Biology subjects

Kurosawa, N.

Publications and source records attributed to Kurosawa, N..

4 recordsLinked to original sources

bioRxiv2024

Novel cell-to-cell interactions revealed by cryotomography of a DPANN coculture system

DPANN is a widespread and highly diverse group of archaea characterised by their small size, reduced genome, limited metabolic pathways, and symbiotic existence. Known DPANN species are predominantly obligate ectosymbionts that depend on their host for their survival and proliferation. Despite the recent expansion in this clade, the structural and molecular details of host recognition, host-DPANN intercellular communication, and host adaptation in response to DPANN attachment remain unknown. Here, we used electron cryotomography (cryo-ET) to reveal that the Candidatus Micrarchaeota (ARM-1) interacts with its host, Metallosphaera javensis through intercellular proteinaceous nanotubes. These tubes ([~]4.5 nm wide) originate in the host, extend all the way to the DPANN cytoplasm and act like tunnels for intercellular exchange. Combining cryo-ET and sub-tomogram averaging, we revealed the in situ architectures of host and DPANN S-layers and the structures of the nanotubes in their primed and extended states, providing mechanistic insights into substrate exchange. Additionally, we performed comparative proteomics and genomic analyses to identify host proteomic changes in response to the DPANN attachment. Our results showed striking alterations in host-proteome during symbiosis and upregulation/downregulation of key cellular pathways. Collectively, these results provided unprecedented insights into the structural basis of host-DPANN communication and deepen our understanding of the host ectosymbiotic relationships.

microbiology↗

bioRxiv2024

A large attachment organelle mediates interaction between a novel Nanobdellota archaeon YN1 and its host

DPANN archaea are an enigmatic superphylum that are difficult to isolate and culture in the laboratory due to their specific culture conditions and apparent ectosymbiotic lifestyle. Here we successfully isolated and cultivated a co-culture system of a novel Nanobdellota archaeon YN1 and its host Sulfurisphaera ohwakuensis YN1HA. We characterised the co-culture system by complementary methods, including metagenomics and metabolic pathway analysis, fluorescence microscopy, and high-resolution electron cryo-tomography (CryoET). We show that YN1 is deficient in essential metabolic processes and requires host resources to proliferate. CryoET imaging revealed an enormous attachment organelle present in the YN1 envelope that forms a direct interaction with the host cytoplasm, bridging the two cells. Together our results unravelled the molecular and structural basis of ectosymbiotic relationship between YN1 and YNHA. This research broadens our understanding of DPANN biology and the versatile nature of their ectosymbiotic relationships.

microbiology↗

bioRxiv2023

Distinct groups of RNA viruses associated with thermoacidophilic bacteria

Recent massive metatranscriptome mining substantially expanded the diversity of the bacterial RNA virome, suggesting that additional groups of riboviruses infecting bacterial hosts remain to be discovered. We employed full length double-stranded (ds) RNA sequencing for identification of riboviruses associated with microbial consortia dominated by bacteria and archaea in acidic hot springs in Japan. Whole sequences of two groups of multisegmented riboviruses genomes were obtained. One group, which we denoted hot spring riboviruses (HsRV), consists of unusual viruses with distinct RNA-dependent RNA polymerases (RdRPs) that seem to be intermediates between typical ribovirus RdRPs and viral reverse transcriptases. We also identified viruses encoding HsRV-like RdRPs in moderate aquatic environments, including marine water, river sediments and salt marsh, indicating that this previously overlooked ribovirus group is not restricted to the extreme ecosystem. The HsRV-like viruses are candidates for a distinct phylum or even kingdom within the viral realm Riboviria. The second group, denoted hot spring partiti-like viruses (HsPV), is a distinct branch within the family Partitiviridae. All genome segments in both these groups of viruses display the organization typical of bacterial riboviruses, where multiple open reading frames encoding individual proteins are preceded by ribosome-binding sites. Together with the identification in bacteria-dominated habitats, this genome architecture indicates that riboviruses of these distinct groups infect thermoacidophilic bacterial hosts.

microbiology↗

bioRxiv2023

Comprehensive analysis of nasal IgA antibodies induced by intranasal administration of the SARS-CoV-2 spike protein

Intranasal vaccination is an attractive strategy for preventing COVID-19 disease as it stimulates the production of multimeric secretory immunoglobulin A (IgA), the predominant antibody isotype in the mucosal immune system, at the target site of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) entry. Currently, intranasal vaccine efficacy is evaluated based on the measurement of polyclonal antibody titers in nasal lavage fluid. However, how individual multimeric secretory IgA protects the mucosa from SARS-CoV-2 infection remains to be elucidated. To understand the precise contribution and molecular nature of multimeric secretory IgA induced by intranasal vaccines, we developed 99 monoclonal IgA clones from nasal mucosa and 114 monoclonal IgA or IgG clones from nonmucosal tissues of mice that were intranasally immunized with the SARS-CoV-2 spike protein. The nonmucosal IgA clones exhibited shared origins and common and unique somatic mutations with the related nasal IgA clones, indicating that the antigen-specific plasma cells in the nonmucosal tissues originated from B cells stimulated at the nasal mucosa. Comparing the spike protein binding reactivity, angiotensin-converting enzyme-2-blocking and in vitro SARS-CoV-2 virus neutralization of monomeric and multimeric secretory IgA pairs recognizing different epitopes showed that even non-neutralizing monomeric IgAs, which represents 70% of the nasal IgA repertoire, can protect against SARS-CoV-2 infection when expressed as multimeric secretory IgAs. We also demonstrated that the intranasal administration of multimeric secretory IgA delivered as prophylaxis in the hamster model reduced infection-induced weight loss. Our investigation is the first to demonstrate the function of nasal IgA at the monoclonal level, showing that nasal immunization can provide effective immunity against SARS-CoV-2 by inducing multimeric secretory IgAs at the target site of the virus infection.

immunology↗