Biology subjects

Coulon, P. M. L.

Publications and source records attributed to Coulon, P. M. L..

4 recordsLinked to original sources

bioRxiv2026

A cis-encoded RNA interaction controls sub-operonic spoVG expression in Staphylococcus aureus

Bacterial operons enable co-transcription of multiple genes, yet post-transcriptional mechanisms permitting differential regulation of individual genes within a polycistronic transcript remains incompletely understood. We demonstrate that a cis-encoded RNA-RNA interaction within the bicistronic yabJ-spoVG transcript forms an RNase III substrate that represses the transcription factor SpoVG in Staphylococcus aureus. Disruption of the cis-encoded regulation elevated monocistronic spoVG expression, reduced biofilm formation and cell wall peptidoglycan thickness, and increased sensitivity to cell wall-targeting antimicrobials in clinical vancomycin-intermediate S. aureus, consistent with phenotypes observed in an independent SpoVG overexpression strain. These findings uncover a previously undescribed mode of cis-regulatory control within a polycistronic operon and establish regulatory mRNA-mRNA interactions as a mechanism for sub-operonic gene regulation.

microbiology↗

bioRxiv2025

Co-isolation of genetically distinct Burkholderia pseudomallei strains from a single patient in North Queensland

While investigating colony morphology variation (CMV) within clinical isolates of Burkholderia pseudomallei (Bp) isolated from a single infection, we identified two distinct strains (based on their multi-locus sequence type) from Bp TSV292. Simultaneous co-infection is rare, previously reported in only 2 of 133 cases. Here, we present the first comprehensive multi-omics characterization of co-infecting Bp strains isolated from a single infection at a hospital in Townsville, Australia in 2018. This finding impacts the design of future diagnosis and treatment of Bp. ImportanceMelioidosis, a severe disease caused by the bacterium Burkholderia pseudomallei, is rarely caused by more than one strain at the same time. In this study, we examined two bacterial strains isolated at once from a patient treated for melioidosis at a hospital in northern Queensland (Australia). By comparing their genomes, proteins, and physical traits, we found important strain differences that may affect how they adapt and survive during infection. Considering strain diversity when studying how this pathogen causes disease is essential, as it directly impacts future diagnosis and treatment.

microbiology↗

bioRxiv2025

Profiling of Burkholderia pseudomallei variants derived from Queensland clinical isolates

Burkholderia pseudomallei (Bp), an environmental bacterium and opportunistic pathogen endemic to tropical regions, is highly adaptive and thrives in diverse environments, from soil to human hosts. Bacterial adaptation is critical for survival, virulence modulation, and persistence during infection and can manifest as colony morphotype variation (CMV). While Bp adaptation has been well studied, CMV remains poorly understood. Here, we characterized five clinical Bp isolates exhibiting heterogeneous populations with rough and smooth colony morphologies. We used phenotypic assays, whole-genome sequencing, and proteomics to investigate the molecular pathways impacted by CMV - by comparing smooth and rough morphotypes. While phenotypic differences in protease activity, haemolysis, mucoid, iron uptake and antibiotic sensitivity --including to antimicrobial agents commonly used to treat infections--were rare, these traits alone could not distinguish morphotypes or group of isolates. Genomic comparisons revealed either no differences or limited isolate-specific mutations, which does not explain the overall difference in phenotypes. In contrast, proteomic analysis uncovered consistent shifts in protein abundance related to virulence, including quorum sensing, DNA methylation, and secretion systems. Rough variants showed higher expression of EPS-associated proteins, the BpsI3/R3 quorum sensing system, and the global regulator ScmR, whereas smooth variants upregulated type III/VI secretion and siderophore biosynthesis pathways. These findings suggest that CMV is driven by phase variation and regulatory mechanisms rather than punctual genomic modifications. Our study underscores the limitations of phenotype or genome-based classification alone in the context of CMV and highlights the value of integrated multi-omics approaches to uncover CMV-associated biomarkers, with potential applications in diagnostics and the development of targeted therapies against persistent and drug-resistant Bp infections.

microbiology↗

bioRxiv2020

Presence of the Hmq system and production of 4-hydroxy-3-methyl-2-alkylquinolines is heterogeneously distributed between Burkholderia cepacia complex species and more prevalent among environmental than clinical isolates

Some Burkholderia cepacia complex (Bcc) strains have been reported to produce 4-hydroxy-3-methyl-2-alkylquinolines (HMAQs), analogous to the 4-hydroxy-2-alkylquinolines of Pseudomonas aeruginosa. Using in silico analyses, we previously showed that the hmqABCDEFG operon, which encodes enzymes involved in the biosynthesis of HMAQs, is carried by about one-third of Bcc strains, with considerable inter- and intra-species variability. In the present study, we investigated by PCR, using consensus primers, the distribution of hmqABCDEFG in a collection of 313 Bcc strains (222 of clinical and 91 of environmental origins) - belonging to 18 Bcc species. We confirmed that the distribution is species-specific, although not all strains within a species carry the hmqABCDEFG operon. Among the 30% of strains bearing the hmqABCDEFG operon, we measured the total HMAQs production and showed that 90% of environmental isolates and 68% of clinically isolated Bcc produce detectable levels of HMAQs when cultured in TSB medium. For the strains having the hmqABCDEFG operon but not producing HMAQs, we studied the transcription and showed that none expressed the hmqA gene under the specified culture conditions. Interestingly, the hmqABCDEFG operon is more prevalent among plant root environment species (e.g. B. ambifaria, B. cepacia) and absent in species commonly found in chronically colonized individuals with cystic fibrosis (e.g. B. cenocepacia, B. multivorans), suggesting that the Hmq system could play a role in niche adaptation by influencing rhizosphere microbial community and could have been lost through evolution. Understanding the Hmq system and its regulation will provide clues concerning the production of HMAQs and their functions in Bcc.

microbiology↗