Fig. 2

Characterization of the microbiome associated with O. minuta. a Relative coverage and sequence size of non-eukaryotic contigs according to their taxa (Table S1, Additional file 1). The microbiome of O. minuta is dominated by a new Thaumarchaeota species that we propose to name Candidatus Cenarchaeum massiliensis and various proteobacteria. b Microsynteny analysis of genomic segments bearing an amo gene cluster in marine Thaumarchaeota showing that the genome Candidatus Cenarchaeum massiliensis has features highly conserved with other marine Thaumarchaeota (arrows of the same color indicate orthologous genes and black arrows represent genes without orthology relationship in these regions from OrthoMCL analysis). Other data concerning Ca. C. massiliensis are available in Tables S3 and S4 and Figs. S1, S2, and S3 of Additional file 1. c Localization of Ca. C. massiliensis in the tissues of O. minuta by Card-FISH using a specific probe (blue = DAPI staining; green = labeled probe) shows the presence of this symbiont in the whole trabecular syncytium including the dermal layer and the flagellated chambers (see also Fig. S4, Additional file 1)