Composition, uniqueness and variability of the epiphytic bacterial community of the green alga Ulva australis

Abstract

Green Ulvacean marine macroalgae are distributed worldwide in coastal tidal and subtidal ecosystems. As for many living surfaces in the marine environment, little is known concerning the epiphytic bacterial biofilm communities that inhabit algal surfaces. This study reports on the largest published libraries of near full-length 16S rRNA genes from a marine algal surface (5293 sequences from six samples) allowing for an in-depth assessment of the diversity and phylogenetic profile of the bacterial community on a green Ulvacean alga. Large 16S rRNA gene libraries of surrounding seawater were also used to determine the uniqueness of this bacterial community. The surface of Ulva australis is dominated by sequences of Alphaproteobacteria and the Bacteroidetes, especially within the Rhodobacteriaceae, Sphingomonadaceae, Flavobacteriaceae and Sapropiraceae families. Seawater libraries were also dominated by Alphaproteobacteria and Bacteroidetes sequences, but were shown to be clearly distinct from U. australis libraries through the clustering of sequences into operational taxonomic units and Bray-Curtis similarity analysis. Almost no similarity was observed between these two environments at the species level, and only minor similarity was observed at levels of sequence clustering representing clades of bacteria within family and genus taxonomic groups. Variability between libraries of U. australis was relatively high, and a consistent sub-population of bacterial species was not detected. The competitive lottery model, originally derived to explain diversity in coral reef fishes, may explain the pattern of colonization of this algal surface.

Bacterial diversity in relation to secondary production and succession on surfaces of the kelp Laminaria hyperborea

“…This model of community assembly is assumed in the neutral theory (Hubbell, 2001), which has successfully predicted species distribution curves for communities of macroscopic organisms (Hubbell, 2005) as well as microbial communities (Sloan et al, 2006). Similar observations indicating a high variability of bacterial OTUs between host individuals have also been reported for the green seaweed Ulva australis (Burke et al, 2011b), suggesting that seaweeds (including both kelps and green algae such as Ulva) display common patterns of surface bacterial community assembly. In the case of U. australis, it was recently shown that this lack of phylogenetic similarity (inferred by 16S rRNA gene sequences) is contrasted by a high similarity of functional genes (Burke et al, 2011a).…”

The microbiome of North Sea copepods

“…The colonisation process itself could be most likely explained by the competitive lottery model as already proposed for the colonisation of algal surfaces (Burke et al 2011b). In this context, we suggest to investigate the link between community structure and function using metagenomic sequence analysis (Burke et al 2011a) in future studies.…”

Changes in assembly processes in soil bacterial communities following a wildfire disturbance

“…It is possible that examining assembly processes using metagenomics or metatranscriptomics would reveal different patterns in the relative importance of niche vs neutral processes. For example, Burke et al (2011) recently showed that microbial community succession on marine algae displayed functional convergence but Figure 3 The three hypothesized phases of community assembly following disturbance. Phase 1 is characterized by more neutral assembly processes; Phase 2 is more niche-based and Phase 3 is increasingly more neutral.…”