The nucleotide sequence of the gtJB gene from Streptococcus mutans coding

No abstract

The aluminium complexes of N(2)O(2)-dipyrrins were synthesized and the absorption/fluorescence spectral changes caused by the complex formation with ZnCl(2), ZnBr(2) and Zn(OAc)(2) were examined.

The polyhydroxyalkanoic acid (PHA) granule-associated 16-kDa protein (GA16 protein) of Paracoccus denitrificans was identified, and its corresponding gene was cloned and analyzed at the molecular level. The N-terminal amino acid sequence of GA16 protein revealed that its structural gene is located downstream from the PHA synthase gene (phaC Pd) cloned recently (S. Ueda, T. Yabutani, A. Maehara, and T. Yamane, J. Bacteriol. 178:774–779, 1996). Gene walking around phaC Pdrevealed two new open reading frames (ORFs) possibly related to PHA synthesis, one of which was the phaP Pd gene, encoding GA16 protein, and the other was thephaR Pd gene, encoding a protein that is putatively involved in the regulation of the expression ofphaP Pd. Overproduction of PhaPPdwas observed in Escherichia coli carryingphaP Pd, but the overproduction was not observed in the presence of phaR Pd. Coexpression ofphaP Pd and PHA biosynthesis genes in E. coli caused increases in both the number of poly-(3-hydroxybutyric acid) (PHB) granules and PHB content and caused decreases in both the size of the granules and the molecular weight of PHB. GA16 protein was considered a phasin protein. ThephaR Pd gene had significant similarities tostdC, a possible transcriptional factor of Comamonas testosteroni, as well as to other ORFs of unknown function previously found in other PHA-synthetic bacteria.

Spontaneous mutants of Streptococcus mutans GS-5 defective in sucrose-dependent colonization of smooth surfaces are generated at frequencies above the spontaneous mutation rate. Southern blot analysis of such mutants suggested rearrangement of the genes coding for glucosyltransferase (GTF) activity. Two strain GS-5 homologous tandem genes, gtfB and gtfC, coding for GTF-I and GTF-S activities respectively, were demonstrated to undergo recombination when introduced into recombination-proficient Escherichia coli transformants. However, the two genes were quite stable when transformed on a single DNA fragment into a recA mutant of E. coli. The DNA fragment coding for GTF activity from one S. mutans colonization-defective mutant, SP2, was isolated and shown also to have undergone recombination between the gtfB and gtfC genes, resulting in reduced GTF activity. These results are discussed relative to the in vivo generation of colonization-defective mutants in cultures of S. mutans.