1) Food poisoning
The saprophytic bacteria cause decay of our food and make it unpalatable. Toxins are produced as a result of bacterial growth on the foodstuffs.
Due to this, food poisoning occurs. Clostridium botulinium causes a fatal form of food poisoning (Botulism).
Bacteria are causative agents of many diseases to plants, animals and humans. Cholera, typhoid, anthrax, plague are examples of animal and human diseases. Examples of plant diseases are citrus canker, wilt diseases, blights etc. 3)
Through nitrification, bacteria enhance the fertility of the soil. The denitrifying bacteria break down the nitrates into nitrites and nitrites into ammonia and then free nitrogen. This means that soil fertility is reduced due to the activities of such bacteria.