Microbiology and Immunology

Contamination and release prevention protocol WORLD OF MICROBIOLOGY AND IMMUNOLOGY

134

•

Another landmark experiment in microbiology also cen-

tered on conjugation. This experiment is known as the inter-

rupted mating experiment (or blender experiment, since a

common kitchen blender was used). Donor and recipient bacte-

ria were mixed together and left to allow conjugation to begin.

Then, at various times, the population was vigorously blended.

This sheared off the pili that were connected the conjugating

bacteria, interrupting the mating process. By analyzing the

recipient bacteria for the presence of known genes that has been

transferred, the speed of conjugation could be measured.

Conjugation has been exploited in the biotechnology

era to permit the transfer of desired genetic information. A tar-

get genecan be inserted into the donor bacterial DNA near the

F genes. Or, an F plasmid can be constructed in the laboratory

and then inserted into a bacterial strain that will function as the

donor. When conjugation occurs, bacteria in the recipient pop-

ulation will acquire the target gene.

See alsoEvolution and evolutionary mechanisms; Laboratory

techniques in microbiology

CONTAMINATION AND RELEASE

PREVENTION PROTOCOLContamination and release prevention protocol

Contamination is the unwanted presence of a microorganism

in a particular environment. That environment can be in the

laboratory setting, for example, in a medium being used for

the growth of a species of bacteriaduring an experiment.

Another environment can be the human body, where contam-

ination of various niches can produce an infection. Still

another environment can be the solid and liquid nutrients that

sustain life. A final example, which is becoming more relevant

since the burgeoning use of biotechnology, is the natural envi-

ronment. The consequences of the release of bioengineered

microorganismsinto the natural environment to the natural

microflora and to other species that depend on the environ-

ment for their welfare, are often unclear.

The recognition of the adverse effects of contamination

have been recognized for a long time, and steps that are now a

vital part of microbiological practice were developed to curb

contamination. The prevention of microbial contamination

goes hand in hand with the use of microorganisms.

Ever since the development of techniques to obtain

microorganisms in pure culture, the susceptibility of such cul-

tures to the unwanted growth of other microbes has been rec-

ognized. This contamination extends far beyond being merely

a nuisance. Differing behaviors of different microorganisms,

in terms of how nutrients are processed and the by-products of

this metabolism, can compromise the results of an experiment,

leading to erroneous conclusions.

In the medical setting, microbial contamination can be

life threatening. As recognized by Joseph Listerin the mid-

nineteenth century, such contamination can be lessened, if not

prevented completely, by the observance of various hygienic

practices in the hospital setting. In modern medicine and sci-

ence, the importance of hand washing and the maintenance of

a sterile operating theatre is taken for granted.

Prevention of microbiological contamination begins in

the laboratory. A variety of prevention procedures are a com-

mon part of an efficient microbiology laboratory. The use of

sterile equipment and receptacles for liquid and solid growth

media is a must. The prevention of contamination during the

manipulations of microorganisms in the laboratory falls under

the term asceptic technique. Examples of asceptic technique

include the disinfectionof work surfaces and the hands of the

relevant lab personnel before and after contact with the

microorganisms and the flaming of the metal loops or rods

used to transfer bacter from one location to another.

In other areas of a laboratory, microorganisms that are

known to be of particular concern, because they can easily

contaminate or be contaminated, or because they represent a

health threat, can be quarantined in special work areas.

Examples of such areas include fume hoods and the so-called

glove box. The latter is an enclosed space where the lab

worker is kept physically separate from the microorganisms,

but can manipulate the organisms by virtue of rubber gloves

that are part of the wall of the enclosure.

In both the laboratory and other settings, such as pro-

cessing areas for foods, various monitoring steps are instituted

as part of a proper quality control regimen to ensure that con-

tamination does not occur, or can be swiftly detected and dealt

with. A well-established technique of contamination monitor-

ing is the air plate technique, where a non-specific growth

medium is exposed to the circulating air in the work area for a

pre-determined period of time. Air-borne microorganisms can

be detected in this manner. More recently, as the importance of

the adherent (biofilm) mode of growth of, in particular, bacte-

ria became recognized, contamination monitoring can also

include the installation of a device that allows the fluid circu-

lating through pipelines to be monitored. Thus, for example,

water used in processing operations can be sampled to deter-

mine if bacterial growthon the pipeline is occurring and also

whether remediation is necessary.

A necessary part of the prevention of microbiological

contamination is the establishment of various quality control

measures. For example, the swiping of a lab bench with a ster-

ile cotton swab and the incubation of the swab in a nonspecific

growth medium is a regular part of many microbiology labo-

ratories quality control regimen. The performance of all equip-

ment that is used for sterilization and microorganism

confinement is also regularly checked.

With the advent of biotechnology and in particular the

use of genetically modified microorganisms in the agricultural

sector, the prevention of the unwanted release of the bioengi-

neered microbes into the natural environment has become an

important issue to address.

The experimentation with genetically engineered

microorganisms in the natural environment is subject to a

series of rigid controls in many countries around the world. A

series of benchmarks must be met to ensure that an organism

is either incapable of being spread or, if so, is incapable of pro-

longed survival.

womi_C 5/6/03 2:05 PM Page 134