Useful and harmful bacteria - class-VIII

Anabaena belongs to the family of filamentous cyanobacteria that is known for its nitrogen fixing ability. While these exists as a plankton, it is known to form symbiotic relationships with the water fern Azolla and are found growing together at the surface of streams and ponds on temperate and tropical regions.
Therefore, the correct answer is option A.

The antibiotics are substances produced by the natural metabolic processes of spore forming aerobic bacteria and fungi as their natural defense against other microorganisms. Among bacteria and fungi, bacterial genera outnumber the fungal genera in production of antibiotics. The highest numbers of antibiotics are derived from bacterial genera Streptomyces and Bacillus and fungal genera Penicillium and Cephalosporium. This makes option A correct. Viruses do not perform any metabolic activity outside the host and hence, do not produce any antimicrobial agents. Angiosperms are most developed flowering plants that have number of adaptation to make them less susceptible for competition for food and space; they do not produce antibiotics. Thus, the correct answer is option is A.

Nitrogen fixing bacteria like rhizobium lives in symbiotic relationship with legumes.

Under optimum condition and temperature, most of the bacteria divides at interval of 20 minutes and this time is called their generation time. This is the time in which one bacterial cell divides and forms two cells. This is also known as the doubling time. 

The plasmid is an extrachromosomal material in bacteria and used as a carrier DNA because it has antibiotic resistance gene which makes it easy to isolate the transformed cell with the desired insert in it.

Azotobacter has a wide variety of metabolic abilities, including the unusual ability to fix atmospheric nitrogen as they produce nitrogenase enzyme and convert it to ammonia. They are free living in soil and do not associate as symbionts. 

Fermentation is a process of anaerobic respiration that converts sugar to acids, gasses or alcohol. It occurs in yeast and bacteria, but also in oxygen-starved muscle cells, as in the case of lactic acid fermentation. The food processing industry depends on this phenomenon for deriving a variety of edible products and beverages. As viruses are the acellular organism, they do not follow respiration. Protista are the eukaryotic unicellular and respire like animals. Thus, the correct answer is option D.

Some bacteria can fix atmospheric nitrogen, e.g., Azotobacter and Clostridium, while others convert ammonia into nitrate, e.g., Nitrosomonas.
A biogeochemical cycle or substance turnover or cycling of substances is a pathway by which chemical nutrients like carbon, oxygen, nitrogen, phosphorus, calcium, and water etc move through both biotic and abiotic compartments of earth. All of these are required to carry out basic life processes as these processes supply with energy and nutrients. Thus, the correct answer is option D.

Cyanobacteria, which have "symbiotic" relationships with cycads are in the order Nostocales. Anabaena cycadeae is a blue green algae (BGA) commonly found in the coralloid roots of cycads. At first, the cycad sprouts without any cyanobacterium. Coralloid roots are formed soon after the primary root.
So answer is - 'Cycas'.

Heterotrophic bacteria require an organic carbon source for growth (i.e., they derive energy and carbon from organic compounds). Economically important uses of heterotrophic bacteria are:

1. They enhance the fertility of the soil by nitrogen fixation.
2. Production of curd and yogurt from milk, cheese, butter, wine
3. Production of antibiotics
4. They form an essential part of biogeochemical cycles during which they release essential elements, such as nitrogen and carbon for recycling.
5. Cleaning of oil spills

Bacteria which directly convert atmospheric nitrogen into nitrogen compounds are called nitrogen fixing bacteria. They could be symbiotic or free- living like Rhizobium and Azotobacter respectively.
So answer is -'Nitrogen fixing bacteria'.

A chemoorganotroph is an organism, that obtains energy from the oxidation of reduced organic compounds. The list of compounds from which chemoorganotrophic organisms can generate energy and their sources of carbon is very long, making these microorganisms extremely versatile. Two mechanisms for energy conservation are known for chemoorganotrophs: fermentation and respiration.
So answer is - 'Chemoorganotrophs'.

Typhoid is a bacterial infection that is caused by the bacteria Salmonella typhi. Symptoms include high fever, diarrhea, vomiting, headache, abdominal pain. It is spread by food or water contaminated with the feces of an infected person. 

Citrus canker is a plant disease caused by the bacterium Xanthomonas citri.

Denitrification is the biological conversion of nitrate to nitrogen gas, nitric oxide or nitrous oxide.  These compounds are gaseous compounds and are not readily available for microbial growth; therefore they are typically released to the atmosphere. Denitrifiers belong to several genera including Pseudomonas,Bacillus, Spirillum, Hyphomicrobium, Propionobacterium, Cornebacterium, Thiobacillus, and Alcaligenes. Biological denitrification is an anaerobic respiration reaction in which nitrate is reduced. Denitrifying bacteria are aerobic autotrophs or heterotrophs that can switch to anaerobic growth when nitrate is used as an electron acceptor.
 So, the answer is option C.

Enzyme nitrogenase, that catalyses nitrogen fixation is oxygen labile. Leguminous plant proteins called leghaemoglobin act as oxygen scavenger facilitating Rhizobium in fixing nitrogen.
So answer is- 'Oxygen removal'.

• Clostridium butylicum - lactic acid is a wrong match of a microbe and its industrial product because Clostridium butylicum forms butyric acid.
• So, the correct answer is 'butyric acid'.

Azotobacter is a well-known genus of free-living, aerobic, nitrogen-fixing bacteria found in soil.

There are basically two methods of pasteurization in use today- batch and continuous flow. In the batch process (batch pasteurizer), a large quantity of milk is held in a heated vat at 149$^{0}$F/65$^{0}$C for 30 minutes, followed by quick cooling to about 39$^{0}$F / 4$^{0}$C. In the continuous flow process (continuous flow pasteurizer) also known as HTST, for high temperature, short time, milk is held at 161$^{0}$F / 72$^{0}$C for at least 16 seconds. Before being chilled back to 39$^{0}$F / 4$^{0}$C. 

Microorganisms are used in brewing, wine-making, baking, pickling and other food-making processes. They are also used to control the fermentation process in the production of cultured dairy products such as yogurt and cheese. The cultures also provide flavour and aroma, and inhibit undesirable organisms. Microbes are used in the biological treatment of sewage and industrial waste effluents. Microbes are used in fermentation to produce ethanol.

After tobacco has been harvested, it is necessary to cure it before consumption. Tobacco curing is also known as colour curing, because when tobacco leaves are cured, the intention is to change their colour and reduce their chlorophyll content. Bacillus megaterium is an endophyte and is a potential agent for the biocontrol of plant diseases. 

Retting is a process employing the action of microorganisms and moisture on plants to dissolve or rot away much of the cellular tissues and pectins surrounding bast fibre bundles and so facilitating separation of the fibre from the stem. Butyric acid bacteria helps in the retting of jute fibre.

Clostridium botulinum is a bacterium that produces a potent neurotoxin, which causes botulism, a severe form of food poisoning.

• Citrus canker is a disease that affects citrus species caused by the bacterium Xanthomonas axonopodis.
  
• The bacteria causing diseases in humans are- Tuberculosis and cholera.
• Cholera is caused by the bacterium Vibrio cholera.
• Tuberculosis is caused by Mycobacterium tuberculosis. 

Mycoderma aceti is an aerobic acetic acid bacterium that converts ethanol into acetic acid in presence of oxygen. The ethanol is first aerobically fermented into acetaldehyde which is then oxidized into acetic acid. The Mycoderma aceti present in wine and in the surrounding air produce acetic acid (vinegar) which imparts sour taste to the wine. The requirement of oxygen for the process. Heat exposure renders the bacteria inactive and acetic acid production is stopped. Long term exposure to UV light affect the phenolic and ester component of wine and render it tasteless; since acetic acid formation is not affected by light, wine is not turned sour in light.

Sterilization refers to a technique that makes the desired material/medium/object completely free from all life forms including microbial spores and viruses. It is done by number of methods like boiling, incineration, pasteurization, hot air sterilization etc. Option A is incorrect. Pasteurization is technique wherein heat is applied to liquids (milk, beverages and dairy products) to kill potential agents of infection and spoilage while retaining the flavour and food value. It includes exposure of the liquid to 71.6°C for 15 seconds (flash method) or to 63°–66°C for 30 minutes (batch method) followed by its cooling. Option B is correct. The conversion of ammonia into nitrates is termed as nitrification and is carried out by chemolithotrophic bacteria; Nitrosomonas and Nitrobacter. Freezing refers to maintenance of bacteria under very low temperature that kill fractions of them but the survivors are maintained as dormants for longer periods as they show no metabolic activity; option D is incorrect. Thus, the correct answer is option B. 

Microorganisms that produce methane as a by-product of its metabolic activities is known as methanogens. They are classified either as bacteria or archaea, these anaerobic organisms are commonly found in wetlands creating the marsh gas, digestive tracts of human beings and animals, marine sediments and hot springs.

Gobar gas is mixture of methane (CH$ _4$), carbon dioxide (CO$ _2$), hydrogen (H$ _2$) and hydrogen sulphide (H$ _2$S) with methane as major component (65%). Methanogens are anaerobic, autotrophic, eukaryote that converts carbon dioxide and hydrogen into methane gas. The hydrogen serves as electron donor for reduction of carbon dioxide. Thus, methogens produce gober gas by anerobic fermentation of biomass in presence of water. The chemolithotrophic bacteria that reduce the organic nitrogen into ammonia are termed as ammonifying bacteria. The chemolithotropic bacteria that converts ammonia NH$ _3$ into nitrates, NO$ _3$-, are termed as nitrifying bacteria; it includes Nitrosomonas and Nitrobacter. The chemolithotrophic bacteria that reduce the nitrates into nitrogen are termed as denitrifying bacteria. Ammonifying, nitrifying and denitrifying bacteria are component of nitrogen cycle and do not serve in gober gas (methane) production. Thus, the correct answer is option A. 

Methane, also called as marsh gas, is a colourless, odourless gas that occurs abundantly in nature as the chief constituent of natural gas. The decomposition of sludge by anaerobic bacteria in sewage-treatment processes produces a gas rich in methane.

Soil is the rich source of water and organic matter. Decomposition of remains of dead organisms adds organic content to the soil. Weathering of minerals add inorganic fraction of soil. Thus, soil fulfils the nutritional requirement of bacteria with diverse feeding habits and serves as richest source of bacteria. Since, bacteria can live on the surface of soil particles in form of biofilms which can be formed on almost any surface; thus type of soil does not affect the bacterial population. Option B is correct. Poor solubility of oxygen and limited penetration of sun light in water limits the distribution of majority of bacteria in limnetic and profundal zone which makes option C incorrect. Owing to extreme temperatures, chemical contamination, and low nutrient environments, air does not serve as good habitat for bacteria and thus, only thick walled resistant bacteria/bacterial structures like endopores are present in air; option A is incorrect. Despite providing favourable nutritional condition for bacterial growth, temperature variations in milk limit their growth. Option D is incorrect. Thus, the correct answer is option B. 

Bacteria are the component of biological nitrogen fixation which included free living or non-symbiotic soil bacteria. It may be aerobic bacteria (Azotobacter spp), anaerobic bacteria (Clostridium spp), photosynthetic bacteria (Rhodospirillum spp), chemosynthetic bacteria (Thiobacillus spp) and blue-green algae. The finger-like projections on roots of legumes, termed as root nodules, carries Rhizobium bacteria which in turn are responsible for nitrogen fixation; legumes depend on of bacteria for nitrogen fixation. None of the parasitic algae or fungal species can fix nitrogen. Thus, the correct answer is option A.

Azotobacter is a free-living aerobic rod-shaped soil bacteria; it is a member of Gammaproteobacteria and fixes the atmospheric nitrogen into the useable form which makes option A correct. Rhizobium is a Gram-negative, motile, rod-shaped bacteria that forms special nitrogen-fixing organs, called as root nodules, in the roots of legumes and fix the gaseous nitrogen into ammonia. Option B is incorrect. Clostridium is an anaerobic free-living nitrogen fixer which makes option C incorrect. Streptomyces is filamentous free-living aerobic bacterium; S. thremoautotropicus have oxygen insensitive nitrogenase enzyme and ability to fix nitrogen. Since not all the Streptomyces spp can fix nitrogen, options D is incorrect. 

Antibiotics serve as metabolic analogs and control the microbial growth by competing with the necessary enzyme to halt the growth of bacterial cells. Antibiotics occupy the enzyme’s active site thereby blocking the binding of its natural substrate to the enzyme. This puts the whole pathway to halt. Inhibition of enzyme activity by a metabolic analog of the natural substrate is termed as competitive inhibition.

Nitrogen gas is converted to nitrate compounds by nitrogen fixing bacteria in soil or root nodules. The Haber process converts nitrogen gas into ammonia used in fertilizers. Ammonia is converted to nitrates by nitrifying bacteria in the soil. Bacteria of the genus Nitrosomonas oxidize NH$ _3$ to nitrites. Bacteria of the genus Nitrobacter oxidize the nitrites to nitrates. Urea and egested material is broken down by decomposers. This results in nitrogen being returned to the soil as ammonia. Decomposers also break down the bodies of dead organisms resulting in nitrogen being returned to the soil as ammonia. In some conditions denitrifying bacteria in the soil break down nitrates and return nitrogen to the air. Thus, it is summarized that the bacteria play a significant role in nitrogen fixation, nitrification and several other operations in all biogeochemical cycles.

Agrobacterium tumefaciens is a soil plant pathogenic bacterium that carries Ti plasmid. It can transfer a particular segment of the tumor-inducing (Ti) plasmid into the nucleus of infected cells. The transferred T-DNA is then integrated into the host genome and transcribed with it. This ability of Agrobacterium tumefaciens to transfer the T-DNA in the host genome is explored in genetic engineering to transfer the desired DNA segment of up 25kb, carrying the gene of the interest, into the genome of selected organisms. Thus, the correct answer is option A.

Lactobacilli are anaerobic, rod shaped bacteria that produce lactic acid by anaerobic fermentation. They are responsible for digestion of milk sugar lactose into lactic acids at suitable temperatures which in turn add sour taste to milk. 

Free-living and symbiotic nitrogen-fixing bacteria fix atmospheric inert nitrogen into biologically useful ammonia thereby adding nitrogen to the soil and increasing its fertility. Algae increase the organic carbon content of the soil upon their death. Mycorrhizae are the symbiotic fungi that reside in roots of higher plants and increase soil fertility by nitrogen fixation. Phages are the bacterial viruses that replicate within the bacterial cell with a polyhedral head, a helical tail and fibers for attachment to the host cell. Thus, the correct answer is option C.

The antibiotics are substances produced by the natural metabolic processes of spore forming aerobic bacteria and fungi as their natural defence against other microorganisms. Immune host is the one which has acquired immunity against certain antigen by administration of antibiotics. It produces antibodies, not the antibiotics which makes option A incorrect. Commercial production of antibiotics by parasitic fungi needs their culture in live host cells which is a tedious and expensive process; Option B is incorrect. Saprophytic bacteria feed on dead and decaying organic matter and therefore, can easily be cultured on synthetic medium; option C is correct. Since, viruses are metabolically inactive outside the host cell and depend on host for their own nutritional requirements, they do not produce antibodies. Option D is incorrect. Thus, the correct answer is option C. 

Biofertilizer is any living organism that imparts fertility to soil. Azotobacter is a free living aerobic rod shaped soil bacteria; it is a member of Gamma-proteobacteria and fix the atmospheric inter nitrogen into biologically usable ammonia and hence, serves as biofertilizer. 

Earth’s atmosphere contains 78% nitrogen but it cannot be used by living organisms due to its inert form. This inert nitrogen is fixed into biologically active ammonia by free living or symbiotic bacteria and other microorganisms. The free living bacteria are present in soil where they perform nitrogen fixation; example: Azotobacter, Azospirillum and Clostridium. This makes option B correct. The finger like projections on roots of legumes, termed as root nodules, carries Rhizobium bacteria which in turn are responsible for nitrogen fixation. Legume get ammonia from Rhizobium and provide carbohydrates as an energy source to them; a symbiotic relation. This makes option C incorrect as root nodules harbour symbiotic bacteria. Nitrogen fixation does not occur in air as none of nitrogen fixing microbes are present in air; option A is incorrect. Thus, the correct answer is option B. 

Bacterias like Azotobacter and Azospirillum fix atmospheric Nitrogen while free living in soil, thus enriching Nitrogen content of soil.

Azotobacter is free-living aerobic non-photosynthetic nitrogen fixing bacterium which have wide variety of metabolic abilities, they fix atmospheric nitrogen as they produce nitrogenase enzyme and convert it to ammonia. They are free living in soil and do not associate as symbionts. 

Azospirillum is a nitrogen-fixing bacterium that is commonly associated with the roots of grasses and cereals, including paddy (rice) fields.

Many micro - organisms grow water bodies and decrease their oxygen level. This is harmful to the other organisms living in those water bodies.

Thermococcus, Methanococcus, and Methanobacterium are Archaea whose histones are shorter than eukaryotic histones and are assembled in tetramers.

Amoebic dysentery is caused by Entamoeba histolytica, a protozoan parasite.  Arthritis is an inflammation of joints. It is caused by attack on immune system, injury or metabolic abnormalities. Beriberi is a disease caused by a vitamin B$ _1$ deficiency. Diphtheria is an infectious disease caused by the bacterium Corynebacterium diphtheriae. 

Cyanobacteria are also called myxobacteria. In which flagella one completely absent but the movement occurs in some genera by special gliding motion. Such movement are connected with the secretion of mucilage.

Tetanus is also called as lockjaw. It is a disease caused by bacterium Clostridium tetani. It affects the nerves that control the muscle movements. Symptoms include difficulty swallowing, difficulty breathing, muscle spasm. Polio is a contagious disease caused by a poliovirus. It attacks the nervous system. It mainly affects the small children. Filaria is a parasitic disease caused by nematode parasites of the order Filariidae. It spreads by mosquitoes and black flies. Malaria is a disease is caused by Plasmodium protozoa. It is transmitted through the bite of the Anopheles mosquito. Symptoms include fever, aches, nausea.

Sterilization by autoclaving is carried out to kill bacteria and other pathogens present in the nutrients, equipment, and materials. In bacterial/ tissue culture, glassware and nutrients are sterilized through autoclave. In this, a pressurized steam is applied with the heat of 121$^0$C for around 15–20 minutes to kill bacteria, spores, and other pathogens.

Crown gall disease is a plant disease that is caused by the bacterium Agrobacterium tumefaciens. It results in the overgrowth appearing as knobbly swellings or galls on stems, roots, trunks, and branches. It affects mostly woody shrubs and herbaceous plants like grapes, raspberries, blackberries, and roses.

Pneumonia is a lung disease caused by bacteria Streptococcus pneumoniae. It causes inflammation of alveoli of lungs. Symptoms include dry cough, chest pain, fever, difficulty breathing.

Crown gall disease is a plant disease that is caused by the bacterium Agrobacterium tumefaciens. It results in the overgrowth appearing as knobbly swellings or galls on stems, roots, trunks, and branches. It affects mostly woody shrubs and herbaceous plants like grapes, raspberries, blackberries, and roses.

Crown gall disease is a plant disease that is caused by the bacterium Agrobacterium tumefaciens. Ti plasmid is essential to cause disease. It transfers bacterial DNA into the host cell where it incorporates itself into the host genome. It results in the overgrowth appearing as knobbly swellings or galls on stems, roots, trunks, and branches. It affects mostly woody shrubs and herbaceous plants like grapes, raspberries, blackberries, and roses.

Citrus canker is a disease that is caused by the bacterium Xanthomonas axonopodis. It affects the Citrus species of fruits such as lime, oranges, grapefruit. It results in the lesions on the leaves, stems, fruit and other parts of the citrus plants.

Abortion is the method of ending the pregnancy by removal of either embryo or foetus. Chlamydia is a sexually transmitted infection. Chlamydia may result into Pelvic Inflammatory Disease (PID). It can lead to serious consequences like infertility, ectopic pregnancy and even abortion.

Trachoma is an infectious disease caused by bacterium Chlamydia trachomatis. It results in the roughening of the inner surface of the eyelids. The symptoms include pain in the eyes, itching and irritation in the eyes, blindness. It is a contagious disease.

Crown gall is a plant disease caused by the soil bacterium Agrobacterium tumefaciens, which transfers DNA into the plant host.

Anthrax is an infectious disease caused by bacterium Bacillus anthracis. It mainly affects rudiments like cattle, buffaloes, horses, sheep. It rarely occurs in humans. Symptoms include sore throat, mild fever, fatigue, muscle aches.

Cholera is caused by Vibrio cholerae and tetanus is caused by Clostridium tetani. Both are bacterial diseases.

The interaction between Agrobacterium tumefaciens and plants is one of the most studied systems in plant-microbe interactions due to its ability to genetically transform plants.

Blight disease of Rice is a deadly disease that affects the cultivated rice. It is caused by bacteria Xanthomonas oryzae. It causes wilting of seedlings and yellowing and drying of leaves.

Gas gangrene is caused by the Clostridium perfringens bacterium. This produces gas in tissues in gangrene. It results in the swelling.  The skin turns pale to brownish-red. 

Toxin is the harmful substance secreted by bacteria. It affects the immune system of the host. It causes infection and disease in the host by damaging the tissues. Paratope is an antigen-binding site present on the antibody. 

Little leaf disease is a disease that affects brinjal. Symptoms include reduction in leaf size and rosette like appearance. It is transmitted by leafhopper. It is caused by Mycoplasma. Apart from this, Mycoplasma also causes witches' broom disease and plant yellows diseases.

Food poisoning or botulism is caused by Clostridium botulinum. It is an anaerobic bacterium. The bacterium infects canned food. The poisoning is accompanied by diarrhoea and vomiting. Common food poisoning is caused by Staphylococcus aureus.

Tetanus is a bacterial disease. It is also known as Lock Jaw. Tetanus is caused by Clostridium tetani. It is a bacilus bacteria.
Polio is a viral disease. It is also known as poliomylelitis. It is caused by polio virus. The virus spreads from person to person.
Filaria is a parasitic diseases which is transmitted by mosquito and flies. It is caused by Wucheria bancrofti and Wucheria malayi.
Malaria is a protozoan disease. It is caused by a plasmodium. It is transmitted by female Anopheles mosquito.

Trachoma is a bacterial infection. It is caused by bacteria Chlamydia trachomatis. It is an eye infection. It causes itching and irritation of eyes. In severe condition, it may result in blindness.

Escherichia coli  is a Gram-negative bacteria. It plays an important role in the field of biotechnology, where it has served as a host organism in recombinant DNA technology. The bacterium can be grown and cultured easily. One of the first useful application of recombinant technology was the manipulation of E.coli to produce human insulin.
Rhizobium meliloti is a Gram-negative, nitrogen-fixing bacterium. It is a symbiotic bacteria lives in the association with legumes. The bacteria possesses nif genes, responsible for the nitrogen fixation.
Bacillus thuringensis is a soil dwelling bacteria. It has been used as a biological pesticide. During spore formation, the bacteria produces crystal proteins called as endotoxins which have insecticidal action.
Crude oil is a complex mixture of hydrocarbons. Several strains of bacterium Pseudomonas putida were known to produce enzymes that degrade these hydrocarbons, i.e., the bacteria ate the hydrocarbons, nourishing themselves and reproducing.

Rickettsial or viral vaccines are produced by cultivating microorganisms in living tissues of animal bodies, such as chick embryos. It is possible in some cases to reduce these effects by harvesting only proteins of the infected tissues. E.g., allantoic fluid of chick embryo. These viruses can be killed or inactivated with formaldehyde, phenol etc. 

Bacteria like E. coli have very short generation times. Combined with the high copy number of plasmid they produce, they duplicate the plasmid with pretty good fidelity for other uses. Agrobacterium tumefaciens is capable of transferring a particular DNA segment of the tumour-inducing (Ti) plasmid into the nucleus of infected cells where it is subsequently integrated into the host genome. 

• pBR322 is a widely-used E. coli cloning plasmid vector. 
• It was created in 1977 in the laboratory of Herbert Boyer at the University of California San Francisco. The p stands for " plasmid " and BR for "Bolivar " and " Rodriguez ", researchers who constructed it. 
• By using  pBR322 plasmid of E.coli Insulin, interferons and somatostatin can be synthesized through the genetic engineering procedure.
• So, the correct answer is 'Escherichia coli'.

The genus Pseudomonas are adapted to very different environments. This capability to thrive in various habitats coincides with an enormous metabolic capacity of this genus to use recalcitrant compounds as carbon source as well as to produce a wide range of secondary metabolites and biopolymers. Environmental applications of various Pseudomonas species in biodegradation of recalcitrant pollutants as well as biocontrol agents in plant growth promotion is very common.

Methanogens are microorganisms that produce methane as a metabolic byproduct in anoxic conditions. They are classified as Archaea, a domain distinct from bacteria. They are common in wetlands, where they are responsible for marsh gas. Cyanobacteria are often called as blue-green algae. Cyanobacteria are a photosynthetic nitrogen fixing group that survive in wide variety of habitats, soils, and water. Mycoplasma refers to a genus of bacteria that lack a cell wall. Mycoplasma can survive without oxygen.

AIDS (Acquired Immunity Deficiency Syndrome) is a sexually transmitted disease. It is caused by HIV virus. Syphilis is a serious disease caused by spirochete Treponema pallidum. It is also a sexually transmitted disease. Gonorrhoea is a sexually transmitted infection caused by bacteria Neisseria gonorrhoeae. Urethritis is inflammation of the urethra. It is caused by bacterial infection caused by Neisseria gonorrhoeae or Chlamydia trachomatis.

Anthrax is a bacterial disease caused by the bacterium Bacillus anthracis. It can occur in four forms: skin, lungs, intestinal, and injection. It commonly affects grazing animals like sheep, pigs, cattle, horses, goats. However, it rarely affects humans as well. Tick fever is a disease spread by the bite of an infected tick. It is caused by spirochete species like Borelliahermsii, Borelliaparkerii. Symptoms include fever, headache, muscles pains, rash. Coccidiosis is a disease of the intestinal tract of animals caused by coccidian protozoa. Symptoms include droopiness, loss of appetite, pale combs and wattles, blood or mucus in the feces, diarrhea, dehydration. Rinderpest is a disease of cattle caused by a paramyxovirus. Symptoms include fever, dysentery, inflammation of the mucous membranes.

a) Treponema pallidum is a spirochaete bacterium that causes syphilis. Syphilis is a sexually transmitted disease. 

Citrus canker is a disease that is caused by the bacterium Xanthomonas axonopodis. It affects the Citrus species of fruits such as lime, oranges, grapefruit. It results in the lesions on the leaves, stems, fruit and other parts of the citrus plants.

• Pneumonia is a serious disease caused by Diplococcus pneumoniae. It affects the lungs.
• Citrus canker disease is caused by bacterium Xanthomonas axonopodis. It affects citrus species like sweet lime, lemon.
• Cholera is caused by Vibrio cholerae. It results in the severe watery diarrhea.
• Leprosy is a serious disease caused by Mycobacterium leprae. It affects the skin, nervous system, mucosal surfaces of the upper respiratory tract and the eyes.
  

The antibiotics are the chemical substances produced by the natural metabolic processes of bacteria and fungi as their natural defense against other microorganisms. Penicillin is an antibiotic that target the peptide cross-links in the peptidoglycan and disrupt the cell wall integrity. Exposure of penicillin to bacteria stops the cell wall synthesis by inhibition of formation of peptide linkage and bacteria become protoplast (a fragile cell bounded only by a membrane) which is highly susceptible to lysis.  Thus, the correct answer is option C.

Rust of Tea is also called as red rust disease. It is caused by algae Cephaleuros parasiticus Karst. It affects the tea plant. Red rot is a disease that affects the sugarcane plant. It is caused by fungus Glomerella tucumanensis. Citrus canker is a bacterial disease affecting Citrus species caused by the Xanthomonas axonopodis. It affects Citrus species like lime, orange. Late blight is an infection caused by fungus Phytophthora infestans. It affects potato and tomato.

VFDF is also called as Very Fast Death Factor. It is an anatoxin produced by a cyanobacteria, Lingbya. It is a neurotoxin. It causes severe overstimulation of respiratory muscles. This ultimately can result in death.

Syphilis is caused by Treponema (a-v). Pathogens of cattle include Corynebacterium (b-iii). Crown gall of apple is caused by Agrobacterium (c-ii). Diphtheria is caused by Corynebacterium, but looking at the options, the correct pairing for Diphtheria is (iii) and cattle pathogen is (iv) Mycobacterium. Option B correctly maps a-v, b-iv, c-ii, and d-iii.

Red rot disease is caused by the fungus Glomerella tucumanensis. It produces a structure called as acervuli. This results in profuse sporulation. Late blight of Potato is caused by fungus Phytophthora infestans. It infects and destroys the leaves, stems, fruits, tubers of potato and tomato plants. Black rot of crucifers is caused by bacterium Xanthomonas campestris. It results in dark brown discoloration of the leaves of fruit and vegetables. Wheat leaf rust is a disease caused by fungus Puccinia triticina. It affects wheat, barley and rye stems, leaves and grains.