Spatial Dynamics of Sulphate-reducing Bacterial Compositions in Sediment along a Salinity Gradient in a UK Estuary

Abstract

The diversity of sulphate-reducing bacteria (SRB) was investigated in sediments along environmental gradients in the River Colne estuary, Essex, UK. DNA samples were collected from four sites; marine-dominated (Alresford Creek), brackish (the Hythe), predominantly freshwater (East Hill Bridge) and freshwater (the Weir) between September 2001 and May 2002. SRB community composition was assessed by PCR amplification, cloning and sequencing of part of the α subunit of dissimilatory sulphite reductase (dsrA) using directly extracted sediment DNA. The majority of the dsrA sequences were associated with members of the Desulfobacteraceae family, the Desulfobulbaceae family and a deeply branched group in the dsrA tree with no cultured representatives. There was some evidence of a salinity-related distribution within both the Desulfobacteraceae and Desulfobulbaceae groups. Clones related to Desulfotomaculum of the xenologues Firmicutes and a phylogenetically distinct Colne group 3 were detected only at the freshwater East Hill Bridge and Weir sites. Conversely, clones related to an uncultured group (Colne group 1) were found only at the marine and brackish sites. A statistical analysis of composition revealed that dsrA sequences from the marine-dominated Alresford Creek and the brackish site at the Hythe were not significantly different from each other (P>0.05), but were significantly different from those of the freshwater-dominated East Hill Bridge and the Weir (P<0.05). The sequences from East Hill Bridge and the Weir were not significantly different from each other (P>0.05). The data presented show a complex distribution of SRB along the estuary with some evidence to support the idea that salinity and sulphate concentrations are an important factor in determining SRB community structure.Key words: dissimilatory sulphite reductase gene, environmental gradients, estuarine sediment, sulphate reduction Sulphate reduction is an important process involved in both the global carbon and sulphur cycles. This process can dominate anaerobic terminal mineralisation of organic matter in high-sulphate sediments, degrading up to 50% of all organic matter in coastal marine sediments 12) and plays a minor but still important role in low-sulphate sediments 26,38) . Rates of sulphate reduction vary in relation to temperature and electron donor and acceptor concentrations with the availability of sulphate an important factor in the control of the rate of sulphate reduction. Sulphate concentrations range from approximately 25 mM in full-strength seawater to <0.2 mM in freshwater 7) . Freshwater-adapted sulphatereducing bacteria (SRB) have a greater affinity for sulphate (K m =5-68 µM) than marine-adapted SRB (K m =200 µM) 8,37) , allowing them to continue sulphate reduction at much lower sulphate concentrations than marine SRB. Physiological differences between freshwater-and marine-adapted SRB may be reflected in differences in species or phylogenetic compositions of SRB communities.The Colne estuary is a small, muddy, macrotidal (3 to 5...

Comparison of the diversity of sulfate-reducing bacterial communities in the water column and the surface sediments of a Japanese meromictic lake

“…They showed that dsrAB sequences related to Desulfotomaculum were dominant in the freshwater SRB community and that δ-Proteobacterial dsrAB sequences dominated at a brackish site, suggesting that sulfate availability and salinity play a signifi cant role in structuring the SRB community in estuarine environments. In addition to sulfate content and salinity, organic carbon content is suggested to be responsible for the differences in the SRB communities in an UK estuary (Kondo et al, 2007). In the surface waters of Lake Suigetsu, cyanobacterial blooms of Microcystis and/or Anabaena occur during the summer season whereas a dinofl agellate dominates during the winter season.…”

Microbial community response to a simulated hydrocarbon spill in mangrove sediments

“…Moreover, in the T75 libraries, members of the Deltaproteobacteria abounded (represented in the libraries by the genera Desulfobacteraceae, Desulfobulbaceae, Desulfuromonadales, Desulfobacterium). These genera encompass major sulphate reducing bacteria (SRB), which are anaerobic bacteria commonly found in freshwater and marine anoxic sediments (Rees and Patel, 2001;Klepac-Ceraj et al, 2004;Asami et al, 2005;Mussmann et al, 2005;Da Silva et al, 2007;Foti et al, 2007;Kjeldsen et al, 2007;Kondo et al, 2007;Miletto et al, 2007;Suzuki et al, 2007aSuzuki et al, , 2007b. SRB are frequently associated with the anaerobic hydrocarbon degradation process (PerezJimenez and Kerkhof, 2005;Kniemeyer et al, 2007;Miralles et al, 2007aMiralles et al, , 2007b.…”

Planktonic Bacterial Population Dynamics with Environmental Changes in Coastal Areas of Suruga Bay

“…Other findings, such as the abundance of Alphaproteobacteria in estuarine and coastal environments 13) and the existence of Archaea in coastal waters 23) , have been revealed by the molecular analysis of prokaryotic microbial communities. The environmental control of bacterial assemblages 4,25) and the relationship between the aquatic environment and the distribution of functional bacterial groups 5,19) were also shown by molecular analyses of bacterial communities 15,18) . Among the methods of molecular analysis, the fluorescence in situ hybridization (FISH) technique, developed by DeLong et al 6) , provides quantitative information about bacterial community structure and the abundance of individual organisms in populations.…”