The Molecular Biology of Photorhabdus Bacteria

Abstract

This book provides an essential update on the startling array of novel insecticidal toxins and drugs produced by the fascinating bacterium Photorhabdus. The respective chapters describe everything from the detailed molecular biology of the 'Toxin complexes' or Tc's to the complexity of insect immune response in relation to both the bacterium and its nematode vector. The volume covers both primary (toxin production and regulation) and secondary (natural product synthesis and regulation) metabolism and emphasises the potential use of toxins and drugs in both agriculture and medicine. It also discusses in detail two totally novel quorum sensing mechanisms and the likely role of LuxR solos in sensing the presence of different bacterial hosts. Lastly, the book explores the unique case of P. asymbiotica, which seems to have evolved the ability to infect both insects and humans. This synthesis proves that Photorhabdus truly does offer a 'gold mine' for the discovery of novel insecticidal proteins and novel natural products with potential uses in agriculture and medicine alike. Preface; Photorhabdus as a Bug for All Seasons; Bugs that Kill Bugs; Bugs that do Drugs; Bugs that Infect Both Insects and Man; Bugs that Just Keep Giving; Contents; Insecticidal Toxins and Virulence Regulation; 55 Insecticidal Toxin Complexes from Photorhabdus luminescens; Abstract; 1 Introduction; 1.1 The Life Cycle of Insecticidal Nematodes; 1.2 Specificity of Insecticidal Toxins; 2 'Toxin Complex' (Tc) Toxins; 2.1 Nomenclature of Tc Toxins; 2.2 TcA-like Proteins of the Toxin Complex; 2.2.1 Interaction of TcA-like Proteins with the Host Cell Membrane 2.2.2 The Molecular and Atomic Structure of TcA-like Proteins2.2.3 Is TcA per se Insecticidal?; 2.3 TcB-like Proteins of the Toxin Complex; 2.4 TcC-like Proteins of the Toxin Complex; 2.5 Structure of the Complete TC Complex; 3 Biological Activities of Tc Toxins; 3.1 TccC3 Is an ADP-Ribosyltransferase that Targets Actin; 3.1.1 Modification of Actin by TccC3 at Threonine148; 3.1.2 Photorhabdus Toxin Photox Modifies Actin at Arginine177; 3.2 TccC5 Is an ADP-Ribosyltransferase that Targets Rho Proteins; 3.2.1 Rho Proteins Are Substrates of TccC5 3.2.2 Functional Consequences of Rho ADP-Ribosylation by TccC54 Conclusions; References; 51 Identifying Anti-host Effectors in Photorhabdus; Abstract; 1 Introduction; 2 A Forward Genetics Approach; 2.1 Rapid Virulence Annotation; 2.2 Secondary Metabolites as Virulence Factors; 2.3 Host Specificity; 3 The Drosophila Embryo System; 4 Immune Cell Phenotype Screen; 5 In Silico Screens; 5.1 Photox-A Toxin Unique to P. luminescens; 5.2 PaTox-A Toxin Unique to P. asymbiotica; 5.3 The Photorhabdus Virulence Cassettes; 6 Future Approaches; References 53 Flagellar Regulation and Virulence in the Entomopathogenic Bacteria-Xenorhabdus nematophila and Photorhabdus luminescensAbstract; 1 Bacterial Motility and Virulence in Pathogenic Bacteria; 2 Flagella Affect Virulence by Facilitating Motility; 3 Flagellar Regulators Affect Virulence by Regulating Non-flagellar Virulence Factors; 4 The Flagella Apparatus as Virulence Factor Secretion System; 5 In Situ Flagellar Gene Expression During Invertebrate Infection; 6 Phenotypic Variation and Bimodal Expression of Flagellar and Virulence Genes; 7 Conclusions and Future Work on P. luminescens