title: Xenorhabdus nematophila lrhA is necessary for motility, lipase activity, toxin expression, and virulence in Manduca sexta insects.
abstract: The gram-negative insect pathogen Xenorhabdus nematophila possesses potential virulence factors including an assortment of toxins, degradative enzymes, and regulators of these compounds. Here, we describe the lysR-like homolog A (lrhA) gene, a gene required by X. nematophila for full virulence in Manduca sexta insects. In several other gram-negative bacteria, LrhA homologs are transcriptional regulators involved in the expression (typically repression) of virulence factors. Based on phenotypic and genetic evidence, we report that X. nematophila LrhA has a positive effect on transcription and expression of certain potential virulence factors, including a toxin subunit-encoding gene, xptD1. Furthermore, an lrhA mutant lacks in vitro lipase activity and has reduced swimming motility compared to its wild-type parent. Quantitative PCR revealed that transcript levels of flagellar genes, a lipase gene, and xptD1 were significantly lower in the lrhA mutant than in the wild type. In addition, lrhA itself is positively regulated by the global regulator Lrp. This work establishes a role for LrhA as a vital component of a regulatory hierarchy necessary for X. nematophila pathogenesis and expression of surface-localized and secreted factors. Future research is aimed at identifying and characterizing virulence factors within the LrhA regulon.
authors.affiliation: Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, USA.
authors.forename: Gregory R
authors.initials: GR
authors.lastname: Richards
authors.forename: Erin E
authors.initials: EE
authors.lastname: Herbert
authors.forename: Youngjin
authors.initials: Y
authors.lastname: Park
authors.forename: Heidi
authors.initials: H
authors.lastname: Goodrich-Blair
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D001427:Bacterial Toxins / Q000096:biosynthesis* / Q000235:genetics; D001483:Base Sequence; D004251:DNA Transposable Elements; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D005407:Flagella / Q000235:genetics; D017353:Gene Deletion; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D016908:Gram-Positive Bacterial Infections / Q000382:microbiology; D008049:Lipase / Q000096:biosynthesis* / Q000235:genetics; D008124:Locomotion; D018402:Manduca / Q000382:microbiology*; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D016019:Survival Analysis; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*; D014774:Virulence; D020593:Xenorhabdus / Q000235:genetics / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; D001427:Bacterial Toxins; D004251:DNA Transposable Elements; D004269:DNA, Bacterial; C095974:LrhA protein, bacteria; D014157:Transcription Factors; D008049:Lipase