AUTHOR=Patwardhan Sushmita , Foustoukos Dionysis I. , Giovannelli Donato , Yücel Mustafa , Vetriani Costantino 

TITLE=Ecological Succession of Sulfur-Oxidizing Epsilon- and Gammaproteobacteria During Colonization of a Shallow-Water Gas Vent

JOURNAL=Frontiers in Microbiology

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2018.02970

DOI=10.3389/fmicb.2018.02970

ISSN=1664-302X

ABSTRACT=<p>In this study, we integrated geochemical measurements, microbial diversity surveys and physiological characterization of laboratory strains to investigate substrate-attached filamentous microbial biofilms at Tor Caldara, a shallow-water gas vent in the Tyrrhenian Sea. At this site, the venting gases are mainly composed of CO<sub>2</sub> and H<sub>2</sub>S and the temperature at the emissions is the same as that of the surrounding water. To investigate the composition of the total and active fraction of the Tor Caldara biofilm communities, we collected established and newly formed filaments and we sequenced the 16S rRNA genes (DNA) and the 16S rRNA transcripts (cDNA). Chemoautotrophic sulfur-oxidizing members of the <italic>Gammaproteobacteria</italic> (predominantly <italic>Thiotrichales</italic>) dominate the active fraction of the established microbial filaments, while <italic>Epsilonproteobacteria</italic> (predominantly <italic>Sulfurovum</italic> spp.) are more prevalent in the young filaments. This indicates a succession of the two communities, possibly in response to age, sulfide and oxygen concentrations. Growth experiments with representative laboratory strains in sulfide gradient medium revealed that <italic>Sulfurovum riftiae</italic> (<italic>Epsilonproteobacteria</italic>) grew closer to the sulfide source than <italic>Thiomicrospira</italic> sp. (<italic>Gammaproteobacteria, Thiotrichales</italic>). Overall, our findings show that sulfur-oxidizing <italic>Epsilonproteobacteria</italic> are the dominant pioneer colonizers of the Tor Caldara biofilm communities and that <italic>Gammaproteobacteria</italic> become prevalent once the community is established. This succession pattern appears to be driven - among other factors - by the adaptation of <italic>Epsilon</italic>- and <italic>Gammaproteobacteria</italic> to different sulfide concentrations.</p>