Bacteria in agriculture and industry

By recycling certain chemical elements and compounds, bacteria make plant and animal life

possible.

Through the process of nitrogen fixation, bacteria turn nitrogen in the air into nutrients that

crops and other plants need to grow. Some of the nitrogen-fixing bacteria attach to the roots of

plants. Through the carbon cycle, bacteria produce the carbon dioxide that plants require for

photosynthesis. Bacteria that live in the stomachs of cud-chewing animals, such as cows and sheep,

help the animals digest grasses.

Bacteria also can be harmful in agriculture because of the major diseases of farm animals

they cause. Many of the bacteria that cause infectious diseases in farm animals resemble those that

cause similar human diseases.

The bacterium Brachyspira hyodysenteria causes a type of diarrhea in pigs that can be

disastrous for pig farmers. Many infectious diseases of farm animals also affect wild animals, such

as deer. Wild animals, in turn, can infect domestic animals, including cats and dogs.

Bacteria are of major importance in the food industry. On the one hand, they cause food

spoilage and foodborne diseases, and so must be controlled. On the other hand, they improve food

flavor and nutrition.

The dairy industry provides prime examples of bacteria’s harmful and helpful roles. Before

the introduction of pasteurization in the late 1800s, dairy products were major carriers for bacteria

that caused such illnesses as tuberculosis and rheumatic heart disease.

On the helpful side, bacteria contribute to the fermentation (chemical breakdown) of many

dairy products people eat every day. Yogurt, considered a healthful food, is produced by bacterial

fermentation of milk.

The variety of fermented foods we eat ranges from pickles, olives, and sauerkraut to

sausages and other cured meats and fish, chocolate, soy sauce, and other products. In most of these

fermentations, bacteria that produce lactic acid play major roles. Alcohol-producing yeasts are the

primary fermentors in the manufacture of beer and wine, but lactic-acid bacteria also are involved,

especially in making wine or cider. Bacteria that produce acetic acid can convert wine, cider, or

other alcoholic beverages to vinegar.

Bacteria are very important in sewage treatment. Standard sewage treatment involves

multiple processes: 1) aerobic phase encouraging oxygen-using bacteria to break down organic

material in the sewage, such as human wastes, to acids and CO2; 2) anaerobic phase (bacteria

that cannot tolerate oxygen) breaking down the sludge to produce methane gas, which can then be

used as a fuel to power the treatment facility.

Bacteria are also effective in cleaning up harmful wastes through bioremediation. In this

process bacteria and other microorganisms convert toxic or otherwise objectionable wastes, such as

pesticides and oil spills, to harmless or even useful products.

An interesting industrial process carried out by bacteria is the recovery of valuable minerals

such as copper from ores. The most important copper ores are copper sulfides, which may contain

only a small percentage of copper.

Some chemical reactions in which bacteria participate are harmful rather than helpful to

industry. Bacteria are major agents of metal corrosion (wearing away) through the formation of

rust, especially on metals containing iron.

Bacteria have been at the center of recent advances in biotechnology—the creation of

products for human benefit through the manipulation of biological organisms. Biotechnology itself

dates back at least as far as ancient Egyptian civilization. Paintings on the walls of Egyptian tombs

depict the brewing of beer, which uses microorganisms in the fermentation process.

Biotechnology grew steadily during the 20th century. In the 1970s scientists used

information about replication of viruses and bacteria and about DNA synthesis (manufacture) to

begin the genetic engineering of bacterial cells.

Bacteria play a role in the production of other products, including certain plastics and

enzymes used in laundry detergents. They also produce many antibiotics, such as streptomycin and

tetracycline. Since the 1980s, bacteria have gained importance in the production of many bulk

chemicals, including ethanol, a form of alcohol made from fermented corn.

Sterilization and disinfection—processes for destroying microorganisms—are integral parts

of the food industry. For example, canning involves heating foods to temperatures of 121oC (250oF)

to kill all organisms, including the most heat-resistant bacterial cells.

Demand for better sterilization and disinfection methods in medicine and other industries

has increased since the 1970s because of fear of spreading infection by the human