D) $2^{6} \times 10^{6}$
To determine the number of bacteria after two hours starting with 10 bacteria, where each bacterium divides into two every 20 minutes, we proceed as follows:
Length of Each Division Cycle: Each bacterium divides every 20 minutes.
Total Time for Consideration: We need to calculate over a span of 2 hours, which equals 120 minutes.
Number of Cycles in Two Hours: $$ \text{Number of cycles} = \frac{120 \text{ minutes}}{20 \text{ minutes per cycle}} = 6 \text{ cycles} $$ This means that every bacterium will have completed 6 cycles of division in 120 minutes.
Calculation of Total Bacteria After 2 Hours: Starting with 10 bacteria, after each cycle, the number of bacteria doubles. Therefore, after 6 cycles, the increase in the number of bacteria can be calculated as follows:
$$ \text{Total bacteria} = \text{Initial number of bacteria} \times 2^{\text{Number of cycles}} = 10 \times 2^6 $$ $$ 2^6 = 64 $$ Therefore, the total number of bacteria = $10 \times 64 = 640$.
The correct calculation shows that the answer **C) $2^6 \times 10$ ** fits our result since $2^6 = 64$ and $64 \times 10 = 640$. This reasoning supports choice C) $2^6 \times 10$ as the correct answer.
Which of the following food materials is made up of fungi? A. Chilgoza B. Mushroom C. Papaya D. Mango
The question asks which food material among the options given is made up of fungi. Let's examine the options provided:
Chilgoza isn't a fungus; it's a type of pine nut from the Pinus genus and belongs to the plant kingdom.
Both Papaya and Mango are fruits and also part of the plant kingdom, not fungi.
The correct answer is Mushroom (Option B). Mushrooms are indeed fungi and are extensively used as food material. Scientifically, many edible mushrooms belong to the genus Agaricus, which is characterized by their distinctive umbrella-shaped appearance. Mushrooms are a staple in various cuisines and are prepared as vegetables.
Thus, the correct answer to the question is: $$ \text{B. Mushroom} $$
Causative agent of Kala azar (Black fever) is:
A. Bacteria
B. Virus
C. Protozoan
D. Fungi
The causative agent of Kala-azar, also known as Black Fever, is Leishmania donovani, which is a type of protozoan. Kala-azar spreads primarily through the bite of infected female phlebotomine sandflies. These sandflies inject the protozoa into the human bloodstream during their bite, where the infection then proliferates, causing the disease symptoms associated with Black Fever.
Considering the characteristics of the pathogen:
It is not a bacteria, virus, or fungus.
It is distinctly a protozoan.
Thus, the correct answer to the question is:
C. Protozoan
Most powerful digestive enzyme occurs in which cell organelles?
A. Mitochondria
B. Chloroplast
C. Golgi body
D. Lysosome
The question is regarding the most powerful digestive enzyme and its association with specific cell organelles in living organisms. Let’s break down the role of each listed organelle to clarify which one houses the most potent digestive enzymes:
Mitochondria are often called the powerhouses of the cell, primarily because they are responsible for producing energy through processes like ATP synthesis. They don't directly participate in digestion through enzymes that break down macromolecules.
Chloroplasts are essential in plants for photosynthesis — converting light energy into chemical energy — but similarly to mitochondria, they don't contribute to macromolecular digestion with enzymes.
The primary function of the Golgi apparatus (Golgi body) involves the sorting and packaging of proteins for secretion. It plays a vital role in modifying proteins and packaging them into vesicles, but it doesn’t produce powerful digestive enzymes.
Lysosomes, on the other hand, are known as the cell’s recycling center. They contain hydrolase enzymes that break down proteins, lipids, carbohydrates, and nucleic acids. This allows lysosomes to perform controlled digestion of macromolecules within the cell, which is critical for the cell's clean-up and turnover. Lysosomes act to degrade both intracellular debris and extracellular materials brought into the cell via endocytosis.
Given these roles, the lysosomes are unequivocally the organelles that house the most powerful digestive enzymes, capable of breaking down a wide variety of biomolecules. Therefore, the correct answer is:
D. Lysosome
Which one of the following substances is changed into amino acid after digestion?
A. Protein
B. Carbohydrate
C. Fat
D. Nucleic acid
The question is asking which of the following substances is changed into amino acids after digestion. Let's examine the options:
Protein undergoes breakdown during digestion to produce amino acids. This is facilitated primarily by enzymes like pepsin and trypsin.
Carbohydrates are broken down into glucose, not amino acids. This happens through digestion but results in simple sugars, specifically glucose.
Fats are broken down and produce fatty acids and glycerol, again, not amino acids.
Nucleic acids, such as DNA and RNA, do not form amino acids when digested. They are broken down into nucleotides or smaller constituents.
From the above explanations, it is clear that the correct answer is:
A. Protein
Proteins are the only substances from the given options that are transformed into amino acids as a result of the digestion process.
Source of Penicillin antibiotic is:
A. Bacteria
B. Fungi
C. Virus
D. Algae
The source of the antibiotic Penicillin is mainly derived from fungi. Specifically, it is produced by a type of fungus known as Penicillium. The discovery of penicillin, which is notably coined by the scientist Alexander Fleming, marked a pivotal moment during World War II. Its effectiveness in combating disease-causing bacteria significantly contributed to treating infected wounds and saved many lives, earning the discoverers the Nobel Prize. Therefore, the correct answer to the question is option: B. Fungi
Nematoblast or stinging cells are found in which phylum of animals?
A) Porifera
B) Annelida
C) Cnideria
D) Arthropoda
Nematoblasts, also known as stinging cells, are specialized cells found predominantly around the mouth and on the tentacles of certain animals. These cells play a crucial role in prey capture and protection. As per the options provided:
Porifera includes sponges, which do not have stinging cells.
Annelida consists of segmented worms that lack these particular cells.
Cnidaria includes creatures like jellyfish and corals, which are known to possess these stinging cells.
Arthropoda encompasses insects, spiders, and other similar creatures without stinging cells.
Therefore, the correct answer to the question is: C) Cnidaria
The presence of nematoblasts or stinging cells is a definitive characteristic of the Cnidaria phylum, used for both offensive and defensive mechanisms.
Which gas is used in aerobic respiration? A. Oxygen B. Carbon dioxide C. Nitrogen D. Methane
The gas used in aerobic respiration is Oxygen (Option A).
Aerobic respiration is a biological process where cells convert glucose and oxygen into energy in the form of adenosine triphosphate (ATP), water, and carbon dioxide. The oxygen in aerobic respiration serves an essential role in the oxidative phosphorylation stage of the process. This reaction primarily occurs in the mitochondria, the powerhouse of the cell.
Here's a simple equation representing aerobic respiration: $$ \text{Glucose} + \text{Oxygen} \rightarrow \text{Energy (ATP)} + \text{Carbon Dioxide} + \text{Water} $$
In summary, oxygen is critical for energy production through aerobic respiration, making it the correct answer to the question.
In a myofibril, the thick filaments are held together in the middle of A-band by a thin fibrous membrane called:
A. Z-line
B. K-line
C. M-line
D. H-line
In a myofibril, the thick filaments are held together in the middle of the A-band by a thin fibrous membrane called the M-line. Here’s a detailed explanation to understand the concept:
A sarcomere is the basic unit of a myofibril in muscle cells. It is defined from one Z-line to another Z-line. The A-band within the sarcomere contains the thick filaments which are primarily composed of the protein myosin.
In the middle of the A-band, there is a thin fibrous membrane known as the M-line. The M-line serves an important role by holding the thick filaments in place. Unlike the thin filaments (which are mainly composed of actin and associated with proteins such as tropomyosin and troponin), the thick filaments remain stationary during muscle contraction.
The M-line is composed of specific proteins, including a key enzyme called M creatine kinase. This enzyme plays a role in cellular energy transfer and structurally supports the arrangement of the thick filaments.
Here is the breakdown of the options provided:
Z-line: Marks the boundary between adjacent sarcomeres and anchors the thin filaments. It is not related to holding the thick filaments together.
K-line: Does not exist within the structure of a sarcomere.
M-line: Correct Answer. It is located in the center of the A-band and holds the thick filaments together.
H-line: There is no such term; however, there is an H-zone which is the area within the A-band where no thin filaments overlap with the thick filaments. The M-line is situated in the center of the H-zone.
So, the correct answer is C. M-line.
Compound soluble in water which does not impede oxygen transportation is:
A) NO
B) $\mathrm{SO}_{2}$
C) $\mathrm{CO}$
D) $\mathrm{SO}_{3}$
To determine which compound is soluble in water and does not impede oxygen transportation, let's analyze the options:
Sulfur Dioxide ($\mathrm{SO}_{2}$)
Sulfur Trioxide ($\mathrm{SO}_{3}$)
Carbon Monoxide ($\mathrm{CO}$)
Nitric Oxide (NO)
Analysis
1. Sulfur Dioxide ($\mathrm{SO}_{2}$):
Solubility: $\mathrm{SO}_{2}$ is soluble in water.
Impact on Oxygen Transportation: It does not compete with oxygen for binding with hemoglobin in the blood, thus not impeding oxygen transportation.
2. Sulfur Trioxide ($\mathrm{SO}_{3}$):
Solubility: $\mathrm{SO}_{3}$ is insoluble in water.
3. Carbon Monoxide ($\mathrm{CO}$):
Solubility: $\mathrm{CO}$ is soluble in water.
Impact on Oxygen Transportation: It competes with oxygen for binding with hemoglobin, thereby impeding oxygen transportation.
4. Nitric Oxide (NO):
Solubility: NO is slightly soluble in water.
Impact on Oxygen Transportation: It competes with oxygen for binding with hemoglobin, thus preventing proper oxygen transportation.
Conclusion
Among the given options, Sulfur Dioxide ($\mathrm{SO}_{2}$) is the compound that is soluble in water and does not impede oxygen transportation.
Thus, the correct answer is:
A) $\mathrm{SO}_{2}$
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Ask Chatterbot AINCERT Solutions - Microbes in Human Welfare | NCERT | Biology | Class 12
Bacteria cannot be seen with the naked eyes, but these can be seen with the help of a microscope. If you have to carry a sample from your home to your biology laboratory to demonstrate the presence of microbes with the help of a microscope, which sample would you carry and why?
If I have to carry a sample from home to the biology laboratory to demonstrate the presence of microbes using a microscope, I would carry a sample of curd.
Reasons:
High Microbial Count: Curd contains Lactobacillus and other lactic acid bacteria (LAB) which are present in large numbers.
Easy to Obtain: Curd is commonly available at home and can be easily transported without special conditions.
Visible Under Microscope: When a drop of curd is spread on a microscope slide and stained appropriately, the bacteria can be easily observed due to their high concentration.
Demonstration of Microbial Activity: LAB play an important role in the fermentation process of converting milk into curd, making it a perfect sample to demonstrate microbial activity as well.
Procedure:
Take a small sample of curd in a sterile container.
In the laboratory, prepare a smear of curd on a glass slide.
Stain the smear using Gram staining or any appropriate staining technique.
Observe under the microscope at an appropriate magnification (e.g., 1500X).
This sample is ideal because curd is a common household product that people can easily relate to and it clearly demonstrates the presence and activity of microbes.
Give examples to prove that microbes release gases during metabolism.
Microbes release gases during their metabolic activities, and various examples illustrate this process:
Curd Formation by Lactic Acid Bacteria (LAB):
During the production of curd from milk, LAB such as *Lactobacillus* are involved. They ferment lactose to produce lactic acid and $ \text{CO}_2 $, giving curd its characteristic texture.
Fermentation in Dough:
The dough used for making foods such as dosa and idli ferments through bacterial action, producing $ \text{CO}_2 $ gas, which causes the dough to puff up.
Bread-making:
Baker’s yeast (*Saccharomyces cerevisiae*) is used in bread-making. The yeast ferments the sugars in the dough, producing ethanol and $ \text{CO}_2 $, causing the dough to rise.
Cheese Production:
In Swiss cheese, the bacterium *Propionibacterium shermanii* produces a large amount of $ \text{CO}_2 $, forming characteristic large holes in the cheese.
Production of Alcoholic Beverages:
Yeast *Saccharomyces cerevisiae* ferments malted cereals and fruit juices to produce ethanol and $ \text{CO}_2 $ in beverages like beer and wine.
Biogas Production:
Methanogenic bacteria, such as *Methanobacterium*, break down organic material in anaerobic conditions, producing a mixture of methane (CH$_4$), $ \text{CO}_2 $, and hydrogen ($ \text{H}_2 $). This biogas can be used as a renewable energy source.
These examples demonstrate how microbes release gases such as $ \text{CO}_2 $, methane, and hydrogen during their metabolic processes.
In which food would you find lactic acid bacteria? Mention some of their useful applications.
You would commonly find lactic acid bacteria (LAB) in curd.
Useful Applications of Lactic Acid Bacteria (LAB):
Conversion of Milk to Curd: LAB such as *Lactobacillus* convert milk into curd by producing acids that coagulate and partially digest milk proteins. This process also increases the nutritional quality of the curd by increasing vitamin B₁₂ content.
Fermentation of Dough: LAB are involved in the fermentation of dough for foods like dosa and idli, resulting in the production of CO₂, which gives the dough its puffed-up appearance.
Preventing Disease: In the human stomach, LAB play a beneficial role in *checking the growth of disease-causing microbes.*
Name some traditional Indian foods made of wheat, rice and Bengal gram (or their products) which involve use of microbes.
Traditional Indian foods made from wheat, rice, and Bengal gram, involving the use of microbes, include:
Wheat:
Bread: Fermented using *Saccharomyces cerevisiae* (baker's yeast).
Naan: A type of flatbread where the dough is often leavened with yeast.
Bhatura: Fermented dough using *Saccharomyces cerevisiae* or naturally occurring wild yeasts.
Rice:
Idli: Rice and black gram batter fermented by naturally occurring lactic acid bacteria.
Dosa: Similar to idli, but typically prepared as a thin crepe, also using naturally fermenting bacteria.
Toddy: A traditional drink fermented from the sap of palm trees.
Bengal Gram (Chickpeas):
Dhokla: Made from a fermented batter of chickpea flour (besan) using *Leuconostoc mesenteroides* and *Lactobacillus fermentum*.
Khaman: Another variation of fermented chickpea flour batter often found in Gujarati cuisine.
These foods utilize the fermentative activities of various microbes to achieve unique textures, flavors, and enhanced nutritional profiles.
In which way have microbes played a major role in controlling diseases caused by harmful bacteria?
Microbes have played a major role in controlling diseases caused by harmful bacteria primarily through the production of antibiotics. Antibiotics are chemical substances produced by some microbes that can kill or retard the growth of other (disease-causing) microbes.
Key Points:
Antibiotics: For example, Penicillin was the first antibiotic discovered by Alexander Fleming. Penicillin and other antibiotics derived from microbes have significantly improved our capacity to treat deadly diseases such as plague, whooping cough, diphtheria, and leprosy.
Antibiotic Discovery: After Penicillin, several other antibiotics were purified from different microbes, enhancing the medical treatment of bacterial infections.
Other Bioactive Molecules: Bioactive molecules like streptokinase (used as a clot buster) and cyclosporin A (an immunosuppressive agent) are derived from microbes, contributing further to human health and medical treatments.
Example:
Penicillin is produced by the mould Penicillium notatum, and it was extensively used during World War II to treat injured soldiers.
These advances have greatly decreased the mortality rates from bacterial infections and improved overall public health.
Name any two species of fungus, which are used in the production of the antibiotics.
Two species of fungus used in the production of antibiotics are:
Penicillium notatum - This fungus produces Penicillin, the first antibiotic discovered.
Cephalosporium acremonium - This fungus is used in the production of Cephalosporins, another group of antibiotics.
What is sewage? In which way can sewage be harmful to us?
Sewage is municipal wastewater that contains large quantities of organic matter, microbes, and human excreta. It is generated daily in cities and towns from households, industry, and stormwater runoff.
Sewage can be harmful in the following ways:
Pathogenic Microbes: Sewage contains many pathogenic microbes which can cause diseases in humans and animals. If untreated sewage is released into natural water bodies, it can lead to the spread of waterborne diseases.
Organic Pollution: The organic matter in sewage can decompose and consume oxygen dissolved in water, leading to the depletion of oxygen levels. This can harm aquatic life as many organisms need oxygen to survive.
Chemical Contaminants: Sewage can contain harmful chemical substances and heavy metals that can pollute the soil and water bodies, leading to long-term environmental damage and health issues for humans.
Eutrophication: Excess nutrients from sewage, such as nitrogen and phosphorus, can cause eutrophication in water bodies. This leads to excessive growth of algae, which can damage aquatic ecosystems and degrade water quality.
Unpleasant Odors: The improper disposal of sewage can create foul odours, making areas uninhabitable and affecting the quality of life.
Proper sewage treatment is crucial to mitigate these harmful effects by removing contaminants and reducing the Biochemical Oxygen Demand (BOD) before releasing the treated water into the environment.
What is the key difference between primary and secondary sewage treatment?
Primary Treatment: This involves the physical removal of particles from the sewage through processes such as filtration and sedimentation. Floating debris is removed by filtration, and grit (soil and small pebbles) is removed by sedimentation. The solids that settle form the primary sludge, while the remaining liquid is known as the primary effluent.
Secondary Treatment: This is a biological treatment where the primary effluent is passed into large aeration tanks. Here, air is pumped in to promote the growth of aerobic microbes that aggregate into flocs. These microbes ingest the organic matter, reducing the biochemical oxygen demand (BOD) of the effluent. After thorough cleaning, the water (effluent) and remaining sludge (activated sludge) are separated.
Do you think microbes can also be used as source of energy? If yes, how?
Yes, microbes can be used as a source of energy. This is primarily through the production of *biogas*. Here’s how:
Biogas Production: Microbes, particularly methanogenic bacteria, can break down organic material under anaerobic conditions to produce biogas. This gas mixture typically contains methane ($\text{CH}_4$), carbon dioxide ($\text{CO}_2$), and traces of other gases.
Process:
Anaerobic Digestion: Organic wastes like cattle dung (rich in cellulose) are fed into a biogas plant where they undergo anaerobic digestion.
Methanogens: Bacteria such as *Methanobacterium* grow in the absence of oxygen and convert these organic wastes into methane.
Biogas: The resulting mixture of gases is called biogas, which can be used as a fuel for cooking, lighting, and electricity generation.
Biogas Plants: These consist of a concrete tank where bio-wastes are collected, and a slurry of dung is fed. The gas produced is collected and can be used directly as a source of energy.
The diagram below illustrates a typical biogas plant:
This method takes advantage of the natural decomposition processes carried out by microbes and repurposes the resulting methane as a valuable energy source.
Microbes can be used to decrease the use of chemical fertilisers and pesticides. Explain how this can be accomplished.
Microbes can be used as biofertilizers and biocontrol agents, playing crucial roles in sustainable agriculture by reducing the dependency on chemical fertilizers and pesticides.
Microbes as Biofertilizers
Biofertilizers are organisms that enhance the nutrient quality of the soil. The main types of biofertilizers include bacteria, fungi, and cyanobacteria.
Bacteria:
Rhizobium: These bacteria form symbiotic relationships with leguminous plants, forming nodules on the roots and fixing atmospheric nitrogen into organic forms available to the plant.
Azospirillum and Azotobacter: These bacteria are free-living and also fix atmospheric nitrogen, enriching the soil with nitrogen content.
Fungi:
Mycorrhiza: Fungi such as those from the genus *Glomus* form symbiotic associations with plant roots, aiding in the absorption of phosphorus from the soil and providing it to the plant. Additionally, mycorrhizal associations enhance plant resistance to pathogens and tolerance to drought and salinity, thereby increasing overall plant growth and development.
Cyanobacteria:
Anabaena, Nostoc, Oscillatoria: These are autotrophic microbes capable of fixing atmospheric nitrogen. They are particularly beneficial in paddy fields, increasing soil fertility by adding organic matter.
Microbes as Biocontrol Agents
Biocontrol involves using biological methods to control plant diseases and pests, thereby reducing or eliminating the need for chemical pesticides.
Bacteria:
Bacillus thuringiensis (Bt): This bacterium produces toxins that are harmful to insect larvae. When sprayed onto plants, the larvae ingest the bacteria and are killed. This method is species-specific and does not harm beneficial insects or other non-target organisms. Bt genes have also been introduced into plants through genetic engineering, such as in Bt-cotton, to confer pest resistance.
Fungi:
Trichoderma species: These are free-living fungi common in root ecosystems and are effective biocontrol agents against various plant pathogens.
Viruses:
Baculoviruses: These pathogens attack insects and other arthropods and are especially useful for species-specific, narrow-spectrum insecticidal applications. They have no adverse effects on plants, mammals, birds, fish, or non-target insects, making them ideal for integrated pest management (IPM) programs.
Benefits of Using Microbes
Reduces Chemical Pollution: Using biofertilizers and biocontrol agents reduces the environmental pollution caused by chemical fertilizers and pesticides.
Sustainable Agriculture: Enhances soil fertility and promotes a healthy ecosystem, leading to more sustainable agricultural practices.
Safety: Biofertilizers and biocontrol agents are non-toxic and are safer for humans, animals, and the environment compared to chemical alternatives.
By incorporating these microbial solutions into agricultural practices, dependency on chemical fertilizers and pesticides can be significantly reduced, leading to more environmentally friendly and sustainable farming methods.
Three water samples namely river water, untreated sewage water and secondary effluent discharged from a sewage treatment plant were subjected to BOD test. The samples were labelled A, B and C; but the laboratory attendant did not note which was which. The BOD values of the three samples A, B and C were recorded as $20 \mathrm{mg} / \mathrm{L}, 8 \mathrm{mg} / \mathrm{L}$ and $400 \mathrm{mg} / \mathrm{L}$, respectively. Which sample of the water is most polluted? Can you assign the correct label to each assuming the river water is relatively clean?
To identify which water sample corresponds to each BOD (Biochemical Oxygen Demand) value, we can use the fact that a higher BOD value indicates a higher level of pollution due to the greater amount of organic matter present in the water.
From the given BOD values:
Sample A: $20 , \text{mg/L}$
Sample B: $8 , \text{mg/L}$
Sample C: $400 , \text{mg/L}$
Interpretation of BOD values:
River water is relatively clean and would likely have the lowest BOD value.
Untreated sewage water is highly polluted and would have the highest BOD value.
Secondary effluent from a sewage treatment plant has undergone some treatment and should have an intermediate BOD value.
Given this understanding, we can now match the BOD values to the respective water samples:
Sample B: With a BOD value of $8 , \text{mg/L}$, it is the lowest and should correspond to the river water.
Sample A: With a BOD value of $20 , \text{mg/L}$, it is intermediate and should correspond to the secondary effluent.
Sample C: With a BOD value of $400 , \text{mg/L}$, it is the highest and should correspond to the untreated sewage water.
Conclusion:
A = Secondary effluent from a sewage treatment plant ($20 , \text{mg/L}$)
B = River water ($8 , \text{mg/L}$)
C = Untreated sewage water ($400 , \text{mg/L}$)
Thus, Sample C is the most polluted.
Find out the name of the microbes from which Cyclosporin A (an immunosuppressive drug) and Statins (blood cholesterol lowering agents) are obtained.
Cyclosporin A is produced by the fungus _Trichoderma polysporum_. Statins are produced by the yeast _Monascus purpureus_.
Find out the role of microbes in the following and discuss it with your teacher.
(a) Single cell protein (SCP)
(b) Soil
(a) Single Cell Protein (SCP)
Single Cell Protein (SCP) refers to protein extracted from microorganisms such as algae, fungi, bacteria, and yeast. These microorganisms can grow on a variety of substrates, including agricultural wastes, and produce high amounts of protein. SCP is used as a supplement to animal feed and can also be used for human consumption. Here’s how microbes contribute:
Microbial Growth: Microbes such as *Spirulina*, *Chlorella* (algae), *Fusarium* (fungus), and *Methylophilus methylotrophus* (bacterium) are grown on substrates like agricultural waste, molasses, and even sewage.
Protein Production: These microorganisms have high protein content in their biomass. For instance, *Spirulina* can contain up to 70% protein.
Sustainable Source: Using microbes for SCP production is sustainable and can utilize waste products, reducing environmental pollution.
Rapid Growth: Microbes can multiply rapidly, leading to large yields of SCP in a short time, making it an efficient protein source.
(b) Soil
Microbes play crucial roles in maintaining soil health and fertility:
Nutrient Cycling: Microorganisms, such as bacteria and fungi, are involved in the decomposition of organic matter, releasing nutrients like nitrogen, phosphorus, and potassium back into the soil. This is critical for plant growth.
Nitrogen Fixation: Certain bacteria, such as *Rhizobium* and *Azotobacter*, convert atmospheric nitrogen into a form that plants can use. For example, *Rhizobium* forms symbiotic relationships with leguminous plants, residing in root nodules.
Soil Structure: Fungal hyphae and bacterial colonies help in the formation of soil aggregates, which improve soil structure and porosity. This enhances water retention and root penetration.
Disease Suppression: Beneficial soil microbes can outcompete harmful pathogens or produce substances that inhibit the growth of these pathogens, protecting plants from diseases.
Composting: Microbes break down organic waste in compost piles, converting it into humus, a rich soil conditioner that improves soil fertility.
Understanding these roles highlights the importance of microbes in SCP production and soil health, emphasizing their key contributions to agricultural sustainability and food security. Discuss these points with your teacher to further elaborate on the specific examples and processes involved.
Arrange the following in the decreasing order (most important first) of their importance, for the welfare of human society. Give reasons for your answer.
Biogas, Citric acid, Penicillin and Curd
1. Penicillin
Reason: Penicillin is an antibiotic discovered by Alexander Fleming, and it has revolutionized medical treatment. It is crucial for treating bacterial infections, which if left untreated, can cause serious illnesses or even death. Antibiotics like Penicillin have saved countless lives and continue to be vital in fighting infectious diseases.
2. Biogas
Reason: Biogas is a renewable source of energy produced by the microbial degradation of organic matter in anaerobic conditions. It provides a sustainable solution to energy needs in rural areas, reduces greenhouse gas emissions, and helps in waste management. The production of biogas from agricultural waste and animal dung also helps in reducing reliance on fossil fuels and minimizes environmental pollution.
3. Curd
Reason: Curd, produced by the fermentation of milk by lactic acid bacteria (LAB), is a significant dietary item in many cultures. It enhances the nutritional quality of milk by increasing vitamin B$_{12}$ content and helps in digestion. Additionally, the LAB present in curd helps in maintaining gut health by checking the growth of harmful pathogens.
4. Citric Acid
Reason: Citric acid is an important organic acid produced typically by the fermentation process using the fungus Aspergillus niger. It has wide applications in food and beverage industries, pharmaceuticals, and as a cleaning agent. However, while essential, its impact on immediate human health and environmental sustainability is somewhat less direct compared to Penicillin, biogas, and curd.
Rank | Product | Reason |
---|---|---|
1 | Penicillin | Crucial for treating bacterial infections and saving lives |
2 | Biogas | Provides renewable energy, reduces greenhouse gas emissions, aids in waste management |
3 | Curd | Nutritional benefits, increases vitamin B$_{12}$, maintains gut health |
4 | Citric Acid | Widely used in industries, but less direct impact on immediate human health and environment |
How do biofertilisers enrich the fertility of the soil?
Biofertilizers enrich the nutrient quality of the soil by utilizing *organisms* that fix atmospheric nitrogen, decompose organic matter, and solubilize phosphorus. Biofertilizers mainly include bacteria, fungi, and cyanobacteria. Here are some specific ways these microorganisms contribute:
Nitrogen Fixation:
Bacteria such as Rhizobium: These form symbiotic associations with the roots of leguminous plants and convert atmospheric nitrogen into organic forms usable by plants.
Free-living Bacteria: Species like *Azospirillum* and *Azotobacter* also fix atmospheric nitrogen independently.
Phosphorus Solubilization:
Mycorrhizal Fungi: Genus *Glomus* forms symbiotic relationships with plants, absorbing phosphorus from the soil and making it available to the plant. This association also offers other benefits like pathogen resistance, drought tolerance, and improved growth.
Organic Matter Decomposition:
Cyanobacteria (e.g., *Anabaena*, *Nostoc*, and *Oscillatoria*): These autotrophic microbes add organic matter to the soil by fixing atmospheric nitrogen and increasing soil fertility. They are especially significant in paddy fields.
Advantages of using biofertilizers include:
Reduced dependence on chemical fertilizers, which can cause environmental pollution.
Sustainable agriculture by enhancing soil health and ecosystem biodiversity.
By employing biofertilizers, farmers can help maintain soil fertility and promote sustainable farming practices.
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Notes - Microbes in Human Welfare | Class 12 NCERT | Biology
Microbes in Human Welfare: Comprehensive Class 12 Notes
Microbes play a pivotal role in various aspects of human welfare, extending far beyond the harmful effects often associated with them. Ranging from their use in household products to industrial applications, sewage treatment, and even agriculture, microbes are indispensable in enhancing our quality of life. This article delves deep into the multifaceted contributions of microbes to human welfare, aligning with the Class 12 curriculum.
Microbes in Household Products
Production of Curd
Microbes such as Lactobacillus and other lactic acid bacteria (LAB) are essential in producing curd from milk. These bacteria grow in milk, converting it into curd by coagulating and partially digesting milk proteins. Adding a small amount of curd to fresh milk acts as an inoculum, facilitating the bacterial growth that improves the nutritional quality of the milk by increasing vitamin B12 levels.
Fermentation of Dough
Dough used for making foods like dosa and idli ferments through bacterial activity, resulting in the puffed-up appearance due to CO2 gas production. Similarly, baker's yeast (Saccharomyces cerevisiae) is employed for bread fermentation. Traditional drinks like 'toddy' and fermented foods such as fish, soybeans, and bamboo shoots also rely on microbial fermentation.
Cheese Production
Microbes have long been used in cheese production, which varies in texture, flavour, and taste based on the specific microbes involved. For instance, Propionibacterium sharmanii is responsible for the large holes in Swiss cheese, while specific fungi impart the unique flavour to Roquefort cheese.
Microbes in Industrial Products
Fermented Beverages
Yeasts, particularly Saccharomyces cerevisiae, have been utilised for ages to produce alcoholic beverages like wine, beer, whisky, brandy, and rum. The fermentation of malted cereals and fruit juices by this yeast results in ethanol production. The type of beverage depends on whether the fermented product undergoes distillation. For instance, wine and beer are produced without distillation, unlike whisky, brandy, and rum.
Antibiotics
Microbial production of antibiotics is one of the major scientific breakthroughs of the 20th century. Penicillin, discovered by Alexander Fleming, was the first antibiotic that revolutionised the treatment of bacterial infections. Subsequent antibiotics from other microbes have enabled us to combat diseases like plague, diphtheria, and leprosy effectively.
Chemicals, Enzymes, and Bioactive Molecules
Microbes are harnessed to produce essential chemicals such as citric acid (Aspergillus niger), acetic acid (Acetobacter aceti), butyric acid (Clostridium butylicum), and ethanol (Saccharomyces cerevisiae). Enzymes like lipases are used in detergents, and pectinases and proteases help clarify fruit juices. Streptokinase from Streptococcus is a 'clot buster' in heart attack treatments, while cyclosporin A from Trichoderma polysporum aids in immunosuppression for organ transplants. Statins from Monascus purpureus are effective in lowering blood cholesterol.
Microbes in Sewage Treatment
Cities generate vast quantities of wastewater daily. Before this sewage can be disposed of into natural water bodies, it undergoes treatment in sewage treatment plants (STPs) to reduce its polluting potential.
Primary Treatment
This stage involves the physical removal of large and small particles through filtration and sedimentation. The resulting primary sludge and effluent move on to secondary treatment.
Secondary Treatment
Involves biological treatment by aerobic microbes in aeration tanks, forming bacterial 'flocs' that significantly reduce the sewage's Biochemical Oxygen Demand (BOD). The sludge from this process is then further digested anaerobically to produce biogas.
graph TD;
A[Sewage] --> B[Primary Treatment: Filtration & Sedimentation];
B --> C[Secondary Treatment: Aeration Tanks];
C --> D[Activated Sludge];
D --> E[Anaerobic Digestion: Biogas Production];
D --> F[Effluent Release]
Microbes in Production of Biogas
Biogas, primarily comprising methane, is produced by anaerobic bacteria that decompose organic materials. Methanogens like Methanobacterium, found in cattle rumen and anaerobic sludge, are integral in this process.
Microbes as Biocontrol Agents
Biocontrol employs natural predators rather than chemicals to manage pests. For example, the bacteria Bacillus thuringiensis control butterfly caterpillars, while Trichoderma fungi combat plant pathogens. Baculoviruses are used as species-specific insecticides that do not harm non-target organisms.
Microbes as Biofertilisers
Biofertilisers enrich soil nutrients and reduce dependence on chemical fertilisers. Bacteria like Rhizobium fix atmospheric nitrogen in leguminous plants, while free-living bacteria like Azospirillum and Azotobacter enhance soil nitrogen content. Mycorrhizal fungi increase plant growth by aiding in phosphorus absorption, and cyanobacteria like Anabaena contribute to soil fertility, especially in paddy fields.
graph TD;
A[Biofertilisers] --> B[Bacteria]
B --> B1[Rhizobium: Nitrogen Fixation in Legumes]
B --> B2[Azospirillum: Free-living Nitrogen Fixation]
B --> B3[Azotobacter: Free-living Nitrogen Fixation]
A --> C[Fungi]
C --> C1[Mycorrhiza in Phosphorus Absorption]
A --> D[Cyanobacteria]
D --> D1[Anabaena in Paddy Fields]
Summary
Microbes are integral to life on earth and contribute significantly to human welfare. From household and industrial products to environmental protection and agriculture, their diverse applications are invaluable. Understanding and utilising these microscopic marvels continue to open new avenues for sustainable living and enhanced health.
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