➢ Microbiology : it is the branch of biology that deals with study of living microorganism viz. Fungi, bacteria, algae, protozoa viruses, nematodes etc.
Importance and scope should include explanation of the following points with suitable examples
i) agriculture: biological nitrogen fixation/bio fertilizers, decomposition of organic matter, microbes as bio control agents, biochemical cycling of elements.
ii) animals husbandry and diary technology.
iii) microbes as tools for biological research.
iv) health and sanitation.
v) biodegradation of agrochemicals and pollutants.
vi) industries/industrial microbiology.
vii) microbes in mineral, petroleum and fuel industry.
viii) microbes in space technology.
ix) organic matter decomposition
x) biological control insect pest.
xi) mushroom production
1) organic matter decomposition – microorganisms like (fungi, bacteria, actinomycetes, protozoa) play important role in decomposition ex. Fungi – aspergillus, penicillium, bacteria – bacillus, psedumonas
2) biological nitrogen fixation – microorganism involve n2 fixation in two categories – i) symbiotic ii) non symbiotic, rhizobium bacteria fixes n2 symbiotically in root nodule of legume.
Q. 2. Enlist branch’s of microbiology.
➢ Branches of microbiology –
1) mycology – study of fungi
2) bacteriology – study of bacteria
3) phycology – study of algae
4) virology – study of viruses
5) nematology – study of nematodes
6) protozology – study of protozoa
Q. 3. Define bacterial growth. Explain in short the various phases of bacterial growth curve.
➢ Bacterial growth : it refers to the increase in cell number or cell population of bacteria. It is brought about by cell multiplication. The time required by the cell to double its number is called generation time.
1) lag phase : it represents an initial period of no growth in terms of increase in cell number. In this phase the cells are metabolically active, capable of repairing cell damages and synthesizing enzymes.
3) log phase : it is period of rapid growth. In this period the bacterial population increases exponentially and is also called as growth phase.
4) stationary phase : no new growth is occurred. Total number of viable cells is remained/maintained constant by a balance between cell division and cell death.
5) death phase : following the stationary phase, bacterial cells die at faster rate than the rate of cell growth. This is due to depletion of essential nutrients and accumulation of toxic/inhibitory products in the medium.
Q. 4. Define bio-fertilizers and enlist their types. Enlist various methods of their application and write in short about seed dressing and seedling root dip.
➢ Definition : bio-fertilizers are microbial inoculants or carrier based preparations containing living or latent cells of efficient strains of nitrogen fixing, phosphate solubilizing and cellulose decomposing microbes intended for seed or soil application and designed to improve soil fertility and plant growth by increasing the number and biological activity of beneficial soil microbes.
Types: rhizobium inoculant, azotobacter inoculnant, azospirillum inoculant, bga. Psm, mycorrhizal fungi, composting cultures and sulphur oxidizing microbes etc
Methods of application : 1) slurry method 2) seed treatment 3) pelleting of seed 4) seedling root dip 5) sugarcane set inoculation 6) bga application 7) azolla application 8) soil application
Seedling root dip : seedlings of vegetables (chilli, tomato, brinjal etc.) And paddy which are grown cultivated by transplanting are treated or inoculated by using this method. The slurry of inoculant either in plane water or jaggary solution is prepared (as described earlier). Then in this slurry solution, complete seeding’s or roots of the seedings are dipped for about 1-2 minutes and then transplanted immediately in the field.
Function or role of biofertilizers in agriculture are:
1) they supplement chemical fertilizers for meeting the integrated nutrient demand of the crops.
2) they can at best minimize the use of chemical fertilizers not exceeding 40-50 kg n/ha under ideal agronomic and pest-free conditions.
3) application of biofertilizers results in increased mineral and water uptake, root development, vegetative growth and nitrogen fixation.
4) they liberate growth promoting substances and vitamins and help to maintain soil fertility.
5) they act as antagonists and suppress the incidence of soil borne plant pathogens and thus, help in the bio-control of diseases.
6) nitrogen fixing, phosphate mobilizing and cellulolytic microorganisms in bio-fertilizer enhance
the availability of plant nutrients in the soil and thus, sustain the agricultural production and farming system.
7) they are cheaper, pollution free and renewable energy sources
8) they improve physical properties of soil, soil tilth and soil health in general.
9) they improve soil fertility and soil productivity.
10) blue green algae like nostoc, anabaena, and scytonema are often employed in the reclamation of alkaline soils.
Q. 5. Draw a neat labelled diagram of typical bacterial cell. Enlist various internal and external structures and describe about cell wall, flagella, pilli.
➢ External structures :
1) flagella (flagellum) and motility
2) pili (fimbriae)
3) capsule
4) sheaths
5) cell wall composition
Internal structures :
1) cytoplasmic membrane
2) protoplast and sphaeroplast
3) mesosomes
4) cytoplasm
5) bacterial chromosome
6) ribosomes
7) spores
8) conidiospores and sporangiospores
9) cysts
Flagella (flagellum) and motility:
bacterial flagella are hair like helical appendages that protrude through the cell wall and are responsible for swimming motility. It grows at the tip unlike hair, which grows at the bottom. A flagellum is composed of 3 parts :
a) basal body associated with cytoplasmic membrane and cell wall
b) a short hook and
c) a helical filament which is usually several times longer than the bacterial cell. flagellar arrangement may be
a) monotrichous – a single polar flagellum
b) lophotrichous – a cluster of polar flagella
c)amphitrichous – flagella either single or clusters, at both cell poles and
d) peritrichous –surrounded by lateral flagella.
Pili (fimbriae):
they are hollow non-helical filamentous appendages that are thinner, shorter and more numerous than flagella. Do not function in motility. Different types of pili have different functions.
f – pilus (sex pilus) serves as the port of entry of genetic material during bacterial mating. Some pili play major role in human infection.
Cell wall composition:
in bacteria the cell wall is very rigid and gives the shape to the cell. Most of the bacteria retain their original cells even after subjected to very high pressure or severe physical conditions. It accounts for 10-40% of dry weight of the cell. Cell walls can be broken by sonic or ultrasonic treatment or by subjecting the cells to extremely high pressure and subsequent sudden release of pressure.
Q. 6. Define nitrogen cycle. Explain in detail nitrogen cycle along with example and describe it’s cycling in nature with biochemical reactions, microbes involved.
➢ Nitrogen cycle is a biogeochemical process which transforms the inert nitrogen present in the atmosphere to a more usable form for living organisms.
The nitrogen cycle mainly involves transformations such as :
i) nitrogen mineralization in which nitrogen complexes are decomposed into simpler or organic forms and converted into inorganic compounds for use by plants
ii) nitrogen immobilization in which nitrogen compounds are assimilated into cellular materials.
Nitrogen mineralization:
In the process of mineralization, proteins, nucleic acids and their components are degraded by microorganisms with the eventual liberation of ammonia and this is called ammonification.
Nitrogen immobilization:
When plant residues or pure carbohydrates are added to the soil, there is a rapid decrease in the amount of available inorganic nitrogen which is referred as “nitrogen immobilization”. It results from the microbial assimilation of inorganic nitrogen.
Biochemical reactions involved :
1) Nitrification : in the second phase, ammonia is converted into nitrate and this process is called nitrification. Nitrification occurs in two steps; first, ammonia is oxidized to nitrite:
2 nh3 + 1 1⁄2 o2 - - - > no2 ̄ + h2o.
2 n h3 + 3 o2 - - - - > 2 h no2 + 2 h2 o
2) Denitrification : the transformation of nitrate to gaseous nitrogen by micro organism in series of biochemical changes, organism – pseudomonas bacillus
3) Proteolysis : the breakdown of protein and get converted into amino acid. Organism – pseudomonas.
4) Ammonification – the production of ammonia from amino acid. Organism – nitro bacteria
5) Nitrate reduction – the process of nitrification is completely reversed which known as nitrate fixation.
Q. 7. Define rhizosphere. State the factors affecting the rhizosphere microflora and write in brief about the soil ph. And soul moisture.
➢ Rhizosphere : it is the zone/region of soil immediately surrounded the plant roots together with the root surface. The factors affecting the microflora are as follows :
1. Soil type and its moisture.
2. Soil amendments and fertilizers.
3. Soil ph/rhizosphere ph.
4. Proximity of roots with soil.
5. Plant species.
6. Age of the plant.
7. Roots exudates/secretion
A. Soil type and its moisture :
Soil type and its moisture -
Microbial activity and population is high in the rhizosphere region of the plants grown in sandy soils and least in the soils with high humus and rhizosphere organisms are more when the soil moisture is low. Thus, the rhizosphere effect is more in the sandy soils with low moisture content.
Soil ph/rhizosphere ph -
Respiration by the rhizosphere microflora may lead to the change in soil rhizosphere ph. If the activity and population of the rhizosphere microflora is more, then the ph of rhizosphere region is lower than that of surrounding soil or non-rhizosphere soil. Rhizosphere effect for bacteria and protozoa is more in slightly alkaline soil and for that of fungi is more in acidic soils.
Q. 8. Define biogas and describe its production along with biochemical reactions and microbes involved.
➢ Definition : it is defined as a mixture of methane and carbon dioxide produced by the decomposition of plant and animal waste and that we can burn to produce heat.
A mixture of ch4, co2 and other gases. Gas % methane 50–75 carbon dioxide 25–50 nitrogen 0–10 hydrogen 0–1 hydrogen sulfide 0–3 oxygen 0–2.
Biogas:
➢ biogas is a fuel used as domestic purpose.
➢ obtained from cow manure, fruit and vegetable waste
➢ biogas is produced by the breakdown of organic waste by bacteria without oxygen anaerobic digestion
Biogas two types of anaerobic digestion
➢ mesophilic process 25-38°c for 14-30 days
➢ thermophilic process 50-60°c for 12-14 days
Biogas plant operation:
The steps required for the operation of biogas plant are:
A feeding - initially feed the digester at optimum level with mixture of water and raw material at a ratio of 1:1. After 1-2 weeks of operation, continuous daily feeding is recommended.
B seeding - common practice involves seeding with an adequate population of both the acid- forming and methanogenic bacteria. Actively digesting sludge from a sewage plant constitutes ideal "seed" material.
C stirring/agitation - stirring of digester contents is recommended at regular intervals may be manually in order to avoid formation of scum.
D gas collection - gas can be collected from the drum through a non-return valve system. Preferably a water pipe is most suitable than gas pipe. Gas pipe should be regularly cleaned to remove moisture contents.
Q. 9. Define mycorrhiza. Write its types and benefits to plants.
➢ A mycorrhiza is a symbiotic association between a green plant and a fungus.
Types –
1) ectomycorrhiza
2) endomycorrhiza - i) erichoid ii) vesicular arbascular iii) monotropid iv) orchid
Uses & benefits
➢ mycorrhizae, meaning “fungus root,” refers to a mutualistic relationship between fungi and plant roots in most plants.
➢ while the fungus assists the plant by expanding its root surface area, the plant benefits the fungus by supplying the carbohydrates necessary for fungal growth.
➢ increased absorption of nutrients and water
➢ reduced need for irrigation
➢ reduced demand for fertiliser
➢ enhanced resistance to drought
➢ improved resistance to pathogens
➢ enhanced plant health and resistance to stress
➢ improved transplant success
Q. 10. What is genetic recombination? Enlist different modes of gene transfer in bacteria and explain conjugation in bacteria.
➢ Def: genetic recombination is the formation of a new genotype by reassortment of genes following an exchange of genetic material between two different chromosomes which have similar genes at corresponding sites.
Modes of gene transfer:
1. Conjugation: direct transfer of dna from one bacterial cell to another.
2. Transformation: naked dna is taken up from the environment by bacterial cells.
3. Transduction: use of a bacteriophages (bacterial virus) to transfer dna between cells.
1) conjugation:
Conjugation in bacteria was first discovered by joshua lederberg (1946) in e. Coli. During conjugation the donor (f+) cell comes in physical contact with the recipient (f-) cell via conjugation bridge formed by sex pili and transfer its genome to receipient ceil (fig.) The process of plasmid (gene) transfer during cojugation was well documented in e. Coli. Transfer of f plasmid dna is initiated by formation of a nick at ori or origin of transfer by the trayz endonuclease. A single strand of plasmid dna transfers to the receipient cell and a replacement strand is synthesized in the donor cell and complementary strand in the receipient cell.
Q. 11. Explain the importance of single cell protein.
➢ i) single-cell protein refers to the crude, a refined or edible protein extracted from pure microbial cultures, dead, or dried cell biomass.
ii) they can be used as a protein supplement for both humans or animals.
iii) the microorganisms utilize the carbon and nitrogen present in these materials and convert them into high-quality proteins which can be used as a supplement in both human and animal feed.
iv) the single-cell proteins can be readily used as fodder for achieving fattening of calves, pigs, in breeding fish and even in animal husbandry – poultry and cattle farming.
v) single cell protein (scp) offers an unconventional but plausible solution to this problem of protein deficiency being faced by the entire humanity.
Q. 12. Write contribution of the following scientists.
1) robert koch : provided proof that a bacterium causes anthrax and provided the experimental
steps, koch’s postulates, used to prove that a specific microbe causes a specific disease.
2) winogradsky : demonstrated the role of bacteria in nitrification.
3) alexander fleming : the discovery of first antibiotics penicillin.
4) antony van leeuwenhoek : i. Who used a microscope with one lens to observe insects and other specimen.
ii. Leeuwenhoek was the first to observe bacteria.
iii. He discovered “simple microscope”.
5) S. A. Waksman :
I. Discovered an antibiotic streptomycin.
Ii. Published the book "principles of soil microbiology".
Iii. Proved soil as the richest source of antagonistic organisms like actinomycetes
6) N. V. Joshi : Isolated and identified different species of rhizobium from legumes
7) louis pasteur :
i. Disproved theory of spontaneous generation
ii. Prepared vaccine against rabies/hydrophobia,
iii. Pasteurization technique.
iv. Showed that microbes are responsible for fermentation
8) J. B. Boussingault : Stated that legumes can fix atmospheric nitrogen and thereby increase nitrogen content in soil.
9) A. B. Frank :
i. Discovered actinomycete 'frankia' inducing nodulation in roots of non- legumes.
ii. Coined term mycorrhiza
10) P. A. Millardet : Discovered bordeaux mixture for the control of downy mildew of grapes.
Q. 13. Define biological nitrogen fixation. Wrote in brief about types of bnf with suitable
examples
➢ Biological nitrogen fixation: is the enzymatic process of reduction of atmospheric nitrogen into ammonia.
A. Symbiotic biological nitrogen fixation: symbiotic nitrogen fixation is part of a mutualistic relationship in which plants provide a niche and fixed carbon to bacteria in exchange for fixed nitrogen.
The various examples of symbiotic biological nitrogen fixation can be grouped under the following three categories:
1. Nitrogen fixation through nodule formation in leguminous plants: e.g. Rhizobium- they established themselves inside specialized structures on the roots called root nodules. The bacteria fix nitrogen only when they are present inside the nodules.
2. Nitrogen fixation through nodule formation in non-leguminous plants:
E.g. Frankia forms root nodules in association with non-leguminous plant.
3. Nitrogen fixation through non-nodulation:
Some of the examples are:
1. Lichens, an association with fungi and algae (cyanobacteria or green algae)
2. Azolla, a fern, in association with anabaena.
B. Non- symbiotic/ asymbiotic biological nitrogen fixation:
Biological nitrogen fixation by microorganisms living freely or staying out of plant cell is called non- symbiotic biological nitrogen fixation. The asymbiotic nitrogen fixers can be classified as follows:
Function or role of biofertilizers in agriculture are:
1) they supplement chemical fertilizers for meeting the integrated nutrient demand of the crops.
2) they can at best minimize the use of chemical fertilizers not exceeding 40-50 kg n/ha under ideal agronomic and pest-free conditions.
3) application of biofertilizers results in increased mineral and water uptake, root development, vegetative growth and nitrogen fixation.
4) they liberate growth promoting substances and vitamins and help to maintain soil fertility.
5) they act as antagonists and suppress the incidence of soil borne plant pathogens and thus, help in the bio-control of diseases.
6) nitrogen fixing, phosphate mobilizing and cellulolytic microorganisms in bio-fertilizer enhance
the availability of plant nutrients in the soil and thus, sustain the agricultural production and farming system.
7) they are cheaper, pollution free and renewable energy sources
8) they improve physical properties of soil, soil tilth and soil health in general.
9) they improve soil fertility and soil productivity.
10) blue green algae like nostoc, anabaena, and scytonema are often employed in the reclamation of alkaline soils.
Q. 5. Draw a neat labelled diagram of typical bacterial cell. Enlist various internal and external structures and describe about cell wall, flagella, pilli.
1) flagella (flagellum) and motility
2) pili (fimbriae)
3) capsule
4) sheaths
5) cell wall composition
Internal structures :
1) cytoplasmic membrane
2) protoplast and sphaeroplast
3) mesosomes
4) cytoplasm
5) bacterial chromosome
6) ribosomes
7) spores
8) conidiospores and sporangiospores
9) cysts
Flagella (flagellum) and motility:
bacterial flagella are hair like helical appendages that protrude through the cell wall and are responsible for swimming motility. It grows at the tip unlike hair, which grows at the bottom. A flagellum is composed of 3 parts :
a) basal body associated with cytoplasmic membrane and cell wall
b) a short hook and
c) a helical filament which is usually several times longer than the bacterial cell. flagellar arrangement may be
a) monotrichous – a single polar flagellum
b) lophotrichous – a cluster of polar flagella
c)amphitrichous – flagella either single or clusters, at both cell poles and
d) peritrichous –surrounded by lateral flagella.
Pili (fimbriae):
they are hollow non-helical filamentous appendages that are thinner, shorter and more numerous than flagella. Do not function in motility. Different types of pili have different functions.
f – pilus (sex pilus) serves as the port of entry of genetic material during bacterial mating. Some pili play major role in human infection.
Cell wall composition:
in bacteria the cell wall is very rigid and gives the shape to the cell. Most of the bacteria retain their original cells even after subjected to very high pressure or severe physical conditions. It accounts for 10-40% of dry weight of the cell. Cell walls can be broken by sonic or ultrasonic treatment or by subjecting the cells to extremely high pressure and subsequent sudden release of pressure.
Q. 6. Define nitrogen cycle. Explain in detail nitrogen cycle along with example and describe it’s cycling in nature with biochemical reactions, microbes involved.
➢ Nitrogen cycle is a biogeochemical process which transforms the inert nitrogen present in the atmosphere to a more usable form for living organisms.
The nitrogen cycle mainly involves transformations such as :
i) nitrogen mineralization in which nitrogen complexes are decomposed into simpler or organic forms and converted into inorganic compounds for use by plants
ii) nitrogen immobilization in which nitrogen compounds are assimilated into cellular materials.
Nitrogen mineralization:
In the process of mineralization, proteins, nucleic acids and their components are degraded by microorganisms with the eventual liberation of ammonia and this is called ammonification.
Nitrogen immobilization:
When plant residues or pure carbohydrates are added to the soil, there is a rapid decrease in the amount of available inorganic nitrogen which is referred as “nitrogen immobilization”. It results from the microbial assimilation of inorganic nitrogen.
Biochemical reactions involved :
1) Nitrification : in the second phase, ammonia is converted into nitrate and this process is called nitrification. Nitrification occurs in two steps; first, ammonia is oxidized to nitrite:
2 nh3 + 1 1⁄2 o2 - - - > no2 ̄ + h2o.
2 n h3 + 3 o2 - - - - > 2 h no2 + 2 h2 o
2) Denitrification : the transformation of nitrate to gaseous nitrogen by micro organism in series of biochemical changes, organism – pseudomonas bacillus
3) Proteolysis : the breakdown of protein and get converted into amino acid. Organism – pseudomonas.
4) Ammonification – the production of ammonia from amino acid. Organism – nitro bacteria
5) Nitrate reduction – the process of nitrification is completely reversed which known as nitrate fixation.
Q. 7. Define rhizosphere. State the factors affecting the rhizosphere microflora and write in brief about the soil ph. And soul moisture.
➢ Rhizosphere : it is the zone/region of soil immediately surrounded the plant roots together with the root surface. The factors affecting the microflora are as follows :
1. Soil type and its moisture.
2. Soil amendments and fertilizers.
3. Soil ph/rhizosphere ph.
4. Proximity of roots with soil.
5. Plant species.
6. Age of the plant.
7. Roots exudates/secretion
A. Soil type and its moisture :
Soil type and its moisture -
Microbial activity and population is high in the rhizosphere region of the plants grown in sandy soils and least in the soils with high humus and rhizosphere organisms are more when the soil moisture is low. Thus, the rhizosphere effect is more in the sandy soils with low moisture content.
Soil ph/rhizosphere ph -
Respiration by the rhizosphere microflora may lead to the change in soil rhizosphere ph. If the activity and population of the rhizosphere microflora is more, then the ph of rhizosphere region is lower than that of surrounding soil or non-rhizosphere soil. Rhizosphere effect for bacteria and protozoa is more in slightly alkaline soil and for that of fungi is more in acidic soils.
Q. 8. Define biogas and describe its production along with biochemical reactions and microbes involved.
➢ Definition : it is defined as a mixture of methane and carbon dioxide produced by the decomposition of plant and animal waste and that we can burn to produce heat.
A mixture of ch4, co2 and other gases. Gas % methane 50–75 carbon dioxide 25–50 nitrogen 0–10 hydrogen 0–1 hydrogen sulfide 0–3 oxygen 0–2.
Biogas:
➢ biogas is a fuel used as domestic purpose.
➢ obtained from cow manure, fruit and vegetable waste
➢ biogas is produced by the breakdown of organic waste by bacteria without oxygen anaerobic digestion
Biogas two types of anaerobic digestion
➢ mesophilic process 25-38°c for 14-30 days
➢ thermophilic process 50-60°c for 12-14 days
Biogas plant operation:
The steps required for the operation of biogas plant are:
A feeding - initially feed the digester at optimum level with mixture of water and raw material at a ratio of 1:1. After 1-2 weeks of operation, continuous daily feeding is recommended.
B seeding - common practice involves seeding with an adequate population of both the acid- forming and methanogenic bacteria. Actively digesting sludge from a sewage plant constitutes ideal "seed" material.
C stirring/agitation - stirring of digester contents is recommended at regular intervals may be manually in order to avoid formation of scum.
D gas collection - gas can be collected from the drum through a non-return valve system. Preferably a water pipe is most suitable than gas pipe. Gas pipe should be regularly cleaned to remove moisture contents.
Q. 9. Define mycorrhiza. Write its types and benefits to plants.
➢ A mycorrhiza is a symbiotic association between a green plant and a fungus.
Types –
1) ectomycorrhiza
2) endomycorrhiza - i) erichoid ii) vesicular arbascular iii) monotropid iv) orchid
Uses & benefits
➢ mycorrhizae, meaning “fungus root,” refers to a mutualistic relationship between fungi and plant roots in most plants.
➢ while the fungus assists the plant by expanding its root surface area, the plant benefits the fungus by supplying the carbohydrates necessary for fungal growth.
➢ increased absorption of nutrients and water
➢ reduced need for irrigation
➢ reduced demand for fertiliser
➢ enhanced resistance to drought
➢ improved resistance to pathogens
➢ enhanced plant health and resistance to stress
➢ improved transplant success
Q. 10. What is genetic recombination? Enlist different modes of gene transfer in bacteria and explain conjugation in bacteria.
➢ Def: genetic recombination is the formation of a new genotype by reassortment of genes following an exchange of genetic material between two different chromosomes which have similar genes at corresponding sites.
Modes of gene transfer:
1. Conjugation: direct transfer of dna from one bacterial cell to another.
2. Transformation: naked dna is taken up from the environment by bacterial cells.
3. Transduction: use of a bacteriophages (bacterial virus) to transfer dna between cells.
1) conjugation:
Conjugation in bacteria was first discovered by joshua lederberg (1946) in e. Coli. During conjugation the donor (f+) cell comes in physical contact with the recipient (f-) cell via conjugation bridge formed by sex pili and transfer its genome to receipient ceil (fig.) The process of plasmid (gene) transfer during cojugation was well documented in e. Coli. Transfer of f plasmid dna is initiated by formation of a nick at ori or origin of transfer by the trayz endonuclease. A single strand of plasmid dna transfers to the receipient cell and a replacement strand is synthesized in the donor cell and complementary strand in the receipient cell.
Q. 11. Explain the importance of single cell protein.
➢ i) single-cell protein refers to the crude, a refined or edible protein extracted from pure microbial cultures, dead, or dried cell biomass.
ii) they can be used as a protein supplement for both humans or animals.
iii) the microorganisms utilize the carbon and nitrogen present in these materials and convert them into high-quality proteins which can be used as a supplement in both human and animal feed.
iv) the single-cell proteins can be readily used as fodder for achieving fattening of calves, pigs, in breeding fish and even in animal husbandry – poultry and cattle farming.
v) single cell protein (scp) offers an unconventional but plausible solution to this problem of protein deficiency being faced by the entire humanity.
Q. 12. Write contribution of the following scientists.
1) robert koch : provided proof that a bacterium causes anthrax and provided the experimental
steps, koch’s postulates, used to prove that a specific microbe causes a specific disease.
2) winogradsky : demonstrated the role of bacteria in nitrification.
3) alexander fleming : the discovery of first antibiotics penicillin.
4) antony van leeuwenhoek : i. Who used a microscope with one lens to observe insects and other specimen.
ii. Leeuwenhoek was the first to observe bacteria.
iii. He discovered “simple microscope”.
5) S. A. Waksman :
I. Discovered an antibiotic streptomycin.
Ii. Published the book "principles of soil microbiology".
Iii. Proved soil as the richest source of antagonistic organisms like actinomycetes
6) N. V. Joshi : Isolated and identified different species of rhizobium from legumes
7) louis pasteur :
i. Disproved theory of spontaneous generation
ii. Prepared vaccine against rabies/hydrophobia,
iii. Pasteurization technique.
iv. Showed that microbes are responsible for fermentation
8) J. B. Boussingault : Stated that legumes can fix atmospheric nitrogen and thereby increase nitrogen content in soil.
9) A. B. Frank :
i. Discovered actinomycete 'frankia' inducing nodulation in roots of non- legumes.
ii. Coined term mycorrhiza
10) P. A. Millardet : Discovered bordeaux mixture for the control of downy mildew of grapes.
Q. 13. Define biological nitrogen fixation. Wrote in brief about types of bnf with suitable
examples
➢ Biological nitrogen fixation: is the enzymatic process of reduction of atmospheric nitrogen into ammonia.
A. Symbiotic biological nitrogen fixation: symbiotic nitrogen fixation is part of a mutualistic relationship in which plants provide a niche and fixed carbon to bacteria in exchange for fixed nitrogen.
The various examples of symbiotic biological nitrogen fixation can be grouped under the following three categories:
1. Nitrogen fixation through nodule formation in leguminous plants: e.g. Rhizobium- they established themselves inside specialized structures on the roots called root nodules. The bacteria fix nitrogen only when they are present inside the nodules.
2. Nitrogen fixation through nodule formation in non-leguminous plants:
E.g. Frankia forms root nodules in association with non-leguminous plant.
3. Nitrogen fixation through non-nodulation:
Some of the examples are:
1. Lichens, an association with fungi and algae (cyanobacteria or green algae)
2. Azolla, a fern, in association with anabaena.
B. Non- symbiotic/ asymbiotic biological nitrogen fixation:
Biological nitrogen fixation by microorganisms living freely or staying out of plant cell is called non- symbiotic biological nitrogen fixation. The asymbiotic nitrogen fixers can be classified as follows:
1) free living nitrogen fixing bacteria :
i) photosynthetic: chlorobium, chromatium
ii) non-photosynthetic: azotobacter, azomonas, derxia, beijerinckia.
The symbiotic free living nitrogen fixers are quite primitive. The fixation is a reduction process independent of respiration.
C. Associative symbiotic nitrogen fixation:
Certain bacteria, living in close contact with the roots of cereal and grasses, fix nitrogen.this association is a loose mutualism, called associative symbiosis. Some of the examples are:
1. Azospirillum brasilense in association with cereal roots.
2. Beijerinckia in association with the roots of sugarcane.
Q. 14. Short notes.
A) Silage production:
➢ Def: it is defined as preservation of green fodder under anaerobic condition called as silage.
I. During the silage making process, the pasture is cut when the grasses contain the highest nutrient levels.
Ii. The reason why it is cut just before they are fully mature is that all forms of preserved grass,such as hay and silage, will have lower amounts of nutrients than fresh pasture, so everything must be done to make the end product be as nutritious as possible.
Iii. During silage preparation, the grass is allowed to wilt in the field for a few hours to reduce the moisture content to around 60-75% as this is the optimum level.
Process in silage making
1) selection of forage crops and their maturity stage.
2) steps in silage making silage making involves four major steps viz., harvesting and transportation, chaffing, filling and compaction and covering of silo.
a. Harvesting and transportation of crop (ensiling)
b. Chaffing
c. filling of silo and compaction
d. Properly sealing and covering of silo pit
B) Biodegradation of organic waste:
➢ The organic matter consists of residues of plant and animal origin at all the stages of decomposition mediated by the microbes.
Composition of plant residues
cellulose - 15-60% Hemicellulose - 10-30%
Lignin - 5-30% Proteins - 2-15%
Sugars, amino acids and org. Acids - 10%
Microbiology of cellulose degradation : Cellulose is a long chain polymer of glucose molecules held together tightly by h2 bonds.the cellulose is degraded to simple compounds as follows by the enzymatic activities of different microbes.
Organisms responsible :
Bacteria - bacillus, cellulomonas, pseudomonas, cytophaga
Fungi - alternaria, fusarium, rhizoctonia, trichoderma
Actinomycetes - nocardia, streptomyces, micromonospora
Microbiology of hemicellulose degradation: These are various polymers of hexoses, pentoses and sometimes uronic acids with monomers like xylose and mannose. Ex. Pectin
Organisms responsible:
Bacteria : bacillus, achromobacter, pseudomonas, cytophaga
Fungi : alternaria, fusarium, rhizopus, aspergillus, penicillium, actinomycetes: streptomyces
Microbiology of lignin degradation: lignin is much more complex than the cellulose and hemicellulose consists of 3 elements like c, h and o.
Organisms responsible:
Bacteria : pseudomonas, flavobacterium
Fungi : clavaria, clitocybe, humicola
C) bacterial insecticide:
➢ Bacterial insecticides / biopesticides:
Bacteria are mostly associated with causing disease in humans as well as plants. However, there are several bacteria that work as pathogens to several insects. These bacteria play an important role in the development of bacterial insecticides. According to several studies, bacteria that can control several insects are highly specific towards its hosts and it makes it efficient enough to develop as an alternative to chemical insecticides. among a large number of bacterial pathogens used for control of crop pests, two bacterial genera viz., bacillus and pseudomonas could achieve major- success as biopesticides.
D) flagellation in bacteria:
➢ Flagella may be seen on bacterial body in following manner :
1. Monotrichous: these bacteria have single polar flagellum. E.g: vibrio cholera
2. Lophotrichous/ cephalotrichous: these bacteria have two or more flagella only at one end of
the cell /a tuft of flagella present at one end. E.g: pseudomonas fluorescence.
3. Amphitrichous: these bacteria have single polar flagella or tuft of flagella at both poles.
E.g :aquaspirillum serpens, nitrosomonas
4. Peritrichous: several flagella present all over the surface of bacteria. E.g: escherichia coli, salmonella typhi.
5. Atrichous: a bacterial cell without flagella is known as atrichous. E.g., lactobacillus, pasteurella
Q. 15. Enlist and explain microbial agents for plant diseases control.
➢ 1) bacillus cereus strains – produce the antibiotic zwittermicin –protect tomato and alf-alfa plants from various soil born fungi –phytophthora and pythium
2) p. Fluorescens, prevents bacterial blotch by competing with p. Tolaasii
3) trichoderma viridae: against root rot, stem rot, wilt, lead spot, early & late blights, tikka disease, downy mildews, etc. Of different crop plants.
Q. 16. Write important characteristics of algae and fungi.
➢ Algae: relatively simple organisms. The most primitive are unicellular. Others are aggregations of similar cells with little or no differentiation in structure or function. Some algae such as large brown algae have a complex structure with cell types specialized for particular functions. Regardless of size or complexity, all algal cells contain chlorophyll and are capable of photosynthesis. Found in aquatic environments or in damp soil.
2) Fungi: eucaryotic lower plants devoid of chlorophyll. They are usually multicellular but are not
differentiated into roots, stems and leaves. They range in size and shape from single celled microscopic yeast to giant multicellular mushrooms and puff balls. True fungi are composed of filaments and masses of cells, which makeup the body of the organism called mycelium. They reproduce by fission by budding or by spores – molds, mildews, yeasts and rusts belong to this group.
Q. 17. Write in brief about generalized and specialized transduction.
➢ Generalized transduction : a fragment of bacterial dna is accidently incorporated into a new
phage particle during viral replication and thereby transferred to another bacterial cell. Generalized transduction, like conjugation and transformation, is also useful for mapping of bacterial genes.
Specialized transduction:
In this certain temperate phage particles can transfer only specific genes from one bacterial cell ito
another. In specialized transduction, the bacterial dna genes transduced is limited to one or a few genes lying adjacent to the prophage.
Q. 18. Define the terms.
A) mycology: branch of microbiology which deals with study of fungi.
B) diazotrophs: associative non-symbiotic nitrogen fixing bacteria are called as diazotrophs/diazotrophic organisms. Ex. Azospirillium
C) phyllosphere: the leaf surface environment characterized by enhanced activity, and population of microorganisms.
D) mesophiles: the bacterium/microorganisms which grows better in the moderate temperature range of 25 to 40 °c.
Q. 19. Differentiate – Prokaryotes And Eukaryotes.
i) photosynthetic: chlorobium, chromatium
ii) non-photosynthetic: azotobacter, azomonas, derxia, beijerinckia.
The symbiotic free living nitrogen fixers are quite primitive. The fixation is a reduction process independent of respiration.
C. Associative symbiotic nitrogen fixation:
Certain bacteria, living in close contact with the roots of cereal and grasses, fix nitrogen.this association is a loose mutualism, called associative symbiosis. Some of the examples are:
1. Azospirillum brasilense in association with cereal roots.
2. Beijerinckia in association with the roots of sugarcane.
Q. 14. Short notes.
A) Silage production:
➢ Def: it is defined as preservation of green fodder under anaerobic condition called as silage.
I. During the silage making process, the pasture is cut when the grasses contain the highest nutrient levels.
Ii. The reason why it is cut just before they are fully mature is that all forms of preserved grass,such as hay and silage, will have lower amounts of nutrients than fresh pasture, so everything must be done to make the end product be as nutritious as possible.
Iii. During silage preparation, the grass is allowed to wilt in the field for a few hours to reduce the moisture content to around 60-75% as this is the optimum level.
Process in silage making
1) selection of forage crops and their maturity stage.
2) steps in silage making silage making involves four major steps viz., harvesting and transportation, chaffing, filling and compaction and covering of silo.
a. Harvesting and transportation of crop (ensiling)
b. Chaffing
c. filling of silo and compaction
d. Properly sealing and covering of silo pit
B) Biodegradation of organic waste:
➢ The organic matter consists of residues of plant and animal origin at all the stages of decomposition mediated by the microbes.
Composition of plant residues
cellulose - 15-60% Hemicellulose - 10-30%
Lignin - 5-30% Proteins - 2-15%
Sugars, amino acids and org. Acids - 10%
Microbiology of cellulose degradation : Cellulose is a long chain polymer of glucose molecules held together tightly by h2 bonds.the cellulose is degraded to simple compounds as follows by the enzymatic activities of different microbes.
Organisms responsible :
Bacteria - bacillus, cellulomonas, pseudomonas, cytophaga
Fungi - alternaria, fusarium, rhizoctonia, trichoderma
Actinomycetes - nocardia, streptomyces, micromonospora
Microbiology of hemicellulose degradation: These are various polymers of hexoses, pentoses and sometimes uronic acids with monomers like xylose and mannose. Ex. Pectin
Organisms responsible:
Bacteria : bacillus, achromobacter, pseudomonas, cytophaga
Fungi : alternaria, fusarium, rhizopus, aspergillus, penicillium, actinomycetes: streptomyces
Microbiology of lignin degradation: lignin is much more complex than the cellulose and hemicellulose consists of 3 elements like c, h and o.
Organisms responsible:
Bacteria : pseudomonas, flavobacterium
Fungi : clavaria, clitocybe, humicola
C) bacterial insecticide:
➢ Bacterial insecticides / biopesticides:
Bacteria are mostly associated with causing disease in humans as well as plants. However, there are several bacteria that work as pathogens to several insects. These bacteria play an important role in the development of bacterial insecticides. According to several studies, bacteria that can control several insects are highly specific towards its hosts and it makes it efficient enough to develop as an alternative to chemical insecticides. among a large number of bacterial pathogens used for control of crop pests, two bacterial genera viz., bacillus and pseudomonas could achieve major- success as biopesticides.
D) flagellation in bacteria:
➢ Flagella may be seen on bacterial body in following manner :
1. Monotrichous: these bacteria have single polar flagellum. E.g: vibrio cholera
2. Lophotrichous/ cephalotrichous: these bacteria have two or more flagella only at one end of
the cell /a tuft of flagella present at one end. E.g: pseudomonas fluorescence.
3. Amphitrichous: these bacteria have single polar flagella or tuft of flagella at both poles.
E.g :aquaspirillum serpens, nitrosomonas
4. Peritrichous: several flagella present all over the surface of bacteria. E.g: escherichia coli, salmonella typhi.
5. Atrichous: a bacterial cell without flagella is known as atrichous. E.g., lactobacillus, pasteurella
Q. 15. Enlist and explain microbial agents for plant diseases control.
➢ 1) bacillus cereus strains – produce the antibiotic zwittermicin –protect tomato and alf-alfa plants from various soil born fungi –phytophthora and pythium
2) p. Fluorescens, prevents bacterial blotch by competing with p. Tolaasii
3) trichoderma viridae: against root rot, stem rot, wilt, lead spot, early & late blights, tikka disease, downy mildews, etc. Of different crop plants.
Q. 16. Write important characteristics of algae and fungi.
➢ Algae: relatively simple organisms. The most primitive are unicellular. Others are aggregations of similar cells with little or no differentiation in structure or function. Some algae such as large brown algae have a complex structure with cell types specialized for particular functions. Regardless of size or complexity, all algal cells contain chlorophyll and are capable of photosynthesis. Found in aquatic environments or in damp soil.
2) Fungi: eucaryotic lower plants devoid of chlorophyll. They are usually multicellular but are not
differentiated into roots, stems and leaves. They range in size and shape from single celled microscopic yeast to giant multicellular mushrooms and puff balls. True fungi are composed of filaments and masses of cells, which makeup the body of the organism called mycelium. They reproduce by fission by budding or by spores – molds, mildews, yeasts and rusts belong to this group.
Q. 17. Write in brief about generalized and specialized transduction.
➢ Generalized transduction : a fragment of bacterial dna is accidently incorporated into a new
phage particle during viral replication and thereby transferred to another bacterial cell. Generalized transduction, like conjugation and transformation, is also useful for mapping of bacterial genes.
Specialized transduction:
In this certain temperate phage particles can transfer only specific genes from one bacterial cell ito
another. In specialized transduction, the bacterial dna genes transduced is limited to one or a few genes lying adjacent to the prophage.
Q. 18. Define the terms.
A) mycology: branch of microbiology which deals with study of fungi.
B) diazotrophs: associative non-symbiotic nitrogen fixing bacteria are called as diazotrophs/diazotrophic organisms. Ex. Azospirillium
C) phyllosphere: the leaf surface environment characterized by enhanced activity, and population of microorganisms.
D) mesophiles: the bacterium/microorganisms which grows better in the moderate temperature range of 25 to 40 °c.
Q. 19. Differentiate – Prokaryotes And Eukaryotes.
