|
|
|
|
|
|
SigM, an Extracytoplasmic Function Sigma Factor of Bacillus subtilis, Is Activated in Response to Cell Wall Antibiotics, Ethanol, Heat, Acid, and Superoxide Stress. Penny D. Thackray, 2003.The extracytoplasmic function sigma M of Bacillus subtilis is required for normal cell growth under salt stress . It is expressed maximally during exponential growth and is further induced by the addition of 0.7 M NaCl . The promoter region of the sigM operon contains two promoters; one (PA) is sigma A dependent, and the other (PM) is sigma M dependent . These have been placed separately at the amy locus, directing expression of a lacZ reporter gene . Only the PM fusion responded to salt induction . This promoter, which was responsive to the level of active sigma M in the cell, was also induced by 5% ethanol, by vancomycin, bacitracin, or phosphomycin (inhibitors of cell wall biosynthesis; 2 µg per ml), and by heat shock of 50°C for 10 min . It was very strongly induced by acid (pH 4.3) and 80 µM paraquat, but after a 15- to 30-min delay . There was no induction by alkali (pH 9), 5 mM H2O2, the detergents 0.1% Triton X-100 and 0.1% Tween 20, or 50 µM monensin . In addition to their reduced tolerance to salt, null mutants of sigM were unable to grow at pH 4.3 and lysed after exposure to 5% ethanol . Genes regulated by SigM were also tested for their response to pH 4.3, 5% ethanol, and 2 µg of vancomycin per ml . Expression of the genes may have been activated by increased levels of sigma M, but at least some were also subject to additional controls, as they responded to one type of stress but not another . Expression of yrhJ, which encodes a cytochrome P450/NADPH reductase, was induced in response to acid and vancomycin . yraA expression was acid, ethanol, and vancomycin induced, whereas yjbD showed only ethanol induction . YraA protein was extremely important to acid survival—a mutation in yraA, like a sigM mutation, resulted in the failure of B . subtilis to grow at pH 4.3 . Sigma M is therefore involved in maintaining membrane and cell wall integrity in response to several different stresses in exponential growth phase and is activated by such stresses . Susceptibility to Thrombin-Induced Platelet Microbicidal Protein Is Associated with Increased Fluconazole Efficacy against Experimental Endocarditis Due to Candida albicans. Michael R. Yeaman, 2004.Platelet microbicidal proteins (PMPs) are believed to be integral to host defense against endovascular infection . We previously demonstrated that susceptibility to thrombin-induced PMP 1 (tPMP-1) in vitro negatively influences Candida albicans virulence in the rabbit model of infective endocarditis (IE) . This study evaluated the relationship between in vitro tPMP-1 susceptibility (tPMP-1s) or resistance (tPMP-1r) and efficacy of fluconazole (FLU) therapy of IE due to C . albicans . Candida IE was established in rabbits with either tPMP-1s or tPMP-1r strains . Treatment groups received FLU (100 mg/kg/day) intraperitoneally for 7 or 14 days; control animals received no therapy . At these time points, cardiac vegetations, kidneys, and spleens were quantitatively cultured to assess fungal burden . At both 7 and 14 days and in all target tissues, the extent of candidal clearance by FLU was greater in animals infected with the tPMP-1s strain than in those infected with the tPMP-1r strain . These differences were statistically significant in the spleen and kidney . Corroborating these in vivo data, FLU (a candidastatic agent), in combination with tPMP-1, exerted an enhanced fungicidal effect in vitro against tPMP-1s and tPMP-1r C . albicans, with the extent of this effect greatest against the tPMP-1s strain . Collectively, these results support the concept that tPMP-1 susceptibility contributes to the net efficacy of FLU against C . albicans IE in vivo, particularly in tissues in which platelets and tPMP-1 likely play significant roles in host defense . Genome Analysis and Strain Comparison of Correia Repeats and Correia Repeat-Enclosed Elements in Pathogenic Neisseria. Shi V. Liu, 2002.Whole genome sequences of Neisseria meningitidis strains Z2491 and MC58 and Neisseria gonorrhoeae FA1090 were analyzed for Correia repeats (CR) and CR-enclosed elements (CREE) . A total of 533, 516, and 256 copies of CR and 270, 261, and 102 copies of CREE were found in these three genomes, respectively . The lengths of CREE range from 28 to 348 bp, and the lengths of multicopy CREE appear mainly in the ranges of 154 to 156 bp and 105 to 107 bp . The distribution of CREE lengths is similar between the two N . meningitidis genomes, with a greater number of 154- to 156-bp CREE (163 and 152 copies in N . meningitidis strain Z2491 and N . meningitidis strain MC58, respectively) than 105- to 107-bp CREE (72 and 77 copies) . In the N . gonorrhoeae strain FA1090 genome there are relatively more 105- to 107-bp CREE (51 copies) than 154- to 156-bp CREE (36 copies) . The genomic distribution of 107-bp CREE also shows similarity between the two N . meningitidis strains (15 copies share the same loci) and differences between N . meningitidis strains and N . gonorrhoeae FA1090 (only one copy is located in the same locus) . Detailed sequence analysis showed that both the terminal inverted repeats and the core regions of CREE are composed of distinct basic sequence blocks . Direct TA dinucleotide repeats exist at the termini of all CREE . A survey of DNA sequence upstream of the sialyltransferase gene, lst, in several Neisseria isolates showed that 5 N . meningitidis strains contain a 107-bp CREE in this region but 25 N . gonorrhoeae strains show an exact absence of a 105-bp sequence block (i.e., the 107-bp CREE without a 5' TA dinucleotide) in the same region . Whole-genome sequence analysis confirmed that this 105-bp indel exists in many homologous 107-bp CREE loci . Thus, we postulate that all CREE are made of target TA with indels of various lengths . Analysis of 107-bp CREE revealed that they exist predominantly in intergenic regions and are often near virulence, metabolic, and transporter genes . The abundance of CREE in Neisseria genomes suggests that they may have played a role in genome organization, function, and evolution . Their differential distribution in different pathogenic Neisseria strains may contribute to the distinct behaviors of each Neisseria species . Flavobacterium johnsoniae GldH Is a Lipoprotein That Is Required for Gliding Motility and Chitin Utilization. Mark J. McBride, 2003.Cells of Flavobacterium johnsoniae move rapidly over surfaces by gliding motility . The mechanism of this form of motility is not known . Six genes (gldA, gldB, gldD, gldF, gldG, and ftsX) that are required for gliding have been described . Tn4351 mutagenesis was used to identify another gene, gldH, which is required for cell movement . GldH mutants formed nonspreading colonies, and individual cells lacked the cell movements and ability to propel latex spheres along their surfaces that are characteristic of wild-type cells . gldH mutants also failed to digest chitin and were resistant to bacteriophages that infect wild-type cells . Introduction of pMM293, which carries wild-type gldH, restored to the gldH mutants colony spreading, cell motility, the ability to move latex spheres, phage sensitivity, and the ability to digest chitin . gldH encodes a predicted 141-amino-acid protein that localized to the membrane fraction . Labeling studies with [3H]palmitate demonstrated that GldH is a lipoprotein . GldB and GldD, which were previously described, also appear to be lipoproteins . GldH does not exhibit significant amino acid similarity to proteins of known function in the databases . Putative homologs of gldH of unknown function are found in motile (Cytophaga hutchinsonii) and apparently nonmotile (Bacteroides thetaiotaomicron, Bacteroides fragilis, Tannerella forsythensis, Porphyromonas gingivalis, and Prevotella intermedia) members of the Cytophaga-Flavobacterium-Bacteroides group .
|
© 2005
Transgalactic Ltd (manufacturer of Bioscreen C software) |
Privacy Statement | P.O. Box
1393, 00101 Helsinki, Finland,
Last modified: May 25, 2005
| ||||||
