Project description:At hydrothermal vent sites, chimneys consisting of sulfides, sulfates, and oxides are formed upon contact of reduced hydrothermal fluids with oxygenated seawater. The walls and surfaces of these chimneys are an important habitat for vent-associated microorganisms. We used community proteogenomics to investigate and compare the composition and in situ protein expression of microbial communities colonizing two actively venting hydrothermal chimneys from the Manus Basin back-arc spreading center (Papua New Guinea).
Project description:Iron-sulfur minerals such as pyrite are found in many marine benthic habitats. At deep-sea hydrothermal vent sites they occur as massive sulfide chimneys. Hydrothermal chimneys formed by mineral precipitation from reduced vent fluids upon mixing with cold oxygenated sea water. While microorganisms inhabiting actively venting chimneys and utilizing reduced compounds dissolved in the fluids for energy generation are well studied, only little is known about the microorganisms inhabiting inactive sulfide chimneys. We performed a comprehensive meta-proteogenomic analysis combined with radiometric dating to investigate the diversity and function of microbial communities found on inactive sulfide chimneys of different ages from the Manus Basin (SW Pacific). Our study sheds light on potential lifestyles and ecological niches of yet poorly described bacterial clades dominating inactive chimney communities.
Project description:Biological carbon fixation is foundational to the biosphere. Most autotrophs are thought to possess one carbon fixation pathway. The hydrothermal vent tubeworm Riftia pachyptila’s chemoautotrophic symbionts, however, possess two functional pathways: the Calvin Benson-Bassham (CBB) and the reductive tricarboxylic acid (rTCA) cycles. Little is known about how Riftia’s symbionts and related organisms coordinate the functioning of these two pathways. Here we investigated net carbon fixation rates, transcriptional/metabolic responses, and transcriptional co-expression patterns of Riftia pachyptila’s endosymbionts by incubating tubeworms at environmental pressures, temperature, and geochemistry. Results showed that rTCA and CBB transcriptional patterns varied in response to different geochemical regimes and that each pathway is allied to specific metabolic processes, suggesting distinctive yet complementary roles in metabolic function. Net carbon fixation rates were also exemplary, and accordingly we propose that co-activity of CBB and rTCA may be an adaptation for maintaining high carbon fixation rates, conferring a fitness advantage in dynamic vent environments.
