Biology subjects

Givaudan, A.

Publications and source records attributed to Givaudan, A..

3 recordsLinked to original sources

bioRxiv2025

Pleiotropic role of PAX cyclolipopeptides in the Xenorhabdus bacterium mutualistically associated with entomopathogenic nematodes

Xenorhabdus is an entomopathogenic bacterium involved in a mutualistic relationship with Steinernema nematodes. Xenorhabdus produces a multitude of specialized metabolites by Non-Ribosomal Peptide Synthetases (NRPSs) pathways to mediate bacterial-nematode- insect interactions. PAX cyclolipopeptides are a family of NRP-type molecules whose ecological role remains poorly understood. In this study, the pleiotropic role of PAX peptides in the life cycle of Xenorhabdus nematophila has been investigated. By mass spectrometry analysis, we first demonstrated that PAX peptides were detected from the pathogenic stage up to the necrotrophic stage. We discovered that the bromothymol blue adsorption phenotype historically used to discriminate Xenorhabdus variants was associated with the presence of PAX peptides. We found that PAX peptides were positively involved in biofilm formation and negatively involved in swimming motility. PAX peptides were also shown to promote in vivo the production of infective Steinernema juveniles, suggesting their involvement in the mutualistic relationship between Xenorhabdus and its nematode partner. Finally, we showed that the paxTABC cluster as well as PAX peptide production was conserved across the whole Xenorhabdus genus except in Xenorhabdus poinarii and Xenorhabdus ishibashii. This work has revealed multiple new ecological roles for NRP-type peptides. ImportanceXenorhabdus bacteria are models of particular interest for their mutualistic relationship with Steinernema nematodes and their ability to produce a wide range of natural NRP-type bioactive metabolites. These compounds are mostly studied for their medical or industrial applications, but their ecological role is poorly understood. This study provides a dynamic characterization of PAX cyclolipopeptide presence during Xenorhabdus nematophila life cycle, as well as confirmation of their production by 7 different strains within the Xenorhabdus genus. We revealed new multiple functions for PAX peptides in biofilm formation, swimming motility and juvenile nematode production. A deeper understanding of how PAX peptides interact with the nematode host would provide a better insight into the role of these cyclolipopeptides in bacterial-nematode mutualism.

microbiology↗

bioRxiv2023

Evidence for increased fitness of a plant pathogen conferred by epigenetic variation

Adaptation is usually explained by adaptive genetic mutations that are transmitted from parents to offspring and become fixed in the adapted population. However, more and more studies show that genetic mutation analysis alone is not sufficient to fully explain the processes of adaptive evolution and report the existence of non-genetic (or epigenetic) inheritance and its significant role in the generation of adapted phenotypes. In the present work, we tested the hypothesis of the role of DNA methylation, a form of epigenetic modification, in adaptation of the plant pathogen Ralstonia solanacearum to the host plant during an experimental evolution. Using SMRT-seq technology, we analyzed the methylomes of 31 experimentally evolved clones that were obtained after serial passages on a given host plant during 300 generations, either on susceptible or tolerant hosts. Comparison with the methylome of the ancestral clone revealed between 12 and 21 differential methylated sites (DMSs) at the GTWWAC motif in the evolved clones. Gene expression analysis of the 39 genes targeted by these DMSs revealed limited correlation between differential methylation and differential gene expression. Only one gene showed a correlation, the RSp0338 gene encoding the EpsR regulator protein. The MSRE-qPCR (Methylation Sensitive Restriction Enzyme - qPCR) technology was used as an alternative approach to assess the methylation state of the DMSs found by SMRT-seq between the ancestral and evolved clones. This approach also found the two DMSs upstream of RSp0338. Using site-directed mutagenesis, we demonstrated the contribution of these two DMSs in host adaptation. As these DMSs appeared very quickly in the experimental evolution, we hypothesize that such fast epigenetic changes can allow rapid adaptation to the plant stem environment. To our knowledge, this is the first study showing a link between epigenetic variation and evolutionary adaptation to new environment.

evolutionary biology↗

bioRxiv2019

Photorhabdus Dam methyltransferase overexpression impairs virulence of the nemato-bacterial complex in insects

Photorhabdus luminescens is an entomopathogenic bacterium found in symbiosis with the nematode Heterorhabditis. Dam DNA methylation is involved in the pathogenicity of many bacteria, including P. luminescens, whereas studies about the role of bacterial DNA methylation during symbiosis are scarce. The aim of this study was to determine the role of Dam DNA methylation in P. luminescens symbiosis with H. bacteriophora. We constructed a strain overexpressing dam by inserting an additional copy of the dam gene under the control of a constitutive promoter in the chromosome of P. luminescens and then achieved association between this recombinant strain and nematodes. The dam overexpressing strain was able to feed the nematode in vitro and in vivo similarly as a control strain, and to re-associate with Infective Juvenile (IJ) stages in the insect. No difference in the amount of emerging IJs from the cadaver was observed between the two strains. Compared to the nematode in symbiosis with the control strain, a significant increase in LT50 was observed during insect infestation with the nematode associated with the dam overexpressing strain. These results suggest that the P. luminescens Dam plays a role in the pathogenicity of the nemato-bacterial complex.

microbiology↗