First Record of Culturable Microbial Communities Associated with the Freshwater Sponge Spongilla alba in Lake Taal, Philippines.

Sponge-microbe symbiosis is considered among the most primitive ecological relationships between metazoans and microorganisms. There is strong interest in understanding the occurrence of microbial communities in sponges due to their integral roles in host ecology, nutrient cycling, and production of potential bioactive secondary metabolites. However, most studies on sponges have been centered on marine species. In this study, the freshwater sponge Spongilla alba and its associated microorganisms were explored for the first time. Sponge samples collected from Lake Taal were taxonomically identified using gross morphology and spicules analysis. Both bacterial and fungal isolates were culturally characterized and molecularly identified using 16S rRNA gene for bacteria and ITS for fungi. Five bacterial species were identified as Pseudomonas sp., Enterococcus sp., Stenotrophomonas sp., Stenotrophomonas maltophilia, and Pseudomonas mosselii plus eight fungal species with spore sizes from 5-10 μm were identified as Colletotrichum truncatum, Trichosporon asahii, Rhizopus microsporus, Puccinia striiformis f. sp. tritici strain, Talaromyces columbinus, Phoma sp., Phomopsis sp., and Lichtheimia ramosa. Phylogenetic analysis revealed microbial sequences belonging to Proteobacteria (n = 4), Firmicutes (n = 1), Ascomycota (n = 4), Zygomycota (n = 2), and Basidiomycota (n = 2). The study reports infrequent occurrences of Enterococcus, Stenotrophomonas, Puccinia, and Lichtheimia species as freshwater sponge-associated microbes. This also presents the culturable microbial composition of freshwater sponges and rare occurrence of marine- and terrestrial-associated fungi T. asahii, R. microsporus, Phoma sp., Phomopsis sp., C. truncatum, and T. columbinus in a unique freshwater ecosystem such as Lake Taal. [ABSTRACT FROM AUTHOR]