"Biofilm" Alert


For years we’ve been hearing about increases in “antibiotic-resistant bacteria.” This was a troubling enough development. Not being a microbiologist, I assumed that the problem was strictly evolutionary–that bacteria were mutating in the presence of substances which would kill some but not all, leaving the hardiest ones intact. I had the idea that bacteria were always free-floating in our bodies or scattered on surfaces, and that all we had to do in order to wipe them out was to introduce the proper disinfectant or antibiotic agent.

Sadly, this is far from reality. Turns out that this free-floating property is the planktonic stage, which is the active phase of bacterial life. But there is another far more insidious stage, where the bacteria encapsulate themselves in a tough membrane, and often nearly cease their metabolism, which allows them to lie dormant and thus be immune to disruption.

This encapsulated phase is called a biofilm, and is also marked by a phenomenon of quorum sensing, where the bacteria detect each other and begin to work together to secrete the substrate of the biofilm, which is composed of tough polymers, and often can contain several species of cooperating bacteria!

From Wikipedia:

Formation of a biofilm begins with the attachment of free-floating microorganisms to a surface. These first colonists adhere to the surface initially through weak, reversible van der Waals forces. If the colonists are not immediately separated from the surface, they can anchor themselves more permanently using cell adhesion molecules such as pili.[1]

The first colonists facilitate the arrival of other cells by providing more diverse adhesion sites and beginning to build the matrix that holds the biofilm together. Some species are not able to attach to a surface on their own but are often able to anchor themselves to the matrix or directly to earlier colonists. It is during this colonization that the cells are able to communicate via quorum sensing. Once colonization has begun, the biofilm grows through a combination of cell division and recruitment. The final stage of biofilm formation is known as development, and is the stage in which the biofilm is established and may only change in shape and size. This development of biofilm allows for the cells to become more antibiotic resistant.

This can increase the antibiotic resistance 1,000 fold. But there are also good properties of biofilms, such as use in sewage treatment, and potentially in bacterial breakdown of cellulose for biofuels. Having a self-constructed matrix allows bacteria to remain in place which can facilitate liquid-flow processes. Biofilms also protect extremophilic bacteria which live in naturally ocurring volcanic acid pools and undersea vents, and potentially harsh industrial environments.

But the news is bad for humans’ epic internal battle with these small creatures. Recent experiments aboard the space shuttle with salmonella confirmed the problem. It seems bacteria exposed to the harsh radiation environment and zero-g became three times more likely to develop a biofilm, and thus three times deadlier. Scientists have not discovered the precise mechanism that causes the change, but are working on further experiments, and also figuring out how to defeat this property.

All this underscores the need for ongoing and accelerated work on figuring out how to control the genomes of these little beasts. It would seem the best way to defeat biofilms would be to prevent them from forming in the first place. Working with bacteria is key to human survival, since we not only need to eliminate the ones that cause us harm, but foster and grow the ones doing useful work. Since the production of biofilms depends on nanomechanical processes, it seems that developments in nanotechnology will not only help us understand (many such discoveries have been through biomimetics), but control the bacterial action.

It’s well known that humans are symbiotic with our gut bacteria, (acidophilus, etc.). But what most people don’t realize is that the energy transition depends on microbes. Yeasts can break down sugars and convert them to alcohols, but to enable use of the vast majority of biomass for fuel, it takes specially engineered bacteria which can break down cellulose. In a sense, we are going to replace OPEC with a bunch of little workhorses to power our transportation.

Two days ago, I had never heard of the term biofilm. Now I understand this to be a hugely important area for research on which we all may quite literally depend for not only our lives, but also our wheels.

Comments (3 comments)

Logicel / September 26th, 2007, 2:32 am / #1

Thanks for this interesting post–the positive/negative implications of biofilms are intriguing.

riri / October 9th, 2007, 12:17 am / #2

I’m pretty sure that biofilms don’t form in people or animals. They become a problem in piping etc, because they cannot be flushed out. Biofilms are hardly a new development, as opposed to antibiotic resistant bacteria.

BlackSun / October 9th, 2007, 12:29 am / #3

Riri, from Wikipedia:

Biofilms have been found to be involved in a wide variety of microbial infections in the body, by one estimate 80% of all infections.[5] Infectious processes in which biofilms have been implicated include common problems such as urinary tract infections, catheter infections, middle-ear infections, formation of dental plaque, gingivitis, coating contact lenses, and less common but more lethal processes such as endocarditis, infections in cystic fibrosis, and infections of permanent indwelling devices such as joint prostheses and heart valves.[6][7]

It has recently been shown that biofilms are present on the removed tissue of 80% of patients undergoing surgery for chronic sinusitis. The patients with biofilms were shown to have been denuded of cilia and goblet cells, unlike the controls without biofilms who had normal cilia and goblet cell morphology.[8] Biofilms were also found on samples from two of 10 healthy controls mentioned. The species of bacteria from interoperative cultures did not correspond to the bacteria species in the biofilm on the respective patient’s tissue. In other words, the cultures were negative though the bacteria were present.[9]

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