Is highly resistant to most antibiotics. In addition, the tb-causing bacteria readily spread from

person to person.

Legionnaires’ disease, a severe form of pneumonia, was first recognized at an American

Legion convention in Philadelphia, Pennsylvania, in 1976. It is caused by a previously unknown

bacterium, Legionella pneumophila, which is most often transmitted through infected water.

Lyme disease, a form of arthritis caused by the bacterium Borrelia burgdorferi, was first

recognized in Lyme, Connecticut, in 1975. A bite from a deer tick that carries the bacteria transmits

the disease to human beings.

A food-borne disease currently causing major concern in the United States, Canada, and

Western Europe is caused by a particular variant of the common intestinal bacterium Escherichia

coli, or E. coli for short.

Our immune system is designed to protect us against harmful bacteria. It works to keep our

normal microflora in check and also to eliminate invaders from outside the body.

In many cases the immune system can wipe out a bacterial infection on its own. But

sometimes people become so sick from a bacterial disease that they require medical treatment.

Antibiotics and other antibacterial drugs are the major weapons against disease-causing bacteria.

Immunization through vaccines is important in the prevention of infectious diseases caused

by bacteria. Vaccines expose a human being or other animal to a disease-causing bacterium or its

toxins without causing the disease. As a result of this exposure, the body forms antibodies to the

specific bacterium. These antibodies remain ready to attack if they meet the bacteria in the future.

Public health measures provide major controls against infectious disease. Especially

important are those measures leading to ready availability of clean water, safe food, and up-to-date

medical care.

Bacteria and the environment

Bacteria play a major role in recycling many chemical elements and chemical compounds in

nature. Without such bacterial activities as the recycling of carbon dioxide (CO2) life on Earth

would be impossible. Plants use CO2 to grow and in the process they produce the oxygen humans

and other animals breathe. Moreover, we would drown in garbage and wastes if bacteria did not

speed the decomposition of dead plant and animal matter.

Bacteria play a key role in making soil fertile. They convert nitrogen in Earth’s atmosphere

into the nitrogen compound ammonia, which plants need to grow.

Bacteria and fungi (yeasts and molds) are vital to another process that makes life on Earth

possible: the carbon cycle. They help produce the gas carbon dioxide (CO2), which plants take from

the atmosphere. During a part of the carbon cycle called photosynthesis, plants turn sunlight and

CO2 into food and energy, releasing oxygen into the atmosphere.

Bacteria are major players in cycles of other elements in the environment. Chemosynthetic

bacteria use chemical energy, instead of the light energy used by plants, to change CO2 into

something that other organisms can eat. Chemosynthesis occurs in vents at the bottom of the ocean,

where light is unavailable for photosynthesis but hydrogen sulfide gas, H2S, bubbles up from below

Earth’s crust.

Bioremediation refers to the use of microorganisms, especially bacteria, to return the

elements in toxic chemicals to their natural cycles in nature. It may provide an inexpensive and

effective method of environmental cleanup, which is one of the major challenges facing human

society today.

Bioremediation has helped in cleaning up oil spills, pesticides, and other toxic materials.