Microbiology and Immunology

WORLD OF MICROBIOLOGY AND IMMUNOLOGY Bioremediation

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to perform its catalytic function. Common cofactors required

for bioluminescent reactions are calcium and ATP, a molecule

used to store and release energy that is found in all organisms.

The terms luciferin and luciferase were first introduced

in 1885. The German scientist Emil du Bois-Reymond

obtained two different extracts from bioluminescent clams and

beetles. When Dubois mixed these extracts they produced

light. He also found that if one of these extracts was first

heated, no light would be produced upon mixing. Heating the

other extract had no effect on the reaction, so Dubois con-

cluded that there were at least two components to the reaction.

Dubois hypothesized that the heat-resistant chemical under-

goes a chemical change during the reaction, and called this

compound luciferin. The heat sensitive chemical, Dubois con-

cluded, was an enzyme which he called luciferase.

The two basic components needed to produce a biolu-

minescent reaction, luciferin and luciferase, can be isolated

from the organisms that produce them. When they are mixed

in the presence of oxygen and the appropriate cofactors, these

components will produce light with an intensity dependent on

the quantity of luciferin and luciferase added, as well as the

oxygen and cofactor concentrations. Luciferases isolated from

fireflies and other beetles are commonly used in research.

Scientists have used isolated luciferin and luciferase to

determine the concentrations of important biological molecules

such as ATP and calcium. After adding a known amount of

luciferin and luciferase to a blood or tissue sample, the cofac-

tor concentrations may be determined from the intensity of the

light emitted. Scientists have also found numerous other uses

for the bioluminescent reaction such as using it to quantify spe-

cific molecules that do not directly participate in the biolumi-

nescence reaction. To do this, scientists attach luciferase to

antibodies—molecules produced by the immune systemthat

bind to specific molecules called antigens. The antibody-

luciferase complex is added to a sample where it binds to the

molecule to be quantified. Following washing to remove

unbound antibodies, the molecule of interest can be quantified

indirectly by adding luciferin and measuring the light emitted.

Methods used to quantify particular compounds in biological

samples such as the ones described here are called assays.

In recent studies, luciferase has been used to study viral

and bacterial infections in living animals and to detect bacte-

rial contaminants in food. The luciferase reaction also is used

to determine DNAsequences, the order of the four types of

molecules that comprise DNA and code for proteins.

Luciferase is often used as a “reporter gene” to study

how individual genes are activated to produce protein or

repressed to stop producing protein. Most genes are turned on

and off by DNA located in front of the part of the genethat

codes for protein. This region is called the gene promoter. A

specific gene promoter can be attached to the DNA that codes

for firefly luciferase and introduced into an organism. The

activity of the gene promoter can then be studied by measur-

ing the bioluminescence produced in the luciferase reaction.

Thus, the luciferase gene can be used to “report” the activity

of a promoter for another gene.

Bioluminescent organisms in the terrestrial environment

include species of fungi and insects. The most familiar of these

is the firefly, which can often be seen glowing during the warm

summer months. In some instances organisms use biolumines-

cence to communicate, such as in fireflies, which use light to

attract members of the opposite sex. Marine environments sup-

port a number of bioluminescent organisms including species

of bacteria, dinoflagellates, jellyfish, coral, shrimp, and fish.

On any given night one can see the luminescent sparkle pro-

duced by the single-celled dinoflagellates when water is dis-

turbed by a ship’s bow or a swimmer’s motions.

See alsoAntibiotic resistance, tests for; Biotechnology; Food

safety; Immunoflorescence; Microbial genetics

BBioremediationIOREMEDIATION

Bioremediation is the use of living organisms or ecological

processes to deal with a given environmental problem. The

most common use of bioremediation is the metabolic break-

down or removal of toxic chemicals before or after they have

been discharged into the environment. This process takes

advantage of the fact that certain microorganismscan utilize

toxic chemicals as metabolic substrates and render them into

less toxic compounds. Bioremediation is a relatively new and

actively developing technology. Increasingly, microorganisms

and plants are being genetically engineered to aide in their

ability to remove deleterious substances.

In general, bioremediation methodologies focus on

one of two approaches. The first approach, bioaugmentation,

aims to increase the abundance of certain species or groups

of microorganisms that can metabolize toxic chemicals.

Bioaugmentation involves the deliberate addition of strains

or species of microorganisms that are effective at treating

particular toxic chemicals, but are not indigenous to or abun-

dant in the treatment area. Alternatively, environmental con-

ditions may be altered in order to enhance the actions of such

organisms that are already present in the environment. This

process is known as biostimulation and usually involves fer-

tilization, aeration, or irrigation. Biostimulation focuses on

rapidly increasing the abundance of naturally occurring

microorganisms capable of dealing with certain types of

environmental problems.

Accidental spills of petroleum or other hydrocarbons on

land and water are regrettable but frequent occurrences. Once

spilled, petroleum and its various refined products can be per-

sistent environmental contaminants. However, these organic

chemicals can also be metabolized by certain microorganisms,

whose processes transform the toxins into more simple com-

pounds, such as carbon dioxide, water, and other inorganic

chemicals. In the past, concentrates of bacteriathat are highly

efficient at metabolizing hydrocarbons have been “seeded”

into spill areas in an attempt to increase the rate of degradation

of the spill residues. Although this technique has occasionally

been effective, it commonly fails because the large concentra-

tions of hydrocarbons stimulates rapid growth of indigenous

microorganisms also capable of utilizing hydrocarbons as

metabolic substrates. Consequently, seeding of microorgan-

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