There are different types. Some are, some arent
it depends on the type of the bacteria. also beneficial bacterias outnumber the population of harmful bacterias.
yes.some of the bacterias are useful but some are not.some specific type of bacterias are using as medicine also.
In your body
e.coli and septic tank
yes, if it is not pasteurized first to kill the bacterias.
lion are useful and harmful
It is not harmful. Also it is not useful
The changes talking place in our surroundings and which are useful to us are called Useful changes. The changes which are not useful but harmful are called Harmful changes
useful
i think its both harmful and useful
bacterias are useful for humans as they are used to make injections, bread
Ozone at ground level is harmful. It is useful in stratosphere as it protects us from harmful UV rays.