Biofilms--the microscopic architecture all around you

by Tara Smith     Department: Health & Life Sciences

When most people think of bacteria, the image that jumps to mind are singular cells, perhaps growing on a petri dish or swimming in a liquid of broth; one of the simplest forms of life on the planet, incapable of complex thought or organization.

They would, of course, be wrong.

Bacteria are much more complex than most people realize. They communicate with each other using chemical signals. Some of these are specific to their own species of bacteria--for example, one E. coli "talking" to another. Others have a much broader effect, and can be recognized by even distantly-related bacteria. These chemical signals are produced in response to various environmental conditions, and can provide other bacteria in the area with information about bacterial population density.

So bacteria can "talk" to each other--why should we care? Well, one consequence of this bacterial communication is the formation of bacterial biofilm. You may have never heard the term before, but you're already quite familiar with biofims. The plaque on your teeth, the scum on your shower curtain--both bacterial biofilms.

At its most basic, a biofilm is a collection of bacteria that's stuck together, and typically adhering to a surface, be it tooth enamel, your bathtub, an indwelling catheter, or even the cells lining your lungs. This life in a biofilm has advantages and disadvantages for the bacterial residents. Unlike their free-floating brethren, they're trapped in place, covered by sticky excretions and organized into a complex architecture consisting of pillars and channels. However, they're also much more resistant to environmental hazards, including antibiotics. This is why the study of biofilm bacteria has grown exponentially over the past decade: when growing in this form within our bodies, biofilm-forming bacteria are incredibly difficult to eradicate, whether they're Pseudomonas aeruginosa in the lungs of patients with cystic fibrosis, or Staphylococcus aureus on a medical device. Their thick sticky layer is difficult for antibiotics to penetrate, and even when they do, they may not reach all the bacterial cells deep within the layers of the biofilm--thereby leaving a reservoir of bacteria to re-seed the host again and again.

Unfortunately, eradicating these biofilms then isn't as easy as entering their bacterial cities and smashing 'em to bits. Since they're so tough to get rid of once they're formed, researchers instead are looking for ways to stop bacteria from creating biofilms in the first place--by disrupting the signals they send amongst each other which causes them to "settle down" into a biofilm structure. There are still many hurdles to be overcome before something like that would be ready for prime-time, but it's caused a shift in the way biologists think about bacteria, and has fostered a return to taking a more ecological approach to the microbiology of disease.

Image from http://upload.wikimedia.org/wikipedia/commons/e/e4/Staphylococcus_aureus_biofilm_01.jpg

Tags: bacteria, biofilms