Phylogenetic characterization of marine microbial biofilms associated with mammal bones in temperate and polar areas

Mammal bones sustain rich chemoautotrophic microbial communities that are consumed by a range of marine invertebrates, with bacteria playing a fundamental role making the organic matter retained in the bones available to other organisms. Our major aim here is to characterize the phylogenetic diversity of bacteria associated with Mediterranean shallow-water bones (whale, pig, and cow) examined at two different times after colonization, and compare it to bacterial communities developing on whale bones in the Southern Ocean. We sequenced 16S amplicons for approximately 50 clones from each of the 5 bone samples studied here, resulting in 215 OTUs. Our preliminary microbial community analysis resulted into two groups. Cluster 1 with cow and whale bones from the Mediterranean (3 months) and whale bones from the Southern Ocean (1 year), characterized by abundant Epsilon-proteobacteria, usually the first colonizers in anaerobic environments. Cluster 2 with Mediterranean cow (9 months) and pig bones (12 months), characterized by abundant Thiotrichales. Among the Thiotrichales, two different species ofBeggiatoaspp. appeared in two different bones in the Mediterranean samples, indicating thatBeggiatoaspp. can occur in the same area. Our work confirms that microbial mats associated with mammal bones in the shallow waters of the Mediterranean and the Southern Ocean are highly diverse with a predominance of Gamma- and Epsilon-proteobacteria.