Biology subjects

Uemura, N. A.

Publications and source records attributed to Uemura, N. A..

3 recordsLinked to original sources

bioRxiv2025

Oligomeric coiled-coil adhesins that drive chain-like adhesion diversify surface colonization strategies in Shiga toxin-producing Escherichia coli

Bacteria frequently colonize host and environmental surfaces under fluid flow. Chain-like adherence pattern (CLAP) is an EibG-mediated surface colonization phenotype of certain Shiga toxin-producing Escherichia coli (STEC) that lack the locus of enterocyte effacement (LEE). EibG, an immunoglobulin-binding oligomeric coiled-coil adhesin, drives CLAP, but the temporal dynamics and genetic diversity underlying chain formation remain unclear. Here, we use live-cell time-lapse imaging to show that chains arise from single cells that elongate and divide without separation. Under flow, chains resist detachment and undergo shear-dependent fragmentation at cell-cell junctions, releasing viable clonal units that disperse downstream. Comparative genomics reveals substantial diversity among EibG-related adhesins and identifies distinct lineages, including chain-like adhesins (cla) that mediate CLAP while lacking IgG binding. Screening of 1,354 LEE-negative STEC genomes from England shows that claB is present in 95.6% of strains from major LEE-negative STEC serotypes, highlighting its epidemiological prevalence. Targeted mutagenesis demonstrates that chain formation and IgG binding are mediated by distinct structural domains, revealing the modular functional architecture of these adhesins. In a mouse infection model, deletion of eibG reduced lethality, indicating that EibG contributes to virulence. Collectively, these findings establish CLAP as a dynamic, surface-associated strategy of LEE-negative STEC and reveal previously unrecognized diversification among adhesins that drive this behavior.

microbiology↗

bioRxiv2025

Bacteria break through one-micrometer-square passages by flagellar wrapping

Confined spaces are omnipresent in the micro-environments, including soil aggregates and intestinal crypts, yet little is known about how bacteria behave under such conditions where movement is challenging due to limited diffusion. Stinkbug symbiont Caballeronia insecticola navigates a narrow gut passage about one micrometer in diameter to reach the stinkbugs symbiotic organ. Here, we developed a microfluidic device mimicking the hosts sorting organ, wherein bacterial cells are confined in a quasi-one-dimensional fashion, and revealed that this bacterium wraps flagellar filaments around its cell body like a screw thread to control fluid flow and generate propulsion for smooth and directional movement in narrow passages. Physical simulations and genetic experiments revealed that hook flexibility is essential for this wrapping; increasing hook rigidity impaired both wrapping motility and infectivity. Thus, flagellar wrapping likely represents an evolutionary innovation, enabling bacteria to break through confined environments using their motility machinery.

microbiology↗

bioRxiv2025

Rapid water flow navigates long-distance migration of thermophilic bacteria

Bacteria thrive in nearly all environments on Earth, demonstrating remarkable adaptability to physical stimuli, as well as chemicals and light. However, the mechanisms by which bacteria locate and settle in ecological niches optimal for their growth remains poorly understood. Here, we show that Thermus thermophilus, a highly thermophilic non-flagellated species of bacteria, exhibits positive rheotaxis, navigating upstream in unidirectional rapid water flow. Mimicking their natural habitat at 70{degrees}C with a water current under optical microscopy, cells traveled distances up to 1 mm in 30 min, with infrequent directional changes. This long-distance surface migration is driven by type IV pili, facilitating vertical attachment at the cell pole, and shear-induced tilting of the cell body, resulting in alignment of the leading pole toward the direction of water flow. Direct visualization of T4P filaments and their dynamics revealed that rheotaxis is triggered by weakened attachment at the cell pole, regulated by ATPase activity, which was further validated by a mathematical modeling. Flow experiments on 16 bacterial strains and species in the Deinococcus-Thermus phylum revealed that positive rheotaxis is highly conserved among rod-shaped Thermaceae, whereas no rheotactic behavior was observed in spherical-shaped Deinococcus. Our findings suggest that thermophilic bacteria reach their ecological niches by responding to the physical stimulus of rapid water flow, a ubiquitous feature in hot spring environments. This study highlights unforeseen survival strategies, showcasing an evolutionary adaptation to a surface-associated lifestyle where swimming bacteria would otherwise be swept away.

microbiology↗