Abstract
A total of 748 isolates from estuarine and marine environments were evaluated for antiviral activity against infectious hematopoietic necrosis virus (INHV) according to plaque reduction assay. Among isolates from estuarine environment, 267 (71%) of 376 strains exhibited a 50% plaque reduction of IHNV, including 58 strains (18%) able to reduce plaques more than 90%. On the other hand, 120 (32%) of 372 strains from marine environment showed a 50% plaque reduction, including 23 strains (6%) showing a 90% plaque reduction. The incidence of bacteria having antiviral activity in the estuarine isolates was approximately twice that of the marine isolates. Most of the bacteria which exhibited plaque reduction of more than 90% belonged to genera Pseudomonas, Achromobacter, and Vibrio.
A representative strain of those, Achromobacter sp. 51HW-25, produced antiviral agents heavily when incubated with shaking at 21°C for 60h. The antiviral products appeared to be two kinds of substances, thermolabile macromolecule and thermostable low molecular compound of molecular weight of less than 1, 000, when the bacterium was grown at 20°C. However, the bacterium grown at 25°C allowed production of only the low molecular compound.
