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Bacteria, Unite!

The (almost) indestructible biofilm.

Bartenders and biologists alike appreciate clean glassware. But in 1972, when William Costerton, a microbiologist, found that even after washing his slides they were spotted with germs, rather than give them another scrub, he took a closer look. The bacteria, he noticed, were spread almost uniformly at intervals of 5 microns. And in between, revealed by a ruthenium red stain, lay a tangled network of microscopic fibers.

Something had organized the bacteria into a regular pattern, but the full significance of what Dr. Costerton was seeing became clear only in the 90s, when the introduction of confocal scanning laser microscopes allowed him to look at wet, living specimens in three dimensions, rather than as inert remains fixed in wax. Under the microscope, he found a miniature ecosystem. The fibers were the residue of a matrix of extracellular polymeric substances threaded with channels that formed a reservoir for water and nutrients. Additionally he found that bacteria linked by this network had specialized into different tasks. Together they formed a tenacious coating that Dr. Costerton dubbed a “biofilm.”

Much of medical history has been a long war against germs, so the discovery of an especially toughened form of bug life can be alarming. Historically, the worst epidemic diseases, like typhoid, diphtheria, and bubonic plague, have been caused by planktonic bacteria, which float freely, swarming into the human body by the millions. Fighting them requires either preparing the body to fend them off itself through the process of inoculation, or killing them directly with disinfectants or antibiotics. But biofilms have evolved a community protection that allows colonies of bacteria to survive medicinal onslaughts like medieval soldiers covering their heads with shields to protect against boiling oil. Bacteria bound together as a biofilm can be as much as 1,000 times more resistant to antibiotics than individual bacteria.1

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1  Ceri, H. et al. (June 1999) The Calgary biofilm device: new technology for rapid determination of antibiotic susceptibilities of bacterial biofilms. Journal of Clinical Microbiology 37:17716.

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