Phylogenetic diversity of culturable fungi associated with two marine sponges: Haliclona simulans and Gelliodes carnosa, collected from the Hainan Island coastal waters of the South China Sea

The diversity and biological activities of fungi associated with the two sponges, Haliclona simulans and Gelliodes carnosa, were investigated using a culture-dependent method followed by analysis of the fungal rDNA-ITS sequences. The two sponges were collected from the coastal waters of Lingshui Bay of Hainan Island in the South China Sea. A total of 37 independent fungal isolates corresponding to 30 different species were obtained from the two sponges. Nearly two thirds of the strains (n = 24, 64.9%) had close affiliations (identity (ID) or similarity a parts per thousand yenaEuro parts per thousand 98%) with their best matches in GenBank. Another one third of the isolates (n = 13, 35.1%) were distantly related to their closest relatives (ID < 98%), implying that these species are possibly different from those previously reported. The two sponges possessed similar fungal diversities. Haliclona simulans harbored a mainly different fungal consortium as compared with that of the same sponge species collected from Irish coastal waters, suggesting that the fungal diversity associated with the sponges is more dependent on the surrounding environment than on the sponge species. Biological activities of the fungal culture extracts were tested against the human tumor cell lines, mainly, a human lung carcinoma cell line (A-549), a human liver carcinoma cell line (Bel-7402), and a human colon carcinoma cell line (HCT-8), and against the Gram positive bacterium Bacillus subtilis. A relatively high proportion of positive results were obtained in this study, demonstrating that fungi isolated from sponges could be a rich source of new biologically active natural products.