Characterization of a deep-sea microbial mat from an active cold seep at the Milano mud volcano in the Eastern Mediterranean Sea

Authors

  • Sander K. Heijs,

    Corresponding author
    1. Department of Microbiology, Center for Ecological and Evolutionary Studies, University of Groningen, 9750 AA Haren, The Netherlands
    Search for more papers by this author
  • Jaap S. Sinninghe Damsté,

    1. Royal Netherlands Institute for Sea Research (NIOZ), Department of Marine Biogeochemistry and Toxicology, Den Burg, The Netherlands
    Search for more papers by this author
  • Larry J. Forney

    1. Department of Microbiology, Center for Ecological and Evolutionary Studies, University of Groningen, 9750 AA Haren, The Netherlands
    Search for more papers by this author
    • 1

      Current address: Department of Biological Sciences, University of Idaho, Moscow, ID 83844-3051, Idaho, USA.


*Corresponding author. Fax: +31 50 363 2154, E-mail address: sander@house-of-media.nl

Abstract

A white, filamentous microbial mat at the Milano mud volcano in the Eastern Mediterranean Sea was sampled during the Medinaut cruise of the R/V Nadir in 1998. The composition of the mat community was characterized using a combination of phylogenetic and lipid biomarker methods. The mat sample was filtered through 0.2 and 5-μm filters to coarsely separate unicellular and filamentous bacteria. Analyses of 16S rRNA gene sequences amplified from the total community DNA from these fractions showed that similar archaeal populations were present in both fractions. However, the bacterial populations in the fractions differed from one another, and were more diverse than the archaeal ones. Lipid analysis showed that bacteria were the dominant members of the mat microbial community and the relatively low δ13C carbon isotope values of bulk bacterial lipids suggested the occurrence of methane- and sulfide-based chemo(auto)trophy. Consistent with this, the bacterial populations in the fractions were related to Alpha-, Gamma- and Epsilonproteobacteria, most of which were chemoautotrophic bacteria that utilize hydrogen sulfide (or reduced sulfur compounds) and/or methane. The most common archaeal 16S rRNA gene sequences were related to those of previously identified Archaea capable of anaerobic methane oxidation. Although the filamentous organisms observed in the mat were not conclusively identified, our results indicated that the Eastern Mediterranean deep-sea microbial mat community might be sustained on a combination of methane- and sulfide-driven chemotrophy.

Ancillary