CBSE - XII Science - Biology - Microbes in Human Welfare
Microorganisms as fertilisers
- Biofertilisers are the microorganisms which enrich the soil by enhancing the availability of nutrients to the crops.
- The microorganisms include bacteria, cyanobacteria and mycorrhizal fungi.
- Bacteria and cyanobacteria bring about nitrogen fixation while mycorrhizal fungi withdraw minerals from organic matter for the plant with which they are associated.
- Phosphate is also solubilised by some bacteria and fungi that form association with the plant roots.
- Examples of biofertilisers: Free living nitrogen fixing bacteria (Azotobacter), free living nitrogen fixing cyanobacteria (Nostoc), loose association of nitrogen fixing bacteria (Azospirillum), symbiotic nitrogen fixing bacteria (Rhizobium), microphos biofertilisers (Aspergillus species) and mycorrhiza (Glomus species).
Microorganisms as bioweapons
- Biological weapons are toxic materials produced from pathogenic microbes or artificially manufactured toxic substances that are used to intentionally interfere with the biological processes of a host.
- These substances work to kill or incapacitate the host.
- Biological weapons may be used to target living organisms such as humans, animals or vegetation.
- They may also be used to contaminate nonliving substances such as air, water and soil.
- Examples: Bacillus anthracis, Clostridium botulinum, Clostridium perfringens.
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