title: Increasing RpoS expression causes cell death in Borrelia burgdorferi.
abstract: RpoS, one of the two alternative σ factors in Borrelia burgdorferi, is tightly controlled by multiple regulators and, in turn, determines expression of many critical virulence factors. Here we show that increasing RpoS expression causes cell death. The immediate effect of increasing RpoS expression was to promote bacterial division and as a consequence result in a rapid increase in cell number before causing bacterial death. No DNA fragmentation or degradation was observed during this induced cell death. Cryo-electron microscopy showed induced cells first formed blebs, which were eventually released from dying cells. Apparently blebbing initiated cell disintegration leading to cell death. These findings led us to hypothesize that increasing RpoS expression triggers intracellular programs and/or pathways that cause spirochete death. The potential biological significance of induced cell death may help B. burgdorferi regulate its population to maintain its life cycle in nature.
authors.affiliation: Department of Pathobiological Sciences, Louisiana State University, Baton Rouge, Louisiana, United States of America.
authors.forename: Linxu
authors.initials: L
authors.lastname: Chen
authors.affiliation: Department of Pathobiological Sciences, Louisiana State University, Baton Rouge, Louisiana, United States of America.
authors.forename: Qilong
authors.initials: Q
authors.lastname: Xu
authors.affiliation: Department of Pathology and Laboratory Medicine, University of Texas Medical School at Houston, Houston, Taxes, United States of America.
authors.forename: Jiagang
authors.initials: J
authors.lastname: Tu
authors.affiliation: Department of Pathobiological Sciences, Louisiana State University, Baton Rouge, Louisiana, United States of America.
authors.forename: Yihe
authors.initials: Y
authors.lastname: Ge
authors.affiliation: Department of Pathology and Laboratory Medicine, University of Texas Medical School at Houston, Houston, Taxes, United States of America.
authors.forename: Jun
authors.initials: J
authors.lastname: Liu
authors.affiliation: Department of Pathobiological Sciences, Louisiana State University, Baton Rouge, Louisiana, United States of America.
authors.forename: Fang Ting
authors.initials: FT
authors.lastname: Liang
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics*; D025065:Borrelia burgdorferi / Q000235:genetics* / Q000254:growth & development / Q000502:physiology; D003001:Cloning, Molecular; D053938:DNA Fragmentation; D015964:Gene Expression Regulation, Bacterial; D050296:Microbial Viability / Q000235:genetics*; D030781:Organisms, Genetically Modified; D012808:Sigma Factor / Q000235:genetics*; D014169:Transformation, Bacterial; D015854:Up-Regulation / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D012808:Sigma Factor; C069567:sigma factor KatF protein, Bacteria