Bacterial Community Structure Associated with a Dimethylsulfoniopropionate-Producing North Atlantic Algal Bloom

Abstract

The bacteria associated with oceanic algal blooms are acknowledged to play important roles in carbon, nitrogen, and sulfur cycling, yet little information is available on their identities or phylogenetic affiliations. Three culture-independent methods were used to characterize bacteria from a dimethylsulfoniopropionate (DMSP)-producing algal bloom in the North Atlantic. Group-specific 16S rRNA-targeted oligonucleotides, 16S ribosomal DNA (rDNA) clone libraries, and terminal restriction fragment length polymorphism analysis all indicated that the marine Roseobacter lineage was numerically important in the heterotrophic bacterial community, averaging >20% of the 16S rDNA sampled. Two other groups of heterotrophic bacteria, the SAR86 and SAR11 clades, were also shown by the three 16S rRNA-based methods to be abundant in the bloom community. In surface waters, the Roseobacter, SAR86, and SAR11 lineages together accounted for over 50% of the bacterial rDNA and showed little spatial variability in abundance despite variations in the dominant algal species. Depth profiles indicated that Roseobacter phylotype abundance decreased with depth and was positively correlated with chlorophyll a, DMSP, and total organic sulfur (dimethyl sulfide plus DMSP plus dimethyl sulfoxide) concentrations. Based on these data and previous physiological studies of cultured Roseobacter strains, we hypothesize that this lineage plays a role in cycling organic sulfur compounds produced within the bloom. Three other abundant bacterial phylotypes (representing a cyanobacterium and two members of the ␣ Proteobacteria) were primarily associated with chlorophyll-rich surface waters of the bloom (0 to 50 m), while two others (representing Cytophagales and ␦ Proteobacteria) were primarily found in deeper waters (200 to 500 m).The bacterial communities associated with oceanic algal blooms play critical roles in carbon and nitrogen cycling through their influence on the formation and fate of dissolved organic matter (4, 7), nutrient availability (24), sinking flux (45), and many other processes. In blooms dominated by algal species that produce dimethylsulfoniopropionate (DSMP), bloom-associated bacteria also play an important role in organic-sulfur cycling. Degradation of DMSP by marine bacteria is one of the primary routes for the formation of dimethyl sulfide (DMS), a volatile sulfur compound that influences global climate through effects on backscatter and cloud formation (6). Recent studies have suggested that marine bacteria may control DMS formation through the expression of a competing pathway that routes the sulfur in DMSP through methanethiol (MeSH) rather than to DMS (21, 27, 46). New evidence is pointing to one particular lineage of marine bacteria as a key participant in DMSP biogeochemistry in the ocean. Both culture-independent (i.e., 16S rRNA-based) and culture-dependent studies indicate that members of the ␣ Proteobacteria belonging to the Roseobacter lineage are abundant in coastal and open-ocean environments (15,17,18), where they ar...

Community Structure of Denitrifiers, Bacteria , and Archaea along Redox Gradients in Pacific Northwest Marine Sediments by Terminal Restriction Fragment Length Polymorphism Analysis of Amplified Nitrite Reductase ( nirS ) and 16S rRNA Genes

“…When we analyzed the nirS T-RFLP reproducibility of two samples, patterns derived from different DNA extracts, PCR amplifications, and restriction hydrolysis were virtually identical, in agreement with published results (28,30). Peak height as a meaningful measure of gene abundance is supported by a positive correlation of relative T-RF abundance and quantitative dot blot hybridization of Ro- seobacter sp.-specific 16S rDNAs in a marine algal bloom (17). Furthermore, relative abundances of T-RFs were demonstrated to be independent of the number of PCR cycles, varying within a range of 5 to 10% until PCR cycle 27, and thereafter remained stable for the majority of peaks (29).…”

Ecology of aerobic anoxygenic phototrophic bacteria along an oligotrophic gradient in the Mediterranean Sea

“…Consistent with the net increase of their abundance after glucose additions in most stations, this supports the view that AAP bacteria represent a physiological group of photoheterotrophs able to use light-derived energy to rapidly grow when organic carbon sources are available. This is in agreement with their high abundances in estuarine waters (Schwalbach and Fuhrman, 2005;Waidner and Kirchman, 2007) and their common association with phytoplankton blooms (Gonzalez et al, 2000;Suzuki et al, 2001).…”

Biogeography of the uncultured marine picoeukaryote MAST-4: temperature-driven distribution patterns

“…Details of these oligo-and mesotrophic environments (up to 3.4 mg chlorophyll l À 1 ) have been already published: NOR , NAT (González et al, 2000), COC (Alonso-Sáez et al, 2007), WE (del Giorgio et al, 2011), BL (Alonso-Sáez et al, 2008, AL (Arin et al, 2002), IND and DH (Díez et al, 2004). Seawater was taken with Niskin bottles attached to a CTD (conductivity, temperature, depth recorder) rosette, prefiltered by a 200-mm nylon mesh and then filtered in succession through a 3-mm pore-size polycarbonate filter and a 0.2-mm pore-size Sterivex unit (Durapore, Millipore, Billerica, MA, USA).…”