Bacteria are the plural of bacterium, which are microscopic one-celled organisms. They are found everywhere and can be harmful, as in infections; or they can be beneficial, as in fermentation or decomposition. Five types of bacteria are: Coccus, Bacillus, Spirillum, Rickettsia, and Mycoplasma.
Here are examples of bacteria that are spherical shaped (Coccus):
Examples of bacteria that are rod shaped (Bacillus):
Here are examples of bacteria that are spiral shaped and gram-negative (Spirillum):
Here are examples of bacteria that behave like viruses and can't live outside living cells (Rickettsia):
Here are examples of bacteria that do not have a cell wall and may be rod shaped or spherical (Mycoplasma):
Here are examples of bacteria used in fermentation:
Here are examples of bacterial infections with the bacteria that cause them:
Now you have seen lots of different examples of bacteria and some of the things that bacteria can do.