Which Bacteria Are Useful to Humans?

At any given moment, the human body contains more bacteria cells than human cells, in fact, a hundred times more. It is not possible for the human body to survive without the millions of bacteria that live on human skin and in the nose, mouth and the rest of the digestive tract. Each human mouth contains a minimum of 25 bacterial species, and one drop of saliva can contain as many as 40 million bacteria cells, according to the University of North Carolina.

Digestion

• Naturally occurring bacteria are now part of a major health industry, with the production of bacterial concoctions, such as powders, drinks and dairy products. Probiotic products contain lactobacilli and bifidobacterium, bacteria found naturally in the human intestines. Intestinal bacteria helps people digest food and protect them from diseases and viruses by preventing growth of harmful bacteria. An imbalance of intestinal flora can cause illnesses such as diarrhea and stomach upset.

Immune System

• Beneficial bacteria clean toxins from the bloodstream and help promote a healthy immune system. They also produce vitamins vital to human survival and well-being. According to Better Health Research, tests show that bacteria, such as bacillus subtilis, help immune system cells to reproduce and form small antibodies within the immune system that help fight viruses and harmful bacteria. They hope studies will lead to the treatment of disease using bacteria.

Food Preparation

• Many varieties of cheese, sausages and sauerkraut depend on fermenting bacteria to produce their flavor. Even cocoa and coffee beans need bacteria to attain a desirable flavor. Yeast is bacteria found in bakery items and yogurt as well as other fermented milk products. Yeast reduces spoilage and enhances tolerance for lactose-intolerant people. Lactic acid is the bacteria used to make cheese and is what gives cheese its texture.

Plant Growth

• People need to eat plants to survive. Bacteria break down fertilizers and convert nitrogen into nitrates so plants are able to absorb them, helping plants grow and produce fruit. Rhizobacteria produce chemicals that stimulate plant growth. Bacteria known as lithotrophs obtain energy from nitrogen, sulfur, iron and hydrogen compounds in order to degrade pollutants.

Environment

• One of the earth's natural gases, methane, lives in an oxygen-free environment, such as the bottoms of swamps and lakes. Bacteria produce methane by breaking down dead plant and animal matter. Bacteria are responsible for the natural process of decomposition. Many bacteria species are capable of eating oil and other harmful substances, helping the world clean up oil spills and gasoline leaks. Alcanivorax is just one of 16 oil-eating bacteria discovered as of 2010.