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Entotheonella (phylum Tectomicrobia) is a filamentous symbiont that produces almost all known bioactive compounds derived from the Lithistida sponge Theonella swinhoei. In contrast to the comprehensive knowledge of its secondary metabolism, knowledge of its lifestyle, resilience, and interaction with the sponge host and other symbionts remains rudimentary. In this study, we obtained two Entotheonella genomes from T. swinhoei from the South China Sea through metagenome binning, and used a RASTtk pipeline to achieve better genome annotation. The high average nucleotide index values suggested they were the same phylotypes as the two Entotheonella phylotypes from T. swinhoei from the Japan Sea. Genomic features related to utilization of various carbon sources, peptidase secretion, CO2 fixation, sulfate reduction, anaerobic respiration, and denitrification indicated the mixotrophic nature of Entotheonella. The endospore-forming potential along with metal- and antibiotic resistance indicated Entotheonella was highly resilient to harsh conditions. The potential for endospore formation also explained the widespread distribution of Entotheonella to some extent. The discovery of Type II (general secretion pathway proteins and the Widespread Colonization Island) and Type VI secretion systems in Entotheonella suggested it could secrete extracellular hydrolases, form tight adhesion, act against phagocytes, and kill other prokaryotes. Overall, the newly discovered genomic features suggest Entotheonella is a highly competitive member of the symbiotic community of T. swinhoei.

Sponge diseases have been widely reported, yet the causal factors and major pathogenic microbes remain elusive. In this study, two individuals of the sponge Crella cyathophora in total that showed similar disease-like characteristics were collected from two different locations along the Red Sea coast separated by more than 30 kilometers. The disease-like parts of the two individuals were both covered by green surfaces, and the body size was much smaller compared with adjacent healthy regions. Here, using high-throughput pyrosequencing technology, we investigated the prokaryotic communities in healthy and disease-like sponge tissues as well as adjacent seawater. Microbes in healthy tissues belonged mainly to the Proteobacteria, Cyanobacteria and Bacteroidetes, and were much more diverse at the phylum level than reported previously. Interestingly, the disease-like tissues from the two sponge individuals underwent shifts of prokaryotic communities and were both enriched with a novel clade affiliated with the phylum Verrucomicrobia, implying its intimate connection with the disease-like Red Sea sponge C. cyathophora. Enrichment of the phylum Verrucomicrobia was also considered to be correlated with the presence of algae assemblages forming the green surface of the disease-like sponge tissues. This finding represents an interesting case of sponge disease and is valuable for further study.

"Entotheonella" (phylum "Tectomicrobia") is a filamentous symbiont that produces almost all known bioactive compounds derived from the Lithistida sponge Theonella swinhoei. In contrast to the comprehensive knowledge of its secondary metabolism, knowledge of its lifestyle, resilience, and interaction with the sponge host and other symbionts remains rudimentary. In this study, we obtained two "Entotheonella" genomes from T. swinhoei from the South China Sea through metagenome binning, and used a RASTtk pipeline to achieve better genome annotation. The high average nucleotide index values suggested they were the same phylotypes as the two "Entotheonella" phylotypes from T. swinhoei from the Japan Sea. Genomic features related to utilization of various carbon sources, peptidase secretion, CO2 fixation, sulfate reduction, anaerobic respiration, and denitrification indicated the mixotrophic nature of "Entotheonella." The endospore-forming potential along with metal- and antibiotic resistance indicated "Entotheonella" was highly resilient to harsh conditions. The potential for endospore formation also explained the widespread distribution of "Entotheonella" to some extent. The discovery of Type II (general secretion pathway proteins and the Widespread Colonization Island) and Type VI secretion systems in "Entotheonella" suggested it could secrete extracellular hydrolases, form tight adhesion, act against phagocytes, and kill other prokaryotes. Overall, the newly discovered genomic features suggest "Entotheonella" is a highly competitive member of the symbiotic community of T. swinhoei.

Sponge diseases have been widely reported, yet the causal factors and major pathogenic microbes remain elusive. In this study, two individuals of the sponge Crella cyathophora in total that showed similar disease-like characteristics were collected from two different locations along the Red Sea coast separated by more than 30 kilometers. The disease-like parts of the two individuals were both covered by green surfaces, and the body size was much smaller compared with adjacent healthy regions. Here, using high-throughput pyrosequencing technology, we investigated the prokaryotic communities in healthy and disease-like sponge tissues as well as adjacent seawater. Microbes in healthy tissues belonged mainly to the Proteobacteria, Cyanobacteria and Bacteroidetes, and were much more diverse at the phylum level than reported previously. Interestingly, the disease-like tissues from the two sponge individuals underwent shifts of prokaryotic communities and were both enriched with a novel clade affiliated with the phylum Verrucomicrobia, implying its intimate connection with the disease-like Red Sea sponge C. cyathophora. Enrichment of the phylum Verrucomicrobia was also considered to be correlated with the presence of algae assemblages forming the green surface of the disease-like sponge tissues. This finding represents an interesting case of sponge disease and is valuable for further study.