Project description:Transcriptionnal analysis of a Photorhabdus luminescens TT01 variant, named VAR*, which is a colonial and phenotypic variant displaying delayed pathogenicity in the insect, Spodoptera littoralis.
Project description:Proteins belonging to the cupin superfamily have a wide range of catalytic and noncatalytic functions. Cupin proteins commonly have the capacity to bind a metal ion with the metal frequently determining the function of the protein. We have been investigating the function of homologous cupin proteins that are conserved in more than 40 species of bacteria. To gain insights into the potential function of these proteins we have solved the structure of Plu4264 from Photorhabdus luminescens TTO1 at a resolution of 1.35 Å and identified manganese as the likely natural metal ligand of the protein.
Project description:Photorhabdus luminescens bacteria alternate lifestyles between its pathogenic insect host and its mutualistic nematode host. We found that Photorhabdus changes radically from the insect pathogenic form (P-form) to slow growing small cells when initiating mutualism (M-form). Here we characterize the gene expression of the M-form relative to the P-form.
Project description:Secretion systems are used as weapons by a variety of Gram-negative bacteria. Among them the Type VI Secretion System (T6SS) gained more interest throughout the last years. The system functions as a molecular nano-weapon: it is used in inter-kingdom competition by various bacteria to deliver toxic effectors in target cells. Here we describe the role of the T6SS in Photorhabdus laumondii subsp. laumondii strain DJC, an entomopathogenic biocontrol agent able to live in different environmental niches, such as in symbiosis with nematodes and in the rhizosphere on plant roots. Using bioinformatic and protein motif analyses we identified four T6SS gene clusters (T6SS-1, T6SS-2, T6SS-3 and T6SS-4) and multiple orphan T6SS related genes in the genome of P. laumondii. Furthermore, we highlighted 11 T6SS effector-immunity pairs, including three undescribed membrane disrupting effectors, each with putatively different antibacterial activities. By label-free mass spectrometry of P. laumondii wild type cells and respective T6SS-deficient strains, we could point out a cross-link between T6SS and other Photorhabdus’ virulence related mechanisms such as PVCs, T3SS and pyocins. Furthermore, a change in motility as well as in the secondary metabolism was observed upon T6SS-deficiency. Here, we shed light on the T6SS in P. laumondii DJC and suggesting a cross-link of various virulence mechanisms, which could help to gain knowledge on T6SS and better figure out the Photorhabdus ability to live in polymicrobial environments.
Project description:Photorhabdus luminescens lives in a mutualistic association with entomopathogenic nematodes and is pathogenic for insects. Variants of Photorhabdus frequently arise. VAR* is a colonial and phenotypic variant displaying delayed pathogenicity in the insect, Spodoptera littoralis. In this study, we evaluated the role of transcriptomic modulation in determining the phenotypic variation and delayed pathogenicity of VAR* with respect to the corresponding wild-type form, TT01alpha. A P. luminescens microarray was used to determine changes in transcript profiles in the exponential and stationary phase growth phase of VAR* and TT01alpha grown in LB broth.