Search

Background and Purpose: Propionibacterium acnes is a Gram-positive bacterium associated with the skin disorder acne. In this study, as fatty acids are considered to be important in the life habitat of P. acnes, we tested our lipopeptide library in an attempt to create potent P. acnes-specific antimicrobial agents.Experimental Approach: The antimicrobial activity of various lipopeptides was determined by measuring their minimal inhibitory concentration (MIC). Lipids from P. acnes were used to explore their mode of action. RAW264.7 cells stimulated with LPS and P. acnes respectively were used to measure their anti-inflammatory activity. Mice ears injected with P. acnes were used to assess the antimicrobial and anti-inflammatory effects of the peptides tested in vivo.Key Results: The most potent candidate, C16-KWKW, was observed to be more active against P. acnes than against other non-targeted bacterial strains, such as Streptococcus mutans, Staphylococcus aureus, and Escherichia coli. The mode of action of C16-KWKW was observed to be through interference with the integrity of the bacterial membrane, thereby impairing membrane permeability and causing leakage of inner contents of bacterial cells. Furthermore, C16-KWKW inhibited the expression of pro-inflammatory cytokines, such as IL-1β, TNF-α, and inducible NOS stimulated by both LPS and P. acnes, thus showing potential anti-inflammatory activity, which was further verified in the in vivo animal studies.Conclusions and Implications: C16-KWKW is a lipopeptide displaying both anti-P. acnes and anti-inflammatory effects in vitro and in vivo and shows potential as a treatment for acne vulgaris induced by P. acnes. [ABSTRACT FROM AUTHOR]

Background and Purpose: Propionibacterium acnes (P. acnes) is a Gram-positive bacterium associated with the skin disorder acne. In this study, we determined the importance of fatty acids in the life habitat of P. acnes; we tested our lipopeptide library in an attempt to create potent P. acnes-specific antimicrobial agents.Experimental Approach: Antimicrobial activity was determined by the minimal inhibitory concentration (MIC). Lipids from P. acnes were used to explore the mode of action. RAW264.7 cells respectively stimulated with LPS and P. acnes were used to measure the anti-inflammatory activity. Mice ears injected with P. acnes were used to assess the antimicrobial and anti-inflammatory effects of the peptides tested in vivo.Key Results: The most potent candidate, C16-KWKW, was observed to be more active against P. acnes, with an MIC of 2 μg·ml-1 , than against other non-targeted bacterial strains, such as Streptococcus mutans, Staphylococcus aureus, and Escherichia coli. The mode of action of C16-KWKW was observed to be through interference with the integrity of bacterial membrane, thereby impairing membrane permeability and causing leakage of the inner contents of bacterial cells. In addition, C16-KWKW inhibited the expression of pro-inflammatory cytokines, such as IL-1β, TNF-α, and inducible NOS, stimulated by both LPS and P. acnes, thus showing potential anti-inflammatory activity, which was further assessed in animal studies in vivo.Conclusions and Implications: C16-KWKW is a lipopeptide displaying both anti-P. acnes and anti-inflammatory effects in vitro and in vivo, and exhibits potential as a treatment for acne vulgaris induced by P. acnes. [ABSTRACT FROM AUTHOR]

Adhesin-mediated bacterial interspecies interactions are important elements in oral biofilm formation. They often occur on a species-specific level, which could determine health or disease association of a biofilm community. Among the key players involved in these processes are the ubiquitous fusobacteria that have been recognized for their ability to interact with numerous different binding partners. Fusobacterial interactions with Streptococcus mutans, an important oral cariogenic pathogen, have previously been described but most studies focused on binding to non-mutans streptococci and specific cognate adhesin pairs remain to be identified. Here, we demonstrated differential binding of oral fusobacteria to S. mutans. Screening of existing mutant derivatives indicated SpaP as the major S. mutans adhesin specific for binding to Fusobacterium nucleatum ssp. polymorphum but none of the other oral fusobacteria tested. We inactivated RadD, a known adhesin of F. nucleatum ssp. nucleatum for interaction with a number of gram-positive species, in F. nucleatum ssp. polymorphum and used a Lactococcus lactis heterologous SpaP expression system to demonstrate SpaP interaction with RadD of F. nucleatum ssp. polymorphum. This is a novel function for SpaP, which has mainly been characterized as an adhesin for binding to host proteins including salivary glycoproteins. In conclusion, we describe an additional role for SpaP as adhesin in interspecies adherence with RadD-SpaP as the interacting adhesin pair for binding between S. mutans and F. nucleatum ssp. polymorphum. Furthermore, S. mutans attachment to oral fusobacteria appears to involve species- and subspecies-dependent adhesin interactions. [ABSTRACT FROM AUTHOR]

Microbes colonize human oral surfaces within hours after delivery. During postnatal development, physiological changes, such as the eruption of primary teeth and replacement of the primary dentition with permanent dentition, greatly alter the microbial habitats, which, in return, may lead to community composition shifts at different phases in people's lives. By profiling saliva, supragingival and mucosal plaque samples from healthy volunteers at different ages and dentition stages, we observed that the oral cavity is a highly heterogeneous ecological system containing distinct niches with significantly different microbial communities. More importantly, the phylogenetic microbial structure varies with ageing. In addition, only a few taxa were present across the whole populations, indicating a core oral microbiome should be defined based on age and oral niches. [ABSTRACT FROM AUTHOR]

Purpose Dentures are often colonized with a variety of microorganisms, including Candida albicans, that contribute to denture stomatitis. Several in vitro models have been previously established to study denture-related microbial colonization and evaluate treatment efficacy of denture cleansers; however, those models typically fail to appreciate the complex topology and heterogeneity of denture surfaces and lack effective ways to accurately measure microbial colonization. The purpose of this study was to study microbial colonization with a new model system based on real dentures, to more realistically mimic in vivo conditions. Materials and Methods Scanning electron microscopy was used to observe topological structures among surfaces from different parts of the denture. Employing C. albicans as a model microorganism, we established microbial colonization on different denture surfaces. Moreover, we applied a modified MTT (3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide) colorimetric assay to quantify C. albicans colonization on dentures without the necessity of biofilm removal and to evaluate treatment efficacy of denture cleansers. Results There were significant variations in topological structures among surfaces from different parts of the denture, with the unpolished side having the highest amounts of indentations and pores. The distinct denture surfaces support microbial colonization differently, with the unpolished side containing the highest level of microbial colonization and biofilm formation. Furthermore, the modified MTT colorimetric assay proved to be an accurate assay to measure biofilm formation on dentures and evaluate treatment efficacy of denture cleansers. Conclusion This new denture model system in conjunction with the MTT colorimetric assay is a valuable tool to study denture-related microbiology and treatment approaches. [ABSTRACT FROM AUTHOR]

Prokaryotes and eukaryotes have long been thought to use very different types of kinases (the His kinases of the ‘bacterial’ two-component systems versus the ‘eukaryotic’ Ser/Thr/Tyr kinases) to carry out signal transduction. This paradigm no longer holds true, because both systems are now found together in an increasing number of prokaryotic organisms and ‘two-component’ His kinase are present in eukaryotes. Pioneering work on bacterial protein serine threonine kinases (PSTKs) has been performed in Myxococcus xanthus, a soil bacterium with a complex life cycle that possesses orthologues of signalling-related kinases ‘typical’ of both the prokaryotic and the eukaryotic kingdoms. In the work reported in this volume of Molecular Microbiology, Nariya and Inouye describe a PSTK cascade that modulates the biochemical activity of MrpC, a CRP-like transcriptional regulator for essential developmental signalling pathways in M. xanthus whose transcription is under the control of a two-component system. This is the first report of both a functional PSTK cascade in bacteria and the use of both PSTK and two-component systems to control a single complex bacterial signalling event. [ABSTRACT FROM AUTHOR]

Social (S)-motility inMyxococcus xanthusis a flagellum-independent gliding motility system that allows bacteria to move in groups on solid surfaces. S-motility has been shown to require type IV pili (TFP), exopolysaccharide (EPS; a component of fibrils) and lipopolysaccharide (LPS). Previously, information concerning EPS biogenesis inM. xanthuswas lacking. In this study, we screened 5000 randomly mutagenized colonies for defects in S-motility and EPS and identified two genetic regions essential for EPS biogenesis: theSynthesis (eps) region and thePS-sociated (eas) region. Mutants with insertions in theepsandeasregions were defective in S-motility and fruiting body formation. These mutants failed to bind the dye calcofluor white, indicating that they lacked EPS; however, they retained normal TFP and LPS. Analysis of theepslocus showed several open reading frames (ORFs) that encode homologues to glycosyltransferases, glucanases and EPS transporters as well as regulatory proteins; theeaslocus contains two ORFs: one exhibits homology to hypothetical proteins with a conserved domain of unknown function and the other displays no apparent homology to other proteins in the database. Further genetic mutagenesis analysis indicates that the wholeepsregion is involved in the biosynthesis of fibrils and fibril EPS. The operon at the proximal end of theepsregion was analysed by generating in-frame deletion mutations. These mutants showed varying degrees of defects in the bacterium's ability to produce EPS or perform EPS-related functions, confirming the involvement of these genes inM. xanthusEPS biogenesis. [ABSTRACT FROM AUTHOR]

Myxococcus xanthus cells aggregate and develop into multicellular fruiting bodies in response to starvation. A new M. xanthus locus, designated dif for defective in fruiting, was identified by the characterization of a mutant defective in fruiting body formation. Molecular cloning, DNA sequencing and sequence analysis indicate that the dif locus encodes a new set of chemotaxis homologues of the bacterial chemotaxis proteins MCPs (methyl-accepting chemotaxis proteins), CheW, CheY and CheA. The dif genes are distinct genetically and functionally from the previously identified M. xanthus frz chemotaxis genes, suggesting that multiple chemotaxis-like systems are required for the developmental process of M. xanthus fruiting body formation. Genetic analysis and phenotypical characterization indicate that the M. xanthus dif locus is required for social (S) motility. This is the first report of a M. xanthus chemotaxis-like signal transduction pathway that could regulate or co-ordinate the movement of M. xanthus cells to bring about S motility. [ABSTRACT FROM AUTHOR]

An obituary for professor Susan Kinder Haake is presented.

G10KHc, a specifically targeted antimicrobial peptide developed in our laboratory, has shown rapid and selective killing activity against Pseudomonas aeruginosa in culture medium. Because of the major role played by this pathogen in cystic fibrosis, we sought to evaluate the utility of G10KHc under more physiologic conditions in vitro. In the current study, we found that robust G10KHc activity could be maintained in expectorated sputum if serine protease-dependent digestion associated with this fluid was inhibited, either by chemical antagonists or by the construction of a D-amino acid enantiomer of G10KHc. Further investigations revealed that specifically targeted antimicrobial peptide activity in sputum could be further enhanced when samples were treated with a combination of peptide and recombinant human DNase. Our results illustrate the importance of investigating combination therapy to treat cystic fibrosis, especially if protease-sensitive peptide-based agents, such as G10KHc, are to be developed as alternatives to, or in conjunction with, conventional small-molecule antibiotics.