Getting out of a sticky situation

Biofilms get a pretty bad rep, and rightly so. Colloquially known as ‘slime’, these sticky scaffolds of polysaccharides, proteins and DNA are produced by colonies of bacteria and let them cling to wet surfaces, whether those are crustacean shells, water pipes or artificial cardiac valves.

Bacteria within biofilms are difficult to kill, which makes them a real problem in hospitals. The bacterial colonies are often more resistant to antibiotics than their free-living relatives, perhaps because the biofilm cocoons the bacteria in the centre and prevents drugs from reaching them. Biofilms are also tricky to remove by cleaning and are impervious to many detergents. Once they’re there, you’re kind of stuck with them, if you’ll excuse the pun.

But what if we could harness the adhesive power of biofilms for good? Could we use them to deliver useful molecules or drugs? A group of researchers is working on that very problem, right now.

Scientists at the Boston Children’s Hospital, USA, are using Vibrio cholera as a test organism because it readily forms biofilms on plankton (as we’ve written about before). In particular, they have been looking at the V. cholera membrane protein RbmA, which helps to stick the biofilm together.

The team created a fusion of two proteins, RbmA and the enzyme ChiA-2, which is also produced by V. cholera and found throughout the biofilm. Importantly, the tacked-on ChiA-2 retained its normal activity, showing that this technique is a feasible way of engineering biofilms to become platforms for protein delivery.

The paper includes several potential biofilm technologies: what if we could use probiotic bacteria to deliver enzymes to the surface of the small intestine in patients who are unable to make them? Or what if biofilms could be used in bioremediation, producing enzymes on contaminated surfaces? The systems would be self-generating and economical, so there would be no need for repeated chemical treatments; we could just let the bacteria grow.

Admittedly, this work is only a proof of concept, and the authors concede that the potentially lethal V. cholera (which causes cholera) “is not the appropriate vehicle for every application”. However, structural proteins with similar roles to RbmA have been found in various species of bacteria, suggesting that it may be time to cut the slime some slack, as it could end up being rather useful.

Benjamin Thompson

Absalon C, Ymele-Leki P, & Watnick PI (2012). The bacterial biofilm matrix as a platform for protein delivery. mBio, 3 (4) PMID: 22807566

Image Credit: Pacific Northwest National Laboratory on Flickr

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