Phylogenetic Diversity And Spatial Distribution Of Prokaryotic Symbiosis In A South China Sea Marine Sponge, Holoxea Sp.

Phylogenetic diversity, abundance and spatial distribution of prokaryoticsymbionts in Holoxea sp., a tropical marine sponge from South China sea,were investigated by molecular technology.Diversity of extracellular ectosymbioes, extracellular endosymbiotes,intracellular endosymbiotes and sponge speciments were investigated bytwelve 16S rRNA gene clone libraries, 563 clones of which were sequencedand grouped into 163 OTUs.Gammaproteobacteria dominated the symbiosis community in Holoxeasp.. Besides Gammaproteobacteria, Bacteroidetes,Acidobacteria,Nitrospira,Verrucomicrobia,Chloroflexi,Firmicutes,Alphaproteobacteria,Betaproteobacteria,Micrococcineae,Propionibacterineae,Corynebacterineae,Acidimicrobidae,Cenarchoetawere detected as well. Statasitical analysis illustrated that the diversity ofintracellular endosymbiotes was higher than the extracellular ones. Thedifferences between different communities were significant:1)Gammaproteobacteria was the only one sub phylum of Proteobacteria insponge cells; 2) Acidobacteria was almost exist in sponge cells only; 3)Propionibacterineae and Corynebacterineae could not be detected in mesohylcommunity but compriesd up to 40% of intracelluar actinobacteriacommunity; 4) Micrococcineae was a kind of endosymbiotes in Holoxea sp. Phylogenetic analysis showed 9 Holoxea-specific clusters and 5 Holoxea-specific intracellular clusters. The nine Holoxea-specific clusters include five actinobacteria clusters ( three Acidimicrobidae clusters) , two Chloroflexi related clusters and two Gammaproteobacteria related ones. The five Holoxea-specific intracellular clusters contained three Gammaproteobacteria clusters, one Acidobacteria cluster and one Corynebacterineae cluster. The archaea community associated with Holoxea sp. was comprised by Cenarchaeota. No bacteria-related amoA genes were recovered but Cenarchaeota affilated AOA were detected in Holoxea sp.Accumulation of Actinobacteria and AOA in sponge cells was demonstrated by real-time quantitive PCR analysis. This result suggested the potential positive roles of Actinobacteria and AOA in elimination of ammonia waste released by sponge.Our study revealed the diversity of intracellular endosymbiotes in marine sponge for the first time. A complex and distinct microbial community embedded in sponge cells was displayed. Nodoubtly our study added a new dimension of spong associated microbes research. Further efforts combined with metagenomic technology and novel culture methods targeting the diversity and function of intracellular symbosis would benefit all aspects of sponge-symbiosis research.