Cultivable yeasts associated with marine sponges in the Gulf of Thailand, South China Sea.

Marine sponges harbor numerous microorganisms, among which sponge-associated yeasts are the least explored. To gain greater knowledge of sponge-associated yeasts, an investigation was therefore performed on marine sponges in Sattahip Bay, Gulf of Thailand, South China Sea. Seventy-one (71) marine sponge samples were collected at sites near Samae-san, Mu, and Khram islands, and were subsequently identified as 17 sponge species in 14 genera. Eighty-seven (87) yeast strains were isolated from 42 samples. The identification of yeasts by similarity analysis of the D1/D2 domain sequences of the large subunit rRNA gene revealed that 64% of the yeast strains obtained belonged to the phylum Basidiomycota, while the remaining strains belonged to the phylum Ascomycota. The strains that belonged to Ascomycota comprised 11 known yeast species in five genera (Candida, Kodamaea, Magnusiomyces, Meyerozyma, and Pichia). The strains belonging to the phylum Basidiomycota comprised 14 known yeast species in eight genera (Cutaneotrichosporon, Cystobasidium, Naganishia, Papiliotrema, Rhodosporidiobolus, Rhodotorula, Trichosporon, and Vishniacozyma). In addition, three strains represented a potential novel species closest to Cys. slooffiae; one strain represented a potential novel species closest to R. toruloides; and one strain represented a potential novel species closest to V. foliicola. The species with the highest occurrence was Rhodotorula mucilaginosa. No marked difference was found in the principal coordinates analysis of the ordinations of yeast communities from the three sampling sites. The estimation using EstimateS software showed that the expected species richness was higher than the observed species richness. As the marine sponge-yeast association remains unclear, more systematic investigations should be carried out.