I want to know about bacteria which are useful and how and also which are harmfu!

I want to know about bacteria which are useful and how and also which are harmful and how?

The good friendly bacteria, or probiotics, promote the body's natural immunity, keep us healthy and help our digestion. They are very necessary and may keep the bad bacteria level lower. There are many types of good bacteria in our body that we need--acidophilus is one that you may have heard of.

Inside each of us live vast numbers of beneficial bacteria which we need to have to stay in good health. Our gastrointestinal tract is home to more than 400 different species of bacteria weighing one and a half kilograms. This is a large quantity of working bacteria which perform very important functions in our body - from the mouth all the way down to the rectum. We live in harmony with them and they provide us with an excellent service if they are given a reasonable diet and kept in good health.

These hard working bacteria keep us healthy by

-increasing the absorption of minerals and vitamins and -improving digestion, especially of milk products (lactose intolerance). Our food or vitamins are only useful if they are properly absorbed and digested.
-improving our immune system by producing antimicrobial substances that deter various bad bacteria. This is important because many debilitating and degenerative diseases begin in the intestinal tract.
-increasing absorption of calcium. Important in the prevention of osteoporosis.
-producing B vitamins.
-supporting healthy liver function.
-normalising bowel elimination problems and promoting regularity.
-preventing intestinal tract infections like Candida and Helicobacter Pylori (present in stomach ulcer condition)
-alleviating bowel wind, bloating and belching.
-assisting in cholesterol management.
-protecting us against harmful bacteria, fungi and viruses.

Here is another article that you may find helpful/interesting:

http://www.livescience.com/humanbiology/...