Community Structure, Cellular rRNA Content, and Activity of Sulfate-Reducing Bacteria in Marine Arctic Sediments

Abstract

The community structure of sulfate-reducing bacteria (SRB) of a marine Arctic sediment (Smeerenburgfjorden, Svalbard) was characterized by both fluorescence in situ hybridization (FISH) and rRNA slot blot hybridization by using group-and genus-specific 16S rRNA-targeted oligonucleotide probes. The SRB community was dominated by members of the Desulfosarcina-Desulfococcus group. This group accounted for up to 73% of the SRB detected and up to 70% of the SRB rRNA detected. The predominance was shown to be a common feature for different stations along the coast of Svalbard. In a top-to-bottom approach we aimed to further resolve the composition of this large group of SRB by using probes for cultivated genera. While this approach failed, directed cloning of probe-targeted genes encoding 16S rRNA was successful and resulted in sequences which were all affiliated with the Desulfosarcina-Desulfococcus group. A group of clone sequences (group SVAL1) most closely related to Desulfosarcina variabilis (91.2% sequence similarity) was dominant and was shown to be most abundant in situ, accounting for up to 54.8% of the total SRB detected. A comparison of the two methods used for quantification showed that FISH and rRNA slot blot hybridization gave comparable results. Furthermore, a combination of the two methods allowed us to calculate specific cellular rRNA contents with respect to localization in the sediment profile. The rRNA contents of Desulfosarcina-Desulfococcus cells were highest in the first 5 mm of the sediment (0.9 and 1.4 fg, respectively) and decreased steeply with depth, indicating that maximal metabolic activity occurred close to the surface. Based on SRB cell numbers, cellular sulfate reduction rates were calculated. The rates were highest in the surface layer (0.14 fmol cell ؊1 day ؊1 ), decreased by a factor of 3 within the first 2 cm, and were relatively constant in deeper layers.

Seasonal composition and activity of sulfate-reducing prokaryotic communities in seagrass bed sediments

“…D. variabilis has been reported in other studies as a prevalent member of SRP communities in coastal marine sediments (Rooney-Varga et al 1997, Sahm et al 1999, Ravenschlag et al 2000, Joulian et al 2001, including saltmarsh sediments (Rooney-Varga et al 1997, Hines et al 1999. Members of the genus Desulfosarcina completely oxidize acetate to CO 2 and are also capable of utilizing a wide variety of other electron donors (benzoate, ethanol, lactate, formate, H 2 ).…”

“…SRP community composition has been extensively studied in marine environments, including vegetated saltmarsh sediments, by 16S rRNA gene sequence comparisons (Rooney-Varga et al 1998, Edgcomb et al 1999, Hines et al 1999, Knoblauch et al 1999, Li et al 1999, Frischer et al 2000, Ravenschlag et al 2000, Joulian et al 2001, King et al 2001, Orphan et al 2001, Pérez-Jiménez et al 2001, Thomsen et al 2001, LlobetBrossa et al 2002. Molecular investigations of seagrass bed microbial communities have focused on 16S rRNA gene sequences (Cifuentes et al 2000) and nif H sequences (Bagwell et al 2002).…”

Bacterial composition and spatiotemporal variation in sediments of Jiaozhou Bay, China

“…Global distribution might be an important ecological characteristic of these marine bacteria groups, and many corresponding clusters included might have flexible adaptation to the various marine sediment environments. Most members of δ-Proteobacteria are chemoorganotrophs related to the sulfate-reducing bacteria (SRB), which play an important role for sulphur cycling in global marine sediments (Ravenschlag et al 2000). Besides SRB, potential sulfuroxidizing bacteria (SOB), which belong to ε-, γ-, and α-subdivision of Proteobacteria also constitute an important fraction in bacterial communities of marine sediments (Zeng et al 2009).…”

Benthic ecosystem functioning in hydrocarbon and heavy-metal contaminated sediments of an Adriatic lagoon

“…The sediment slurry was kept at 4°C for 24 h, then washed twice with 3 ml of 1× phosphatebuffered saline (PBS) (pH: 7.2) by centrifuging at 500 × g to remove the supernatant, and stored in 1 × PBS-ethanol (1:1) at −20°C (Ravenschlag et al 2000). For the subsequent sample processing, a modified protocol by Lunau et al (2005) was followed: 100 µl of sediment slurry was diluted with 900 µl sterilised Milli-Q water and 100 µl methanol.…”