Economic Importance of Bacteria
Bacteria are single-celled microscopic organisms which can live in different types of environment and survive in extreme conditions. They contain high protective coating in their body, which enhances to live any severe conditions. Many bacteria possess flagella which help them to move around, but some have hair-like structures which help them live in hard surfaces and the cells of the human body. Bacteria possess significant economic importance concerning human being. Bacteria cause many harmful effects, including diseases in man, animals and plants. At the same time, they show many beneficial effects.
Beneficial Effects of Bacteria
Role of Bacteria to Increase in Soil Fertility
Plants do not utilize atmospheric nitrogen directly. In this case, there are many symbiotic and free-living bacteria which can fix free nitrogen from the atmosphere and converts it into nitrogenous compounds. Azotobacter is soil-inhabiting bacteria which fixes the atmospheric free nitrogen and turns it into organic forms; some amount of which mixes with the soil and increase the fertility of the soil. Another free-living soil bacterium is Clostridium, which also increases soil fertility. Rhizobium is a symbiotic bacterium which lives in the root nodules of leguminous plants.
Nitrifying Bacteria: Nitrifying bacteria are chemolithotrophic aerobic microorganisms (family Nitrobacteraceae) which play an essential role in the nitrogen cycle, convert the soil ammonia to nitrates and make the usable compounds by plants. Some notable nitrifying bacteria are Nitrosococcus, Nitrosomonas, Nitrobacter, Nitrococcus, etc. These bacteria receive their energy from the inorganic nitrogen compounds. They can convert the soil ammonia into nitrate by the oxidation. In this case, Nitrosomonas bacterium can convert ammonia to nitrous acid by the oxidation while the Nitrobacter can convert nitrous acid to nitric acid by the oxidation.
Proteins of dead plants and animals are converted into organic nitrogenous substances and amino acids by the action of some saprophytic bacteria. Besides these, many ammonifying bacteria such as Clostridium sp., Proteus vulgaris, Bacillus ramosus, etc. can convert amino acids R-CH(NH2)-COOH] into ammonia(NH3). This ammonia is mixed with carbon dioxide (CO2) and water (H2O) to form (NH4)2CO3 (ammonium carbonate) which are used as a nitrogen source by many plants.
There are many nitrogen-fixing bacteria which can fix nitrogen from the direct atmosphere. Among them, Rhizobium bacteria live in the root nodules of leguminous plants(Fabaceae) such as alfalfa, peas, beans, lentils, soy, and peanuts, etc. They have the ability to fix atmospheric nitrogen about 100-400 kg/hectare/year. Besides these, other nitrogen-fixing filamentous bacteria, Frankia sp. that live in root nodules of legumes (family Fabaceae) or actinorhizal plants which can fix nitrogen about 150 kg/ hectare/year from the atmosphere with the help of nitrogenase enzyme. These bacteria provide sufficient nitrogen for the host plants. For this reason, actinorhizal plants can quickly grow and colonize in any low nutrient soil conditions. Clostridium and Azotobacter are also free-living nitrogen fixers which can fix nitrogen about 25-50 kg/hectare/year.
The following table shows the list of some Nitrogen Fixing Bacteria:
Name of Bacteria
Mode of Life
Rhizobium leguminosum (Rhizobiaceae)
Root nodules of Legumes
Rhizobium gallicum (Rhizobiaceae)
Root nodules of legumes
Rhizobium bangladeshense (Rhizobiaceae)
Root nodules of lentils
Root Nodules of LegumesSoybean
Nodules of Casuarina, Alnus, etc
Aerobic and soil inhabiting
Anaerobic and soil inhabiting
Role of Bacteria in Dairy Industry
Lactic acid bacteria (LAB) play an important role in the fermentation process in the dairy industry. Some lactic acid bacteria (LAB) such as Streptococcus lactis, S. thermophilic, Lactococcus lactis, Lactobacillus plantarum, Lactobacillus casei, Lactobacillus acidophilus, Lactobacillus helveticus, Lactobacillus bulgaricus, etc. are used to produce butter, cheese, curd, etc. These bacteria make fermentation the lactose in the milk to produce lactic acid, which helps in curd coagulation and texture formation during the cheese production. During cheese production, the low pH helps to keep in check the growth of pathogen and spoilage organisms. In this case, the LAB converts lactose sugar to glucose and then glucose to lactic acid. Lactic acid sours the milk and coagulates the casein (milk protein) and forms the curd.
Role of Bacteria in the Vinegar industry
Acetic acid bacteria (AAB) are used in the vinegar industry for the production of certain foods and vinegar. These are Gram-negative bacteria which belong to the family Acetobacteraceae. They can produce acetic acid during oxidative fermentation by performing oxidation reaction producing vinegar as a byproduct. For the production of ascorbic acid, gluconic acid, dihydroxyacetone, and cellulose, acetic acid bacterias` oxidation mechanism is utilized. Besides these, acetic acid bacterias are also used as biocatalysts for the improvement of eco-friendly fermentation processes.
The following list shows the most frequently used acetic acid bacteria (AAB) species for the production of vinegar:
- Acetobacter aceti,
- A. cerevisiae,
- A. malorum,
- A. oeni,
- A. pasteurianus,
- A. pomorum,
- Gluconacetobacter entanii,
- G. liquefaciens,
- G. oxydans,
- Komagataeibacter europaeus,
- K. hansenii,
- K. intermedius,
- K. medellinensis,
- K. oboediens,
- K. xylinus
Role of Bacteria in Medicine
Antibiotics are the chemical materials which are produced from microorganisms for preventing the growth and development of other microorganisms. Many bacteria are used in the pharmaceutical industry for the production of antibiotics, probiotics, drugs, vaccines, starter cultures, insecticides, medically-useful enzymes, etc. Bacteria can also be programmed to make various medicines in genetic engineering technology. Antibiotics like Tetracyclines, erythromycin, streptomycin, rifamycin and ivermectin are produced by using bacteria Streptomyces spp. while bacitracin and polymyxin are produced from Bacillus and Paenibacillus species. Bacteria are also used in the manufacture of vaccines. These vaccines are used against infectious diseases such as whooping cough, diphtheria, typhoid fever, tetanus, and cholera. In the twentieth century, the widespread uses of antibiotics and vaccination (immunization) against infectious disease have radically increased the lifespan of individuals in developed countries.
The following table shows the list of notable bacteria which are useful sources of antibiotics:
Name of bacteria
Syphilis, Lymphonema or Reticulosis.
Intestinal and Urinary Infections
Pneumonia, Meningitis, Tuberculosis and Local Infection.
Hepatic encephalopathy, skin infections, ear infections
Streptomyces venezualae, S.lavendulae
Typhus, Typhoid, Whooping cough, Bacterial Urinary Infections, A typical Pneumonia
Effective against Gram (+) bacteria
Typhoid, Common Pneumonia and Diphtheria, Whooping Cough, etc.
Osteomyelitis, Whooping Cough, Viral pneumonia, and Eye infections.
It is used against Salmonella and Shigella.
Penicillium chrysogenum, P.notatum
Gnonorrhea, Rheumatic Fever Tonsilitis, Sore Throat, some Pneumonia types.
Role of Bacteria in the Production of Vitamins
Different probiotic bacteria have several health benefits, including vitamin production. These bacteria have commercial importance for the production of Vitamin including the species Lactococcus lactis, Lactobacillus gasseri, Lactobacillus reuteri, Pseudomonas denitrificans, Clostridium butylicum and Bifidobacterium adolescentis. They are able to synthesize vitamin K and B vitamins, such as biotin, nicotinic acid, cobalamin (Vitamin B12), panthotenic acid, folates, pyridoxine, riboflavin (Vitamin B2), and thiamine, etc. Among these bacteria, Pseudomonas denitrificans is used to produce Cobalamin (Vitamin B12) while Clostridium butylicum is used to synthesize Riboflavin (Vitamin B2).
The following table shows the list of bacteria with corresponding yields of Vitamin):
Name of Bacteria
Role of Bacteria in Wastewater Treatment
Wastewater is very detrimental to the environment and acts as a source of several types of waterborne diseases. There are many well-known bacteria which play an essential role in keeping sewage clean. In this case, putrifying bacteria treat and purify the wastewater and make it less harmful to our surrounding environment. These bacteria work under the anaerobic condition to remove the solid and semi-solid constituent of sewage. After finishing the treatment process, the constituents get decayed and liquefied which are filtered, and the liquid is drained out in the river.
Role of Bacteria in Butanol and Acetone Production
Butanol or butyl alcohol (C4H9OH) and acetone or propanone [(CH3)2CO] are produced by using bacteria in a different industry. In this case, Clostridium acetobutylicum is the most well-known and widely used species for the production of Butanol and acetone as a commercial basis. Clostridium beijerinckii is also used to produce Butanol and acetone with excellent results.
Role of Bacteria in Fiber Retting
Microbiological processes are used for discharge of the fiber. In this case, there are many bacteria help in the retting of jute, hemp and flax fibers. These bacteria grow under low oxygen condition, which can cause hydrolysis of the pectic substances that help to blind the fibers with the stem and make easy for the discharge of the fibers. The following list shows some notable bacteria species which play an important role in the process of fiber retting.
- Achromobacter parvulus
- Aerobacter cloacae
- Aerobacter aerogenes
- Bacillus brevis
- Bacillus cereus
- Bacillus megaterium
- Bacillus sphaericus
- Bacillus subtilis
- Clostridium butylicum
- Clostridium beijerinckii
- Clostridium saprogenes
- Clostridium perenne
- Pseudomonas aeruginosa
- Pseudomonas pseudomallei
Role of Bacteria for Curing of Tea and Tobacco
Tea and tobacco are cured to give particular taste, flavor or smell by using some bacteria. In this case, the helpful bacteria are Bacillus megatherium and Micrococcus candisans which are used in the curing and fermentation of tea and tobacco leaves for commercial purposes.
Role of Bacteria for Biological Control of Insect
Biological control is also known as biocontrol. It is the process for controlling different types of pests like insects, weeds, mites, and plant diseases by using other organisms. Many microorganisms such as a bacterium, virus, fungus, or protozoan, etc. are used as the active ingredient for the preparation of microbial insecticides to control many different kinds of pests. These microbial insecticides are essentially nonpathogenic and non-toxic to humans, wildlife, and other organisms. Bacillus thuringiensis is more effective to control Aedes aegypti while B. sphaericus strain is effective to control Culex quinquefasciatus. In this case, Bacillus thuringiensis secrete proteinaceous substances which are highly toxic to caterpillars and insects under the order Lepidoptera.
The following table shows the list of Bacteria, product name and their uses.
Name of Bacteria
Bacillus thuringiensis var. kurstaki
Bactur®, Caterpillar Killer®, Bactospeine®, Bioworm®, Javelin®, Dipel®, Futura®, Thuricide®,SOK-Bt®, Tribactur®, Worthy Attack®,Topside®,
Effective for foliage-feeding caterpillars and Indian meal moth of stored grain.
Bacillus thuringiensis var. israelensis
Aquabee®, Bactimos®, Gnatrol®, LarvX®, Skeetal®, Mosquito Attack®, Vectobac®, Teknar®,
Effective against larvae of Aedes and Psorophora mosquitoes(Psorophora ciliata), black flies, and fungus gnats only.
Bacillus thuringiensis var. tenebrinos
It is highly effective against larvae of Colorado potato beetle and the elm leaf beetle(Xanthogaleruca luteola).
Bacillus thuringiensis var. aizawai
It is used only for control of wax moth infestations in honeybee hives.
Bacillus popilliae and Bacillus lentimorbus
Effective against larvae (grubs) of Japanese beetle
Effective against larvae of Culex, Psorophora, and Culiseta mosquitos, larvae of some Aedes spp.
Role of Bacteria in the Degradation of Petroleum
Hydrocarbon contamination is one of the major environmental problems today. It occurs due to the accidental releases of petroleum products from the petrochemical industry, oil tankers, ships, etc. The ultimate natural mechanism is the microbial degradation which can clean up the pollutants of petroleum hydrocarbon from the environment. There are many indigenous microorganisms which live in water and soil, and they can eliminate hydrocarbon contaminants. The following bacteria species can degrade hydrocarbon pollutants from crude oil:
- Pseudomonas fluorescens,
- P. aeruginosa,
- Bacillus subtilis
- Alcaligenes sp.
- Acinetobacter lwoffi
- Flavobacterium sp.
- Micrococcus roseus, and
- Corynebacterium sp.
Role of Bacteria for Decomposition of Dead Animals
Decomposition is the natural process which breaks down the dead animal or plant tissue by the action of different types of the organism such as invertebrates, fungi and bacteria. These organisms are known as decomposers. In this case, some bacteria play an essential role to decompose the dead organic matters into an inorganic form which increase the fertility of the soil by mixing with it, and finally the plants absorb it as nutrients.
Harmful Effect of Bacteria
Role of Bacteria in Food Spoilage
Some bacteria cause food Spoilage. Micrococcus can cause vegetable spoilage, Pseudomonas, Clostridium can cause deterioration of meat while Enterobacter causes decay of syrup, Acetobacter can cause decay of orange. Streptococcus, Micrococcus and Lactobacillus also can cause decay of milk and different milk products. Sometimes foods are poisoned by the bacteria like Streptococcus aureus and Clostridium botulinum. Clostridium botulinum causes botulism disease by producing exotoxin showing the symptoms like double vision, respiratory disturbances, and swelling of the tongue. By releasing exotoxins in foods which makes the food unsuitable for the consumption of human being. Under favourable temperature and conditions, bacteria grow in food materials and change the appearance, flavour and smell of food. By consuming those foods, different types of diseases such as gastroenteritis, dysentery, etc. are exposed, even death may occur.
Role of Bacteria in Water Pollution
Water is polluted by different bacteria which make the water unsuitable for drinking. Those polluted water are transmitted by drinking and can cause diseases like cholera (Vibrio cholera), typhoid (Salmonella typhi) and bacillus dysentery (Shigella dysenteriae).
Role of Bacteria in the Reduction of Soil Fertility
Moist soil-inhabiting bacteria are capable of transforming soil nitrates into gaseous nitrogen. This process is called denitrification, and those bacteria are called denitrifying bacteria. By the process of denitrification, the following bacteria such as Pseudomonas, Micrococcus, Thiobacillus, Achrobacter Thiobacilus, Micrococcus, Achrobacter, Bacillus denitrificus etc. convert nitrates of the land into gaseous nitrogen; as a result, a good loss of nitrogen occurs from the soil causing reduction of soil fertility.
Role of Bacteria as Disease-Causing Agents
Many parasitic bacteria induce diseases in plants and animals, including human. Diseases cause by different types of bacteria in plants decrease the yield of crops. A list of pathogenic bacteria, the respective diseases and their site of infection are shown in the following table:
Name of Bacteria
Site of Infection
Scab disease of potato
Ringrot disease of potato
Black rot disease of cabbage
Young branches, leaves and fruits of citrus
Black rot disease of potato
Stem and tuber of potato
Vascular tissue of pear
Cauliflower spot disease
Wilt disease of potato
Wilt disease of corn(Stewards disease)
Vascular tissue of corn
Hairy root disease of apple
Meristematic tissue of apple
Pathogens for man
Alimentary canal of man
Intestinal tract of man
Lungs of man
Skin of man
Lungs of man
Throat of man
Joints tendons, ligaments, bones, and muscles
Blood vascular system of man
Intestinal tract of man
Urethra, rectum or throat
Birds and rats
Bacteria are single-celled microscopic organisms which can live in different types of environment and survive in extreme conditions. They contain high protective coating in their body, which enhances to live any severe conditions. Many bacteria live in the stomach and mouth of a human. They are also found in soil, water, food and surface areas of our environment. There are many bacteria which live in the digestive system or gut of the human body. They help digestion of food and make the body healthy. Some bacteria provide oxygen which is used to make antibiotics while some other bacteria can decompose dead leaves, release CO2 and nutrients in the environment, which is essential for the plant's growth. Besides these, many bacteria show harmful effects on plants, animals and human being.