ISOLATION AND CHARACTERIZATION OF AN ARYL-BETA-D-GLUCOSIDE UPTAKE ANDUTILIZATION SYSTEM (ABG) FROM THE GRAM-POSITIVE RUMINAL CLOSTRIDIUM SPECIES C-LONGISPORUM

A phosphotransferase-dependent aryl-beta-glucoside uptake and utilisat ion system (abg) was isolated from the ruminal Clostridium (''C. longi sporum''). The system is composed of three genes, abgG, abgF and abgA, and a number of regulatory regions, including terminator/antiterminat or type stem-loop structures preceding the abgG and abgF genes. Simila rity analysis of the proteins encoded by these genes indicated that th ey were responsible for the regulation of the abg system through antit ermination (AbgG), the uptake and phosphorylation of aryl-beta-glucosi des (AbgF) and the hydrolysis of the intracellular phosphorylated glyc osides (AbgA). Experimental evidence for the functions of AbgF and Abg A was obtained. Although it was not possible to demonstrate any functi on for AbgG, a promoter 5' to the abgG gene was identified which was r esponsible for expression of the downstream genes. The abg system is r emarkably similar to operons from the gram negative Enterobacteriaceae , both in the coding and non-coding regulatory regions.