Structure, dynamics and predicted functional role of the gut microbiota of the blue (Haliotis fulgens) and yellow (H. corrugata) abalone from Baja California Sur, Mexico

The GI microbiota of abalone contains a highly complex bacterial assemblage playing an essential role in the overall health of these gastropods. The gut bacterial communities of abalone species characterized so far reveal considerable interspecific variability, likely resulting from bacterial interactions and constrained by the ecology of their abalone host species; however, they remain poorly investigated. Additionally, the extent to which structural changes in the microbiota entail functional shifts in metabolic pathways of bacterial communities remains unexplored. In order to address these questions, we characterized the gut microbiota of the northeast Pacific blue (Haliotis fulgens or HF) and yellow (Haliotis corrugata or HC) abalone by 16S rRNA gene pyrosequencing to shed light on: (i) their gut microbiota structure; (ii) how bacteria may interact among them; and (iii) predicted shifts in bacterial metabolic functions associated with the observed structural changes. Our findings revealed that Mycoplasma dominated the GI microbiome in both species. However, the structure of the bacterial communities differed significantly in spite of considerable intraspecific variation. This resulted from changes in predominant species composition in each GI microbiota, suggesting host-specific adaptation of bacterial lineages to these sympatric abalone. We hypothesize that the presence of exclusive OTUs in each microbiota may relate to host-specific differences in competitive pressure. Significant differences in bacterial diversity were found between species for the explored metabolic pathways despite their functional overlap. A more diverse array of bacteria contributed to each function in HC, whereas a single or much fewer OTUs were generally observed in HF. The structural and functional analyses allowed us to describe a significant taxonomic split and functional overlap between the microbiota of HF and HC abalone.