Biology subjects

Usui, M.

Publications and source records attributed to Usui, M..

5 recordsLinked to original sources

bioRxiv2024

Modulation of hippocampal sharp-wave ripples by behavioral states and body movements in head-fixed rodents

Hippocampal sharp-wave ripples (SWRs) are critical events implicated in memory consolidation, planning, and the reactivation of recent experiences. Under freely moving conditions, a well-established dichotomy exists: hippocampal networks predominantly generate theta oscillations during periods of reward pursuit (preparatory behaviors) and exhibit pronounced SWR activity once the reward is achieved (consummatory behaviors). Here, we examined how SWRs are modulated by reward delivery and subtle movements in head-fixed rats. Contrary to the canonical view established in freely moving settings, we found that the dominant and more enduring effect was a sustained suppression of SWR activity immediately following water delivery. Moreover, even minor, localized movements (such as whisking or body adjustments) decreased SWR occurrence, demonstrating that hippocampal ripple generation is highly sensitive to motor engagement, irrespective of reward timing. Such movement-induced suppression of ripples persisted during both sleep-like states and quiet wakefulness, suggesting that while large-scale brain states modulate the overall likelihood of SWR generation, local motor-related influences exert a state-independent inhibitory effect on hippocampal ripples. Our results show that SWR modulation by behavioral states and body movements is more context-dependent than previously appreciated.

neuroscience↗

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↗

bioRxiv2022

Intermittent antibiotic treatment of bacterial biofilms favors the rapid evolution of resistance

The rise of antibiotic resistance in bacterial pathogens is a major health concern and the determinants of this emergence are actively studied. By contrast, although biofilms are an important cause of infections due to their high tolerance to a broad range of antimicrobials, much less is known on the development of antibiotic resistance within the biofilm environment, an issue potentially aggravating the current antibiotic crisis. Here, we compared the occurrence of resistance mutations in pathogenic Escherichia coli planktonic and biofilm populations exposed to clinically relevant cycles of lethal treatments with the aminoglycoside antibiotic amikacin. This experimental evolution approach revealed that mutations in sbmA and fusA are rapidly selected in biofilm but not in planktonic populations. The apparition of these bona fide resistance --and not tolerance-- mutations is favored by the biofilm preexisting tolerance and high mutation rate. Moreover, we showed that while fusA mutations displayed a high fitness cost in planktonic conditions, these mutations were maintained in biofilms, a phenomenon further possibly amplified by the selection of fimH mutations favoring biofilm formation itself. Our study therefore provides new insights into the dynamic evolution of antibiotic resistance in biofilms, which could lead to clinically practical antibiotic regimen limiting biofilm-associated infections, while mitigating the emergence of worrisome antibiotic resistance mutations.

microbiology↗

bioRxiv2020

EXOC1 regulates cell morphology of spermatogonia and spermatocytes in mice

Spermatogenesis requires high regulation of germ cell morphology. The spermatogonia regulates its differentiation state by its own migration. The male germ cells differentiate and mature with the formation of syncytia, failure of forming the appropriate syncytia results in the arrest of spermatogenesis at the spermatocyte stage. However, the detailed molecular mechanisms of male germ cell morphological regulation are unknown. Here, we found that EXOC1 is important for the pseudopod formation of spermatogonia and spermatocyte syncytia in mice. We found that while EXOC1 contributes to the inactivation of Rac1 in the pseudopod formation of spermatogonia, in spermatocyte syncytium formation, EXOC1 and SNAP23 cooperate with STX2. Our results showed that EXOC1 functions in concert with various cell morphology regulators in spermatogenesis. Since EXOC1 is known to bind to several cell morphogenesis factors, this study is expected to be the starting point for the discovery of many morphological regulators of male germ cells.

developmental biology↗

bioRxiv2019

Analysis host-recognition mechanism of staphylococcal kayvirus phiSA039 reveals a novel strategy that protects Staphylococcus aureus against infection by Staphylococcus pseudintermedius Siphoviridae phages

Following the emergence of antibiotic resistant bacteria such as methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant Staphylococcus pseudintermedius (MRSP), phage therapy has attracted significant attention as an alternative to antibiotic treatment. Bacteriophages belonging to kayvirus (previously known as Twort-like phages) have broad host range and are strictly lytic in Staphylococcus spp. Previous work revealed that kayvirus {phi}SA039 has a host-recognition mechanism distinct from those of other known kayviruses: most of kayviruses use the backbone of wall teichoic acid (WTA) as their receptor; by contrast, {phi}SA039 uses the {beta}-N-acetylglucosamine ({beta}-GlcNAc) residue in WTA. In this study, we found that {phi}SA039 could switch its receptor to be able to infect S. aureus lacking the {beta}-GlcNAc residue by acquiring a spontaneous mutation in open reading frame (ORF) 100 and ORF102. Moreover, {phi}SA039 could infect S. pseudintermedius, which has a different WTA structure than S. aureus. By comparison with newly isolated S. pseudintermedius-specific phage (SP phages), we determined that glycosylation in WTA of S. pseudintermedius is essential for adsorption of SP phages, but not {phi}SA039. Finally, we describe a novel strategy of S. aureus which protects the bacteria from infection of SP phages. Notably, glycosylation of ribitol phosphate (RboP) WTA by TarM or/and TarS prevents infection of S. aureus by SP phages. These findings could help to establish a new strategy for treatment of S. aureus and S. pseudintermedius infection, as well as provide valuable insights into the biology of phage-host interactions.

microbiology↗