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Helicobacter acinonychis: Genetic and Rodent Infection Studies of a Helicobacter pylori-Like Gastric Pathogen of Cheetahs and Other Big Cats. Daiva Dailidiene, 2004.Insights into bacterium-host interactions and genome evolution can emerge from comparisons among related species . Here we studied Helicobacter acinonychis (formerly H . acinonyx), a species closely related to the human gastric pathogen Helicobacter pylori . Two groups of strains were identified by randomly amplified polymorphic DNA fingerprinting and gene sequencing: one group from six cheetahs in a U.S . zoo and two lions in a European circus, and the other group from a tiger and a lion-tiger hybrid in the same circus . PCR and DNA sequencing showed that each strain lacked the cag pathogenicity island and contained a degenerate vacuolating cytotoxin (vacA) gene . Analyses of nine other genes (glmM, recA, hp519, glr, cysS, ppa, flaB, flaA, and atpA) revealed a  2%
base substitution difference, on average, between the two H .
acinonychis groups and a
8%
difference between these genes and their homologs in H . pylori
reference strains such as 26695 . H . acinonychis derivatives
that could chronically infect mice were selected and were found to be
capable of persistent mixed infection with certain H . pylori
strains . Several variants, due variously to recombination or new
mutation, were found after 2 months of mixed infection . H .
acinonychis ' modest genetic distance from H . pylori, its
ability to infect mice, and its ability to coexist and recombine with
certain H . pylori strains in vivo should be useful in studies
of Helicobacter infection and virulence mechanisms and studies
of genome evolution .
In Vitro Activities of Garenoxacin and Levofloxacin against Chlamydia pneumoniae Are Not Affected by Presence of Mycoplasma DNA. Raymond P. Smith, 2004.We studied 20 Chlamydia pneumoniae isolates obtained from respiratory sites and atheroma tissue of patients from various geographic areas to determine the susceptibilities of these isolates to a new des-fluoroquinolone, garenoxacin, and to levofloxacin . In addition, we assessed the cultures with these isolates by PCR for the presence or absence of Mycoplasma sp . DNA . Both the MIC at which 90% of isolates are inhibited (MIC90) and the minimal bactericidal concentration at which 90% of isolates are killed (MBC90) for garenoxacin were 0.06 µg/ml, and both the MIC90 and the MBC90 for levofloxacin were 2.0 µg/ml . The activity of garenoxacin against C . pneumoniae was 32-fold greater than that of levofloxacin . Mycoplasma sp . DNA was detected by PCR in 17 of 20 cultures . Mycoplasma amplicons from five Mycoplasma DNA-positive C . pneumoniae cultures were sequenced and found to represent four Mycoplasma species . Our data demonstrate that C . pneumoniae cultures frequently contain Mycoplasma DNA and that its presence in C . pneumoniae cultures does not appear to affect the susceptibility results for the two fluoroquinolones that we tested . MazG, a Nucleoside Triphosphate Pyrophosphohydrolase, Interacts with Era, an Essential GTPase in Escherichia coli. Junjie Zhang, 2002.Era is an essential GTPase in Escherichia coli, and Era has been implicated in a number of cellular functions . Homologues of Era have been identified in various bacteria and some eukaryotes . Using the era gene as bait in the yeast two-hybrid system to screen E . coli genomic libraries, we discovered that Era interacts with MazG, a protein of unknown function which is highly conserved among bacteria . The direct interaction between Era and MazG was also confirmed in vitro, being stronger in the presence of GDP than in the presence of GTP  S . MazG was characterized as a nucleoside triphosphate pyrophosphohydrolase which can hydrolyze all eight of the canonical ribo- and deoxynucleoside triphosphates to their respective monophosphates and PPi, with a preference for deoxynucleotides . A mazG deletion strain of E . coli was constructed by replacing the mazG gene with a kanamycin resistance gene . Unlike mutT, a gene for another conserved nucleotide triphosphate pyrophosphohydrolase that functions as a mutator gene, the mazG deletion did not result in a mutator phenotype in E . coli .
An Extracellular Matrix-Associated Zinc Metalloprotease Is Required for Dilauroyl Phosphatidylethanolamine Chemotactic Excitation in Myxococcus xanthus. Daniel B. Kearns, 2002.An extracellular matrix connects bacteria that live in organized assemblages called biofilms . While the role of the matrix in the regulation of cell behavior has not been extensively examined in bacteria, we suggest that, like mammalian cells, the matrix facilitates cell-cell interactions involved with regulation of cohesion, motility, and sensory transduction . The extracellular matrix of the soil bacterium Myxococcus xanthus is essential for biofilm formation and fruiting body development . The matrix material is extruded as long, thin fibrils that mediate adhesion to surfaces, cohesion to other cells, and excitation by the chemoattractant dilauroyl phosphatidylethanolamine . We report the identification of a putative matrix-associated zinc metalloprotease called FibA (fibril protein A) . Western blotting with FibA-specific monoclonal antibody 2105 suggests extensive proteolytic processing of FibA during assembly into fibrils, consistent with the autoprocessing observed with other members of the M4 metalloprotease family . Disruption of fibA had no obvious effect on the structure of the fibrils and did not inhibit cell cohesion, excitation by dioleoyl phosphatidylethanolamine, or activity of the A- or S-motility motors . However, the cells lost the ability to respond to dilauroyl phosphatidylethanolamine and to form well-spaced fruiting bodies, though substantial aggregation was observed . Chemotactic excitation of the fibA mutant was restored by incubation with purified wild-type fibrils . The results suggest that this metalloprotease is involved in sensory transduction . Sources of Campylobacter Colonization in Broiler Chickens. D. G. Newell, 2003.
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