Heterotrophic bacteria derive energy from organic compounds. They are widely distributed and most abundant forms. They may be aerobic or anaerobic. They are omnipresent and found in the food, soil, water. They help in recycling of natural substances.
They are mostly responsible for the decomposition of organic matter. They also live as a parasite and cause various diseases in plants, animals and humans. They are also present as a symbiont in organisms, e.g. Rhizobium in the root nodules of legumes, etc.
Bacteria are used for making curd, antibiotics, nitrogen-fixation, etc. Heterotrophic bacteria can decompose organic matter such as cellulose, keratin, lignin, chitin, etc.
What are the different types of Heterotrophic Bacteria?
According to their habitat, food source and association with other organisms, heterotrophic bacteria can be divided into three main categories:
- Parasitic – They derive their food from living organisms
- Saprophytic – They feed on dead and decaying organic matter
- Symbiotic – They live in symbiotic association with other organisms.
Heterotrophic Bacteria Types and Examples
Parasitic bacteria may be a parasite on animals or plants. Not all parasitic bacteria are pathogenic, e.g. microbial flora of the human body, present in skin, digestive tract, mucous membranes and other organs, coexist without harming.
Pathogenic heterotrophic bacteria are known to cause many diseases. They have different modes of infection and transmission. Some examples are:
Citrus canker – Xanthomonas axonopodis
Crown gall – Agrobacterium tumefaciens
Blight of beans – Xanthomonas campestris
Wildfire of Tobacco – Pseudomonas syringae
Granville wilt – Pseudomonas solanacearum
Cholera – Vibrio cholerae
Typhoid – Salmonella typhi
Tetanus – Clostridium tetani
Whooping cough – Bordetella pertussis
Lyme disease – Borrelia
Diphtheria – Corynebacterium diphtheriae
Diarrhoea – Escherichia coli
Tuberculosis – Mycobacterium tuberculosis
Gonorrhoea – Neisseria gonorrhoeae
Rhizobium present in root nodules of legumes is a common example of symbiotic bacteria. Bacteria present in the gut of humans and ruminants help in digesting food. They also help in producing vitamins.
They are the main decomposers of the food chain with fungi. They break down complex organic matter to simple compounds and assimilate them. They help in nutrient recycling. They decompose dead and decaying plants and animal remnants and help in biodegradation.