THE ROLE OF WHALE-FALL MICROBIAL COMMUNITIES ON BONE CORROSION EXPLORED WITH METAGENOMICS

Bones from modern and fossil whale carcasses deposited in low energy environments (whale-falls) are often found heavily corroded. Mechanism(s) of bone corrosion are commonly attributed to the metabolic process of microbes; however the relative importance of different metabolic processes remains unknown. The secretion of collagenase enzymes, or the release of acid by metabolic processes such as sulfide oxidation are two potentially important processes. In an effort to better understand the process of bone corrosion, we queried three publicly available metagenomes from two modern whale fall environments (a gray whale carcass 1674 m deep off coast of CA, and a trawled whale bone 560 m deep off the West Antarctic Peninsula Shelf) for genes associated with the production of collagenase to determine if the microbial communities subsisting on whale-falls have the potential to degrade bone. From the metagenomes, we found 29 genes related to collagenase production, all of which appeared to be strongly correlated with specific taxonomic groups (blastp analysis). The only collagenase genes common in all three metagenomes were collagenases belonging to sulfide-oxidizing alphaproteobacteria.. The largest metagenome also contained numerous collagenases belonging to sulfide-oxidizing epsilonproteobacteria. The other taxa with collagenases were flavobacteria, delta-proteobactera, and the gamma-proteobacteria groups. Our results indicate that whale-fall microbial communities possess diverse collagenase genes, related to collagen degradation, and some of these organisms also oxidize sulfide, potentially generating acidic micronevironments in the bone. These results suggest two mechanisms, which may co-occur in the same organisms, both of which have the potential to contribute to bone degradation. Ongoing taphonomic experiments may resolve the relative impact of these processes when evaluating mechanisms for post-mortem bone corrosion in marine environments.