Interactions among microorganisms found in coral mucus can be either symbiotic or competitive. It has been hypothesized that microbial communities fo

The aetiological agent of bleaching of the coral Oculina patagonica was characterized as a new Vibrio species on the basis of 16S rDNA sequence, DNA-DNA hybridization data and phenotypic properties, including the cellular fatty acid profile. Based on its 16S rDNA and DNA-DNA hybridization, the new Vibrio species is closely related to Vibrio mediterranei. The name Vibrio shiloi sp. nov. is proposed for the new coral-bleaching species, the type strain being AK1T (= ATCC BAA-91T = DSM 13774T).

Summary: Diversity, distribution and genetic comparison of Archaea associated with the surface mucus of corals from three genera, namely Acanthastrea sp., Favia sp. and Fungia sp., from the Gulf of Eilat, Israel and from Heron Island, Australia were studied. Sequencing of the 16S rRNA gene of the coral‐associated Archaea revealed dominance of Crenarchaeota (79%, on average). In this phylum, 87% of the sequences were similar (≥ 97%) to the Thermoprotei , with 76% of these being similar (≥ 97%) to the ammonium oxidizer, Nitrosopumilus maritimus . Most of the coral‐associated euryarchaeotal sequences (69%) were related to marine group II, while other euryarchaeotal clades were found to be related to anaerobic methanotrophs (8%), anaerobic nitrate reducers (i.e. denitrification, 15%) and marine group III (8%). Most of the crenarchaeotal and euryarchaeotal coral‐associated 16S rRNA gene sequences from Heron Island (61%) and from the Gulf of Eilat (71%) were closely related (≥ 97%) to sequences previously derived from corals from the Virgin Islands. Analysis of archaeal amoA sequences obtained from the fungiid coral, Fungia granulosa , divided into three clades, all related to archaeal sequences previously obtained from the marine environment. These sequences were distantly related to amoA sequences previously found in association with other coral species. Preliminary experiments suggest that there is active oxidation of ammonia to nitrite in the mucus of F. granulosa . Thus, coral‐associated Archaea may contribute to nitrogen recycling in the holobiont, presumably by acting as a nutritional sink for excess ammonium trapped in the mucus layer, through nitrification and denitrification processes.