The versatile in situ gene expression of an E psilonproteobacteria ‐dominated biofilm from a hydrothermal chimney

Summary The E psilonproteobacteria , including members of the genus S ulfurovum , are regarded as important primary producers in hydrothermal systems. However, their in situ gene expression in this habitat has so far not been investigated. We report a metatranscriptomic analysis of a S ulfurovum ‐dominated biofilm from one of the chimneys at the L oki's C astle hydrothermal system, located at the A rctic M id O cean R idge. Transcripts involved in hydrogen oxidation, oxidation of sulfur species, aerobic respiration and denitrification were abundant and mostly assigned to S ulfurovum , indicating that members of this genus utilize multiple chemical energy sources simultaneously for primary production. S ulfurovum also seemed to have a diverse expression of transposases, potentially involved in horizontal gene transfer. Other transcripts were involved in CO 2 fixation by the reverse TCA cycle, the CRISPR ‐ C as system, heavy metal resistance, and sensing and responding to changing environmental conditions. Through pyrosequencing of PCR amplified 16 S rRNA genes, the S ulfurovum ‐dominated biofilm was compared with another biofilm from the same chimney, revealing a large shift in the community structure of E psilonproteobacteria ‐dominated biofilms over a few metres.