Tissue-Specific Microbiomes of the Red Sea Giant Clam Tridacna maxima Highlight Differential Abundance of Endozoicomonadaceae

Abstract

Giant clams (subfamily Tridacninae) are prevalent members of coral reef communities and engage in symbioses with algal photosymbionts of the family Symbiodiniaceae, similar to their scleractinian coral counterparts. However, we know little about their associated bacterial microbiome members. Here, we explored bacterial community diversity of digestive system, gill, and mantle tissues associated with the giant clam Tridacna maxima across a cross-shelf gradient (inshore, midshore, and offshore reef sites) in the central Red Sea using 16S rRNA gene amplicon sequencing. Different tissues harbor spatially stable and distinct microbial communities. Notably, diverse assemblages of bacteria affiliated to the family Endozoicomonadaceae were prevalent in all tissues, but particularly abundant in gills and to a lesser extent in digestive tissues. Besides Endozoicomonadaceae, bacteria in the families Pasteurellaceae, Alteromonadaceae, and Comamonadaceae were common associates, depending on the tissue queried. Taxonomy-based functional inference identified processes related to nitrogen cycling (among others) to be enriched in giant clam tissues and contributed by Endozoicomonadaceae. Our study highlights the tissue-specificity and broad taxonomic range of Endozoicomonadaceae associates, similar to other marine invertebrates, and suggests their contribution to nitrogen-related pathways. The investigation of bivalve-associated microbiome communities provides an important addition to the pathogen-focused studies for commercially important bivalves (e.g., oysters).

Surface Topography, Bacterial Carrying Capacity, and the Prospect of Microbiome Manipulation in the Sea Anemone Coral Model Aiptasia

“…However, we did not detect Endozoicomonas in the microbiome of inoculated anemones (i.e., SYM+ACRinoc, APO+ACRinoc). This suggests that Endozoicomonas exhibit high (coral) host specificity, despite their broad and prevalent distribution across marine invertebrates (Neave et al, 2016(Neave et al, , 2017Rossbach et al, 2019). Moreover, Endozoicomonas reside within coral tissues (Neave et al, 2016(Neave et al, , 2017, which may explain their absence after microbiome transplantation, because mucus-associated bacteria may be easier to transfer than tissue-associated bacteria.…”

Light-Dependent Phenomena and Related Molecular Mechanisms in Giant Clam-Dinoflagellate Associations: A Review

“…In fact, the success of giant clams in nutrient-poor waters in the tropics is partly attributable to the recycling of N, especially endogenous ammonia, between the host and its symbionts. Furthermore, there are indications that N assimilation and recycling in the ctenidium of giant clams can involve Endozoicomonadaceae bacteria (Rossbach et al, 2019a). The symbiotic dinoflagellates of T. squamosa can generate glutamate using ammonia produced by the clam host because they possess enzymes of the glutamate synthase (GS1-GOGAT) cycle (Fam et al, 2018).…”

Dimethylsulfoniopropionate concentration in coral reef invertebrates varies according to species assemblages

“…Marine bacterial genera degrading DMSP or DMS in the water column, associated or not with corals and/or giant clams. DMSP-degrading (green circle) and DMS-degrading (brown circle) found in the water column, bacterial genera found in corals (blue oval) and in giant clams (green oval) (adapted from 37,40 ; and further developed from [71][72][73][74][75][76][77] ).…”