Final Activity Report Summary - VENTSULFURMICDIV (Biodiversity of microbial communities involved in sulphur cycling at a shallow water hydrothermal vent)
Shallow water hydrothermal vents have been largely ignored by microbial ecologist although these usually sulphide-rich vents are exciting model systems for the co-occurrence of chemoautotrophic and phototrophic microbial communities. It was thus the objective of this project to expand our knowledge on the microbiology of sulphur cycling at shallow-water hydrothermal vents by using the marine hydrothermal vent system of Champagne, located at the Island of Dominica in the Lesser Antilles, as a model system. The area of venting occurs near shore and comprises about 40 to 50 active vents at a water depth of 3 to 4 m. A representative collection of vent sites, ranging from high (65 degrees Celsius) to no hydrothermal activity (28 degrees Celsius), was sampled for the analyses of physicochemical parameters and microbial community structure. 16S rRNA gene-based diversity surveys surprisingly revealed that the number of bacterial taxa was positively correlated with temperature. Comparative sequence analysis demonstrated the presence of diverse bacterial phyla such as the Bacteroidetes, Cyanobacteria and Proteobacteria.
The diversity and abundance of sulfate-reducing (SRPs) and sulfide-oxidising prokaryotes (SOPs) in the hydrothermal sand patch was subsequently investigated in greater detail by exploiting their apsA genes as molecular markers. This gene encodes the alpha subunit of the adenosine-5-phosphosulfate reductase, a key enzyme in the sulphur metabolism of all SRPs and many SOPs. A representative vent site contained more than twice the number of different apsA sequence types than a non-hydrothermal control site. With one exception, all apsA sequence types were either phylogenetically affiliated with (i) the deltaproteobacterial SRP families Desulfobulbaceae or Desulfobacteraceae, (ii) the chemotrophic SOP Thiobacillus denitrificans, or (iii) a group containing the phototrophic SOP Chlorobium tepidum and the thermophilic SRP Thermodesulfovibrio islandicus. In conclusion, our results demonstrate that Champagne hydrothermal vents are literally "hot spots'? of bacterial diversity in general and, more specifically, harbour a higher diversity of prokaryotes with a dissimilatory sulphur metabolism.
Another outcome with implications beyond the scope of this project was the discovery and establishment of a novel functional marker, namely the genes (dsrAB) coding for subunits of a reverse sulphite reductase, for detection of those SOPs that employ this type of enzyme for dissimilatory sulphur oxidation. It is anticipated that the developed dsrAB-based polymerase chain reaction assay will find widespread application for cultivation-independent surveys of SOPs in environmental and biotechnological settings.
The diversity and abundance of sulfate-reducing (SRPs) and sulfide-oxidising prokaryotes (SOPs) in the hydrothermal sand patch was subsequently investigated in greater detail by exploiting their apsA genes as molecular markers. This gene encodes the alpha subunit of the adenosine-5-phosphosulfate reductase, a key enzyme in the sulphur metabolism of all SRPs and many SOPs. A representative vent site contained more than twice the number of different apsA sequence types than a non-hydrothermal control site. With one exception, all apsA sequence types were either phylogenetically affiliated with (i) the deltaproteobacterial SRP families Desulfobulbaceae or Desulfobacteraceae, (ii) the chemotrophic SOP Thiobacillus denitrificans, or (iii) a group containing the phototrophic SOP Chlorobium tepidum and the thermophilic SRP Thermodesulfovibrio islandicus. In conclusion, our results demonstrate that Champagne hydrothermal vents are literally "hot spots'? of bacterial diversity in general and, more specifically, harbour a higher diversity of prokaryotes with a dissimilatory sulphur metabolism.
Another outcome with implications beyond the scope of this project was the discovery and establishment of a novel functional marker, namely the genes (dsrAB) coding for subunits of a reverse sulphite reductase, for detection of those SOPs that employ this type of enzyme for dissimilatory sulphur oxidation. It is anticipated that the developed dsrAB-based polymerase chain reaction assay will find widespread application for cultivation-independent surveys of SOPs in environmental and biotechnological settings.