Answer:
- Bacteria are unicellular prokaryotic organisms which are found in different environments.
- Bacteria are not only responsible for causing diseases but, some of them are also very useful to us. The two ways in which bacteria are useful for us are:
1. They aid in digestion- Our gut is enriched with bacteria and, they form what is known as the microbiotic flora of the gut. If this flora is disturbed, it is often associated with digestive problems and other diseases. One such example of a bacteria that aids in digestion is E.coli.
2. Production of antibiotics - antibiotics are the substances produced by bacteria that are used to kill bacteria and hence are very useful as they aid in controlling bacterial diseases. An example is Streptomyces.