Author: sylvadonaldson

Delphine Dufour, Camila Leiva-Sabadini, Sebastian Aguayo, Céline M Lévesque

J Bacteriol. 2026 Aug 20;208(8):e0032326. doi: 10.1128/jb.00323-26.

Pubmed ID: 42447300

Abstract

Quorum sensing (QS) plays a central role in the adaptive biology of Streptococcus mutans, yet the extent to which competence-stimulating peptide (CSP) signaling intersects with membrane vesicle production and function remained unclear. In this study, CSP activation markedly increased membrane vesicle output during the stationary phase and drove extensive changes in vesicle protein composition. Proteomic analysis revealed broad remodeling of vesicle cargo, including shifts in subcellular origin, and enrichment of multiple functional protein classes. Notably, CSP-induced vesicles carried the persistence-associated peptide Pep299, suggesting a link between QS-dependent cargo loading and antibiotic survival. To examine the functional consequences of this remodeling, S. mutans cells were pre-exposed to vesicles prior to antibiotic challenge. Vesicles derived from CSP-induced cultures promoted persister formation in a concentration-dependent manner, whereas vesicles from non-induced cultures exhibited minimal activity. Wild-type vesicles increased persistence, and vesicles from Pep299-overexpressing cells further enhanced this phenotype at lower vesicle concentrations. In contrast, vesicles derived from a Δ299 mutant failed to promote persistence, demonstrating that Pep299 is a key determinant of this activity. At higher vesicle abundance, the responses of wild-type and Pep299-enriched vesicles converged, consistent with endogenous CSP-dependent Pep299 loading. Fusion assays using R18 dequenching showed that vesicles from wild-type, Pep299-overexpressing, and Δ299 strains fused with comparable efficiency, indicating that differences in persistence arise from cargo composition rather than altered delivery efficiency. Together, these findings reveal that CSP QS coordinates biogenesis and selective cargo remodeling in S. mutans and identify Pep299-containing vesicles as a quorum-regulated mechanism promoting antibiotic persistence.IMPORTANCEQuorum sensing enables bacterial populations to coordinate adaptive behaviors, yet its influence on membrane vesicle biology is not fully understood. This study shows that competence-stimulating peptide (CSP) signaling in Streptococcus mutans not only increases vesicle production but also remodels vesicle protein cargo, including enrichment of the persistence-associated peptide Pep299. CSP-induced vesicles enhance the formation of persister cells through a cargo-dependent mechanism rather than through changes in vesicle-cell fusion. These findings uncover a previously unrecognized connection between quorum sensing and vesicle-mediated persistence and reveal a strategy through which S. mutans modulates community behavior and resilience within the oral biofilm environment.

Keywords: Streptococcus mutans; antibiotic tolerance; membrane vesicles; peptide signaling; persister cells; quorum sensing.

Amandeep Kaur, Jeffrey B Jones, Erica M Goss, Yesim Aysan, Marcus M Dillon

Access Microbiol. 2026 Feb 27;8(2):001144.v3. doi: 10.1099/acmi.0.001144.v3.

Pubmed: 41767906

Abstract

Xanthomonas spp. are increasingly recognized as a global threat to agriculture, impacting a broad range of economically important crops. We report the whole-genome sequences of six Xanthomonas strains isolated from tomato and pepper plants in Turkey that were experiencing symptoms of bacterial spot disease. Phylogenomic analysis with representative Xanthomonas genomes from each species revealed that three of these strains belonged to Xanthomonas perforans, two to Xanthomonas euvesicatoria and one to Xanthomonas campestris. We then analysed the phylogenomic relatedness of these strains with other strains from these respective species and characterized their type III secreted effector content. These genomic data represent a valuable resource for understanding the genetic diversity and local epidemiology of bacterial spot disease in Turkey.

Keywords: Xanthomonas; bacterial spot disease; phylogenomics; type III secretion effectors; whole-genome sequencing.

Sara Shama, Michelle R Asbury, Alex Kiss , Nicole Bando , James Butcher, Elena M Comelli, Julia K Copeland , Adrianna Greco , Akash Kothari , Philip M Sherman, Alain Stintzi , Amel Taibi, Christopher Tomlinson, Sharon Unger , Pauline W Wang ; OptiMoM Feeding Group; Deborah L O’Connor

Cell Rep Med. 2024 Sep 17;5(9):101729. doi: 10.1016/j.xcrm.2024.101729.

Pubmed: 39243753

Abstract

Mother’s milk contains diverse bacterial communities, although their impact on microbial colonization in very-low-birth-weight (VLBW, <1,500 g) infants remains unknown. Here, we examine relationships between the microbiota in preterm mother’s milk and the VLBW infant gut across initial hospitalization (n = 94 mother-infant dyads, 422 milk-stool pairs). Shared zero-radius operational taxonomic units (zOTUs) between milk-stool pairs account for ∼30%-40% of zOTUs in the VLBW infant’s gut. We show dose-response relationships between intakes of several genera from milk and their concentrations in the infant’s gut. These relationships and those related to microbial sharing change temporally and are modified by in-hospital feeding practices (especially direct breastfeeding) and maternal-infant antibiotic use. Correlations also exist between milk and stool microbial consortia, suggesting that multiple milk microbes may influence overall gut communities together. These results highlight that the mother’s milk microbiota may shape the gut colonization of VLBW infants by delivering specific bacteria and through intricate microbial interactions.

Trial registration: ClinicalTrials.gov NCT02137473.

Keywords: antibiotics; direct breastfeeding; donor milk; human milk; microbiome; microbiota; mother’s milk; nutrient fortification; preterm infant; very-low-birth-weight infant.

Anna van Weringh, Paul J Gamueda, Hasna Khan, Asher Pasha, Eddi Esteban, Nicholas J Provart

Plant Cell. 2025 Oct 8;37(10):koaf218. doi: 10.1093/plcell/koaf218.

Pubmed: 40973624

Abstract

Drought is an important environmental stress that limits crop production. Guard cells (GCs) act to control the rate of water loss. To better understand how gene expression in GCs changes during progressive drought, we generated GC-specific RNA-seq transcriptomes during mild, moderate, and severe drought stress. Additionally, we sampled re-watered plants after severe drought. These transcriptomes were generated using the INTACT (isolation of nuclei tagged in specific cell types) system to capture the RNA from GC nuclei. We optimized the INTACT protocol for Arabidopsis thaliana leaf tissue, incorporating fixation to preserve RNA during nuclear isolation. To identify gene expression changes unique to GCs, we also generated INTACT transcriptomes from all leaf cell types, using the 35S viral promoter. These data sets highlight shared and unique gene expression changes between GCs and the bulk leaf tissue. Only GCs have detectable gene expression changes at the earliest drought time point, and a high percentage of moderate drought GC DEGs are not observed in severe drought, unlike the bulk leaf tissue, showing that GCs tailor their gene expression changes to drought severity. A thermal imaging screen of mutants of 80 candidate early drought-responsive genes revealed that 10 of these exhibit a cooler-than-wild-type phenotype under moderate drought conditions. The drought-responsive GC and leaf RNA-seq transcriptomes are available in the Arabidopsis ePlant at the Bio-Analytic Resource for Plant Biology website. These findings provide valuable insights into GC-specific drought responses and identify targets for enhancing drought tolerance in crops.

Zachary Kileeg, G Adam Mott

BMC Biol. 2025 Aug 26;23(1):266. doi: 10.1186/s12915-025-02364-y

Pubmed: 40859252

Abstract

Background: The receptor-like kinases (RLKs) are the largest family of proteins in plants. Characterized members play critical roles in diverse processes from growth to immunity, and yet the majority do not have a known function. Assigning function to RLKs poses a significant challenge due to the specificity of ligand recognition and because of the often pleiotropic or redundant functions RLKs possess. These problems inhibit the important work of identifying stress-related receptors that may be targets for crop improvement. Identification of stress-related evolutionary signatures can provide a way to expedite the discovery of candidate receptors. Pan-genome analysis can be used to compare naturally occurring variants within a species to identify evolutionary signatures that may otherwise be hidden by using only a single ecotype.

Results: Using 146 ecotypes of Arabidopsis, we generated a pan-RLKome to investigate species-wide natural diversity and identify structural variation and other patterns indicative of stress adaptation. We discovered significant presence/absence variation across a subset of RLKs, most of which occurred in specific subclades nested within receptor subfamilies. These same subclades tended to have arisen through proximal or tandem duplication, both of which are common mechanisms during the expansion of stress-related genes. We also identified strong positive selection across many gene subfamilies and a bias of positive selection in the extracellular domains of receptors. This suggests escape from adaptive conflict within the extracellular domain may have played a large role in the evolution and adaptation of the RLKs.

Conclusion: Taken together, this work represents an excellent tool for the comparative study of RLKs and has identified lineages and subclades within RLK subfamilies with the hallmarks of involvement in stress adaptation.

Keywords: PTI; Pan-RLKome; Plant immunity; RLK evolution; RLKs.