Some of the major harmful activities of bacteria are as follows:
1. Food poisoning 2. Spoilage of food 3. Destruction of domestic articles 4. Reduction of Soil fertility 5. Denitrification 6. Biowar/Bioterrorism.
1. Food poisoning:
Bacterial toxins present in food causes food poisoning. This leads into nausea, vomiting, abdominal discomfort diarrhea and even death. The food poisoning bacteria are Clostridium botulinum, Salmonella enteritis, Staphylococcus aureus etc.
2. Spoilage of food:
Souring of milk, rotting of vegetables and meat are caused by many saprotrophic bacteria.
3. Destruction of domestic articles:
Spirochaete cytophaga cause cellulose degradation thereby destroying textiles, wooden articles and canvas.
4. Reduction of Soil fertility:
Denitrifying bacteria like Thiobacillus denitrificans, Micrococcus denitrificans, Pseudomonas aeroginosa convert soil nitrates and ammonia into free nitrogen and thus reduce the soil fertility.
The denitrifying bacteria decompose nitrogen compound into free nitrogen.
The improved variety of infective agents (bioweapons) are widely been used as an agent of effective weapon of bioterrorism. The antibiotic resistant microorganisms like Bacillusanthracis are being produced at large scale and when these are released at strategic locations, they cause acute infection of anthrax. The spores of B. anthracis can be produced and stored in a dry from keeping them vaible for decades in storage or after release. An attack with bioweapons (antibiotic resistant strains mould) leads to spread of communicable diseases like anthrax and plague etc.