Biology subjects

Nakatani, H.

Publications and source records attributed to Nakatani, H..

7 recordsLinked to original sources

bioRxiv2026

Structural characterization of a pseudaminic acid-modified lateral flagellar filament from Vibrio alginolyticus

Bacterial flagellar filaments are often modified by glycans, but the structural basis and physiological significance of flagellin glycosylation remain poorly understood in many species. Vibrio alginolyticus produces lateral flagella for surface-associated motility in viscous environments, with LafA forming its filament as flagellin. A maf homolog encoding a putative flagellin glycosylation factor is located immediately downstream of lafA, suggesting that the lateral filament is glycosylated. To investigate this possibility, we purified the lateral flagellar filament from V. alginolyticus and determined the structure at 2.37 [A] resolution by electron cryomicroscopy. Upon model building of LafA in the map, we identified additional densities connected to five serine residues, possibly corresponding to O-linked pseudaminic acid modifications. Mass spectrometric analyses identified these modifications as pseudaminic acid attached to Ser148, Ser173, Ser183, Ser189, and Ser197. Deletion of maf abolished lateral flagella formation and motility, and these defects were restored by complementation with maf. These results demonstrate that the Vibrio lateral flagellar filament is extensively modified by pseudaminic acid and that Maf is required for filament formation. Our findings provide the first structural insight into the glycosylation of Vibrio lateral flagellar filament and establish a framework for understanding the role of flagellin glycosylation in surface-associated motility.

microbiology↗

bioRxiv2026

Requirements for swarming ability by lateral flagella on an agar surface in marine Vibrio cells

The marine bacterium Vibrio alginolyticus and the food poisoning bacterium V. parahaemolyticus possess two types of flagella in one cell: proton-driven lateral flagella (Laf) extending from the periphery of the cell body, and sodium ion-driven polar flagella (Pof) extending from a cell pole. For swimming in seawater they use polar flagella, suppressing the expression of lateral flagella. When they attach to the body surface of fish or intestinal tract, lateral flagella are induced, allowing it to crawl along the surface or through mucus. The dynamometer hypothesis, which proposes that polar flagella sense rotation and control the expression of lateral flagellar genes, has been widely accepted. However, how rotation is sensed and how expression is controlled remains unclear. Although swarming has recently been analyzed by physical, biological, or biochemical perspectives, it remains unclear how this motility is controlled, or which substances and conditions are necessary for swarming ability. In this study, we discovered that adding gelatin to agar medium promotes swarming on the agar surface by the lateral flagella of Vibrio. Our data suggested that surfactants or viscous polysaccharides secreted extracellularly are important for promoting swarming on the agar surface and we identified that swarming is likely to be driven by S (social)-motility, in which bacteria move by interacting with each other, and A (adventure)-motility, in which bacteria move by interacting with the agar surface. Our study provides clues that help clarify the mechanism of bacterial swarming IMPORTANCEWe discovered that adding gelatin to hard agar medium promoted swarming on agar surfaces by the lateral flagella of Vibrio cells. The surfactants or viscous polysaccharides secreted extracellularly seem to be important for swarming ability on agar surfaces. We proposed that the swarming is thought to occur through S(social)-motility, where cells move by interacting with cell bodies each other, and A(adventure)-motility, where cells move by interacting with the agar surface and cell body. The present study should provide the clues to clarify the mechanism of bacterial swarming and how to move in a viscous environment.

microbiology↗

bioRxiv2026

Division of labor between ERK and Notch signaling coordinates distinct stem cell populations during jellyfish tentacle regeneration

Regeneration restores lost tissues through diverse cellular strategies that vary across species and tissue contexts. In many systems, regeneration involves blastema formation; however, how blastema formation is coordinated in tissues employing multiple stem/progenitor populations remains unclear. Here, we investigate tentacle regeneration in the hydrozoan jellyfish Cladonema, in which two distinct proliferative populations contribute to regeneration: resident homeostatic stem cells (RHSCs), which supply differentiated cell types, and repair-specific proliferative cells (RSPCs), which are transiently induced upon injury to form the blastema. While extensive cell death occurs shortly after injury, it is largely dispensable for blastema formation. Using pharmacological inhibition and cell proliferation analyses, we identify ERK/MAPK signaling as a key regulator of blastema formation. ERK signaling is rapidly activated at the injury site and selectively promotes proliferation of RSPCs without affecting RHSC proliferation. In contrast, inhibition of Notch signaling disrupts nematocyte differentiation and induces hyperproliferation of RHSCs, while leaving RSPC proliferation unchanged, indicating that Notch signaling governs the balance between differentiation and self-renewal in RHSCs. Together, these findings reveal a division of labor between conserved signaling pathways and support a model in which regeneration is achieved through spatially and functionally compartmentalized control of distinct stem cell populations.

developmental biology↗

bioRxiv2026

Aging disrupts tissue homeostasis and constrains blastema-mediated regeneration in the Cladonema medusa

Regenerative capacity varies widely across animals, yet aging is often accompanied by declining tissue homeostasis and regenerative potential. In many species, regeneration of complex structures relies on epimorphic programs that form a blastema, coordinating cell proliferation and pattern reorganization after injury. Although aging-associated regeneration defects have been documented in several bilaterian models, how aging shapes regeneration in early-branching metazoans with robust regenerative abilities remains unclear. Here, we investigate aging and regeneration in the medusa stage of Cladonema pacificum, a cnidarian that retains high regenerative capacity within a finite lifespan. We show that aging in Cladonema medusae is accompanied by progressive morphological and functional deterioration, including shrinkage of the umbrella and manubrium, tentacle shortening, and reduced reproductive output, along with increased DNA damage. At the cellular level, aging is associated with depletion of differentiated cell populations, including nematocytes and neurons, as well as reductions in stem cell-associated populations and proliferative activity in the tentacle bulb. Consistent with these changes, tentacle regeneration is markedly impaired in aged medusae and is characterized by delayed wound closure, defective blastema formation, and incomplete functional recovery. Together, our findings indicate that aging disrupts both tissue homeostasis and blastema-mediated regeneration in Cladonema medusae, establishing a tractable model for studying aging-regeneration interactions and supporting the view that aging imposes broadly shared constraints on regenerative systems across metazoans.

developmental biology↗

bioRxiv2025

Trophic transfer of nanoplastics reduces larval survival of marine fish more than waterborne exposure

Microplastics (MPs) and nanoplastics (NPs) are widespread contaminants in marine environments and pose significant risks to aquatic organisms. However, physiological effects and survival consequences of different MP and NP exposure pathways during early developmental stages of marine fish remain poorly understood. We investigated effects of direct and indirect consumption of MPs and NPs by larvae of red sea bream (Pagrus major) using a controlled laboratory system. Larvae were exposed to fluorescently labeled polystyrene particles (3 {micro}m and 0.2 {micro}m) either directly from the water or indirectly via contaminated zooplankton prey. MPs and NPs were detected in digestive tracts of all exposed individuals, regardless of the exposure route. However, survival was significantly reduced in larvae that consumed NPs via rotifer predation, suggesting that ingestion of contaminated prey organisms may represent a greater hazard than direct uptake from water. In both groups, antioxidant enzymes, superoxide dismutase (SOD) and catalase (CAT) were elevated, suggesting induction of oxidative stress. Relative gene expression revealed greater upregulation of several stress and immune-related genes in larvae exposed to MPs via rotifer predation than via direct consumption. Our findings provide clear evidence that both MPs and NPs can alter physiological and molecular responses in marine fish larvae, especially via rotifer predation. This study suggests the importance of considering trophic interactions in ecotoxicological assessments of plastic pollution to address plastic bioavailability and toxicity during early life stages. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=114 SRC="FIGDIR/small/675286v1_ufig1.gif" ALT="Figure 1"> View larger version (24K): org.highwire.dtl.DTLVardef@1de4a22org.highwire.dtl.DTLVardef@d53060org.highwire.dtl.DTLVardef@5b13fborg.highwire.dtl.DTLVardef@17cd662_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LILarval survival was significantly reduced by nanoplastics via trophic transfer C_LIO_LIGrowth of larvae was not affected by micro-and nanoplastics C_LIO_LIMicro- and nanoplastics cause oxidative stress by both exposure routes C_LIO_LIUp-regulated gene expression revealed that larvae undergo various stresses C_LI

developmental biology↗

bioRxiv2025

Antimicrobial-producing Bacteria from Fish Epidermal Mucus Alter the Fish Epidermal Bacterial Flora and Host Resistance to Infection

The emergence of antimicrobial-resistant bacteria in aquaculture has raised the need for alternative strategies to control fish infections. Antimicrobial-producing bacteria have been explored as probiotics or biocontrol agents, but their mechanisms of action and impact on host-associated microbiota remain poorly understood. Here, we identified Pseudomonas mosselii KH-ZF1, a bacterium isolated from fish epidermal mucus, as a producer of antimicrobial substances. When applied to zebrafish, KH-ZF1 transiently adhered to the epidermal mucus and altered the composition of the skin microbiota. Under an appropriate administration condition, KH-ZF1 treatment significantly improved survival in zebrafish infected with Yersinia ruckeri, and suppressed pathogen growth on the skin surface. However, in the absence of KH-ZF1 or inappropriate conditions, Y. ruckeri dominated the epidermal bacterial community. The antimicrobial compound produced by KH-ZF1 was identified as Fluviol C (FluC), a pigmented metabolite previously reported from Pseudomonas fluorescens. FluC inhibited the growth of multiple fish pathogens at low concentrations, but exhibited toxicity to zebrafish even below its minimum inhibitory concentration. Intriguingly, FluC at sub-inhibitory levels induced bacterial substitution in the epidermal microbiota, mimicking the effects of KH-ZF1. These findings demonstrate that KH-ZF1 alters host resistance to infection by promoting bacterial substitution on the fish skin by producing FluC. Our study highlights a microbiota-mediated mechanism by which antimicrobial-producing bacteria can control infection through fish epidermis, offering a potential alternative to traditional antibiotics in aquaculture. ImportanceWe demonstrated for the first time that bacteria producing antibacterial substances, isolated from fish skin mucus, can inhibit percutaneous infections in aquatic environments. These bacteria effectively altered the skin mucus bacterial flora and suppressed pathogen growth. Fish skin acts as a barrier against infections, with its microorganisms being considered to play a crucial role in prevention. Our study highlighted the potential use of these specific microorganisms in the fish skin mucus as a novel fish disease control strategy. By targeting fish skin mucus bacteria that produce antimicrobial substances, we could develop a new approach to managing diseases in aquaculture like probiotics for fish skin. This research underscores the importance of studying fish epidermal microorganisms for innovative disease management.

microbiology↗

bioRxiv2018

Development of the Brief Personal Values Inventory for sense of values in the Japanese general population

The Portrait Values Questionnaire (PVQ) is a widely used questionnaire for assessing sense of values; however, it has limitations, especially for children. Therefore, the present study aims to develop a questionnaire for sense of values, called the Brief Personal Values Inventory (BPVI), consisting of simple questions and a smaller number of items compared to the PVQ. We first created 12 items for the BPVI and then tested their validity and reliability in 167 Japanese general population (81 males, mean age (SD) [range]: 23.4 (8.2) [15-57] years). Each of these items was correlated with one or more values in the PVQ-57. The BPVI items covered all higher-order values in Schwartzs theory (Openness to Change, Self-Enhancement, Conservation, and Self-Transcendence). In sum, the BPVI has an acceptable criterion-related validity and corresponds to higher-order values in Schwartzs value theory. The BPVI is suitable for a reliable and direct comparison of sense of values between children and adults, which may be useful for elucidating the developmental pathway of personal sense of values.

scientific communication and education↗