FACTORS INFLUENCING BETA-GALACTOSIDASE ACTIVITY OF AEROMONAS-CAVIAE

Aeromonas caviae, often reported to be associated with diarrhoeal pati ents, elaborates several virulence factors as well as catabolic enzyme s such as xylanase and beta-galactosidase. Studies on the kinetics of growth of A. caviae and synthesis of beta-galactosidase suggested that the activity was cell associated and reached a peak during the late l ogarithmic phase of growth. The optimum pH for beta-galactosidase acti vity was 7.0 and required Ca2+ and glutathione for enhancement of its activity; IPTG also slightly improved the activity. Aerobic cultivatio n of A. caviae in LB containing glucose, fructose, maltose and sucrose completely inhibited the activity possibly due to acetic acid product ion. Addition of 100 mM cAMP to the media containing glucose (0.25%, w /v) restored the relative activity by 8.8%; however, the final pH of t he media remained acidic. Aerobic growth of A. caviae with other carbo n sources did not affect beta-galactosidase activity, probably as ther e was no acid production and thereby the final pH of the media unalter ed. Arabinose, xylose and galactose induced the A. caviae beta-galacto sidase activity by several folds and lactose moderately enhanced its a ctivity.