How chemotaxis helps the bacteria in their survival?

One way that they help is by helping us digest our food. We have what are called intestinal flora, a group of many different bacteria in our digestive system that help us by breaking down food...

Bacteria helps us break down food. I believe they also help to break down dead organism and release the oxygen as well as nutrients of the organism back to the earth.

because they take over other bad bacterias and they can be good or bad

There are literally thousands. Some help us digest our food. Some process our food so that it is not toxic for us to even eat. Some process our foods to increase / add flavor. Some process our...

it decomposes dead stuff and gives the plant the nutrients from the dead thing.