Biology subjects

Takano, S.

Publications and source records attributed to Takano, S..

8 recordsLinked to original sources

bioRxiv2026

ELAplus: Fast and accurate analysis platform for energy landscape analysis facilitated by fine-tuning optimization algorithm.

1. Large-scale community-composition datasets, especially from microbiome studies, increasingly provide opportunities to identify major community compositional types (e.g., enterotypes in human microbiomes) and potential transitions depending on environmental factors. Energy landscape analysis based on maximum entropy models has emerged as a promising framework for characterizing such multi-stability in ecological communities. However, its application to diverse, high-dimensional compositional datasets remains limited by computational inefficiency, insufficient evaluation of predictability, and lack of systematic assessment of uncertainty. 2. Here, we present a computationally tractable inference framework for energy landscape analysis of multispecies communities, implemented in the R package ELAplus. We introduce a framework combining cross-validation-based selection of optimization settings, enabling accurate and computationally efficient model fitting across a wide range of simulated community datasets. In addition, we incorporate a bootstrap-based approach to quantify the reliability of inferred stable states, providing a systematic measure of uncertainty in landscape structures. 3. Simulation analyses demonstrate improved predictive performance and robustness compared to existing implementations. Applications to empirical datasets further illustrate how the framework can reveal stable states, basins of attraction, and potential tipping points under varying environmental conditions. The package also provides visualization tools, including disconnectivity graphs and energy surface plots, to facilitate intuitive interpretation of complex ecological landscapes. 4. Our framework enables robust and computationally efficient inference of ecological stability from compositional and environmental data, expanding the applicability of energy landscape approaches in diverse natural communities.

ecology↗

bioRxiv2026

Major microbiota transitions across liver disease progression are mediated by key taxa linking host environments and microbial communities

The gut microbiome plays a critical role in chronic liver disease, yet quantitative methods that integrate microbial community structure with clinical indices remain limited. Here, we applied an energy landscape analysis (ELA)-based framework to characterize transitions in gut microbiota along a clinical gradient of liver disease severity, as measured by the FibroScan-AST (FAST) score. The analysis revealed characteristic community states corresponding to low, intermediate, and high FAST scores, indicating that liver disease progression is associated with structured transitions in microbial community organization rather than simple changes in overall diversity. To further dissect community-level organization, we developed the community shaping index (CSI), which quantifies how strongly individual taxa are associated with specific community structures. Integrating CSI with species-environment association parameters identified key taxa with distinct ecological roles, including unclassified Subdoligranulum taxon, an unclassified Ruminococcus gnavus group taxon, and Streptococcus salivarius, that link host environmental conditions with community composition. Exploratory causal discovery suggested that Streptococcus salivarius and the unclassified Subdoligranulum may play distinct, potentially active roles in linking liver health with gut microbial organization, but with contrasting associations: S. salivarius was linked to disease-related liver deterioration and dysbiotic states, whereas the unclassified Subdoligranulum was associated with healthier liver function and coherent community organization. Overall, this ecologically grounded framework provides a unified and mechanistic foundation for analyzing microbiome structure and disease-associated transitions.

ecology↗

bioRxiv2026

Long-term single-particle tracking by NIR imaging using Au42 (gold) quantum needles

Single-particle tracking (SPT) over time enables direct observation of molecular transport and interactions in living cells. Fluorescence-based SPT has provided insights into intracellular processes such as endocytosis, receptor signaling, and drug delivery. Extending the observation window to several hours and beyond is critical for capturing slow intracellular dynamics, including the full course of endosomal trafficking, the long-term accumulation of particles within subcellular compartments, and transitions between transport modes that occur on hour-scale timescales. However, long-term intracellular SPT under visible-wavelength excitation remains challenging because fluorescence probes generally suffer from photobleaching and phototoxicity. While near-infrared (NIR) excitation can simultaneously mitigate these issues, generally weak emission of NIR-emitting dyes has hindered its wide application in long-term SPT. Here, we demonstrate long-term NIR SPT using atomically precise gold quantum needles, Au42(PET)32 (PET = 2-phenylethanethiolate). Continuous tracking of intracellular particles in living HEK293 cells was achieved for up to 12 h. Trajectory analysis revealed temporal transitions between directional and diffusive transport, as well as the accumulation of multiple particles within localized intracellular domains over several-hour timescales. The high photostability of Au42, combined with low phototoxicity of NIR excitation, enables visualization of intracellular transport dynamics over timescales difficult to access using conventional visible fluorescent probes. These results establish Au42-based NIR imaging as a platform for long-term, low-phototoxicity intracellular SPT and provide a framework for investigating slow intracellular dynamics in living systems.

biophysics↗

bioRxiv2024

Droplet Sequencing Reveals Virulence Gene Clusters in Oral Biofilm Extracellular Vesicles

Bacterial extracellular vesicles (BEVs), produced by a broad spectrum of bacteria, play a crucial role in enhancing intercellular communication through DNA transfer. A vital determinant of their gene transfer efficiency is the gene content diversity within BEVs, an aspect that conventional metagenomics fails to capture. Our study bridges this gap with a novel microdroplet-based sequencing technique that precisely details DNA content within hundreds of individual BEVs. This technique revealed a unique DNA profile in BEVs from the oral pathogen Porphyromonas gingivalis, pinpointing specific genomic regions related to DNA integration (e.g., DNA transposition and CRISPR-Cas systems). These enriched genes, overlooked by standard analyses that aggregate total read counts, indicate that our method offers a more focused view into the genetic contents of BEVs. Applying our technique to dental plaque-derived BEVs, we discovered a hundredfold higher prevalence of DNA encapsulation than previously estimated, with over 30% of BEVs containing DNA. Specifically, we identified a substantial presence of O-antigen biosynthesis genes, prominent hotspots of frequent horizontal gene transfer, from Alcaligenes faecalis. Given that O-antigens mediate host-bacterial interactions, this gene enrichment in the large fraction of BEVs suggests a potential novel pathway by which BEVs could influence pathogenicity within oral biofilms. Our research unveils critical insights into the potential functions of vesicular DNA in microbial communities, establishing a powerful platform for studying vesicular DNA in microbiomes. This technical breakthrough provides a foundational basis for future research in microbial communication and the development of potential therapeutic or diagnosis strategies. Significance StatementBEVs have been studied for decades, yet their roles in nature and disease are just beginning to be appreciated. Our study makes a significant leap in understanding the roles of BEVs as gene transfer vehicles. By developing a microdroplet-based sequencing technique, we have uncovered detailed DNA profiles within individual BEVs, a task beyond the capabilities of conventional metagenomic methods. This breakthrough highlights specific genomic regions enriched in BEVs from pure culture and human dental plaque. Furthermore, the high prevalence of biofilm BEVs enriched in O-antigen biosynthesis genes, suggests a potential impact on the pathogenicity of oral biofilms. This research establishes a new methodological platform for exploring the intricacies of BEV-mediated interactions in a complex microbial community.

microbiology↗

bioRxiv2023

Segment-specific axon guidance by Wnt/Fz signaling diversifies motor commands in Drosophila larvae

Functional diversification of homologous neuronal microcircuits is a widespread feature observed across brain regions as well as across species, while its molecular and developmental mechanisms remain largely unknown. We address this question in Drosophila larvae by focusing on segmentally homologous Wave command-like neurons, which diversify their wiring and function in a segment-specific manner. Anterior Wave (a-Wave) neurons extend axons anteriorly and connect to circuits inducing backward locomotion, whereas posterior Wave (p-Wave) neurons extend axons posteriorly and trigger forward locomotion. Here, we show that Frizzled receptors DFz2 and DFz4, together with the DWnt4 ligand, regulate the segment-specific Wave axon projection. DFz2 knock-down (KD) not only reroutes Wave axons to posterior neuromeres but also biases its motor command to induce forward instead of backward locomotion as tactile response. Thus, segment-specific axon guidance diversifies the function of homologous command neurons in behavioral regulation. Since control of anterior-posterior (A-P) axon guidance by Wnt/Fz-signaling is evolutionarily conserved, our results reveal a potentially universal molecular principle for formation and diversification of the command system in the nerve cord. Furthermore, this work indicates that sensorimotor transduction can be rerouted by manipulating a single gene in a single class of neurons, potentially facilitating the evolutionary flexibility in action selection. Impact statementRewiring the command neurons in the tactile circuit suffices to change the behavioral strategy of a whole animal, implying a "plug-and-play" flexibility in sensorimotor circuits.

neuroscience↗

bioRxiv2023

The architecture of metabolic networks constrains the evolution of microbial resource hierarchies

Microbial strategies for resource use are an essential determinant of their fitness in complex habitats. When facing environments with multiple nutrients, microbes often use them sequentially according to a preference hierarchy, resulting in well-known patterns of diauxic growth. In theory, the evolutionary diversification of metabolic hierarchies could represent a mechanism supporting coexistence and biodiversity by enabling temporal segregation of niches. Despite this ecologically critical role, the extent to which substrate preference hierarchies can evolve and diversify remains largely unexplored. Here we used genome-scale metabolic modeling to systematically explore the evolution of metabolic hierarchies across a vast space of metabolic network genotypes. We find that only a limited number of metabolic hierarchies can readily evolve, corresponding to the most commonly observed hierarchies in genome-derived models. We further show how the evolution of novel hierarchies is constrained by the architecture of central metabolism, which determines both the propensity to change ranks between pairs of substrates and the effect of specific reactions on hierarchy evolution. Our analysis sheds light on the genetic and mechanistic determinants of microbial metabolic hierarchies, opening new research avenues to understand their evolution, evolvability and ecology.

evolutionary biology↗

bioRxiv2020

Transcriptome signature in E. coli under a prolonged starvation environment

Background"Non-growing" is a dominant life form of microorganisms in nature, where available nutrients and resources are extremely limited. However, the knowledge of the manner in which microorganisms resist nutrient deficiency is still rudimentary compared to those of the growing cells. In laboratory culture, Escherichia coli can survive for several years under starvation, denoted as long-term stationary phase (LSP), where a small fraction of the cells survive by recycling resources released from the starved nonviable cells and constitute a model system for understanding survival mechanisms under long-term starvation. Although the physiology by which viable cells in LSP adapt to long-term starvation is of great interest, their genome-wide response has not yet been fully understood. ResultsTo understand the physiological state of viable cells in the LSP environment, we analyzed the transcriptional profiles of cells exposed to the supernatant of LSP culture. We found that high expression of transporter genes and low expression of biosynthesis genes are the primary responses of the cells in the LSP supernatant compared to growing cells, which display similar responses to cells entering the stationary phase from the exponential growth phase. We also revealed some specific transcriptional responses in the LSP supernatant, such as higher expression of stress-response genes and lower expression of translation-related genes, compared to other non-growing conditions. This suggests that cells in LSP are highly efficient in terms of cellular survival and maintenance functions under starvation conditions. We also found population-density-dependent gene expression profiles in LSP, which are also informative to understand the survival mechanism of bacterial population. ConclusionOur current comprehensive analysis of the transcriptome of E. coli cells provides an overview of the genome-wide response to the long-term starvation environment. We detected both common and distinctive responses in the primary transcriptional changes between the short- and long-term stationary phase cultures, which could provide clues to understand the possible molecular mechanisms underlying survivability in the starved environment.

microbiology↗

bioRxiv2019

Dynamics of bacterial cell proliferation inhibited by specific proteins for effective horizontal transmission of the integrative and conjugative element ICEclc

The integrative and conjugative element ICEclc, a prevalent mobile element in proteobacteria, is one of the experimental models for horizontal gene transfer. ICEclc is usually retained in a bacterial chromosome, but can be excised and transferred from the donor to other bacterial lineages. The horizontal transmission is accomplished by developing specialized transfer competent (tc) cells in the donor population. The tc cells entirely dedicate to the ICE transmission by sacrificing their proliferation, which results in an increase in the transfer frequency. The cell growth impairment is mediated by two specific genes, parA and shi, on ICEclc, but its mechanistic details and cellular dynamics are still unknown. We here developed fluorescence reporter strains to monitor intracellular behavior of ParA and Shi proteins as well as host cellular proliferation at the single-cell level. Superresolution imaging revealed that ParA colocalized with the host nucleoid while Shi diffused in cytoplasm during the growth impairment. Mutations in the Walker A motif of ParA diminished the inhibitory effect. Combining quantitative time-lapse microscopy and numerical simulations using mathematical models, we found that ParA and Shi initially blocked cell division and then, as time elapsed, inhibited cellular elongation. The parA-shi locus is highly conserved in other ICEs, and the ParA-Shi-mediated growth inhibition was still observed in different proteobacterial species, suggesting that the ICEs have evolved the system to efficiently distribute themselves in the niche. The results of our study provide mechanistic insight into the novel and unique system on ICEs and help to understand such epistatic interaction between ICE genes and host physiology that entails efficient horizontal gene transfer.\n\nAuthor summaryHorizontal gene transfer is a major diving force for bacterial evolution, which is frequently mediated by mobile DNA vectors, such as plasmids and bacteriophages. Integrative and conjugative elements (ICEs) are a relatively new class of mobile vectors, which normally integrate in a host chromosome but under certain conditions can be excised and transferred from the host to a new recipient cell via conjugation. Recent genomic studies estimated that ICEs are more abundant than plasmids among bacteria. Why so prevalent? One of the characteristics of ICEclc, an ICE model in proteobacteria, is that it develops specialized cells which entirely dedicate to the ICE horizontal transmission by repressing their proliferation. Here, we qualitatively and quantitatively describe two proteins, which are expressed from ICEclc when it transfers, and how they actually inhibit the host cell growth. Our results suggest that the system has evolved for the efficient horizontal transmission and is widely conserved in the ICE family.

microbiology↗