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  • 刊频： Biweekly, May 2001-
  • NLM标题： FEMS Microbiol Lett
  • iso缩写： -
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共387条结果
  • 1.

    【2hr】Mucin can enhance growth, biofilm formation and survival of Streptococcus mutans

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    机译 粘蛋白可以增强变形链球菌的生长，生物膜形成和存活
    摘要：Streptococcus mutans is a member of the dental plaque and is the primary causative agent of dental caries. It can survive extended periods of starvation, which may occur in different niches within the oral cavity. We have found that mucin compensated for the absence of amino acids to promote exponential growth and biofilm formation of S. mutans in minimal medium supplemented with glucose and sucrose, respectively. Mucin extended survival in conditions where there was no net growth provided the operon encoding the pyruvate dehydrogenase complex was intact. Mucin extended survival in conditions of amino acid sufficiency provided the tagatose pathway for galactose utilization was intact, suggesting that S. mutans can scavenge sufficient galactose from mucin to enhance survival, though not to serve as a primary carbon and energy source. The results suggest that mucin has a metabolic role in promoting survival of S. mutans.
  • 2.

    【2hr】An attenuated mutant of the Rv1747 ATP-binding cassette transporter of Mycobacterium tuberculosis and a mutant of its cognate kinase, PknF, show increased expression of the efflux pump-related iniBAC operon

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    机译 结核分枝杆菌的Rv1747 ATP结合盒转运蛋白的减毒突变体和其同源激酶PknF的突变体显示外排泵相关的iniBAC操纵子表达增加。
    摘要：The ATP-binding cassette transporter Rv1747 is required for the growth of Mycobacterium tuberculosis in mice and in macrophages. Its structure suggests it is an exporter. Rv1747 forms a two-gene operon with pknF coding for the serine/threonine protein kinase PknF, which positively modulates the function of the transporter. We show that deletion of Rv1747 or pknF results in a number of transcriptional changes which could be complemented by the wild type allele, most significantly up-regulation of the iniBAC genes. This operon is inducible by isoniazid and ethambutol and by a broad range of inhibitors of cell wall biosynthesis and is required for efflux pump functioning. However, neither the Rv1747 or pknF mutant showed increased susceptibility to a range of drugs and cell wall stress reagents including isoniazid and ethambutol, cell wall structure and cell division appear normal by electron microscopy, and no differences in lipoarabinomannan were found. Transcription from the pknF promoter was not induced by a range of stress reagents. We conclude that the loss of Rv1747 affects cell wall biosynthesis leading to the production of intermediates that cause induction of iniBAC transcription and implicates it in exporting a component of the cell wall, which is necessary for virulence.
  • 3.

    【2hr】Cortex synthesis during Bacillus subtilis sporulation depends on the transpeptidase activity of SpoVD

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    机译 枯草芽孢杆菌孢子形成过程中的皮质合成取决于SpoVD的转肽酶活性
    摘要：The nonessential process of peptidoglycan synthesis during Bacillus subtilis sporulation is one model to study bacterial cell wall biogenesis. SpoVD is a class B high-molecular-weight penicillin-binding protein that is specific for sporulation. Strains lacking this protein produce spores without the peptidoglycan cortex layer and are heat sensitive. The detailed functions of the four different protein domains of SpoVD are unknown, and the observed phenotype of strains lacking the entire protein could be an indirect defect. We therefore inactivated the transpeptidase domain by substitution of the active-site serine residue. Our results demonstrate that endospore cortex synthesis depends on the transpeptidase activity of SpoVD specifically.
  • 4.

    【2hr】Chimeric Ply187 endolysin kills Staphylococcus aureus more effectively than the parental enzyme

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    机译 嵌合Ply187内溶素比亲本酶更有效地杀死金黄色葡萄球菌
    摘要：Peptidoglycan hydrolases are an effective new source of antimicrobials. A chimeric fusion protein of the Ply187 endopeptidase domain and LysK SH3b cell wall binding domain is a potent agent against Staphylococcus aureus in four functional assays.
  • 5.

    【2hr】Two ABC transporter systems participate in siderophore transport in the marine pathogen Vibrio anguillarum 775(pJM1)

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    机译 两个ABC转运系统参与海洋病原体鳗弧菌775（pJM1）中的铁载体转运
    摘要：ORF40 (named fatE) in the Vibrio anguillarum pJM1 plasmid encoding anguibactin iron transport systems is a homologue of ATPase genes involved in ferric-siderophore transport. Mutation of fatE did not affect ferric-anguibactin transport indicating that there must be other ATPase gene(s) in addition to fatE. By searching the genomic sequence of V. anguillarum 775(pJM1) we identified a homologue of fatE named fvtE on chromosome 2. It is of interest that in this locus we also identified homologues of fatB, fatC and fatD that we named fvtB, fvtC and fvtD, respectively. The fvtE mutant still showed ferric-anguibactin transport while the double fatE and fvtE mutation completely abolished the ferric-anguibactin transport indicating that fatE and fvtE are functional ATPase homologues for ferric-anguibactin transport. Furthermore, we demonstrate that fvtB, fvtC, fvtD and fvtE are essential for ferric-vanchrobactin and ferric-enterobactin transport.
  • 6.

    【2hr】Longitudinal Analysis of the Lung Microbiome in Lung Transplantation

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    机译 肺移植中肺微生物组的纵向分析
    摘要：Lung transplant recipients experience poor long-term survival, largely due to chronic rejection. The pathogenesis of chronic rejection is incompletely understood, but bacterial colonization of the lung is associated with chronic rejection, while antibiotic use slows its progression. The lung harbors a bacterial community, termed the microbiome, which is present both in health and disease. We hypothesize that the lung microbiome will change following transplantation, and these changes may correspond to the development of rejection. Twelve bronchoalveolar lavage fluid (BALF) samples were obtained from four patients at three time points after transplantation and two BALF samples were obtained from healthy, non-transplant controls. The microbiome of each sample was determined by pyrosequencing the 16S rDNA hypervariable 3 region. The data were analyzed using mothur, Ribosomal Database Project Classifier, Fast UniFrac, and Metastats. Transplanted lungs contained more bacterial sequences and demonstrated more microbial diversity than did control lungs. Bacteria in the phyla Proteobacteria (class Betaproteobacteria) predominated in the transplant samples. In contrast, the microbiome of the healthy lung consisted of the phyla Proteobacteria (class Gammaproteobacteria) and Firmicutes. The microbiome of the transplanted lung is vastly different from that of healthy lungs, mainly due to the presence of the family Burkholderiaceae in transplant samples.
  • 7.

    【2hr】Escherichia coli glutathionylspermidine synthetase/amidase: Phylogeny and effect on regulation of gene expression

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    机译 大肠杆菌谷胱甘肽亚精胺合成酶/酰胺酶：系统发育及其对基因表达调控的影响
    摘要：Glutathionylspermidine synthetase/amidase (Gss) and the encoding gene (gss) have only been studied in Escherichia coli and several members of the Kinetoplastida phyla. In the present paper we have studied the phylogenetic distribution of Gss, and have found that Gss sequences are largely limited to certain bacteria and Kinetoplastids, and are absent in a variety of invertebrate and vertebrate species, Archea, plants and some Eubacteria. It is striking that almost all of the 75 Enterobacteria species that have been sequenced contain sequences with very high degree of homology to the E. coli Gss protein. In order to find out the physiological significance of glutathionylspermidine in E. coli, we have performed global transcriptome analyses. The microarray studies comparing gss+ and Δgss strains of E. coli show that a large number of genes are either upregulated (76 genes more than 3-fold) or downregulated (35 genes more than 3-fold) by the loss of the gss gene. Most significant categories of up-regulated genes include sulfur utilization, glutamine and succinate metabolism, polyamine and arginine metabolism, and purine and pyrimidine metabolism.
  • 8.

    【2hr】EPS-I Polysaccharide Protects Mycoplasma pulmonis from Phagocytosis

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    机译 EPS-1多糖可保护肺炎支原体免于吞噬作用
    摘要：Few mycoplasmal polysaccharides have been described and little is known about their role in pathogenesis. The infection of mice with Mycoplasma pulmonis has been utilized in many in vivo and in vitro studies to gain a better understanding of host-pathogen interactions during chronic respiratory infection. Although alveolar macrophages have a primary role in host defense, M. pulmonis is killed inefficiently in vitro. One antiphagocytic factor produced by the mycoplasma is the family of phase- and size-variable Vsa lipoproteins. However, bacteria generally employ multiple strategies for combating host defenses, with capsular polysaccharide often having a key role. We show here that mutants lacking the EPS-I polysaccharide of M. pulmonis exhibit increased susceptibility to binding and subsequent killing by alveolar macrophages. These results give further insight into how mycoplasmas are able to avoid the host immune system and sustain a chronic infection.
  • 9.

    【2hr】Analysis of energy sources for Mycoplasma penetrans gliding motility

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    机译 支原体穿透滑行运动的能源分析
    摘要：Mycoplasma penetrans, a potential human pathogen found mainly in HIV-infected individuals, uses a tip structure for both adherence and gliding motility. To improve our understanding of the molecular mechanism of M. penetrans gliding motility, we used chemical inhibitors of energy sources associated with motility of other organisms to determine which of these is used by M. penetrans, and also tested whether gliding speed responded to temperature and pH. M. penetrans gliding motility was not eliminated in the presence of a proton motive force inhibitor, a sodium motive force inhibitor, or an agent that depletes cellular ATP. At near-neutral pH, gliding speed increased as temperature increased. The absence of a clear chemical energy source for gliding motility and a positive correlation between speed and temperature suggest that energy derived from heat provides the major source of power for the gliding motor of M. penetrans.
  • 10.

    【2hr】The Role of Ionic Interactions in the Adherence of the S. epidermidis Adhesin SdrF to Prosthetic Material

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    机译 离子相互作用在表皮葡萄球菌粘附素SdrF对修复材料粘附中的作用
    摘要：Staphylococcus epidermidis infections are common complications of prosthetic device implantation. SdrF, a surface protein, appears to play a critical role in the initial colonization step by adhering to type I collagen and Dacron™. The role of ionic interactions in S. epidermidis adherence to prosthetic material was examined. SdrF was cloned and expressed in Lactococcus lactis. The effect of pH, cation concentration and detergents on adherence to different types of plastic surfaces was assessed by crystal violet staining and bacterial cell counting. SdrF, in contrast with controls and other S. epidermidis surface proteins, bound to hydrophobic materials such as polystyrene. Binding was an ionic interaction and was affected by surface charge of the plastic, pH and cation concentration. Adherence of the SdrF construct was increased to positively charged plastics and was reduced by increasing concentrations of Ca2+ and Na+. Binding was optimal at pH 7.4. Kinetic studies demonstrated that the SdrF B domain, as well as one of the B subdomains was sufficient to mediate binding. The SdrF construct also bound more avidly to Goretex™ than the lacotococcal control. SdrF is a multifunctional protein that contributes to prosthetic devices infections by ionic, as well as specific receptor-ligand interactions.
  • 11.

    【2hr】Transcriptional downregulation of agr expression in Staphylococcus aureus during growth in human serum can be overcome by constitutively active mutant forms of the sensor kinase AgrC

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    机译 在人类血清中生长期间，金黄色葡萄球菌中agr表达的转录下调可以通过传感器激酶AgrC的组成型活性突变体形式克服
    摘要：The temporal and cell density-dependent regulation of expression of virtually all the Staphylococcus aureus virulon is under the control of the agr (accessory gene regulatory) operon. The expression of the agr operon is subject to transcriptional regulation by the AgrA/C two-component response regulator/sensor kinase pair. During bacteraemia, a frequent syndrome caused by methicillin-resistant S. aureus (MRSA), the transcriptional downregulation of agr expression has been attributed to the sequestration of the quorum-signalling molecule auto-inducing peptide (AIP) by the human serum component apolipoprotein B as part of an innate immune response to infection. However, it is not known whether transcriptional downregulation of agr expression during growth in human serum is additionally subjected to regulation by transcription regulatory proteins that either directly or indirectly affect transcription from the agr operon promoters. Here, using chromosomal fluorescence reporters of agr expression in S. aureus, we show that the transcriptional downregulation of agr expression in human serum can be overcome using constitutive active mutant forms of AgrC. Therefore, it seems that the sequestration of the AIP is likely to be the only mechanism by which the host innate immune response limits agr expression at the transcriptional level to maintain the host–pathogen balance towards a noninvasive outcome.
  • 12.

    【2hr】Amino acid residues involved in inactivation of the Escherichia coli multidrug resistance repressor MarR by salicylate, 2,4-dinitrophenol, and plumbagin

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    机译 水杨酸酯，2,4-二硝基苯酚和李白素与大肠埃希菌多药耐药阻遏物MarR失活有关的氨基酸残基
    摘要：MarR is the dedicated autorepressor of the marRAB operon found in seven genera of the Enterobacteraceae. The MarA transcriptional regulator directly activates numerous genes involved in multidrug resistance and other environmental responses. MarR is inactivated by certain phenolic ligands, such as salicylate, by an unknown mechanism. Our recent work has shown that several amino acid residues of Escherichia coli MarR affecting ligand binding are located between the dimerization and DNA-binding domains. To further characterize the ligand-binding region of MarR, we have now examined seven point mutants generated by random mutagenesis and eleven site-directed alanine replacement mutants for inactivation by three ligands: salicylate, 2,4-dinitrophenol, and plumbagin. Inactivation of MarR was quantitated in intact cells by loss of MarR-mediated repression of a chromosomal mar-lacZ transcriptional fusion. The results showed that most of the residues important for ligand effectiveness lay in the α1 and α2 helices of MarR, between the putative DNA-binding domain and the dimerization domain of MarR, reinforcing our earlier findings. Moreover, the three ligands had different, but overlapping, sets of residues impacting their effects on MarR.
  • 13.

    【2hr】Promoter Deletions of Klebsiella pneumoniae Carbapenemase (KPC)-Encoding Genes (blaKPC-2) and Efflux Pump (AcrAB) on β-Lactam Susceptibility in KPC-Producing Enterobacteriaceae

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    机译 肺炎克雷伯氏菌碳青霉烯酶（KPC）编码基因（blaKPC-2）和外排泵（AcrAB）对生产KPC的肠杆菌科细菌中β-内酰胺敏感性的启动子缺失。
    摘要：Klebsiella pneumoniae carbapenemase (KPC)-encoding genes containing promoter-deletions (blaKPC-2a, blaKPC-2b, and blaKPC-2c) have disseminated in Enterobacteriaceae. The minimal inhibitory concentrations (MICs) to β-lactams in clinical KPC-producing Enterobacteriaceae are ranging from susceptible to high-level resistant resulting in diagnostic problems. In order to better understand the variability in β-lactam MICs among KPC-producing Enterobacteriaceae, three isoforms of blaKPC-2 gene were used to transform E. coli W4573 and its deletion mutant of an efflux pump (AcrAB) to examine the effects on β-lactam susceptibility. MICs to β-lactams in E. coli W4573 and its acrAB mutant strain increased 1- to 500-fold (MIC from 0.125 to 64 µg/mL of aztreonam) in the blaKPC-2a, blaKPC-2b, and blaKPC-2c transformants compared with the cloning vector alone. However, transformants of the acrAB mutant strain remained susceptible to all β-lactams tested except for aztreonam and carbenicillin. Levels of the three promoters’ length and carbapenemase activities in the transformants harboring the blaKPC-2a, blaKPC-2b, and blaKPC-2c were correlated to the levels of β-lactam MICs in both E. coli W4573 and its mutant of an efflux pump (AcrAB). Overall, these results suggest that promoter-deletions of blaKPC-2 gene and AcrAB may be associated with the variability in β-lactam MICs in KPC-producing Enterobacteriaceae.
  • 14.

    【2hr】Specific TonB-ExbB-ExbD energy transduction systems required for ferric enterobactin acquisition in Campylobacter

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    机译 弯曲杆菌中铁肠杆菌素采集所需的特定TonB-ExbB-ExbD能量转导系统
    摘要：Ferric enterobactin (FeEnt) acquisition plays a critical role in the pathophysiology of Campylobacter, the leading bacterial cause of human gastroenteritis in industrialized countries. In Campylobacter, the surface-exposed receptor, CfrA or CfrB, functions as a “gatekeeper” for initial binding of FeEnt. Subsequent transport across the outer membrane is energized by TonB-ExbB-ExbD energy transduction systems. Although there are up to three TonB-ExbB-ExbD systems in Campylobacter, the cognate components of TonB-ExbB-ExbD for FeEnt acquisition are still largely unknown. In this study, we addressed this issue using complementary molecular approaches including: comparative genomic analysis, random transposon mutagenesis, and site-directed mutagenesis in two representative C. jejuni strains, NCTC 11168 and 81-176. We demonstrated that CfrB could interact with either TonB2 or TonB3 for efficient Ent-mediated iron acquisition. However, TonB3 is a dominant player in CfrA-dependent pathway. The ExbB2 and ExbD2 components were essential for both CfrA- and CfrB-dependent FeEnt acquisition. Sequences analysis identified potential TonB boxes in CfrA and CfrB, and the corresponding binding sites in TonB. In conclusion, these findings reveal identities of specific TonB-ExbB-ExbD energy transduction components required for FeEnt acquisition, and provide insights into the complex molecular interactions of FeEnt acquisition systems in Campylobacter.
  • 15.

    【2hr】bkaR is a TetR-type repressor that controls an operon associated with branched-chain keto-acid metabolism in Mycobacteria

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    机译 bkaR是一种TetR型阻遏物，可控制与分枝杆菌中支链酮酸代谢相关的操纵子
    摘要：This study describes how bkaR, a highly conserved mycobacterial TetR-like transcriptional repressor, regulates a number of nearby genes that have associations with branched-chain keto-acid metabolism. bkaR (MSMEG_4718) was deleted from the nonpathogenic species Mycobacterium smegmatis, and changes in global gene expression were assessed using microarray analysis and reporter gene studies. bkaR was found to directly control the expression of 10 genes in M. smegmatis, and its ortholog in Mycobacterium tuberculosis (Rv2506) is predicted to control at least 12 genes. A conserved operator motif was identified, and binding of purified recombinant M. tuberculosis BkaR to the motif was demonstrated. Analysis of the stoichiometry of binding showed that BkaR binds to the motif as a dimer.
  • 16.

    【2hr】The challenge of constructing, classifying and representing metabolic pathways

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    机译 构建，分类和代表代谢途径的挑战
    摘要：Scientists, educators, and students benefit from having free and centralized access to the wealth of metabolic information that has been gathered over the decades. Curators of the MetaCyc database work to present this information in an easily understandable pathway-based framework. MetaCyc is used not only as an encyclopedic resource for metabolic information but also as a template for the pathway prediction software that generates pathway/genome databases for thousands of organisms with sequenced genomes (available at ). Curators need to define pathway boundaries and classify pathways within a broader pathway ontology to maximize the utility of the pathways to both users and the pathway prediction software. These seemingly simple tasks pose several challenges. This review describes these challenges as well as the criteria that need to be considered, and the rules that have been developed by MetaCyc curators as they make decisions regarding the representation and classification of metabolic pathway information in MetaCyc. The functional consequences of these decisions in regard to pathway prediction in new species are also discussed.
  • 17.

    【2hr】The 216 bp marB gene of the marRAB operon in Escherichia coli encodes a periplasmic protein which reduces the transcription rate of marA

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    机译 大肠杆菌marRAB操纵子的216 bp marB基因编码一种周质蛋白，可降低marA的转录速率
    摘要：The marRAB operon is conserved in seven genera of enteric bacteria (Escherichia, Shigella, Klebsiella, Enterobacter, Salmonella, Cronobacter, and Citrobacter). MarA is a transcriptional regulator affecting many genes involved in resistance to stresses, and MarR is an autorepressor of the operon, but a role for the marB gene has been unclear. A recent work reported that deletion of marB causes resistance to certain stresses and increases the amount of marA transcript. We show here that the small (216 bp) marB gene encodes a protein, not an sRNA, since two different stop codons within the predicted open reading frame of marB prevented plasmid-borne marB from complementing ΔmarB::Kan. The ΔmarB::Kan mutation did not increase the stability of the marA transcript, suggesting that MarB does not destabilize the marA transcript but rather reduces its rate of transcription. Placing the putative signal sequence of MarB upstream of signal-sequence-less alkaline phosphatase guided the phosphatase to its normal periplasmic location. We conclude that MarB is a small periplasmic protein that represses the marRAB promoter by an indirect mechanism, possibly involving a signal to one of the cytoplasmic regulators of that promoter.
  • 18.

    【2hr】Expression of the Collagen Adhesin ace by Enterococcus faecalis Strain OG1RF is not Repressed by Ers but Requires the Ers box

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    机译 粪肠球菌OG1RF菌株对胶原粘附素ace的表达不会被Ers抑制，但需要Ers框
    摘要：Expression of adhesin to collagen of Enterococcis faecalis (ace), a known virulence factor, is increased by environmental signals such as the presence of serum, high temperature, and bile salts. Currently, the enterococcal regulator of survival (Ers) of E. faecalis strain JH2-2 is the only reported repressor of ace. Here, we show that for strain OG1RF, Ers is not involved in the regulation of ace. Our data showed similar levels of ace expression by OG1RF and its Δers derivative in the presence of bile salts, serum, and high temperature. Using ace promoter-lacZ fusions and site-directed mutagenesis, we confirmed these results and further showed that, while the previously designated Ers box is important for increased expression from the ace promoter of OG1RF, the region responsible for the increase is bigger than the Ers box. In summary, these results indicate that, in strain OG1RF, Ers is not a repressor of ace expression. Although JH2-2 and OG1RF differ by 6 nucleotides in the region upstream of ace as well as in production of Fsr and gelatinase, the reason(s) for the difference in ace expression between JH2-2 and OG1RF and for increased ace expression in bile, serum and at 46°C remain(s) to be determined.
  • 19.

    【2hr】Pre-sporulation stages of Streptomyces differentiation: state-of-the-art and future perspectives

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    机译 链霉菌分化的孢子形成前阶段：最新和未来展望
    摘要：Streptomycetes comprise very important industrial bacteria, producing two-thirds of all clinically relevant secondary metabolites. They are mycelial microorganisms with complex developmental cycles that include programmed cell death (PCD) and sporulation. Industrial fermentations are usually performed in liquid cultures (large bioreactors), conditions in which Streptomyces strains generally do not sporulate, and it was traditionally assumed that there was no differentiation. In this work, we review the current knowledge on Streptomyces pre-sporulation stages of Streptomyces differentiation.
  • 20.

    【2hr】Spermine impairs biofilm formation by Neisseria gonorrhoeae

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    机译 精胺会破坏淋病奈瑟菌的生物膜形成
    摘要：Neisseria gonorrhoeae is a strict human pathogen that causes the sexually transmitted infection termed gonorrhea. Recent reports indicate that gonococci can form a biofilm in vivo and under laboratory conditions. It is unclear, however, if formation of such biofilms or their dispersal are influenced by host factors that would be encountered during infection. In this respect, physiological levels of polyamines have been reported to influence biofilm structures formed by other Gram-negative bacteria as well those formed by Gram–positive bacteria and can cause dispersal of a biofilm formed by Bacillus subtilis. Based on these reports, we examined the influence of polyamines on gonococcal biofilm formation and their dispersal. We now report that physiological levels of certain polyamines, notably spermine, can significantly decrease the capacity of gonococci to form a biofilm, but do not cause dispersal of a pre-formed biofilm. In the context of natural gonococcal infection, the presence of physiological levels of spermine may be antagonistic for gonococci to form a biofilm and this may be of importance in the spread of the pathogen from a localized region.
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