Biology 2 Marks Questions

Primary (1°) treatment is a physical process that involves for removal of particulate as settelable particle. Secondary (2°) treatment is purely a biological treatment involving microbial oxidation.

Sewage is the municipal waste matter that is carried away in sewers and drains. It includes both liquid and solid wastes, rich in organic matter and microbes. Many of these microbes are pathogenic and can cause several water - borne diseases. Sewage water is a major cause of polluting drinking water. Hence, it is essential that sewage water is properly collected, treated, and disposed.

1. Making of dough for bread, dosa and idli with the help of fermenting microbes. Heat expels the gases and makes the food spongy.
2. Production of biogas.

1. Cyclosporin-A is obtained from the fungus Trichoderma polysporum.
2. Statins is obtained from Monascus purpureus.

Soil
Microbes play an important role in maintaining soil fertility. They help in the formation of nutrient-rich humus by the process of decomposition. Manyspecies of bacteria and cyanobacteria have the ability to fix atmospheric nitrogen into usable form. Rhizobium is a symbiotic bacteria found in the root nodules of leguminous plants. Azospirillium and Azotobocter are free living nitrogen-fixing bacteria, whereas Anabena, Nostoc, and Oscillitoria are examples of nitrogen-fixing cyanobacteria.

Single cell protein (SCP):
A single cell protein is a protein obtained from certain microbes, which forms an alternate source of proteins in animal feeds. The microbes involved in the preparation of single cell proteins are algae, yeast, or bacteria. These microbes are grown on an industrial scale to obtain the desired protein. For example, Spirulina can be grown on waste materials obtained from molasses, sewage, and animal manures. It serves as a rich supplement of dietary nutrients such as proteins, carbohydrate, fats, minerals, and vitamins. Similarly, micro-organisms such as Methylophilus and methylotrophus have a large rate of biomass production. Their growth canproduce a large amount of proteins.

Curd can be used as a sample for the study of microbes. Curd contains numerous lactic acid bacteria (LAB) or Lactobacillus. These bacteria produce acids that coagulate and digest milk proteins. A small drop of curd contains millions of bacteria, which can be easily observed under a microscope.

Saccharomyces cerevisiae- ethanol/alcohol.
Monascus purpureus- statin.

Azospirillium/Azotobacter, Rhizobium.
They enrich soil nutrient/nitrogen fixation.

In anaerobic sludge digester, methanogens, i.e. anaerobic bacteria, digest the bacteria and fungi of the floe in the activated sludge.
This produces mixture of methane, hydrogen sulphide and carbon dioxide, i.e. biogas. This gas is used as a source of energy as it is inflammable.

• Trichoderma polysporum, cyclosporin A.
• Aspergillus niger, citric acid.
• Monascus purpureus, statin.
• Saccharomyces cerevisiae, ethanol/alcohol.
• Penicillium notatum, Penicillin.

Supernatant from the primary treatment is passed into large aeration tanks during secondary treatment. In these tanks, the effluent is agitated mechanically and air is pumped into it. This causes vigorous growth of the bacteria that lead to the formation of floc, which consists of bacteria and fungal filaments in a mesh-like structure. While growing, these microbes consume the major part of organic matter in the effluent; it decreases the biological oxygen demand (BOD).
After a significant drop in BOD is observed, effluent is passed on to the settling tank.

1. Monascus purpureus.
2. Aspergillus niger.
3. Penicillium notatum.
4. Clostridium butylicum.

Physical removal of particles (large and small), mutualism by filtration and sedimentation, forming primary sludge/sedimented solids, forming effluent (supernatant) for secondary treatment.

Species specific, narrow spectrum, insecticidal application (IPM), no negative impact on plants/mammals/birds/fish/even non target insects.

1. Defective gene not producing ADA, immune system is affected.
2. A retroviral vector is used, recipient cells are lymphocytes.

Streptokinase,
Used as a clot buster/for removing clots from the blood vessels (in a patient suffering from myocardial infarction/or in a heart patient).

Restriction enzymes cut the DNA sequence a little away from the centre of the palindrome site but between the same two bases on the opposite strands, leaving single stranded portions at the ends these over hanging stretches are called sticky ends on each strand. They form hydrogen bonds with the complementary cut counterparts, facilitates the action of ligase enzymes to join the foreign and the vector DNA strands.

1. Lactobacillus.
2. Trichoderma polysporum.
3. Yeast.
4. Penicillin.

Cyclosporin ASource- Trichoderma polysporum.
Purpose- Immuno suppressive agent.

Sedimentation of flocs to form activated sludge, sludge pumped to anaerobic sludge digester, growth of anaerobic bacteria, digestion of sludge by bacteria to release biogas.

Glomus forms mycorrhizal association, absorbs phosphorus, provide resistance to root borne pathogens, enhanced to tolerate salinity/drought.

Effluent from the primary settling tank passed into aeration tank, agitated mechanically and air is pumped into it, vigorous growth of aerobic microbes into flocs, microbes consume major part of the organic matter in effluent.

Oxygen is used up by microorganisms involved in biodegradation resulting in sharp decline at the point of sewage discharge, the concentration of oxygen increases as we move farther from the point of sewage discharge.

During the secondary treatment of the primary affluent (Primary effluents are passed into a large aeration tank, where it is constantly agitated, and air is pumped into it) vigorous growth of useful aerobic microbes, into flocs takes place, these microbes use major part of the organic matter, and this reduces BOD.

1. Penicillium notatum.
2. Acetic acid.
3. Fungus.
4. Saccharomyces cerevisiae.

During secondary treatment of primary effluents, vigorous growth of useful aerobic microbes into flocs occur when it is agitated mechanically and air is pumped into it in a large aeration tank. These microbes while growing consume major part of the organic matter in the effluent. This significantly reduces BOD.

• Useful aerobic microbes grow rapidly and form flocs.
• Flocs are masses of bacteria associated with fungal filaments to form mesh-like structures.
• The growing microbes consume organic matter and thus reduce the biochemical oxygen demand (BOD).

Anaerobic methane producing bacteria are called methanogens. Methanogens generate biogas when they act by anaerobic decomposition on cellulose rich biowaste (anaerobically).

• Swiss cheese: Propionibacterium
• Roquefort cheese: Penicillium roqueforti

Due to increasing urbanisation, sewage is being produced in much larger quantities than ever before. However the number of sewage treatment plants has not increased enough to treat such large quantities. So the untreated sewage is often discharged directly into rivers leading to their pollution and increase in water-borne diseases.

Cyanobacteria as biofertilisers:

• They fix atmospheric nitrogen and increase the organic matter of the soil through their photosynthetic activity, e.g., Nostoc, Anabaena, Oscillatoria, etc.
• Blue-green algae increase the soil fertility by adding organic matter to the soil.

Azotobacter is a free-living bacteria serving as a biofertiliser. This bacteria absorb free nitrogen from the soil, air and convert it into salts of nitrogen compounds and enrich the soil nutrients.
Rhizobium is a symbiotic bacterium that lives in the root nodules of legumes and fixes atmospheric nitrogen into organic compounds and enrich the soil nutrients.

• The fungus absorbs phosphorus from the soil and passes it to the plant.
• Plants with mycorrhiza show resistance to root-borne pathogens.
• They show increased tolerance to salinity and drought.
• There is an overall increase in plant growth and development.

The gas produced by the anaerobic action of bacteria on biomass is known as biogas. It is preferred over other conventional energy fuels because it is a cleaner fuel, has no foul smell and can be used as a source of energy as it is inflammable.

It is a traditional drink of some parts of Southern India. It is made by fermenting sap from palm trees, coconut, etc. Microbes are also used to ferment fish, soybean, bamboo shoos, etc. to make food.

1. Lipases.
2. Pectinases and proteases.

BOD stands for biochemical oxygen demand which represents the amount of dissolved oxygen that would be consumed if all the organic matter in one litre of water were oxidised by microorganisms. More BOD value means the water sample is polluted by organic matter.

Toddy is a traditional drink of southern India which is prepared by the yeast fermentation of coconut water.

Fungi	Products/ Bioactive molecules produced
Trichoderma polysporum	Cyclosporin A
Aspergillus niger	Citric Acid
Monascus purpureus	Statin
Saccharomyces cerevisiae	Ethanol/alcohol
Penicillium notatum	Penicillin

Streptococcus bacterium produces streptokinase.
It is used for removing clots from the blood vessels in a patient suffering from myocardial infarction/ or in a heart patient.

The microbial flora in the rumen of cattle facilitates digestion of cellulose. If such microbial flora will be present in our intestine then humans will also be able to digest cellulose.

Leguminous plants possess root nodules where nitrogen is fixed by symbiotic nitrogen fixing bacteria Rhizobium whereas cereals do not possess nitrogen fixing bacteria in their root nodules, so, they cannot fertilise the soil.

Some molecules are called bioactive molecules, because microbes like bacteria or fungi are used in their production.
Example:

• Citric acid: Acetic acid
• Butyric acid: Lactic acid
• Ethanol: Lipase
• Streptokinase: Cyclosporin A

Flocs are masses of bacteria associated with fungal filaments to form mesh like structure. Flocs digest most of the organic material from the sludge. Thus, floc helps in reducing the BOD (Biochemical Oxygen Demand) of the effluent. This helps in further treatment of sludge.

Ganga Action Plan tends to save the major rivers from pollution. Under these plans, a large number of sewage treatment plants were built so that only treated sewage is discharged in the rivers.

Bacillus thuringiensis products are endotoxin which when ingested and released in the gut of the larvae of insect pest disrupts the insect gut lining thereby killing them.

Plasmid DNA and Chromosomal DNA

Plasmid DNA is an extra-chromosomal DNA molecule in bacteria that is capable of replicating, independent of chromosomal DNA.

Chromosomal DNA is the entire DNA of an organism present inside chromosomes.

Antibiotics have created a revolution in treatment of diseases. Many infectious diseases which were incurable earlier can now be treated with antibiotics. Antibiotics have helped in saving millions of life.

1. Azotobacter, Azospirillum, Nostoc, Anabaena.
2. Leguminous crops harbour Rhizobium in their root nodules; this bacterium fixes atmospheric nitrogen as nitrogen compounds in the soil.

Aerobic and anaerobic bacteria or fungi exist in sewage water. After the primary treatment of water, aerobic bacteria are added in aeration tanks. Growth of these bacteria reduces BOD as they consume organic matter. Anaerobic bacteria are added in anaerobic sludge digesters, where these digest the sludge and form biogas, etc.

Biological control means life against life. It’s a natural and ecofriendly concept. It employs the natural organisms to control the population of pathogens and pests in an ecosystem. Classical examples are Trichoderma which is antagonist against many soilborne plant pathogens. Similarly, Penicillium inhibits the growth of Staphylococcus and therefore has been successfully used in the production of penicillin antibiotic to control many human bacterial pathogens.

Curd contains lactic acid bacteria which checks the growth of disease-causing microbes and protects the gastrointestinal tract.

Citric acid.

Common yeast is employed in the fermentation of:

1. Dough, used for making bread, cakes in bakeries.
2. Fruit juices and malt in breweries for the production of alcoholic beverages; hence it is known as both as baker's and brewer's yeast.

Following are some bioactive molecules of fungal origin which help in restoring good health in humans:

• Cyclosporin A is produced by Trichoderma polysporum and is used as immunosuppressive agent.
• Penicillin is a major antibiotic which is produced from Penicillium notatum.

1. The fungus absorbs phosphorus from the soil and passes it to the plant.
2. Plants with mycorrhiza show resistance to root-borne pathogens.
3. They show increased tolerance to salinity and drought.
4. These show an overall increase in plant growth and development.

A broad spectrum antibiotic is one which can inhibit the growth of both gram positive and gram negative bacteria. For example, tetracycline, which is obtained from Streptomyces aureofaciens.

The effluent is passed into a settling tank where the bacterial ‘flocs’ are allowed to sediment. This is called activated sludge. The sludge is pumped into anaerobic sludge digesters where they are anaerobically digested. During this digestion, bacteria produce biogas.

When a small amount of curd as starter is added to fresh milk, millions of lactic acid bacteria(LAB) present in the starter grow in milk and convert it to curd. During this process, acids are produced by LAB that coagulate and partially digest the milk proteins.
LAB increases vitamin B12 content along with other vitamins in the curd.

Flocs are masses of bacteria associated with fungal filaments to form mesh-like structures. These consume the major part of the organic matter in the effluent, significantly reducing the BOD. The effluent is then passed into a settling tank where the flocs sediment. A part of this sediment (activated sludge) is pumped into anaerobic sludge digestors where anaerobic digestion of sludge takes place, producing biogas in the process.

Saccharomyces cerevisiae (Baker’s yeast) causes the alcoholic fermentation of sugars in wheat flour and produce ethanol and CO2. CO2 raises the bread when baked and makes it soft.

1. The bacterium is Rhizobium.
2. It fixes atmospheric nitrogen in the form of nitrogenous compounds in the soil; thus the legume crop is benefitted with nitrogen.

Azospirillium/ Azotobacter and Rhizohium act as biofertilisers. They are so called because they enrich soil nutrient by nitrogen fixation.

Streptokinase produced by the bacterium Streptococcus and modified by genetic engineering is used as a ‘clot buster’ for removing clots from the blood vessels of patients who have undergone myocardial infarction leading to heart attack.

Primary sludge includes all solid substances which got settled after primary treatment. It traps lot of microbes and debris.
Activated sludge is sediment formed from effluent after secondary treatment. It contains bacterial flocs.

Swiss cheese.

Penicillium notatum.

Nucleopolyhydro viruses are used for controlling pests and other arthropods in farms. These are narrow spectrum viruses and do not harm plants, cattle and humans or even on non-target insects.

1. Aspergillus niger - Citric acid.
2. Acetobacter aceti - Acetic acid.
3. Clostridium butylicum - Butyric acid.
4. Lactobacillus - Lactic acid.

The mycorrhizal fungi absorb phosphorus from the soil and transfer them to the host cells. They also impart resistance to host plants against root pathogens. They also help plants to tolerate salinity and draught.

• The primary effluent is passed into large aeration Tanks; it is constantly agitated mechanically and air is pumped into it.
• The useful aerobic microbes grow vigorously to form flocs, which are the mesh-like structures formed by masses of bacteria in association with fungal hyphae.
• During their growth, these microbes consume a major part of the organic matter and hence, there is a significant reduction in the BOD of the effluent.

Microbes are also used for production of enzymes. Lipases are used in detergent formulations and are helpful in removing oily stains from the laundry. Lipases are produced by Candida lipolytica (fungus).

The products are vinegar and toddy.

Biofertilisers are organisms that enrich the nutrient quality of the soil. The main sources of biofertilisers are bacteria, fungi and cyanobacteria.

Distillation increases the alcohol content in alcoholic drinks.

Mycorrhizae absorb phosphorus, provide resistance to root-borne pathogens and enhance the tolerance of the plants towards salinity and drought.

Trichoderma polysporum. It acts as an immuno-suppresant and is used in organ transplant patient

1. With distillation: Brandy, Whisky, Rum
2. Without distillation: Wine and Beer.

Cyclosporin A is used as an immunosuppressive agent in organ transplant patient.

Lactobacillus lactis and Streptococcus lactis bacterias produce acids which cause coagulation of milk protein called casein and changes milk into curd.

Bread/ alcoholic drinks.

1. Trichoderma polysporum.
2. Immuno-suppressive agent.
3. Fungus.
4. Blood cholesterol lowering agent.

Statin is produced by the yeast Monascus purpureus. It acts as a bloodcholesterol lowering agent, by competitively inhibiting the enzyme responsible for synthesis of cholesterol.

Its full potential as an effective antibiotic was established much later by Ernest Chain and Howard Florey. This antibiotic was extensively used to treat American soldiers wounded in World War II. Fleming, Chain and Florey were awarded the Nobel Prize in 1945, for this discovery.

The yeast Monascus purpureus is used for commercial production of stain. Stain competitively inhibits the enzyme responsible for cholesterol formation and thus helps in lowering the blood cholesterol level.

An antibiotic which are effective against most of the common pathogenic bacteria is called a broad spectrum antibiotic. Cefoperazone and Ceftazidime are examples of broad spectrum antibiotic.

Cyanobacteria are autotrophic, free-living or symbiotic microbes. They can fix atmospheric nitrogen. Blue-green algae also add organic matter to the soil and increases its fertility. They replenish soil nutrients and reduce dependence on chemical fertilisers.

The raw material for the biogas plant is mainly cow dung, which is available in plenty in rural areas where cattle are used. The biogas is used for lighting and cooking in these areas, as distribution is only in short distances. The spent slurry from the biogas plant is used as manure in agriculture; hence biogas plants are more suitable in rural areas.

Methanogens are bacteria which grow anaerobically on cellulosic material. They are present in the rumen of cattles. These bacteria are responsible for the breakdown of cellulose help in nutrition of animal.

Even in industry, microbes are used to synthesise a number of products valuable to human beings. Beverages and antibiotics are some of the examples. Production on an industrial scale, requires growing microbes in very large vessels called fermentors.

Cyclosporin-A.

Lactic acid bacteria increase vitamin B12 absorption and also checks diseasecausing microbes.

These all are acid producers. Examples of acid producers are Aspergillus niger (a fungus) of citric acid, Clostridium butylicum (a bacterium) of butyric acid and Lactobacillus (a bacterium) of lactic acid.

The activated sludge is pumped into large tanks called anaerobic sludge digesters. Here, bacteria which grow anaerobically digest the bacteria and the fungi in the sludge. During this digestion, bacteria produce a mixture of gases which form biogas. Biogas is made up of methane, hydrogen sulphide and carbon dioxide.

Puffed up appearance of dough is due to production of CO2 as a result of fermentation.

Penicillin was an accidental discovery. Sir Alexander Fleming observed that in unwanted culture plates of Staphylococcus a mould of Penicillium was growing This mould inhibited the growth of Staphylococcusaround it. Later the antibiotic penicillin was isolated from this fungus.

Swiss cheese.

Convert milk to curd.

Roquefort cheese are ripened by growing a specific fungi, Penicillium roquefortii on them, which gives them a particular flavour.

Chakravarthy bug is a super bug of Pseudomonas with multiple plasmids. They are helpful in removing oil spills.

Cheese is partially degraded flavoured milk curd formed by the activity of microorganisms. Processed cheese is formed by blending and emulsifying different types of cheese with or without cream.

Monascus purpureus.

Bottled juices appear clearer because the proteases along with pectinases are used in clearing of juice. Pectinases are obtained from Byssochlamys fulvo. These are also used in rettling of fibres and preparation of green coffee.

Rhizobium is present in the root nodules of leguminous plants. Theirs is a symbiotic relationship in which the bacterium obtains food and shelter from the plant and the plant gets fixed nitrogen in return. These bacteria fix atmospheric nitrogen into organic forms, which is used by the plant as nutrient.

Mycorrhizae is a symbiotic association of a fungus with roots of higher plants. The fungus absorbs phosphate from soil and passes it to the plant. It also provides resistance to root-borne pathogen and increase the tolerance of plant to salinity and drought. This way they act as biofertilisers.
Genus of fungi: Glomus

1. LAB: Lactic Acid Bacteria.
2. BOD: Biochemical Oxygen Demand.

Streptokinase is the clot buster and its microbial source is Streptococcus.

Lady bird and dragonflies.

Many harmful chemicals are produced as byproduct of modern lifestyle. These chemicals are finally dumped in soil and end up contaminating the soil. Help of microbes can be taken to reduce soil contamination. The removal of soil contamination with the help of microbes is called bioremediation. This is usually achieved by bio-augmentation of soil flora.

A bacterium called Propionibacterium shermanii produces a large amount of carbon dioxide during fermentation. This is the reason of big holes in Swiss cheese.

Cyanobacteria are autotrophic microbes widely distributed in aquatic and terrestrial environments many of which can fix atmospheric nitrogen, e.g. Anabaena, Nostoc, Oscillatoria, etc. In paddy fields, cyanobacteria serve as an important biofertiliser. Blue green algae also add organic matter to the soil and increase its fertility.

• Those bacteria which produce large quantities of methane, are referred to as methanogens.

Characteristics:

1. They are anaerobes.
2. They grow on cellulosic material.

Three enzymes of industrial importance are proteases, pectinases and lipases.

1. The Lactobacillus naturally present in our stomach and intestine are killed by the antibiotics; to regenerate them, Lactobacillus is provided along with the antibiotics.
2. The insect pests are not eradicated because the beneficial predatory insects and other parasites which depend on these insects can survive.

Biopesticides are living organisms which are able to kill or repel specific pests. Nowadays biopesticides are used in place of chemical fertilisers. Bacillus thuringiensis (Bt) is the first bacterial biopesticide to be used on commercial scale.

The secondary treatment is also called biological treatment because in secondary treatment living organisms like bacteria and fungi are used.

Type of microbe	Name	Commercial product
Bacterium	a	Clot buster enzyme
b	Aspergillus niger	Citric acid
Fungus	Trichoderma polysporum	c
Bacterium	d	Butyric acid

1. Streptococcus
2. Fungus
3. Cyclosporin A
4. Clostridium butylicum

This is because wine is produced without distillation whereas whisky and rum are produced by distillation of the fermented broth.