GLUCOSE STIMULATES CAMP ACCUMULATION IN THE ORAL BACTERIUM ACTINOMYCES-VISCOSUS

Actinomyces viscosus T14V, a Gram-positive bacterium found in the oral cavity, was found to be insensitive to glucose-mediated catabolite re pression. Basal levels of beta-galactosidase (18-26 U) were observed a t all phases of growth regardless of the culture conditions. Further, beta-galactosidase could not be induced with lactose, or with a known inducer of the enzyme, isopropyl-beta-D-thiogalactoside, or with dibut yryl cAMP. Glucose, on the other hand, stimulated cAMP accumulation in a concentration-dependent manner. Fructose and sucrose mimicked the e ffects of glucose on cAMP accumulation, whereas galactose, mannose and maltose had lesser stimulatory effects. Other carbon sources, i.e., l actose, alpha-methylglucoside, ribose, xylose and succinate were witho ut effect. Glucose and alpha-methylglucoside were found to stimulate c AMP accumulation in toluene-permeabilized cells, in the presence of th e phosphodiesterase inhibitor, theophylline. Glucose did not stimulate cAMP levels in other Gram-positive bacteria including Streptococcus m utans, S. sanguis and S. salivarius but did cause cAMP accumulation in other strains of A. viscosus. The results suggest that glucose effect s on cAMP metabolism are independent of the induction of beta-galactos idase as presently defined for Escherichia coli, and that the effects appear to be selective to the A. viscosus bacteria. The results also s uggest that glucose stimulates cAMP accumulation via activation of ade nylate cyclase.