CONTACT: L. E. OHMAN
283 Medical Laboratories
Iowa City IA 52242
(319) 335-6660; fax (319) 335-8034
Release: Embargoed until 4:00 p.m. EST Thursday, April 9
Scientists discover a secret of bacterial communication
IOWA CITY, Iowa -- The war against bacteria rages on, but a new battle
plan has been drawn.
Bacteria existing together in a structure called biofilm are often more
resistant to attack by antibiotics and the immune system than they are
as individual cells.
This resistance presents a difficult problem for physicians, but recent
research has revealed a way in which the biofilm fortress might be attacked.
Dr. E.P. Greenberg, University of Iowa professor of microbiology and UI
colleague, Matthew Parsek, together with investigators at Montana State
University and the University of Rochester, have discovered a signal molecule
released by bacteria called Pseudomonas aeruginosa that is essential
for the development of biofilm. This finding is reported in the April 10
issue of the journal Science.
"This is basic research, but it leads us in two research directions,"
Greenberg says. "It may help us find a way to dislodge the biofilm,
or it could lead to ways in which we could impair a biofilm, making it
more sensitive to antibiotics."
Scientists are now learning that despite their reputation as rugged
individualists, bacteria spend a considerable amount of time in communities.
When a single, free-floating bacterium recognizes a surface, such as a
rock in a stream or cell lining a blood vessel, it may attach to it. At
first the bacterial cells multiply and spread across the surface, but when
they reach a certain density, they build a complex biofilm structure with
built-in water tunnels to carry nutrition into the cells and carry the
waste out. Scientists call this process differentiation. The message that
initiates differentiation has puzzled researchers for some time.
Greenberg and his colleagues discovered the chemical message that Pseudomonas
aeruginosa uses to "tell" the community that it is time to
build the biofilm structure. Pseudomonas aeruginosa, the organism
that can infect catheters or medical implants, and causes lung infections
in cystic fibrosis patients, secretes two signal molecules that accumulate
as the number of bacteria on a surface increase. When the signal molecules
reach a specific concentration they initiate various cell activities. Both
turn on the genetic machinery that produces bacterial toxins, but only
one is responsible for the cell-to-cell instructing the bacteria to build
the biofilm. When the gene required for production of the signal was removed
from the bacteria, the community did not differentiate into a normal biofilm.
However, when the signal was added back by the investigators the biofilm
structure developed as usual -- indicating that the signal molecule triggers
Currently, the researchers are working to determine if this finding
for Pseudomonas aeruginosa can be generalized to other bacteria
and, if so, how the information might be used to dislodge or impair the
biofilms. The scientists hope that this finding will lead to the production
of more effective antibiotics or novel therapeutic approaches to fight