Inhibition of transformation of Bacillus subtilis by heavy metals

Effect of heavy metals on marine Bacillus sp. and Flavobacterium sp

: Responses to varying concentrations of Hg, Cd, and Zn were studied in two strains of bacterial isolates (Flavobacterium sp. and Bacillus sp.) from Indian coastal waters. Growth responses showed inhibition (in terms of percentage reduction with respect to control) and the order of inhibition was Hg>Zn>Cd in the case of Bacillus sp. and Hg>Cd>Zn in the case of Flavobacterium sp. With prolonged incubation Bacillus sp. overcame the inhibitory effect whereas Flavobacterium sp. did not. Higher concentrations of glucose in the growth medium increased the inhibitory effect of the metal. At lower concentrations (15μg ml(-1)) there was a stimulatory effect on [(14)C] glucose uptake on Flavobacterium sp. Our studies showed that the Gram positive isolate was less adaptable to metals than the Gram negative.

DNA-directed cell-free protein-synthesizing system of Bacillus subtilis

A cell-free coupled system of transcription and translation using cell extracts from Bacillus subtilis and DNA from phage SP82 has been developed. Under optimum conditions, it incorporated approx. 300 pmol methionine during a 1 h incubation. The activity of the system increased linearly as the concentration of S-150 supernatant fraction protein increased from 125 to 325 microgram per assay. The optimum Mg2+ concentration was 12.5-15 mM. Ribosomes required treatment with DNAase in order to reduce endogenous activity, but the S-150 fraction was kept DNAase-free to prevent degradation of exogenously added DNA. The coupled system was sensitive to inhibitors of RNA and protein synthesis. Kinetic studies showed that the number of pmol of nucleotides present in newly synthesized RNA increased linearly for the first 20-min reaction and that the rate of amino acid incorporation increased linearly for the first 30 min. Polyacrylamide gel electrophoresis of the in vitro synthesized products yielded a band pattern that closely resembled the pattern of early phage SP82 proteins produced in vivo.

Purification and properties of a manganese-stimulated endonuclease from Bacillus subtilis

An endonuclease stimulated by manganese or calcium ions was isolated from Bacillus subtilis. This enzyme attacked double- or single-stranded deoxyribonucleic acid from a variety of sources, including B. subtilis, and was purified from the material released into the medium during protoplast formation. The enzyme appeared as a single peak after glycerol gradient centrifugation and comprised approximately 30 to 35% of the protein in the most purified preparations, as estimated by gel electrophoresis. It had a molecular weight of about 46,000. The mode of action of the enzyme was endonucleolytic, and circular deoxyribonucleic acid was readily cleaved. The enzyme introduced a limited number of both double- and single-strand breaks into native deoxyribonucleic acid, generally yielding products of 1 X 10(6) daltons or more in size. The reasons for this limitation of cleavage were not clear. The activity of the enzyme was inhibited by low levels of Cu2+, Co2+, Hg2+, and Zn2+. It was also inhibited by high concentrations of NaCl. A role for this enzyme in bacterial transormation is suggested.