Biology subjects

Trottier, M.

Publications and source records attributed to Trottier, M..

4 recordsLinked to original sources

bioRxiv2025

Glacial history and landscape features shape the hierarchical population genetic structure of woodland caribou (Rangifer tarandus caribou) in western Canada

Caribou, listed as a species at risk across Canada, have experienced a wide range of evolutionary and selective pressures at multiple scales, from large-scale range shifts and recolonisations driven by glacial cycles to more localized contemporary habitat degradation and fragmentation. Given these multi-scale evolutionary forces, genetic variation and diversity are expected to be hierarchically structured. Characterising hierarchical population structure is crucial to understanding a species evolutionary history and informing effective conservation and management strategies. In this study, we analysed genomic diversity and variation in woodland caribou (Rangifer tarandus caribou) across western Canada using genotypes from [~]33,000 Single Nucleotide Polymorphism (SNP) loci from 759 geo-referenced individuals spanning 45 pre-defined subpopulations. We employed genetic clustering methods and measures of genetic differentiation to characterize hierarchical population structure in the region and tested for latitudinal changes in heterozygosity resulting from post-glacial recolonisation and hybridisation. Our results confirm that woodland caribou genetic diversity and differentiation occur at multiple hierarchical levels, reflecting post-glacial recolonisation patterns and landscape heterogeneity. Notably, the major genetic clusters identified in our study do not align with current conservation units for the species in this region. We also observe elevated heterozygosity in the mid-latitudes of the sampled range, indicative of hybridisation following secondary contact during post-glacial recolonisation. These findings underscore the need to consider and include genetic diversity at all hierarchical levels in conservation planning, as wide-ranging species often experience diverse and complex evolutionary histories and pressures.

evolutionary biology↗

bioRxiv2025

PqsE is conserved and functionally relevant in Pseudomonas aeruginosa

The bacterium Pseudomonas aeruginosa is an opportunistic pathogen responsible for several acute and chronic infections. It produces a diverse array of virulence and survival determinants, many of which are tightly regulated by three interlinked quorum sensing (QS) systems named las, rhl and pqs. RhlR, the transcriptional regulator of the rhl system, activates multiple virulence genes upon binding to its cognate autoinducer signal. Meanwhile, the pqs system relies on 4-hydroxy-2-alkylquinolines (HAQs) as signaling molecules to induce the transcriptional regulator MvfR (PqsR). MvfR then activates the transcription of the pqsABCDE operon, encoding enzymes for HAQ biosynthesis. The final gene in this operon encodes PqsE, a multifunctional protein unique to P. aeruginosa. Beyond its thioesterase activity in HAQ biosynthesis, PqsE stabilizes RhlR, facilitating its regulation of target genes, some of which are implicated in virulence. Because of its role in pathogenicity, PqsE is regarded as a promising therapeutic target for combating P. aeruginosa infections. While the role of PqsE towards the RhlR regulon is increasingly understood in prototypical P. aeruginosa strains such as PA14 and PAO1, its broader relevance as an anti-virulence target remains underexplored. Here, we confirm that PqsE is functionally relevant across a panel of twelve genetically diverse P. aeruginosa strains using metabolite quantification and phenotypic assays. Significant strain-to-strain variations further highlight the importance of studying QS regulation among diverse isolates. Moreover, this study underscores PqsE as a key QS regulator with a conserved role in coordinating virulence determinant production and social behaviors across diverse P. aeruginosa populations. IMPORTANCEPseudomonas aeruginosa is a versatile opportunistic pathogen, naturally tolerant and readily acquiring resistance to multiple antibiotics. Consequently, the World Health Organization identified this bacterium as a high priority pathogen for researching and developing new antimicrobial strategies. P. aeruginosa utilizes quorum sensing, a cell-to-cell communication system, to regulate the expression of several of its virulence factors. Here, we confirm that the PqsE protein is conserved and that its function in quorum sensing, especially towards the RhlR regulator, is maintained across a panel of twelve genetically diverse P. aeruginosa strains. Since PqsE is conserved and unique to this bacterium, it could serve as an ideal target for anti-virulence therapies, offering new alternatives to combat antimicrobial resistance.

microbiology↗

bioRxiv2022

Pseudomonas aeruginosa strains from both clinical and environmental origins readily adopt a stable small colony variant (SCV) phenotype resulting from single mutations in c-di-GMP pathways

A subpopulation of Small Colony Variants (SCVs) is a frequently observed feature of Pseudomonas aeruginosa isolated from colonized cystic fibrosis lungs. Since most SCVs have until now been isolated from clinical samples, it remains unclear how widespread is the ability of P. aeruginosa to develop this phenotype and the genetic mechanism(s) behind SCVs emergence according to the origin of the isolate. In the present work, we investigated the ability of 22 P. aeruginosa isolates from various environmental origins to, under laboratory culture conditions, spontaneously adopt a SCV-like smaller alternative morphotype distinguishable from the ancestral parent strain. We found that all the P. aeruginosa strains tested could adopt a SCV phenotype, regardless of their origin. Whole genome sequencing of SCVs obtained from clinical and environmental sources revealed single mutations exclusively in two distinct c-di-GMP signaling pathways, Wsp and YfiBNR. We conclude that the ability to switch to a SCV phenotype is a conserved feature of P. aeruginosa and results from the acquisition of a stable genetic mutation, regardless of the origin of the strain. IMPORTANCEP. aeruginosa is an opportunistic pathogen that thrives in many environments. It poses a significant health concern, notably because this bacterium is the most prevalent pathogen found in the lungs of people with cystic fibrosis. In infected hosts, its persistence is considered related to the emergence of an alternative small colony variant (SCV) phenotype. By reporting the distribution of P. aeruginosa SCVs in various non-clinical environments and the involvement of c-di-GMP in SCV emergence from both clinical and environmental strains, this work contributes to understanding a conserved adaptation mechanism used by P. aeruginosa to adapt readily in all environments. Hindering this adaptation strategy could help control P. aeruginosa persistent infection.

microbiology↗

bioRxiv2021

The ability of Pseudomonas aeruginosa to adopt a Small Colony Variant (SCV) phenotype is conserved, and not restricted to clinical isolates

A subpopulation of Small Colony Variants (SCVs) is a frequently observed feature of Pseudomonas aeruginosa isolated from cystic fibrosis (CF) lungs biofilms. SCVs have almost exclusively been reported from infected hosts, essentially CF individuals or, by extension, from laboratory cultivation of strains originated from infected hosts. We previously reported the identification of P. aeruginosa SCVs emerging from a non-clinical strain and displaying features shared with clinical SCVs. In the present work, we investigated the ability of 22 P. aeruginosa isolates from various environmental origins to, under laboratory culture conditions, spontaneously adopt a SCV-like smaller alternative morphotype distinguishable from the ancestral parent strain. Unexpectedly, we found that all the P. aeruginosa strains tested have the ability to adopt a SCV morphotype, regardless of their origin. Based on the phenotypes already described for SCVs, the SCV-like morphotypes obtained were clustered in two groups displaying various phenotypic profiles, including one characteristic of already described SCVs. We conclude that the ability to switch to a SCV phenotype is a conserved feature in Pseudomonas aeruginosa. IMPORTANCEP. aeruginosa is an opportunistic pathogen that thrives in many environments. It is significant public health concern, notably because it is the most prevalent pathogen found in the lungs of people with cystic fibrosis (CF). In infected hosts, its persistence is believed to be related to the emergence of an alternative small colony variant (SCV) phenotype. By reporting the distribution of P. aeruginosa SCVs in various non-clinical environments, this work contributes to understanding a conserved adaptation mechanism used by P. aeruginosa to rapidly adapt in all environments. Counteraction of this strategy could prevent P. aeruginosa persistent infection in the future.

microbiology↗