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Abstract:
Metal-sulfides are wide-spread in marine benthic habitats. At deep-sea
hydrothermal vents, they occur as massive sulfide chimneys formed by
mineral precipitation upon mixing of reduced vent fluids with cold
oxygenated sea water. Although microorganisms inhabiting actively
venting chimneys and utilizing compounds supplied by the venting fluids
are well studied, only little is known about microorganisms inhabiting
inactive chimneys. In this study, we combined 16S rRNA gene-based
community profiling of sulfide chimneys from the Manus Basin (SW
Pacific) with radiometric dating, metagenome (n = 4) and metaproteome (n
= 1) analyses. Our results shed light on potential lifestyles of yet
poorly characterized bacterial clades colonizing inactive chimneys.
These include sulfate-reducing Nitrospirae and sulfide-oxidizing
Gammaproteobacteria dominating most of the inactive chimney communities.
Our phylogenetic analysis attributed the gammaproteobacterial clades to
the recently described Woeseiaceae family and the SSr-clade found in
marine sediments around the world. Metaproteomic data identified these
Gammaproteobacteria as autotrophic sulfide-oxidizers potentially
facilitating metal-sulfide dissolution via extracellular electron
transfer. Considering the wide distribution of these
gammaproteobacterial clades in marine environments such as hydrothermal
vents and sediments, microbially accelerated neutrophilic mineral
oxidation might be a globally relevant process in benthic element
cycling and a considerable energy source for carbon fixation in marine
benthic habitats.
