Sponges (Porifera) are the most primitive metazoan and are widely distributed in benthic community playing essential roles in the substance cycling and energy flow in the ecosystem. Recently studies has demonstrated the diversity and specificity of the microorganisms in sponges. However, the metabolism, function and evolution of the microorganisms, especially the potential symbionts, remains largely unknown. In this thesis, we studied the diversity and structures of the microbial communities, metabolisms, function and evolution of potential symbionts, selective effects of environmental stresses on the microbial community in the shallow water and deep-sea sponges through 16S rRNA gene amplicon sequencing, metagenomic sequencing, differential coverage binning and genomics analysis...[ Read more ]

Sponges (Porifera) are the most primitive metazoan and are widely distributed in benthic community playing essential roles in the substance cycling and energy flow in the ecosystem. Recently studies has demonstrated the diversity and specificity of the microorganisms in sponges. However, the metabolism, function and evolution of the microorganisms, especially the potential symbionts, remains largely unknown. In this thesis, we studied the diversity and structures of the microbial communities, metabolisms, function and evolution of potential symbionts, selective effects of environmental stresses on the microbial community in the shallow water and deep-sea sponges through 16S rRNA gene amplicon sequencing, metagenomic sequencing, differential coverage binning and genomics analysis. Our studies demonstrated the autotrophic metabolisms of the ammonia-oxidation, nitrite-oxidation and sulfur-oxidation in the potential symbionts of both shallow water and deep-sea sponges. The autotrophs were considered to play symbiotic roles through scavenging toxic substrates and providing carbohydrates for the host sponges. The unique genomic features in comparison to their free-living relatives indicated a coevolution with the hosts. The treatment studies indicated selective effects of the heavy metal and organic pollutants on the composition and function of the microbial communities in the sponges. This thesis extend our knowledge of the symbiosis in the environmentally important sponges, and provide insights into the function and evolution of the potential symbionts.