Microbiology and Immunology

WORLD OF MICROBIOLOGY AND IMMUNOLOGY Coulter counter

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be comprised of several species, the bacteria were referred to

as diphtheroids. Diphtheria is apparent as an inflammationand

bleeding of the throat and as a generalized toxic poisoning of

the body, due to the release of a powerful toxin by the bacte-

ria. The toxin spreads throughout the body via the bloodstream

and has a particular affinity for tissues such as the heart, nerve

endings and the adrenal glands. Diphtheria is treatable with

antibiotics.

Other species of the genus Corynebacteriumcause mas-

titis in cows (an infection and inflammation of the udder),

infection of the lymph nodes of sheep, and skin rashes and

ulcerations in humans. Rhodococcus equi, which inhabits soil,

is an important pathogen of young horses. Another human

pathogen is It is also a normal resident on skin surfaces, and

can cause an infection in those receiving chemotherapy.

See alsoGram staining

CCosterton, John WilliamOSTERTON, JOHNWILLIAM(1934- )

Canadian microbiologist

J. William (Bill) Costerton is a Canadian microbiologist who

has pioneered the recognition of bacterial biofilmsas the dom-

inant mode of growth of bacteria, and who first demonstrated

their importance in the resistance of bacteria to antibacterial

agents and the persistence of some chronic bacterial infections.

Costerton was born in Vernon, British Columbia. His

early education was in that province. In 1955, he received a

B.S. in bacteriology and immunologyfrom the University of

British Columbia, followed by a M.S. in the same discipline

from UBC in 1956. He then studied in the laboratory of Dr.

Robert Murrayat the University of Western Ontario in London,

Ontario, where he received a Ph.D. in 1960. Following post-

doctoral training at Cambridge University, Costerton moved to

MacDonald College of McGill University, in the Canadian

province of Quebec, where he became first a Professional

Associate in 1966 then an Assistant Professor in 1968. In 1970

he moved to the University of Calgary as an Associate

Professor. He became a tenured Professor at Calgary in 1975.

From 1985 to 1992, he held positions at Calgary as the AOS-

TRA Research Professor followed by the National Sciences

and Engineering Research Council Industrial Research Chair.

These two appointments freed him from teaching to concen-

trate on his burgeoning research into bacterial biofilms.

Research on biofilms has occupied Costerton since his

move to Calgary. Costerton and his colleagues demonstrated

the existence of biofilms and when on to show that biofilms

are the dominant mode of growth for bacteria. The elabora-

tion of an extensive sugar network that adheres bacteria to

surfaces and subsequently buries them was revealed.

Research over a decade demonstrated the importance of this

exopolysaccharide in enabling the bacteria to survive doses of

antibacterial agents, including antibioticsthat readily killed

bacteria grown in conventional lab cultures. This research

was so convincing that an initially skeptical scientific com-

munity became convinced of the importance and widespread

nature of biofilms.

In 1993, Costerton left Calgary to take up the post of

Director of the Center for Biofilm Engineering at Montana

State University, Bozeman. Since then, he and his colleagues

have used techniques such as confocal microscopy to probe

intact biofilms without disrupting them. These studies have

revealed the complex nature of biofilm structure and the coor-

dinated nature of the interaction between the bacterial popula-

tions in the biofilms. As well, Costerton discovered the

so-called bioelectric effect, in which an application of current

makes a biofilm much more susceptible to antibiotic killing.

These discoveries are having profound influence on the design

of strategies to combat chronic infections, such as the

Pseudomonas aeruginosalung infections that occur, and can

ultimately kill those afflicted with cystic fibrosis.

For these and other pioneering contributions to biofilm

research, Costerton has received many awards. These include

the Sir Frederick Haultain Prize for outstanding achievement

in the physical sciences (1986), the Isaak Walton Killam

Memorial Prize for Scientific Achievement in Canada (1990),

and a Fellowship in the American Association for the

Advancement of Science (1997).

Costerton continues his research at Montana State and

is actively involved internationally in promoting the multi-

disciplinary structure of the Center’s research and education

curriculum.

See alsoAntibiotic resistance, tests for; Bacterial adaptation;

Glycocalyx

CCoulter counterOULTER COUNTER

A Coulter counter is a device that is used to measure the num-

ber of cells in a certain volume of a sample suspension. The

counter achieves this enumeration by monitoring the decrease

in electrical conductivity that occurs when the cells pass

through a small opening in the device. While originally devel-

oped for use with blood cells, the Coulter counter has found

great use in a diverse number of disciplines, including micro-

biology, where it is used to determine the total number of bac-

teriain samples.

Because the device operates on the physical blockage of

electrical conductivity by particles in a sample, the Coulter

counter cannot distinguish between living and dead bacteria.

An indication of the total number of bacteria (alive, dormant,

and dead) is provided. The number of living bacteria can,

however, usually be easily determined using another volume

from the same sample (e.g., the heterotrophic plate count).

The Coulter counter is named after its inventor. Wallace

H. Coulter conceived and constructed the first counter in the

basement of his home in Chicago in the early 1950s. Then as

now, the device relies on a vacuum pump that draws a solution

or suspension through an electrically charged tube that has a

tiny hole at the other end. As particles pass through the hole

the electrical field is interrupted. The pattern of the interrup-

tion can be related to the number of particles and even to par-

ticle type (e.g., red blood cell versus bacteria).

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