Effects of substratum type on bacterial community structure in biofilms in relation to settlement of plantigrades of the mussel Mytilus coruscus

In this study, Illumina MiSeq sequencing was used to characterize the bacterial communities in the biofilms that formed on different substratum types including glass, steel, acrylic and hydrophobic glass. The link between bacterial community structure and plantigrade settlement of the mussel Mytilus coruscus was explored. The settlement preference of plantigrades for non-biofilmed substrata was also examined. High-throughput sequencing revealed that the bacterial communities of biofilms varied on different substrata. The overwhelming majority of sequences (>80% of all sequences) belonged to only three bacterial phyla: Proteobacteria, Bacteroidetes and Firmicutes. The phylum Proteobacteria was the dominating group in all biofilm samples. Cluster analysis based on Bray-Curtis distances analysis showed that communities in glass samples differed from those on other samples. The bacterial densities of the biofilms developed on glass were higher than those on other three samples. The present results showed that the percentage of plantigrade settlement was higher in biofilms on glass and steel samples than that in acrylic and hydrophobic glass samples. The variation of bacterial community structure might lead to differences of biofilm activity. There was no selective choice of non-biofilmed substratum for plantigrades. Thus, substratum type affected cell densities of bacteria and bacterial communities of biofilms, which were differentially attractive to plantigrades of M. coruscus.