Metabolic activity on Biolog FF MicroPlate suggests organic substrate decomposition by Aspergillus terreus NTOU4989 isolated from Kueishan Island Hydrothermal Vent Field, Taiwan

Aspergillus terreus NTOU4989 was isolated from sulfur sediment collected at Kueishan Island Hydrothermal Vent Field, Taiwan, and was shown to be able to grow at 45 °C and pH 3 in seawater, characteristics of hydrothermal vent sites. Fungi are one of the major decomposers in the marine environment, and to find out whether A. terreus NTOU4989 can fulfill such a role at the site, this study investigated its metabolic activity using the Biolog FF MicroPlate™ under different growth conditions (45 °C/pH 3, 45 °C/pH 7, 25 °C/pH 3, 25 °C/pH 7) with/without addition of Al³⁺, Fe²⁺ and Mn²⁺, major metal ions in the vent effluent. The greatest metabolic activity was observed at 25 °C/pH 3 with/without the metal ions based on substrate richness (R_S, metabolic richness), average well colour development (AWCD, metabolic capacity) and average well turbidity development (AWTD, mycelial production). Significant low R_S, AWCD and AWTD were observed at 45 °C, suggesting that A. terreus NTOU4989 is a thermotolerant fungus. The presence of the metal ions did not have a significant effect on its metabolic activity. Monomers of lignin, cellulose and hemicellulose, and common sugars and amino acids of algae were utilized in selected conditions, providing evidence of wood and algal decomposition by the fungus at the hydrothermal vent site.