Hydrocarbon-Degrading Bacteria and Potential Symbiosis with Deep-Sea Organisms: Using Ctenophores as a Model

Abstract

Microbiomes and the functions of microbes as they relate to their host have been of interest in many areas of research. Microbes have been of great interest in the deep sea as they serve as potential symbionts for the organisms that reside there where they may participate in macro ecosystem nutrient cycling in an extreme habitat that is limited by lack of light, colder temperatures, and high hydrostatic pressure. Some organisms are known for being able to perform functions such as alkane degradation at the same efficiency at depth as they do at surface level and tend to be more abundant at depth. Such organisms include alkane-degrading bacteria such as Alcanivorax and various other microbes capable of hydrocarbon degradation. Bacteria capable of this function have also been detected as part of the microbiomes of ctenophores. It was hypothesized that ctenophores living in the photic zone of the ocean would have significantly different microbiomes than those living in the aphotic zone. Secondly, it was hypothesized that ctenophores living in the aphotic zone will have a higher relative abundance of hydrocarbon-degrading bacteria than photic-dwelling ctenophores. Lastly, it was hypothesized that genus-level diversity of hydrocarbon-degrading bacteria would increase with depth. Our results indicate that the microbiomes of ctenophores did in fact differ when comparisons between bacterial communities of photic samples were compared to aphotic samples, but neither the abundance nor diversity of hydrocarbon-degrading bacteria differed significantly between photic and aphotic ctenophores