MICROBIOLOGY - REPORT

							THE GROWTH OF BACTERIAL CULTURES

Control of Microbial Growth
The factors or agents that influence the growth of microorganisms are subject to continual study. On the basis of these studies, researchers learn how beneficial microbes can be encouraged to grow while growth of pathogenic microbes can be controlled, inhibited, or destroyed.

Control of certain microorganisms is important: (1) to prevent and control infectious diseases in humans, animals, and plants; (2) to preserve food; (3) to prevent contaminating microbes from interfering with certain industrial processes; and (4) to prevent contamination of pure culture research.

Preventing the spread of infectious diseases and controlling infections require many different procedures. The source of infection can be controlled by: (1) destroying or inhibiting disease-causing microbes; (2) blocking the sources, routes, and vectors of transmission of disease agents; and (3) protecting an infected person from the consequences of disease by building up the body’s defenses and administering appropriate chemotherapeutic drugs.

Encouraging the Growth of Microorganisms In Vitro
There are many reasons why the growth of microorganisms is encouraged in microbiology laboratories. For example, technologists and technicians who work in clinical microbiology laboratories must be able to isolate microorganisms from clinical specimens and grow them on culture media so they can gather information that will enable identification of any pathogens that are present.

In microbiology research laboratories, scientists must culture microbes so that they can learn more about them, harvest antibiotics, and other microbial products, test new antimicrobial agents, and produce vaccines. Microbes must also be cultured in genetic engineering laboratories and in the laboratories of certain food and beverage companies, as well as other industries.

Culturing Bacteria in the Laboratory
In many ways, modern microbiology laboratories resemble those 50, 100, or even 150 years ago. Today’s laboratories still use many of the same basic tools that were used in the past. For example, microbiologists still use compound light microscopes. Petri dishes containing liquid culture media, Bunsen burners, wire inoculating loops, bottles of staining reagents, and incubators.

However, a closer inspection will reveal many modern, commercially available products and instruments that would have been inconceivable in the days of Louis Pasteur and Robert Koch.

Bacterial Growth
Bacterial growth refers to an increase in the number
of organisms rather than an increase in their size. When each bacterial cell reaches its optimum size, it divides by binary fission into two daughter cells. On solid medium, binary fission continues through many generations until a colony is produced. A bacterial colony is a mound or pile of bacteria containing millions of cells. Binary fission continues for as long as the nutrient supply, water, and space allow and ends when the nutrients are depleted or the concentration of cellular waste products reaches a toxic level.

The time it takes for one cell to become two cells by binary fission is called the generation time. The generation time varies from one bacterial species to another. Bacteria with short generation times are referred to as rapid growers, whereas those with long generation times are referred to as slow growers.

Inhibiting the Growth of Microorganisms In Vitro
In certain environments, it is necessary or desirable to inhibit the growth of microbes. In hospitals, nursing homes, and other healthcare institutions, for example, it is necessary to inhibit the growth of pathogens so that they will not infect patients, staff members, or visitors. Other environments in which it is necessary or desirable to inhibit microbial growth include food and beverage processing plants, restaurants, kitchens, and bathrooms.

Definition of Terms
Sterilization
is the complete destruction of all microorganisms, including cells, spores, and viruses.  when something is sterile, it is devoid of microbial life.  can be accomplished by dry heat, autoclaving (steam under pressure), gas, various chemicals, and certain types of radiation.


Disinfection
 is

the destruction or removal of pathogens from nonliving objects by physical or chemical methods.

Pasteurization
used to eliminate pathogens from milk and most other beverages.  is not a sterilization procedure, because not all microbes are destroyed.
 is

Disinfectants
chemicals used to disinfect inanimate objects, such as bedside equipment and operating rooms.  are strong chemical substances that cannot be used on living tissue.
 are

Antiseptics
 are

solutions used to disinfect skin and other living tissues.

Sanitization
 is

the reduction of microbial populations to levels considered safe by public health standards.
one that kills microbes. necessarily

Microbicidal agent
 is

Bactericidal agent
 kills

bacteria, but not endospores of bacteria.

Microbistatic agent
 is

a drug or chemical that inhibits growth and reproduction of microorganisms.

Lyophilization  is a process that combines dehydration (drying) and freezing. Sepsis  refers to the presence of pathogens in blood or tissues. Asepsis  means the absence of pathogens. Antiseptic technique  developed by Joseph Lister in 1867.  refers to the use of antiseptics.

Sterile technique  is practiced when it is necessary to exclude all microorganisms from a particular area, so that the area will be sterile.