Bacteria are ecologically very important. They are highly adaptable as a group and are found nearly everywhere. They are able to decompose organic matter and play a significant role in the completion of cycles of nitrogen, phosphorus, sulfur and carbon.
Bacteria are used in number of industries, including food, drugs (production of antibiotics and vaccines) and in biotechnology. Bacteria are also responsible for spoilage of food and vegetables. Many plant pathogens adversely affect the agricultural industry.
Bacteria are very contmon pathogens of humans. Approximately 200 species are known to cause diseases in humans. Many bacteria normally inhabit the bodies of man and other animals.
Control of bacteria
Control of microorganisms is essential in home, industry as well as in medical fields. By controlling microorganisms one can prevent and treat diseases, spoilage of foods and other industrial products can be inhibited by controlling microorganisms.
Microorganisms can be controlled by various methods.
Physical methods: in this, steam, dry heat, gas filtration and radiation are used to control bacteria. The process in which we use physical agents to control bacteria/microorganism is known as sterilization process. Sterilization is destruction of all life forms.
High temperature is usually used in microbiological labs for control of microbes, both dry heat and moist heat are effective. Moist heat causes coagulation of proteins and kills the microbes. Dry heat causes oxidation of chemical constituents of microbes and kills them.
Certain electromagnetic radiations below 300 nm are effective in killing of microorganisms. Gamma rays are in general used for sterilization process.
Heat sensitive compounds like antibiotics, seras , hormones etc can be sterilized by means of membrane filters.
One can use antiseptics, disinfectants and chemotherapeutic agents for microbial control. Chemical substances used on living tissues that inhibit the growth of microorganism are called antiseptics.
The important chemical agents used for disinfection are oxidizing and reducing agents. For example halogens and phenols, hydrogen peroxide, potassium permanganate, alcohol and formaldehyde etc. inhibit the growth of vegetative cells and are used on nonliving materials.
Chemotherapeutie agents and antibiotics work with natural defense and stop the growth of bacteria and other microbes. These are sulfonamides, tetracycline, penicillin, etc. they destroy or inhibit the growth of microorganisms in living tissues.
Microbicidal effect is one that kills the microbes immediately
Microbistatic inhibits the reproductive capacities of the cells and maintains the microbial population at constant size.
Modes of action of different chemical and physical agents of control vary. Damage can result malfunctions in cell wall. Cell membranes, cytoplasmic enzymes, or nucleic acid.
Immunization and vaccination: methods of prevention and treatement that have been introduced to control microbial diseases include immunization (e.g. vaccination), antisepsis (procedures to eliminate or reduce the possibility of infection), chemotherapy and public health measures (e.g. water purification, sewage disposal, and food preservation).
Pasteur made many discoveries concerning the eause and prevention of infectious diseases. In 1880’s he isolated the bacterium responsible for chicken cholera. He grew it in a pure culture. To prove that he really had isolated the bacterium responsible for this disease Pasteur made use of the fundamental techniques devised by Koch. He arranged experiments for a public demonstration in which he repeated an experiment that had been successful in many previous trials in his laboratory.
He inoculated healthy chicken with his pure cultures and waited for them to develop chicken cholera and die. But to his dismay, the chickens failed to get sick and die. Reviewing each step of the experiment, Pasteur found that he had accidentally used the cultures several weeks old instead of fresh one grown especially for the demonstration. He soon discovered that somehow bacteria could lose their virulence, or ability to produce disease, after standing and growing old. But these attenuated, or less virulent, bacteria could still stimulate the host (in this case the chicken) against infection due to subsequent exposure to the virulent organism.
Pasteur next applied this principle of inoculation with attenuated cultures to the prevention of anthrax, and again it worked. He called the attenuated cultures of bacterial vaccine (aterm derived from the latin Vacca, “cow”) and immunization with attenuated cultures of bacteria, vaccination.
Pasteur honoured Edward Jenner (1749-1823), who had successfully vaccinated a boy against small pox in 1796. Jenner had learned that milkmaids who contracted cowpox from the cows, they milked, never subsequently contracted the much more virulent small pox. Accordingly he tested this hypothesis by inoculating young James Phipps first with cowpox causing material and later with small pox causing material. The boy did not get small pox.
Then Pasteur also made a vaccine for hydrophobia, or rabies, a disease transmitted to people by bites from rabid dogs, cats, and other animals.