Biology subjects

Aikawa, C.

Publications and source records attributed to Aikawa, C..

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↗

bioRxiv2020

Intracellular Group A Streptococcus induces Golgi fragmentation to impair host defenses through Streptolysin O and NAD-glycohydrolase

Group A Streptococcus (GAS; Streptococcus pyogenes) is a major human pathogen that causes streptococcal pharyngitis, skin and soft-tissue infections, and life-threatening conditions such as streptococcal toxic-shock syndrome. During infection, GAS not only invades diverse host cells, but also injects effector proteins such as NAD-glycohydrolase (Nga) into the host cells through a streptolysin O (SLO)-dependent mechanism without invading the cells; Nga and SLO are two major virulence factors that are associated with increased bacterial virulence. Here, we have shown that the invading GAS induces fragmentation of the Golgi complex and inhibits anterograde transport in the infected host cells through the secreted toxins SLO and Nga. GAS infection-induced Golgi fragmentation required both bacterial invasion and SLO-mediated Nga translocation into the host cytosol. The cellular Golgi network is critical for the sorting of surface molecules and thus is essential for epithelial barrier integrity and the immune response of macrophages to pathogens. In epithelial cells, inhibition of anterograde trafficking by invading GAS and Nga resulted in the redistribution of E-cadherin to the cytosol and an increase in bacterial translocation across the epithelial barrier. Moreover, in macrophages, interleukin-8 secretion in response to GAS infection was found to be suppressed by intracellular GAS and Nga. Our findings reveal a previously undescribed bacterial invasion-dependent function of Nga as well as a previously unrecognized GAS-host interaction that is associated GAS pathogenesis. ImportanceTwo prominent virulence factors of GAS, SLO and Nga, have been established to be linked to enhanced pathogenicity of prevalent GAS strains. Recent advances show that SLO and Nga are important for intracellular survival of GAS in epithelial cells and macrophages. Here, we found that invading GAS disrupt the Golgi complex in host cells by SLO and Nga. We showed that GAS-induced Golgi fragmentation requires bacterial invasion into host cells, SLO pore-formation activity, and Nga NADase activity. GAS-induced Golgi fragmentation resulted in the impairment of epithelial barrier and chemokine secretion in macrophages. This immune inhibition property of SLO and Nga by intracellular GAS indicates that the invasion of GAS is associated with virulence exerted by SLO and Nga.

microbiology↗