Bacteria are microscopic one-celled organisms. Only some of them cause illness.There is a bacteria that I personally think is very bad called the Vibrio vulnificus -- also known as “flesh-eating” bacteria and it thrives in the summer.

 

Bacteria (sing. bacterium) are very small organisms. They are single celled microorganisms. Bacterial cells do not have a nucleus(the center of an atom), and most have no organelles with membranes around them. Most have a cell wall. They do have DNA, and their biochemistry is basically the same as other living things. They are amongst the simplest and the oldest organisms. They function as independent organisms.

Almost all bacteria are so tiny they can only be seen through a microscope. Bacteria are made up of one cell, so they are a kind of unicellular organism. They are among the simplest single-celled organisms on Earth, and were one of the earliest forms of life. They include a number of extremophiles which live in extreme habitats.

There are probably more individual bacteria than any other sort of organism on the planet. Most bacteria live in the ground or in water, but many live inside or on the skin of other organisms, including humans. There are about bacterial cells as human cells in each of our bodies. Some bacteria can cause diseases, but others help us in everyday activities like digesting food (gut flora). Some even work for us in factories, producing cheese and yogurt.