title: Role of the Porphyromonas gingivalis extracytoplasmic function sigma factor, SigH.
abstract: Little is known about the regulatory mechanisms that allow Porphyromonas gingivalis to survive in the oral cavity. Here we characterize the sigma (σ) factor SigH, one of six extracytoplasmic function (ECF) σ factors encoded in the P. gingivalis genome. Our results indicate that sigH expression is upregulated by exposure to molecular oxygen, suggesting that sigH plays a role in adaptation of P. gingivalis to oxygen. Furthermore, several genes involved in oxidative stress protection, such as sod, trx, tpx, ftn, feoB2 and the hemin uptake hmu locus, are downregulated in a mutant deficient in SigH designated as V2948. ECF σ consensus sequences were identified upstream of the transcriptional start sites of these genes, consistent with the SigH-dependent regulation of these genes. Growth of V2948 was inhibited in the presence of 6% oxygen when compared with the wild-type W83 strain, whereas in anaerobic conditions both strains were able to grow. In addition, reduced growth of V2948 was observed in the presence of peroxide and the thiol-oxidizing reagent diamide when compared with the W83 strain. The SigH-deficient strain V2948 also exhibited reduced hemin uptake, consistent with the observed reduced expression of genes involved in hemin uptake. Finally, survival of V2948 was reduced in the presence of host cells compared with the wild-type W83 strain. Collectively, our studies demonstrate that SigH is a positive regulator of gene expression required for survival of the bacterium in the presence of oxygen and oxidative stress, hemin uptake and virulence.
authors.affiliation: The Philips Institute of Oral and Craniofacial Molecular Biology, Virginia Commonwealth University, Richmond, VA 23298-0566, USA.
authors.forename: S S
authors.initials: SS
authors.lastname: Yanamandra
authors.forename: S S
authors.initials: SS
authors.lastname: Sarrafee
authors.forename: C
authors.initials: C
authors.lastname: Anaya-Bergman
authors.forename: K
authors.initials: K
authors.lastname: Jones
authors.forename: J P
authors.initials: JP
authors.lastname: Lewis
mesh_terms: D001426:Bacterial Proteins / Q000187:drug effects / Q000502:physiology*; D001431:Bacteriological Techniques; D002874:Chromosome Mapping; D016384:Consensus Sequence / Q000235:genetics; D003958:Diamide / Q000494:pharmacology; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics; D006427:Hemin / Q000378:metabolism; D006801:Humans; D050296:Microbial Viability / Q000235:genetics; D009055:Mouth / Q000382:microbiology; D009154:Mutation / Q000235:genetics; D016877:Oxidants / Q000494:pharmacology; D018384:Oxidative Stress / Q000235:genetics; D010100:Oxygen / Q000494:pharmacology; D010545:Peroxides / Q000494:pharmacology; D016966:Porphyromonas gingivalis / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D018085:Regulon / Q000235:genetics; D012808:Sigma Factor / Q000187:drug effects / Q000502:physiology*; D013439:Sulfhydryl Reagents / Q000494:pharmacology; D014158:Transcription, Genetic / Q000235:genetics; D015854:Up-Regulation / Q000187:drug effects; D014774:Virulence / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D016877:Oxidants; D010545:Peroxides; C120328:SigH protein, bacteria; D012808:Sigma Factor; D013439:Sulfhydryl Reagents; D003958:Diamide; D006427:Hemin; D010100:Oxygen