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Effects of Fluoroquinolones on the Migration of Human Phagocytes through Chlamydia pneumoniae-Infected and Tumor Necrosis Factor Alpha-Stimulated Endothelial Cells. Silvia M. Uriarte, 2004.The anti-inflammatory activities of three quinolones, levofloxacin, moxifloxacin, and gatifloxacin, were investigated with an in vitro model of transendothelial migration (TEM) . Human umbilical vein endothelial cells (HUVEC) were seeded in Transwell inserts, treated with serial dilutions of antibiotics, infected with Chlamydia pneumoniae, or stimulated with tumor necrosis factor alpha (TNF-  ) . Neutrophils or monocytes were also preincubated with serial dilutions of each antibiotic . TEM was assessed by light microscopic examination of the underside of the polycarbonate membrane, and levels of interleukin-8 (IL-8) and monocyte chemotactic protein 1 (MCP-1) were measured by enzyme-linked immunosorbent assay . In HUVEC infected with C . pneumoniae or stimulated with TNF-, all fluoroquinolones significantly decreased neutrophil and monocyte TEM, compared to antibiotic-free controls . Moxifloxacin and gatifloxacin produced a significant decrease in IL-8 in C . pneumoniae-infected and TNF--stimulated HUVEC; however, moxifloxacin was the only fluoroquinolone that produced a significant decrease in MCP-1 levels under both conditions . Results from this study indicate similarities in the anti-inflammatory activities of these fluoroquinolones, although no statistically significant decrease in chemokine secretion was observed when levofloxacin was used . Mechanisms of neutrophil and monocyte TEM inhibition by fluoroquinolone antibiotics are unknown but may be partially due to inhibition of IL-8 and MCP-1 production, respectively .
Effects of rodA and pbp2b Disruption on Cell Morphology and Oxidative Stress Response of Streptococcus thermophilus CNRZ368. Annabelle Thibessard, 2002.Insertional mutagenesis was used to isolate clones from Streptococcus thermophilus CNRZ368 that were modified in their abilities to tolerate oxidative stress . During this process, two menadione-sensitive clones (6G4 and 18C3) were found to display abnormal cell morphologies and distorted chain topologies and were further studied . Molecular characterization of both 6G4 and 18C3 mutants indicated that they were disrupted in open reading frames homologous to rodA and pbp2b, respectively . Both genes encoded proteins in Escherichia coli that were described as being implicated in peptidoglycan synthesis during the process of cell elongation and to function in determining the rod shape of the cell . This work reports a possible connection between peptidoglycan biosynthesis and oxidative stress defense in S . thermophilus CNRZ368 . Role for Vitamin B12 in Light Induction of Gene Expression in the Bacterium Myxococcus xanthus. María Cervantes, 2002.A light-inducible promoter (PB) drives the carB operon (carotenoid genes) of the bacterium Myxococcus xanthus . A gene encoding a regulator of carotenoid biosynthesis was identified by studying mutant strains carrying a transcriptional fusion to PB and deletions in three candidate genes . Our results prove that the identified gene, named carA, codes for a repressor of the PB promoter in the dark . They also show that the carA gene product does not participate in the light activation of two other promoters connected with carotenoid synthesis or its regulation in M . xanthus . CarA is a novel protein consisting of a DNA-binding domain of the family of MerR helix-turn-helix transcriptional regulators, directly joined to a cobalamin-binding domain . In support of this, we report here that the presence of vitamin B12 or some other cobalamin derivatives is absolutely required for activation of the PB promoter by light . The sloABCR Operon of Streptococcus mutans Encodes an Mn and Fe Transport System Required for Endocarditis Virulence and Its Mn-Dependent Repressor. Sehmi Paik, 2003.Streptococcus mutans belongs to the viridans group of oral streptococci, which is the leading cause of endocarditis in humans . The LraI family of lipoproteins in viridans group streptococci and other bacteria have been shown to function as virulence factors, adhesins, or ABC-type metal transporters . We previously reported the identification of the S . mutans LraI operon, sloABCR, which encodes components of a putative metal uptake system composed of SloA, an ATP-binding protein, SloB, an integral membrane protein, and SloC, a solute-binding lipoprotein, as well as a metal-dependent regulator, SloR . We report here the functional analysis of this operon . By Western blotting, addition of Mn to the growth medium repressed SloC expression in a wild-type strain but not in a sloR mutant . Other metals tested had little effect . Cells were also tested for aerobic growth in media stripped of metals then reconstituted with Mg and either Mn or Fe . Fe at 10 µM supported growth of the wild-type strain but not of a sloA or sloC mutant . Mn at 0.1 µM supported growth of the wild-type strain and sloR mutant but not of sloA or sloC mutants . The combined results suggest that the SloABC proteins transport both metals, although the SloR protein represses this system only in response to Mn . These conclusions are supported by 55Fe uptake studies with Mn as a competitor . Finally, a sloA mutant demonstrated loss of virulence in a rat model of endocarditis, suggesting that metal transport is required for endocarditis pathogenesis .
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