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	Where Living	Mode of Life
Rhizobium leguminosum (Rhizobiaceae)	Root nodules of Legumes	Mutualistic symbiotic
Rhizobium gallicum (Rhizobiaceae)	Root nodules of legumes	Mutualistic Symbiotic
Rhizobium bangladeshense (Rhizobiaceae)	Root nodules of lentils	Mutualistic Symbiotic
Bradyrhizobium japonicum	Root Nodules of LegumesSoybean	Mutualistic Symbiotic
Frankia spp.	Nodules of Casuarina, Alnus, etc	Mutualistic Symbiotic
Azobacter agilis	Aerobic and soil inhabiting	Free living
Clostridium pneumoniae	Anaerobic and soil inhabiting	Free living

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	Antibiotics	Action
Bacillus subtilis	Bactracin	Syphilis, Lymphonema or Reticulosis.
Bacillus polymyxa	Polymixin	Antifungal
Streptomyces rumosus	Teramycin	Intestinal and Urinary Infections
Streptomyces griseus	Streptomycin	Pneumonia, Meningitis, Tuberculosis and Local Infection.
Streptomyces fradiae	Neomycin	Hepatic encephalopathy, skin infections, ear infections
Streptomyces venezualae, S.lavendulae	Chloramphenicol, Chloromycetin	Typhus, Typhoid, Whooping cough, Bacterial Urinary Infections, A typical Pneumonia
Micromonosopora purpurea	Gentamycin	Effective against Gram (+) bacteria
Streptomyces erythreus	Erythromycin	Typhoid, Common Pneumonia and Diphtheria, Whooping Cough, etc.
Streptomyces aureofaciens	Tetracyclines	Osteomyelitis, Whooping Cough, Viral pneumonia, and Eye infections.
Aspergillus fumigatus	Fumagillin	It is used against Salmonella and Shigella.
Penicillium chrysogenum, P.notatum	Pencillin	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 Bifidobacteriumadolescentis. 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	Vitamin	Yield (mg/l)
Clostridium acetobutylicum	B₂ (Riboflavin)	0.097
C. butylicum	B₂ (Riboflavin)	0.120
Mycobacterium smegmatis	B₂ (Riboflavin)	0.060
Bacillus megaterium	B₁₂(Cobalamin)	0.51
Streptomyces olivaceus	B₁₂(Cobalamin)	3.31
Butyribacterium rettgeri	B₁₂(Cobalamin)	5.00
Micronospora sp.	B₁₂(Cobalamin)	11.5
Propionibacterium freudenreichii	B₁₂(Cobalamin)	19.0
P. shermanii	B₁₂(Cobalamin)	35.0
Pseudomonas denitrificans	B₁₂(Cobalamin)	60.0

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	Product Name	Uses
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	Foil®, M-Track®,M-One®,Trident®,Novardo®	It is highly effective against larvae of Colorado potato beetle and the elm leaf beetle(Xanthogaleruca luteola).
Bacillus thuringiensis var. aizawai	Certan®	It is used only for control of wax moth infestations in honeybee hives.
Bacillus popilliae and Bacillus lentimorbus	Grub Attack®	Effective against larvae (grubs) of Japanese beetle
Bacillus sphaericus	Vectolex CG®,Vectolex WDG®	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	Diseases	Site of Infection
Plant Pathogens:	Cell	Cell
Streptococcus scabies	Scab disease of potato	Potato tuber
Corynebacterium rependonicium	Ringrot disease of potato	Potato tuber
Xanthomonas campestris	Black rot disease of cabbage	Young branches, leaves and fruits of citrus
Erwinia atroseptica	Black rot disease of potato	Stem and tuber of potato
Erwinia amylovora	Pear diseases(Pyrus)	Vascular tissue of pear
Pseudomonas maculicola	Cauliflower spot disease	Cauliflower
Pseudomonas solanacaerum	Wilt disease of potato	Potato, tomato
Bacterium stewartii	Wilt disease of corn(Stewards disease)	Vascular tissue of corn
Agrobacterium rhizogens	Hairy root disease of apple	Meristematic tissue of apple
Pathogens for man	Cell	Cell
Salmonella typhi	Typhoid	Alimentary canal of man
Vibrio cholerae	Asiatic cholera	Intestinal tract of man
Mycobacterium tuberculosis	Tuberculosis	Lungs of man
Mycobacterium leprae	Leprosy.	Skin of man
Diplococcus spp.	Pneumonia	Lungs of man
Corynobacterium diptheriae	Diptheria	Throat of man
Streptococcus sp.	Rheumatism	Joints tendons, ligaments, bones, and muscles
Clostridium septicum	Gas gangrine	Muscle tissue
Clostridium tetani	Tetanus	Blood vascular system of man
Bacillus dysenteriae	Dysentery	Intestinal tract of man
Nesseria gonorrhoea	Gonorrhea	Urethra, rectum or throat
Leptospina hemorrahagiae	Jaundice	Liver
Animal Pathogens	Cell	Cell
Bacillus antracis	Anthrax disease	Cattle
Yersinia pestis	Plague	Rodents
Coxiella burnetti	Q fever	Birds and rats
Leptospira interrogans	Leptospirosis	Dog

image of Black rot disease of cabbage — Black rot disease of cabbage

image of Black rot disease of potato — Black rot disease of potato

Concluding Remarks

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.