Abstract

PHYLOGENETIC DIVERSITY OF CULTURABLE FUNGI ASSOCIATED WITH SPONGES LEUCOSOLENIA SP. AND HEXACTINOSA SP. IN HA TIEN SEA, KIEN GIANG, VIETNAM

Prof. Dr. Cao Ngoc Diep*, Dr. Ngo Thanh Phong, Dr. Ho Thanh Tam,
MSc. Dao Thi Minh Chau

ABSTRACT

The diversity and biological activities of fungi associated with the two sponges, Leucosolenia sp. and Hexactinosa sp. were investigated by using a culture-dependent method followed by analysis of the fungal rDNA-ITS sequences. Total of 33 fungal isolates were isolated from 23 sponge samples of Leucosolenia sp. and Hexactinosa sp. at four islands in Ha Tien Sea, Kien Giang province of the Mekong Delta of Vietnam. There were 28 isolates had the ability of antibacterial activity; however, there were 18 isolates made halos (sterile zones) with diameter >2 mm and 10 isolates made small halos (<1.5 mm), these isolates were chosen to identify based on nucleotide sequence from internal transcribed spacer (ITS) rDNA. The sequences from selected fungal isolates showed high degrees of similarity to those of the GenBank reference strains (99% - 100%), all of them were identified as various species of Aspergillus. There were 8 strains having ability against bacterial pathogens of humans, bacterial pathogens on fish and Candida albicans, and the fungal isolates had higher antimicrobial activity against tested Gram-negative bacteria (particularly against Salmonella enterica) than Gram-positive bacteria. Based on Pi value (nucleotide diversity), Aspergillus group had the highest Theta value and Theta values (per sequence) from S of SNP for DNA polymorphism were calculated from each group and Aspergillus group had the highest value. Our results suggest that the potential of fungi associated with Ha Tien Sea sponges, particularly Aspergillus, would be valuable sources of antimicrobial compounds, especially against yeast (Candida albicans). To our knowledge, this is the first report describing the biodiversity and the metabolic potential of fungi associated with marine sponges of Ha Tien Sea, Kien Giang province, Vietnam.

Keywords: 18S-rDNA-ITS, Aspergillus, antibacterial ability, fungal diversity, marine sponge.