|
|
|
|
|
|
Ribosomal P0 Protein Domain Involved in Selectivity of Antifungal Sordarin Derivatives. C. Santos, 2004.The ribosomal stalk protein P0 is involved in the susceptibility to the antifungal sordarin derivatives, as reported for a number of Saccharomyces cerevisiae resistant mutants . Mammals and some lower eukaryotes are naturally resistant to these compounds . It is shown here that expression in S . cerevisiae of the ribosomal protein P0 from Homo sapiens and from other sordarin-resistant organisms results in a decrease in the sensitivity of the cells to an agent of this class . To further characterize the P0 region responsible for inducing sordarin resistance, a series of protein chimeras containing complementary regions of the human and yeast P0 proteins were constructed and expressed in yeast . The chimeras complement the absence of the native yeast P0 except in chimeras containing the human P0 carboxyl-terminal domain . Resistance to sordarins was found to be associated with the presence of an HsP0 amino acid sequence comprising P118 to F138, which unexpectedly led to higher resistance than the presence of the complete human P0 . A comparison of the corresponding region in P0 from yeast and sordarin-insensitive organisms, followed by site-directed mutagenesis, indicates that residues in positions 119, 124, and 126 have an important role in determining resistance to sordarins . Moreover, since sordarins block the eukaryotic elongation factor 2 (EF2) function, the P0 region affecting sordarin susceptibility must correspond to EF2-interacting domains of the ribosomal stalk protein, which affects the drug-binding site in the elongation factor . Detection and Quantification of Gene Expression in Environmental Bacteriology. Freddie H. Sharkey, 2004. Evolutionary History of hrgA, Which Replaces the Restriction Gene hpyIIIR in the hpyIII Locus of Helicobacter pylori. T. Ando, 2003.A recently identified Helicobacter pylori gene, hrgA, was previously reported to be present in 70 (33%) of 208 strains examined (T . Ando, T . M . Wassenaar, R . M . Peek, R . A . Aras, A . I . Tschumi, L.-J . Van Doorn, K . Kusugami, and M . J . Blaser, Cancer Res . 62:2385-2389, 2002) . Sequence analysis of nine such strains indicated that in each strain hrgA replaced hpyIIIR, which encodes a restriction endonuclease and which, together with the gene for its cognate methyltransferase, constitutes the hpyIII locus . As a consequence of either the hrgA insertion or independent mutations, hpyIIIM function was lost in 11 (5%) of the 208 strains examined, rendering chromosomal DNA sensitive to MboI digestion . The evolutionary history of the locus containing either hpyIII or hrgA was reconstructed . By homologous recombination involving flanking sequences, hrgA and hpyIIIR can replace one another in the hpyIII locus, and there is simultaneous replacement of several flanking genes . These findings, combined with the hpyIM/iceA2 locus discovered previously, suggest that the two most strongly conserved methylase genes of H . pylori, hpyIIIM and hpyIM, are both preceded by alternative genes that compete for presence at their loci . Regulation of Photosynthesis Genes in Rubrivivax gelatinosus: Transcription Factor PpsR Is Involved in both Negative and Positive Control. Anne-Soisig Steunou, 2004.Induction of biosynthesis of the photosystem in anoxygenic photosynthetic bacteria occurs when the oxygen concentration drops . Control of this induction takes place primarily at the transcriptional level, with photosynthesis genes expressed preferentially under anaerobic conditions . Here, we report analysis of the transcriptional control of two photosynthesis promoters, pucBA and crtI, by the PpsR factor in Rubrivivax gelatinosus . This was accomplished by analyzing the photosystem production in the wild type and in the PPSRK (ppsR::Km) mutant grown under anaerobic and semiaerobic conditions and by assessing the ß-galactosidase activity of lacZ transcriptionally fused to promoters possessing the putative PpsR-binding consensus sequences . It was found that under semiaerobic conditions, inactivation of the ppsR gene resulted in overproduction of carotenoid and bacteriochlorophyll pigments, while the production of LH2 was drastically reduced . The ß-galactosidase activity showed that, in contrast to what has been found previously for Rhodobacter species, PpsR acts in R . gelatinosus as an aerobic repressor of the crtI gene while it acts as an activator for the expression of pucBA . Inspection of the putative PpsR-binding consensus sequences revealed significant differences that may explain the different levels of expression of the two genes studied . Characterization of Microbial Communities in Gas Industry Pipelines. Xiang Y. Zhu, 2003.Culture-independent techniques, denaturing gradient gel electrophoresis (DGGE) analysis, and random cloning of 16S rRNA gene sequences amplified from community DNA were used to determine the diversity of microbial communities in gas industry pipelines . Samples obtained from natural gas pipelines were used directly for DNA extraction, inoculated into sulfate-reducing bacterium medium, or used to inoculate a reactor that simulated a natural gas pipeline environment . The variable V2-V3 (average size, 384 bp) and V3-V6 (average size, 648 bp) regions of bacterial and archaeal 16S rRNA genes, respectively, were amplified from genomic DNA isolated from nine natural gas pipeline samples and analyzed . A total of 106 bacterial 16S rDNA sequences were derived from DGGE bands, and these formed three major clusters: beta and gamma subdivisions of Proteobacteria and gram-positive bacteria . The most frequently encountered bacterial species was Comamonas denitrificans, which was not previously reported to be associated with microbial communities found in gas pipelines or with microbially influenced corrosion . The 31 archaeal 16S rDNA sequences obtained in this study were all related to those of methanogens and phylogenetically fall into three clusters: order I, Methanobacteriales; order III, Methanomicrobiales; and order IV, Methanosarcinales . Further microbial ecology studies are needed to better understand the relationship among bacterial and archaeal groups and the involvement of these groups in the process of microbially influenced corrosion in order to develop improved ways of monitoring and controlling microbially influenced corrosion .
|
© 2005
Transgalactic Ltd (manufacturer of Bioscreen C software) |
Privacy Statement | P.O. Box
1393, 00101 Helsinki, Finland,
Last modified: May 25, 2005
| ||||||
