Bacteria are one of the species of microorganism. It is an unicellular organism. These are harmful for our health and environment. These are responsible for infectious diseases like pneumonia, tuberculosis, diphtheria, syphilis, tooth decay, etc. Most of these disease-causing bacteria can be eliminated by sterilizing or disinfecting exposed surfaces, instruments, tools and other utilities. These methods include- application of heat, disinfectants, UV radiations, pasteurization, boiling, etc. At the same time, it is useful in fermentation, converting milk into curd,etc.
Bacteria also known as germs in common language are microscopic organisms that you won't be able to see with your naked eyes. Bacteria can be found everywhere be it outside your body or inside. Bacteria can survive in any environment, no matter if it is cold or hot. Some Bacteria may be good for you while others may be bad. The 4 types of Bacteria are- Coccus, Bacillus, Spirillum and Vibrio.