[P006] Poster

1:00 PM - 1:50 PM JST(4:00 AM - 4:50 AM UTC)

[P03-400] Rewiring bacterial surface motility via hybrid histidine kinase mutation enhances colony expansion in Cupriavidus

○ZHIYU XIONG¹, Shoko Hirano¹, Hiromi Kato¹, Kohei Kishida¹, Leonardo Stari¹, Yoshiyuki Otsubo¹, Yuji Nagata¹ (1. TOHOKU UNIVERSITY (Japan))

Keywords:

two-component system,hybrid histidine kinase,Cupriavidus,twitching motility,colony morphology,γ-hexachlorocyclohexane

Surface-associated motility plays a critical role in the environmental adaptation, spatial organization, and functional performance of bacteria in heterogeneous ecosystems. However, the genetic mechanisms underlying the regulation and plasticity of such behaviors in environmental bacteria remain incompletely understood. In this study, we investigated a spontaneous mutant of Cupriavidus sp. strain TKC, originally isolated from a γ-hexachlorocyclohexane (γ-HCH)-degrading microbial community, that exhibits a thin and continuously expanding colony phenotype (TCE+) even under nutrient-rich conditions. Whole-genome resequencing identified an in-frame 48-bp deletion in tceS, a gene encoding a hybrid histidine kinase. Genetic analyses, including allelic replacement and complementation, confirmed that this mutation is responsible for the TCE+ phenotype. Unlike a complete deletion of tceS, which did not reproduce the phenotype, the tceSΔ48 allele appears to generate an altered signaling output, suggesting a signal-rewiring mechanism rather than simple loss of function. Transcriptome analysis revealed that the tceSΔ48 mutation induces coordinated upregulation of genes associated with type IV pili and twitching motility, while repressing genes involved in flagellar motility and chemotaxis. These transcriptional changes were consistent with phenotypic observations, including reduced swimming motility and loss of flagella. Importantly, deletion of pilH abolished the TCE+ phenotype, demonstrating that PilH-dependent surface motility is essential for colony expansion in the mutant strain. These results indicate that a single mutation in a hybrid histidine kinase can trigger a major shift in motility strategy, from flagella-dependent swimming to pili-mediated surface expansion. Such phenotypic plasticity may enhance bacterial dispersal and persistence in structured environments, including contaminated soils where spatial access to substrates is limited. From an environmental biotechnology perspective, the ability to modulate bacterial surface motility and colony expansion through targeted regulatory changes provides a novel strategy for controlling microbial behavior. Enhanced surface spreading could improve the efficiency of pollutant-degrading consortia by facilitating spatial colonization and substrate access, whereas suppressing such behaviors may help limit the spread of undesirable microorganisms. Overall, this study demonstrates that signal rewiring via mutation of a regulatory kinase can profoundly alter bacterial surface-associated behavior, offering new insights into microbial adaptability and providing a conceptual framework for engineering microbial functions relevant to bioremediation and environmental management.