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Attenuation of Mycobacterium tuberculosis by Disruption of a mas-Like Gene or a Chalcone Synthase-Like Gene, Which Causes Deficiency in Dimycocerosyl Phthiocerol Synthesis. Tatiana D. Sirakova, 2003.Tuberculosis is one of the leading preventable causes of death . Emergence of drug-resistant tuberculosis makes the discovery of new targets for antimycobacterial drugs critical . The unique mycobacterial cell wall lipids are known to play an important role in pathogenesis, and therefore the genes responsible for their biosynthesis offer potential new targets . To assess the possible role of some of the genes potentially involved in cell wall lipid synthesis, we disrupted a mas-like gene, msl7, and a chalcone synthase-like gene, pks10, with phage-mediated delivery of the disruption construct, in which the target gene was disrupted by replacement of an internal segment with the hygromycin resistance gene (hyg) . Gene disruption by allelic exchange in the case of each disruptant was confirmed by PCR and Southern blot analyses . Neither msl7 nor pks10 mutants could produce dimycocerosyl phthiocerol, although both could produce mycocerosic acids . Thus, it is concluded that these gene products are involved in the biosynthesis of phthiocerol . Both mutants were found to be attenuated in a murine model, supporting the hypothesis that dimycocerosyl phthiocerol is a virulence factor and thus the many steps involved in its biosynthesis offer potential novel targets for antimycobacterial therapy . Nisin-Controlled Production of Pediocin PA-1 and Colicin V in Nisin- and Non-Nisin-Producing Lactococcus lactis Strains. Nikki Horn, 2004. Characterization of the parB-Like yyaA Gene of Bacillus subtilis. Jörg Sievers, 2002.We have characterized the yyaA gene of Bacillus subtilis, located near the origin of chromosome replication (oriC) . Its protein product is similar to the Spo0J protein, which belongs to the ParB family of chromosome- and plasmid-partitioning proteins . Insertional inactivation of the yyaA gene had no apparent effect on chromosome organization and partitioning during vegetative growth or sporulation . Subcellular localization of YyaA by immunofluorescence microscopy indicated that it colocalizes with the nucleoid, and gel retardation studies confirmed that YyaA binds relatively nonspecifically to DNA . Overexpression of yyaA caused a sporulation defect characterized by the formation of multiple septa within the cell . This phenotype indicates that YyaA may have a regulatory role at the onset of sporulation .
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