Some mutants of Vibrio parahaemolyticus defective in maltose utilization (Mal-) were found to be hyperinducible for synthesis of extracellular amylase (Amy+h). Such mutants were used conveniently to study the mechanisms of catabolite repression exerted on amylase synthesis. Amylase synthesis in an Amy+h Mal- mutant, strain 3122, grown with maltotriose as the inducer, was repressed to various extents by each of 14 carbon and energy sources included in the medium. As expected, a high inverse correlation (r=-0.71) was found between thedifferential rates (DR) of enzyme synthesis and the specific growth rate constants μ observed with the individual cultures. Cyclic adenosine 3', 5'-monophosphate (cAMP) added to the cultures generally stimulated amylase synthesis, but its extent varied greatly with the carbon and energy sources employed. The effect was demonstrated most clearly when glycerol was the carbon source, and the maximum DR obtained was about 8 times higher than that obtained without cAMP. cAMP was much less effective on stimulation of amylase synthesis when added to cultures grown on mannose, glucose, galactose, pyruvate or gluconate as the carbon and energy source. These suggest that factor (s) other than cAMP may also be involved in the enzyme repression under these conditions of cultivation.
A lactose-positive strain of Salmonella litchfield was isolated from periproctal absess. The lactose-positive character of the strain was attributed to a plasmid with a molecular weight of about 130 megadaltons. This plasmid, pRY82, was conjugally nontransmissible but was mobilized by plasmid pTH10. Resistance to chloramphenicol, streptomycin, sulfamethoxazole, tetracycline and potassium tellurite as well as inhibition of development of bacteriophages T7 and lambda were mediated by pRY82. It was suggested that pRY82 is a member of the H2 incompatibility group. During the course of the test for incompatibility, recombination between pRY82 and R478 DNAs occurred in high frequency to form new plasmids mediating lactose-utilization and resistance to kanamycin.
An immunostimulatory agent partially purified from the aqueous phase of phenol-water extracts of BCG was studied for its anti-tumor effects in mice. The agent exerted marked suppressive effects on sarcoma 180 inoculated into ICR mice and caused extensive hemorrhagic necrosis and regression and high incidence of complete cure of Meth A fibrosarcoma established in BALB/c mice as did a reference Escherichia coli lipopolysaccharide (LPS), although much higher doses of the agent than those of LPS were used. The antitumor effects of the agent were accompanied with considerable loss of body weight of test animals, but the weight loss was less than that caused by the reference LPS and ceased when the drug administration was stopped. A synergistic anti-Meth A tumor effect was noted in combined use of the agent and Nα-(N-acetylmuramyl-L-alanyl-D-isogulutaminyl)-Nε-stearoyl-L-lysine under the experimental conditions where each compound was scarcely active.