Growth, protease production, and pH change in response to salinity, temperature and substrate in aspergilli

Aspergillus sydowii is an opportunistic fungal pathogen of the coral Gorgonia venialina. Only marine strains cause disease on corals. To determine how strains of A. sydowii differ in virulence, five strains of Aspergillus were measured for growth, protease production, and pH change in response to salinity (0%, 2%, 3.5%), temperature (25°C, 28°C, 32°C), protein substrate (yeast extract, crushed coral), and initial pH (4.5, 5.2, 6.3, 7.7). Pathogenic strains of A. sydowii were uniquely able to survive high salinity and low temperature environments such as that which would be found in the ocean. At 3.5% salinity, the terrestrial strain was unable to produce proteases on crushed coral substrate. It also showed a significant decrease in growth and protease production in acidic media. These results indicate that virulence of A. sydowii may be linked to salt, temperature, pH tolerance, and the ability to produce protease proteases capable of degrading coral tissue.