Biology subjects

Mitobe, J.

Publications and source records attributed to Mitobe, J..

2 recordsLinked to original sources

bioRxiv2025

Genome-scale dissection of phase-variable gene function in Campylobacter jejuni using a stabilized phasotype library

Phase variation (PV) enables bacterial pathogens to rapidly alter their surface structures through reversible mutations in simple sequence repeats, promoting immune evasion and environmental adaptation. In Campylobacter jejuni, the stochastic nature of PV has hindered the systematic functional analysis of phase-variable genes (PVGs). Here, we introduce PV-GenShift, a genome-scale screening platform built on a genetically stabilized library of phase-locked C. jejuni variants. By fixing the ON/OFF states of 15 PVGs, PV-GenShift enables reproducible, high-resolution analysis of phasotypes, defined as unique ON/OFF combinations across multiple PVGs, under defined selective pressures. Using models of human serum exposure, murine colonization, and chicken gut passage, we identified distinct phasotypes associated with serum resistance and with enrichment during mouse colonization, particularly involving capsular polysaccharide modifications such as O-methyl phosphoramidation and methylation. In contrast, chicken gut passage resulted in heterogeneous ON/OFF shifts without a dominant phasotype. These findings highlight the combinatorial impact of PVG expression states on bacterial adaptation and establish PV-GenShift as a broadly applicable framework for dissecting PV-driven phenotypic diversity. This approach provides a scalable strategy for exploring genotype-phenotype relationships and offers insights relevant to vaccine design and targeted therapeutics. Significance StatementPhase variation generates phenotypic diversity that enables pathogens to evade immunity and adapt to changing environments; however, its random nature has long obscured functional analysis. This study introduces PV-GenShift, a genome-scale platform that stabilizes phase-variable gene expression in Campylobacter jejuni, allowing the systematic identification of gene combinations that influence survival under selective pressures. Using PV-GenShift, we identified phasotypes associated with serum resistance and enrichment during mouse colonization, while chicken passage produced diverse but non-specific shifts. These results demonstrate how combinatorial ON/OFF states of multiple genes shape bacterial adaptation and provide a generalizable strategy for studying phase variation across pathogens, with implications for vaccine design and targeted therapeutics.

microbiology↗

bioRxiv2025

Exposure to third generation cephalosporin induces L-form transition in Shigella sonnei, potentially acting as a bacterial reservoir for persistent infection

Shigellosis remains a major global health burden, and the increasing prevalence of multidrug-resistant (MDR) Shigella strains is complicating effective antibiotic therapy. Bacteria may survive antibiotics by transitioning into cell wall-deficient L-forms, which are intrinsically resistant to {beta}-lactams and can revert to a virulent state, potentially causing relapsing infections. Here we characterized a clinical MDR isolate Shigella sonnei HK8, a.k.a. PD552A, whose genome contains key resistance (gyrA, PBP3) and virulence (icsA) genes. Exposure to ceftriaxone induced a transition into a viable L-form state that was hyper-adhesive to macrophages in vitro. However, this survival adaptation was linked to a profound loss of pathogenicity. Using murine and guinea pig models, the L-form variant was shown to be profoundly attenuated, failing to cause the keratoconjunctivitis, diarrheal disease, or significant histopathology characteristic of the wild-type strain. These findings reveal a critical virulence-survival trade-off, positioning the L-form as a "stealth" phenotype that enables bacterial persistence at the expense of acute virulence. This offers a potential mechanism for asymptomatic carriage and recurrent infections, highlighting a previously underappreciated mechanism by which antibiotic treatment may resolve acute symptoms while permitting the persistence of a cryptic bacterial reservoir capable of driving recurrent infection. ImportanceOur research provides critical insight into the challenge of antibiotic treatment failure in shigellosis. By integrating experimental validation of reversible L-form transitions with mathematical modelling, we uncover a crucial virulence-survival trade-off. We show that MDR S. sonnei survives ceftriaxone by adopting a "stealth" phenotype, quantified by a high Stealth Index - maintaining bacterial burden while evading host inflammatory detection. These findings imply that standard antibiotics may resolve acute symptoms while inadvertently selecting for a cryptic, persistent reservoir poised for relapse. This work challenges the conventional view of therapeutic success and highlights an urgent need to develop novel diagnostic and therapeutic strategies capable of identifying and eliminating these resilient, "stealth" L-form persisters to achieve true bacterial clearance and prevent chronic infections.

microbiology↗