Identification of Members of the Metabolically Active Microbial Populations Associated with Beggiatoa Species Mat Communities from Gulf of Mexico Cold-Seep Sediments

Abstract

In this study, the composition of the metabolically active fraction of the microbial community occurring in Gulf of Mexico marine sediments (water depth, 550 to 575 m) with overlying filamentous bacterial mats was determined. The mats were mainly composed of either orange-or white-pigmented Beggiatoa spp. Complementary 16S ribosomal DNA (crDNA) was obtained from rRNA extracted from three different sediment depths (0 to 2, 6 to 8, and 10 to 12 cm) that had been subjected to reverse transcription-PCR amplification. Domainspecific 16S PCR primers were used to construct 12 different 16S crDNA libraries containing 333 Archaea and 329 Bacteria clones. Analysis of the Archaea clones indicated that all sediment depths associated with overlying orange-and white-pigmented microbial mats were almost exclusively dominated by ANME-2 (95% of total Archaea clones), a lineage related to the methanogenic order Methanosarcinales. In contrast, bacterial diversity was considerably higher, with the dominant phylotype varying by sediment depth. An equivalent number of clones detected at 0 to 2 cm, representing a total of 93%, were related to the ␥ and ␦ classes of Proteobacteria, whereas clones related to ␦-Proteobacteria dominated the metabolically active fraction of the bacterial community occurring at 6 to 8 cm (79%) and 10 to 12 cm (85%). This is the first phylogenetics-based evaluation of the presumptive metabolically active fraction of the Bacteria and Archaea community structure investigated along a sediment depth profile in the northern Gulf of Mexico, a hydrocarbon-rich cold-seep region.

Characterization of Microbial Community Structure in Gulf of Mexico Gas Hydrates: Comparative Analysis of DNA- and RNA-Derived Clone Libraries

“…Prior to comparative sequence analysis, vector sequences flanking the bacterial 16S rRNA gene and crDNA inserts were man- Phylogenetic and statistical analyses. Sequence analysis was performed as previously described by Mills et al (22,23). Multiple sequences of individual inserts were initially aligned using the program BLAST 2 Sequences (41) available through the National Center for Biotechnology Information and were assembled with the program BioEdit v5.0.9 (11).…”

Gas Seepage along the Edge of the Aquitaine Shelf (France): Origin and Local Fluxes

“…In the current context of on-going climate change, it is therefore essential to locate them on continental margins and shelves and then to assess the fate of these hydrocarbons and quantify their potential contribution to atmospheric methane contents [29,30]. Second, they represent key locations for the development of microbial activity, which oxidizes hydrocarbon compounds, 2 Geofluids and supply, in turn, energy for symbiotic communities living near the seafloor [31][32][33][34][35]. Third, for the oil and gas industry, the detection of hydrocarbon seepages at the seafloor is indicative of the presence of either possible reserves that are economically exploitable or potential geohazards [36][37][38][39].…”

Archaeal Populations in Hypersaline Sediments Underlying Orange Microbial Mats in the Napoli Mud Volcano

“…Microbial communities in sediments underlying microbial mats have been shown to support high rates of sulfate reduction (7,26), sulfur oxidation (49), nitrate reduction (7,26), and anaerobic methane oxidation (7,26). Members of these communities have been previously identified as filamentous sulfur-oxidizing bacteria of the Beggiatoa, Thioplaca, Leucothrix, Thirotrix, and Desmanthos genera (23), as well as diverse Proteobacteria (23,42) and Archaea (41,42). Interestingly, the archaeal communities in sediments underlying seep-associated microbial mats are dom-inated by methanogens and methane oxidizers (34).…”