Meeting Abstract
Siboglinid symbioses are enabled by specialized hemoglobin that is able to bind hydrogen sulfide for transportation to their chemosynthetic endosymbionts. Sulfur-binding capabilities are hypothesized to be due to cysteine residues at key positions in both vascular and coelomic hemoglobins. Interestingly, members of the genus Osedax, which live on whale bone, do not have chemosynthetic endosymbionts, but instead house heterotrophic bacteria capable of breaking down complex organic compounds. Although sulfur-binding capabilities are important in other siboglinids, we questioned whether Osedax retained the ability to bind hydrogen sulfide. We sought to answer this question using high throughput sequencing to isolate and analyze hemoglobin sequences from nine siboglinid lineages including Osedax mucofloris. Once identified, hemoglobin sequences from gene subfamilies A2 and B2 were translated and aligned to determine conservation of cysteine residues at key positions in these sequences. Our results suggest that hemoglobin in O. mucofloris has retained some ability to bind hydrogen sulfide. This characteristic may have been retained when Osedax diverged from other siboglinids. However, toxic hydrogen sulfide has been shown to bind with a higher affinity to hemoglobin than cytochrome-c oxidase in other siboglinids suggesting there could still be selection for this trait due to the abundance of hydrogen sulfide production within whalebones.
