Economic importance of Bacteria
Bacteria play significant role in day to day activates of human beings.
a) Role in agriculture
i) Decay and decomposition of organic matter : they bring about decay and decomposition of dead remains of plants and animals. These are the most important for mineral cycling
ii) Sewage disposal : The bacteria decompose the organic matter present in the sewage, converting into simpler inorganic substances. The inorganic substances thus formed, being soluble, pass out through filter along with water which is highly useful of irrigation purposes, g., Clostridium, E. Coli.
iii) Nitrogen cycle : The proteins present in dead remains of living organisms are converted into amino acids by different types of saprophytic bacteria. Amino acid are converted into ammonia by ammonifying bacteria (Bacillus vulgaris, B. ramosus). Nitrifying bacteria convert ammonium salts first into nitrites (Nitrosomonas, Nitrococcus) which are subsequently converted into nitrates (Nitrobacter). In presence of denitrifying bacteria (pseudomonas denitrificans) , nitrates and nitrites of soil are converted to gaseous nitrogen.
iv) Nitrogen Fixation : It is the biological process in which atmospheric nitrogen is converted into nitrogenous compounds by nitrogen fixing bacteria. These bacteria are of 2 types : a) Free living b) Symbiotic
a) Free living bacteria are Azotobacter and Beijerinckia (aerobic) and Clostridium (anaerobic).
b) Common symbiotic bacteria are Rhizobium Leguminosarum and Xanthomonas. These convert nitrogen into ammonia which is directly converted into amino acids by plants.
v) Manure preparation : Saprotrophic bacteria help in preparation of farmyard manure by converting farm refuse, dung and other organic wastes into humus.
b) Role in industry : Man has utilized the metabolic activates of bacteria in preparation of a number of industrial products as listed below :
i) Butter milk and sour cream
v) Retting of fibres : Retting is a controlled microbial decomposition for separation of fibres. The tissues are immersed in water tanks where anaerobic butyric acid bacteria dissolve the pectin of middle lamella of cells, thus, separating the fibres. Clostridium perfringens and Pseudomonas fluorescence are useful in this process.
vi) Curing of leaves : To improve the flavor and taste in tea, using Micrococcus candidans and in tobacco leaves by Bacillus megatherium.
vii) Single cell proteins (SCP) : like – Methylohilus methyoltropus and Rhodopseudomonas capsulata.
c) Role in Medicine : Bacteria have been used extensively in preparation of antibiotics, vaccines, serums and vitamins.
i) Antibiotics : The term antibiotic was given by Waksman, who discovered streptomycin, these are the organic substances produced by microorganisms which inhibit the growth of other organisms (mostly pathogens) but do not affect the growth of organisms secreting these. The first commercial antibiotic penicillin was discovered by Flemming (1959) from a fungus called Penicillium.
Some antibiotics of eubacterial origin :
- a) Bacitracin ……………………… Bacillus licheniformis
- b) Polymixin ……………………… Bacillus polymyxa
- c) Gramicidin …………………….. B. brevis
- d) Subtilin …………………………. B.subtilis
- ii) Vaccine production
vaccines and serums against typhoid, cholera TB, pertussis, tetanus and diphtheria are made with the help of bacteria or their toxins e.g., DPT ( against diphtheria, pertussis and tetanus), TT(against tetanus), BCG (Bacille of Calmette – Guerin against TB ) , DT ( against diphtheria and tetanus)
iii) Vitamins : Escherichia coli present in human intestine produces large quantities of B- complex vitamin K. bacteria are utilized in industrial production of a number of vitamins like riboflavin from clostridium butylicum, Cobalarmin (B12) from Bacillus megatherium and Pseudomonas denitrificans.
iv) Pollution control : Pseudomonas putida degrades petroleum wastes. Flavobacterium can decompose 2 , 4-D. DDT can be decomposed by Acetobacter aerogens. Gange’s water contains Bdellovibiro bacteriovorus that maintains purity of its water.
i) Spoilage of food : Saprophytic bacteria cause decay of vegetables, fruit, meat, bread and other foods, making these unfit for human consumption. Some bacteria even produce strong toxins in the infected food stuffs which cause food poisoning when consumed.
ii) Deterioration of Domestic Articles : Some saprophytic bacteria like Cellulomonas, Spirochaete cytophaga cause deterioration of domestic articles of daily use such as leather, woolen, canvas articles etc.
iii) Denitrification of Soils : Denitrifying bacteria like Thiobacillus denitrificans, Micrococcus denitrificans and Pseudomonas convert nitrates and nitrites present in the soil into gaseous nitrogen, thus depleting the soil nitrogen, thereby decreasing soil fertility.
iv) Desulphurification : Desulphovibrio desulphuricans.
v) Diseases : Common disease of humans, animals and plants are listed below respectively –
Table : 2
Name of causal organism Name of the human diseases
Shigella dysenteriae, S. sonnei, S. boydis- Bacillary dysentery
Clostridium botulinum – botulism
Vibrio cholera Cholera
Leptotrichia bucccalis Dental plaque
Corynebacterium diphtheriae Diphtheria
Salmonella typhimurium staphylococcus aureus – Food poisoning
Clostridium perfringens Gangrene
Escherichia coli, Salmonella Gastroenteritis
Neisseria gonorrhoeae or Salmonella Gonorrhoea
Mycobacterium leprae (Hensen’s bacillus) Leprosy
Neisseria meningitidis Meningitis
Heliobacter pylori – Peptic ulcer
Staphylococcus aureus Pimples
Yersinia pestis Plague
Diplococcus pneumonia Pneumonia
Streptococcus species Rheumatic fever
Treponema pallidum Syphilis
Clostridium tetani Tetanus
Streptococcus pyrogenes Tonsilitis
Mycobacterium tuberculosis Tuberculosis
Salmonella typhosa / typhi Typhoid
Gardineralla vaginalis Vaginitis
Bordetella pertussis / Hemophilous pertusis Whooping cough
Salmonella typhimurium Enteric fever (paratyphoid)
Mycoplasma hominis – Male sterility and female abortion in humans
Table : 3
Name of causal organism Name of the animal diseases
Brucella sui Brucellosis
Clostridium chanvei Black leg
Bacillus anthracis Anthrax
Salmonella abortusovis Abortion
Table : 3
Name of causal organism Name of the plant diseases
Pseudomonas solanacearum Potato wilt
Xanthomonas citri Citrus canker
Agrobacterium tumefaciens Crown gall
Erwinia amylovora Fire blight of apple
Xanthomonas oryzae Bacterial blight of rice
Xanthomonas malvacearum angular leaf spot of Gossypium
Canthomonas phaseoli Bean blight of Phaseolus
Pseudomonas rubrilineans Red stripe of sugarcane
Eruinia cartovora Soft rot of carrot
Corynebacterium tritici Tundu (bacterial rot) of wheat
Xanthomonas campestris Black rot of cabbage
Streptomyces scabies Potato scab
Pseudomonas tobaci Wild fire of tobacco
- Spherical bacteria with chain like arrangement of different length is
- Select incorrect statement w.r.t eubacteria
- Have very simple structure
- Peptidoglycan nature of cell wall
- Heterotrophs are most abundant in nature
- Show most simple metabolic diversity
- Gram positive bacteria differs from Gram negative bacteria in the
- Presence of NAG and NAM
- Absence of diaminopimelic acid
- Presence of L-alanine
- Absence of D-glutamic acid
- Bacterial cell envelope is
- Glycocalyx only
- Cell wall only
- Glycocalyx and nucleoid
- Glycocalyx, cell wall and plasma membrane
- Nucleoid is
- Histoneless linear ss- DNA
- Circular DNA with histone proteins
- Circular DNA packaged with polyamines
- DNA with free ends
- Bacteria capable of switching over to anaerobic mode to get energy for their survival, are called
- Facultative anaerobes
- Obligate anaerobes
- Obligate aerobes
- Facultative aerobes
- Find odd one out w.r.t. phototrophic nutrition
- Chromatium and chlorobium
- Rhodopseudomonas and Thiospirillum
- Chloronema and Chloroflexus
- Pseudomonas and Clostridium
- Mark the incorrect option (w.r.t. nitrifying bacteria0
- Genetic recombination in which a small double stranded piece of DNA is transferred from donor bacterium to recipient bacterium by a bacteriophage was first demonstrated by
- Lederberg and Tatum
- Zinder and Lederberg
- Avery et.al.
- Select correct match
Column – I Column – II
a.Retting of fibres i) Pseudomonas putida
- Pollution control ii) Pseudomonas fluorescence
- Riboflavin iii) Bacillus brevis
- Gramicidin iv) Clostridium butylicum
1) a(ii), b(i), c(iv), d(iii)
2) a(ii), b(i), c(iii), d(iv)
3) a(i), b(iii), c(iv), d(iii)
4) a(iii), b(i), c(iv), d(ii)