Phylogenetic Diversity and Specificity of Bacteria Closely Associated with Alexandrium spp. and Other Phytoplankton

Abstract

While several studies have suggested that bacterium-phytoplankton interactions have the potential to dramatically influence harmful algal bloom dynamics, little is known about how bacteria and phytoplankton communities interact at the species composition level. The objective of the current study was to determine whether there are specific associations between diverse phytoplankton and the bacteria that co-occur with them. We determined the phylogenetic diversity of bacterial assemblages associated with 10 Alexandrium strains and representatives of the major taxonomic groups of phytoplankton in the Gulf of Maine. For this analysis we chose xenic phytoplankton cultures that (i) represented a broad taxonomic range, (ii) represented a broad geographic range for Alexandrium spp. isolates, (iii) grew under similar cultivation conditions, (iv) had a minimal length of time since the original isolation, and (v) had been isolated from a vegetative phytoplankton cell. 16S rRNA gene fragments of most Bacteria were amplified from DNA extracted from cultures and were analyzed by denaturing gradient gel electrophoresis and sequencing. A greater number of bacterial species were shared by different Alexandrium cultures, regardless of the geographic origin, than by Alexandrium species and nontoxic phytoplankton from the Gulf of Maine. In particular, members of the Roseobacter clade showed a higher degree of association with Alexandrium than with other bacterial groups, and many sequences matched sequences reported to be associated with other toxic dinoflagellates. These results provide evidence for specificity in bacterium-phytoplankton associations.

Variability and abundance of the epiphytic bacterial community associated with a green marine Ulvacean alga

“…A prevalence of sequences from these two bacterial groups has been reported in a DGGE based study of phytoplankton (Jasti et al, 2005), and on brackish submerged macrophytes (Hempel et al, 2008). In addition to these two groups, Gammaproteobacteria and unaffiliated sequences similar to the candidate bacterial phylum OP11, were identified in this study.…”

“…A 16S rRNA gene clone library of the epiphytic bacterial community associated with U. australis and the red alga Deslisea pulchra (Longford et al, 2007) also contained sequences belonging to these bacterial groups and several of our DGGE bands were expectedly related to these clones. These broad phylogenetic groups, with the exception of the OP11-like sequences, have also been detected in molecular-based community analyses of bacterial assemblages associated with the tropical green macro-alga Caulerpa taxifolia (Meusnier et al, 2001), filamentous green algae of sphagnum bogs (Fisher et al, 1998), marine diatoms (Grossart et al, 2005) and phytoplankton (Jasti et al, 2005), and hence appear to emerge as important associates of algae in general.…”

Aerobic Degradation of Petroleum Components by Microbial Consortia

“…The composition of free-living marine microbial communities is frequently very different from those attached to microalgae [208], with certain groups often preferring the attached lifestyle and showing higher levels of activity [194]. Moreover, different species of microalgae host distinct bacterial communities that change with time and environmental conditions [209,210]. However, there is likely to be a large spectrum of bacterial heterotroph-phototroph specificity [211], and certainly many attached bacteria can also live in the absence of a microalgal or cyanobacterial host [212].…”

Observation of bacteria over the surface of released oogonia from Fucus vesiculosus L. (Phaeophyceae)

“…Algae are especially susceptible to epibiosis being covered by diverse microbial communities (Goecke et al 2010). Interactions between bacteria and algae are thought to be important in controlling the dynamics of both communities (Jasti et al 2005). Although some of the macroalga-bacteria interactions have been discussed earlier, the ecological relevance of most naturally occurring bacterial communities on macroalgae remains unclear (Ivanova et al 2002).…”