Antibiotics as a Carbon Source
Here’s the context: “Eighty years after Alexander Fleming discovered penicillin on a moldy culture dish, the battle against killer bugs is faltering. More and more bacteria - including insidious tuberculosis strains that have cropped up2 - now shrug off almost all antibiotics. Meanwhile, few new antibiotics are reaching the clinic. Medicine is on the defensive, says microbiologist and physician Stuart Levy of Tufts University School of Medicine in Boston. ‘We are not keeping up with the bacteria.’” Antibiotic resistance has been a remarkable instance of natural selection in progress.
Now there is something even more remarkable concerning the seemingly endless capacity for microbes to do just about anything biochemically. They can even bacteria that can survive with nothing to eat but antibiotics. It’s not clear why the soil bacteria examined by Geneticist George Church and team appear particularly skilled at converting cytotoxic antibiotics into a carbon source, nor whether this is connected to the development of antibiotic resistance in human-specific pathogens - it’s just plain surprising.
But perhaps we shouldn’t be too surprised. We’ve known for a few years now that the primary microbial antibiotic-resistance mechanisms include efflux pumps, target gene-product modifications, and enzymatic inactivation of the antibiotic compound. We’ve also known for a few years that microbes can biochemically degrade just about anything, including cyclic hydrocarbons of probably any flavor, as well as bioremediation of heavy metals and radionuclides. [Incidentally, the image above is of Geobacter metallireducens as posted at Green Brooklyn]
While the biochemical wonders that microbes can spawn are amazing, and can be good for cleaning up our environment, what about the instance that began this post - microbial subsistence on antibiotics (much less resistance)? As I mentioned, this is a clear example of both the power of natural selection and the versatility of biochemistry. How then do we use our knowledge of these things to better control the pathogens that we seek to eradicate with antibiotics?
We have to use antibiotics more wisely, and perhaps almost not at all, just as we learned to get by without insecticides half a century ago in agriculture. Just as better ecology was the answer then, microbial ecology is an answer now. And an even better answer is to find ways to boost the best tool for combating disease that natural selection has given us: our immune system.
See ScienceFriday for two interesting discussions on antibiotics as a carbon source and phages for combatting pathogenic bacteria.
- Leslie, Mitch (2008) Germs Take a Bite Out of Antibiotics. Science 320(5872):33. DOI
- Koenig, Robert (2008) In South Africa, XDR TB and HIV Prove a Deadly Combination. Science 319(5865):894-897. DOI
- Dantas G, Sommer MOA, Oluwasegun RD, Church GM (2008) Bacteria Subsisting on Antibiotics. Science 320(5872):100-103. DOI
molecular biology
