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Erwinia chrysanthemi O Antigen Is Required for Betaine Osmoprotection in High-Salt Media. Thierry Touzé, 2004.Cellular components necessary for osmoprotection are poorly known . In this study we show that O antigen is specifically required for the effectiveness of betaines as osmoprotectants for Erwinia chrysanthemi in saline media . The phenotype is correlated with the inability of rfb mutant strains to maintain a high accumulation level of betaines in hypersaline media . Bordetella Interspecies Allelic Variation in AlcR Inducer Requirements: Identification of a Critical Determinant of AlcR Inducer Responsiveness and Construction of an alcR(Con) Mutant Allele. Timothy J. Brickman, 2002.Previous studies established the critical roles of AlcR and alcaligin inducer in positive regulation of alcaligin siderophore biosynthesis and transport genes in Bordetella pertussis and Bordetella bronchiseptica . Transcriptional analyses using plasmid-borne alcR genes of B . pertussis UT25 and B . bronchiseptica B013N to complement the alcR defect of B . bronchiseptica strain BRM13 (  alcR1 alcA::mini-Tn5 lacZ1) revealed interspecies differences in AlcR inducer requirements for activation of alcABCDER operon transcription . Whereas the B . pertussis UT25 AlcR protein retained strong inducer dependence when produced from multicopy plasmids, B . bronchiseptica B013N alcR partially suppressed the alcaligin requirement for transcriptional activation . Functional analysis of AlcR chimeras produced by interspecies domain swapping and interspecies reciprocal site-specific mutagenesis determined that the phenotypic difference in AlcR inducer dependence was due to a single amino acid difference within the proposed inducer-binding and multimerization domain of AlcR . Structural predictions guided the design of a mutant AlcR protein with a single amino acid substitution at this critical position, AlcR(S103T), that was fully constitutive not only when produced from multicopy plasmids but also at a single-copy gene dosage . These results indicate that AlcR residue 103 affects a critical determinant of alcaligin inducer dependence of AlcR-mediated transcriptional activation . The alcR(S103T) mutant allele is the first alcR(Con) mutant allele identified .
Genome Diversification in Phylogenetic Lineages I and II of Listeria monocytogenes: Identification of Segments Unique to Lineage II Populations. Chaomei Zhang, 2003.Thirteen different serotypes of Listeria monocytogenes can be distinguished on the basis of variation in somatic and flagellar antigens . Although the known virulence genes are present in all serotypes, greater than 90% of human cases of listeriosis are caused by serotypes 1/2a, 1/2b, and 4b and nearly all outbreaks of food-borne listeriosis have been caused by serotype 4b strains . Phylogenetic analysis of these three common clinical serotypes places them into two different lineages, with serotypes 1/2b and 4b belonging to lineage I and 1/2a belonging to lineage II . To begin examining evolution of the genome in these serotypes, DNA microarray analysis was used to identify lineage-specific and serotype-specific differences in genome content . A set of 44 strains representing serotypes 1/2a, 1/2b, and 4b was probed with a shotgun DNA microarray constructed from the serotype 1/2a strain 10403s . Clones spanning 47 different genes in 16 different contiguous segments relative to the lineage II 1/2a genome were found to be absent in all lineage I strains tested (serotype 4b and 1/2b) and an additional nine were altered exclusively in 4b strains . Southern hybridization confirmed that conserved alterations were, in all but two loci, due to absence of the segments from the genome . Genes within these contiguous segments comprise five functional categories, including genes involved in synthesis of cell surface molecules and regulation of virulence gene expression . Phylogenetic reconstruction and examination of compositional bias in the regions of difference are consistent with a model in which the ancestor of the two lineages had the 1/2 somatic serotype and the regions absent in the lineage I genome arose by loss of ancestral sequences . Detection and Typing of Campylobacter jejuni and Campylobacter coli and Analysis of Indicator Organisms in Three Waterborne Outbreaks in Finland. Marja-Liisa Hänninen, 2003.Waterborne outbreaks associated with contamination of drinking water by Campylobacter jejuni are rather common in the Nordic countries Sweden, Norway, and Finland, where in sparsely populated districts groundwater is commonly used without disinfection . Campylobacters, Escherichia coli, or other coliforms have rarely been detected in potential sources . We studied three waterborne outbreaks in Finland caused by C . jejuni and used sample volumes of 4,000 to 20,000 ml for analysis of campylobacters and sample volumes of 1 to 5,000 ml for analysis of coliforms and E . coli, depending on the sampling site . Multiple samples obtained from possible sources (water distribution systems and environmental water sources) and the use of large sample volumes (several liters) increased the chance of detecting the pathogen C . jejuni in water . Filtration of a large volume (1,000 to 2,000 ml) also increased the rate of detection of coliforms and E . coli . To confirm the association between drinking water contamination and illness, a combination of Penner serotyping and pulsed-field gel electrophoresis (digestion with SmaI and KpnI) was found to be useful . This combination reliably verified similarity or dissimilarity of C . jejuni isolates from patient samples, from drinking water, and from other environmental sources, thus confirming the likely reservoir of an outbreak . Rapid Staining and Enumeration of Small Numbers of Total Bacteria in Water by Solid-Phase Laser Cytometry. Susan C. Broadaway, 2003.The nucleic acid stain SYBR Green I was evaluated for use with solid-phase laser cytometry to obtain total bacterial cell counts from several water sources with small bacterial numbers . Results were obtained within 30 min and exceeded or equaled counts on R2A agar plates incubated for 14 days at room temperature .
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