Wood falls are organic substrates sunken on the ocean floor that house a diversified fauna of marine invertebrates. Among them, the echinoid Asterechinus elegans is found in various localities from the West-Pacific region and observations of its gut content indicate that it is a wood-feeding species. The diversity of the microflora associated with its gut content was investigated by 16 rRNA gene cloning analysis and identified Proteobacteria, Planctomycete, Firmicutes, Cytophaga-Flexibacter-Bacteroides and Actinobacteria. Clones were related to bacteria from the gut of phytophageous (including wood-feeding) animals but also from sulphide-rich environments such as whale carcasses, mangrove soils and marine sediments of notably hydrothermal vents and cold seeps. Furthermore, the analysis of the adenosine 5'-phosphosulphate (APS) reductase gene Put in evidence the presence of several sulphide-oxidizing bacteria (SOB) belonging to the Alpha- and Gamma-proteobacteria While some sulphate-reducing bacteria (SRB) affiliated to the Delta-proteobacteria were also detected. APS reductase clones were related to thioautotrophic symbionts of various marine invertebrates including tube worms and gutless oligochaetes. These results suggest that a part of the bacterial community associated with the gut content of A. elegans would be able to participate in the wood digestion and therefore to the echinoid nourishment. Further analyses are however needed to clarify several aspects of this association.