Two days ago, an article was released by Science on their Sciencexpress website with some of the first data coming out of the Gulf with regard to the microbial ecology of the deep-sea in response to the massive quantities of oil released by the Macondo well. This is one of those moments when I embrace how truly nerdy I really am and I actually get a little flutter of excitement from reading the peer-reviewed literature.
Essentially, what happened is that the well was pumping oil into the deep ocean, then BP started pumping Corexit 9500 down near the burst wellhead, and the result (beyond the oil slicks and tar balls at the surface) is a massive plume of “dispersed” oil between 1,099 and 1,219 m (3,600 – 4,000 f) below the ocean surface. This plume runs more than 6 miles out away from the wellhead. This makes for an unprecedented oil-spill situation, for which we have no similar data on record and a wellspring of opportunity to find out about deep-sea microbial ecology.
So, what’s happening with the microbes down there?
Terry Hazen and his colleagues discovered that not only are there much greater numbers of microorganisms in the plume than in the surrounding waters, but also that the organisms of the plume are unique with regard to anything we’ve ever seen before.
They were able to identify over 900 species of bacteria in the plume, 16 of which were greatly enriched compared to the surrounding water without oil contamination. In fact, 90% of all the bacterial sequences they were able to recover from the plume belonged to a single organism, most closely related to the genus Oceanospirillales. These organisms only made up 5% of the sequences in the non-plume samples. What makes this really interesting is that we have no known cultured representative of this genus, but it’s lipid profile (the fats the microbes use to build their cell membranes and walls) is similar to Antarctic hydrocarbon-degrading marine organisms. Keep in mind, the average temperature of the plume waters is around 4.7° C, or 40°F, which makes these little guys pyschrophiles.
The authors also discovered that the number of genes involved in hydrocarbon degradation were significantly increased in the oil plume samples over the non-plume samples and that these genes were significantly correlated with the constituents of the oil (isoproplybenzene, naphthalene, etc). So, not only do we have a huge enrichment of previously undescribed organisms within the oil plume, but these new organisms contains a large number of the genes we know to be required for oil degradation. Additionally, scientists aren’t observing the fatal drop in oxygen tensions that had been expected with this level of microbial hydrocarbon break-down. Don’t misunderstand me here, there was a drop, but not to the levels that could kill off other marine life and result in a much-expanded dead-zone. These data could suggest that these organisms are employing metabolic pathways of hydrocarbon degradation that are also (at least in part) previously undescribed. How cool is that?!
This confirms that not only do a variety of hydrocarbon degrading bacterial populations exist in the newly created deep-sea oil plume, but also, as the authors state “that the microbial communities appear to be undergoing rapid dynamic adaptation in response to oil contamination.” They speculate that the episodic oil leaks from natural and anthropogenic sources have allowed these deep-sea microbial communities the opportunity to develop these pathways over a long period of time, so they were poised to respond. I’ve posted before about the “priming effect” of soil microbial community exposure to a toxin and how it can speed recovery, but now we’re getting to see it in action in the gulf!
The authors also note the “potential for intrinsic bioremediation” and in this case no known microbial inoculants could have worked as well as nature herself.
Overall, a very nicely done article, out quickly and written concisely. Nice job to the folks at the Lawrence Berkeley National Lab! Looking forward to seeing more about this fascinating topic.
Hazen, T., Dubinsky, E., DeSantis, T., Andersen, G., Piceno, Y., Singh, N., Jansson, J., Probst, A., Borglin, S., Fortney, J., Stringfellow, W., Bill, M., Conrad, M., Tom, L., Chavarria, K., Alusi, T., Lamendella, R., Joyner, D., Spier, C., Baelum, J., Auer, M., Zemla, M., Chakraborty, R., Sonnenthal, E., D’haeseleer, P., Holman, H., Osman, S., Lu, Z., Van Nostrand, J., Deng, Y., Zhou, J., & Mason, O. (2010). Deep-Sea Oil Plume Enriches Indigenous Oil-Degrading Bacteria Science DOI: 10.1126/science.1195979