記述言語：英語   出版者・発行元：(一社)歯科基礎医学会  

口腔内常在菌であるStreptococcus sanguinisのSK36株の繊毛は3種のピリン(pilin)、PilA、PilB、PilCから構成される。同株でpilC遺伝子に隣接しているssa1635遺伝子も繊毛の成分をコードしているか決定し、それがバイオフィルム形成および真核細胞への接着に果たしている役割を明らかにした。SSA1635(PilXと新たに命名)はPilA～Cと複合体を形成した。ソルターゼC(SrtC)の遺伝子はpilC～A遺伝子と並んで存在しており、SrtCは繊毛特異的なトランスペプチダーゼとして働いていると推定されている。このSrtCの働きにより、PilXは先端部のピリンとして繊毛構造に組み込まれることが判明した。pilX遺伝子を欠失させると他のピリンの重合は障害され、その欠失型の菌株ではバイオフィルム形成が野生型株・再導入株よりも低減した。一方でHeLa細胞への付着率に関しては欠失型株も野生型株・再導入株と同程度であった。まとめると、PilXは繊毛内でピリンの最先端に位置し、他のピリンの重合を促通している可能性が考えられた。PilXはバイオフィルム形成に寄与しているが、HeLa細胞への接着には必要とされないように思われた。PilXの結合特異性の特徴をさらに究明することで、S.sanguinisの定着機序に関し重要な知見が与えられるものと予想された。

記述言語：日本語   出版者・発行元：Journal of Oral Biosciences  

Objectives: Streptococcus sanguinis is an oral commensal bacterium that promotes dental biofilm formation and causes infective endocarditis. S. sanguinis strain SK36 produces pili comprising PilA, PilB, and PilC. This study determined whether the ssa1635 gene adjacent to the pilus-related gene locus encodes a pilus component and its roles in biofilm formation and eukaryotic cell adhesion. Methods: Using a series of mutant strains and antisera against PilA, PilB, PilC, and SSA1635, immunoblot analyses and immunoprecipitation assays were performed for SSA1635 characterization. Both involvement of the deduced pilus-specific transpeptidase SrtC in pilus assembly and SSA1635 localization were examined by immunoblot analysis of various mutant strains. Furthermore, biofilm formation assays on saliva-coated surfaces and adhesion to HeLa cells were conducted to assess functions. Results: SSA1635, designated as PilX, formed complexes with PilA, PilB, and PilC. PilX was identified as a tip pilin incorporated into the pilus structure by SrtC. Notably, deletion of pilX impaired polymerization of other pilins. Furthermore, a pilX deletion mutant exhibited decreased biofilm formation compared with the wild-type and revertant strains and comparable rates of adherence to HeLa cells. Conclusions: PilX is a potential pilin tip that may aid in facilitating the polymerization of other pilins. PilX contributes to biofilm formation, although it appears to be dispensable for adhesion to HeLa cells. Further characterization of PilX-binding specificities will provide valuable insights into the colonization mechanism of S. sanguinis.

DOI： 10.1016/j.job.2025.100664

Scopus

PubMed

記述言語：日本語   出版者・発行元：Msphere  

Aggregatibacter actinomycetemcomitans is a Gram-negative facultative anaerobe and is associated with periodontal disease. This bacterium is exposed to environmental stresses, such as osmotic pressure, temperature shifts, pH shifts, and antimicrobial substances, including reactive oxygen species (ROS), in the human oral cavity. The bacterial two-component system ArcAB modulates gene expression in response to environmental changes, primarily by sensing oxygen pressure in several pathogens belonging to the γ-proteobacteria. It is also known to provide adaptation to ROS stress; however, its function in A. actinomycetemcomitans remains unclear. In this study, we found that the expression of sod, which encodes superoxide dismutase, was increased in the inactivated mutant of arcA, which encodes a response regulator. The mutant exhibited reduced susceptibility to superoxide and hydrogen peroxide (H<inf>2</inf>O<inf>2</inf>). Additionally, this strain showed reduced susceptibility to H<inf>2</inf>O<inf>2</inf> from Streptococcus sanguinis and increased survival in macrophages. Since ArcB is the cognate histidine kinase of ArcA, the inactivated mutant of arcB was analyzed for its phenotypes. The arcB mutant exhibited reduced susceptibility to superoxide and H<inf>2</inf>O<inf>2</inf>. ompared to wild type, the phosphorylation level of ArcA in the arcB mutant was decreased. These results suggest that the ArcA response regulator receives phosphate groups from ArcB histidine kinase and negatively regulates the expression of sod, thereby affecting bacterial survival in response to ROS produced by oral commensals and host immune cells.

DOI： 10.1128/msphere.00019-25

Scopus

PubMed

記述言語：日本語   出版者・発行元：Journal of Oral Microbiology  

Objective: Mitis group streptococci (MGS) are the predominant oral bacteria that cause bacteremia and infective endocarditis. Although membrane vesicle (MV) secretion has been reported in Streptococcus pneumoniae among MGSs, comprehensive studies using various streptococcal species are limited. We aimed to determine whether MGS species produce MVs and to examine their biological functions. Materials and methods: MVs were isolated from MGS cultures using density gradient ultracentrifugation. The particle sizes of MVs were measured, and proteins in MVs were identified by liquid-chromatography tandem mass spectrometry analysis. Effects of MVs on host cells and oral pathogenic bacteria were investigated. Results: MV production was confirmed in Streptococcus mitis strains NCTC12261, Nm-65, and Nm-76, with particle diameters ranging from 100 to 120 nm. The MVs contained numerous cytoplasmic proteins. The MVs showed internalization into alveolar epithelial cells and induced the production of multiple cytokines, including TNF-α, IL-8, IL-6, IL-1β, and IL-10, in macrophages while suppressing phagocytic activity. In neutrophil-differentiated cells, MVs induced IL-8 but not TNF-α production. MVs from S. pneumoniae TIGR4 and S. mitis Nm-65 inhibited biofilm formation of Aggregatibacter actinomycetemcomitans. Conclusions: MVs play crucial roles in MGS survival strategies through immune modulation and interspecies competition, contributing to their pathogenicity and host-pathogen interactions.

DOI： 10.1080/20002297.2025.2557962

Scopus

PubMed

記述言語：日本語   出版者・発行元：Peptides  

Inflammation, especially neuroinflammation, which is caused by stress, leads to central nervous system (CNS) dysfunction. Because lipopolysaccharides (LPSs) cause neuroinflammation, we investigated the effect of LPSs to CNS. In PC-12 cells, LPSs derived from oral bacteria reduced the expression of KCC2, a Cl⁻ transporter. LPS derived from P. gingivalis (P. g) administered to rat primary cultured cells also reduced the KCC2 expression. However, LPSs derived from E. coli did not reduce the KCC2 expression. LPS treatment activated TLR4, IL-1β, and REST gene expressions, which led to KCC2 inactivation in PC-12 cells. The mechanism of KCC2 has been shown to play an important role in brain maturation, function (such as the GABA switch), and behavioral problems, we investigated the GABA function. We found that the GABA function was changed from inhibitory to excitatory by the LPS derived from P. g treatment. We demonstrated that the GSK3β also involved in the KCC2 reduction by LPS treatment. We show that oxytocin rescued the reduction in KCC2 expression caused by LPSs by inhibiting GSK3β signaling but vasopressin could not. Considered together, our results indicate that the LPSs from oral bacteria but not the LPS from E. coli increase the risk for brain disorders and oxytocin might be a candidate to overcome the abnormal behavior caused by brain disorders such as psychiatric disorders.

DOI： 10.1016/j.peptides.2021.170734

Scopus

PubMed

記述言語：英語   出版者・発行元：John Wiley & Sons Australia, Ltd  

Streptococcus mutans UA159より同定された6種のソルターゼA(SrtA)依存性タンパク質(SpaP、WapA、WapE、DexA、FruA、GbpC)について検討した。6種のタンパク質とSrtAを欠損したS.mutans変異株を作製した。その結果、SrtA欠損変異株では唾液成分への結合性、バイオフィルム形成、細菌共凝集活性、疎水性、細胞マトリックス結合性が劇的に低下した。SpaP欠損変異株を除いて、SrtA依存性タンパク質欠損変異株は唾液成分への結合性を大きくは変化させなかった。このため、6種のタンパク質が協同でこれらの活性に寄与していると考えられた。S.mutans125株の表面タンパク質のアミノ酸配列を比較したところ、株ごとに異なっていた。

記述言語：日本語   出版者・発行元：Microbiology and Immunology  

Streptococcus mutans, a cariogenic pathogen, adheres to the tooth surface and forms a biofilm. Bacterial cell surface proteins are associated with adherence to substrates. Sortase A (SrtA) mediates the localization of proteins with an LPXTG motif-containing proteins to the cell surface by covalent binding to peptidoglycan. In S. mutans UA159, six SrtA-dependent proteins, SpaP, WapA, WapE, DexA, FruA, and GbpC, were identified. Although some of these proteins were characterized, a comprehensive analysis of the six proteins has not been reported. In this study, we constructed mutants deficient in each of these proteins and the SrtA-deficient mutant. The SrtA-deficient mutant showed drastically decreased binding to salivary components, biofilm formation, bacterial coaggregation activity, hydrophobicity, and cellular matrix binding (collagen type I, fibronectin, and laminin). The SpaP-deficient mutant showed significantly reduced binding to salivary components and partially increased coaggregation with Porphyromonas gingivalis, and decreased hydrophobicity, and collagen binding. The WapA-deficient mutant showed slightly decreased coaggregation with Fusobacterium nucleatum. Although the SrtA-deficient mutant showed drastically altered phenotypes, all SrtA-dependent protein-deficient mutants, except the SpaP-deficient mutant, did not show considerable alterations in binding to salivary components. These results indicate that the six proteins may coordinately contribute to these activities. In addition, using genomic data of 125 S. mutans strains, the amino acid sequences of each surface protein were compared and many variations were found among strains, which may affect the phenotype of cell surface proteins in S. mutans.

DOI： 10.1111/1348-0421.12958

Scopus

PubMed

記述言語：日本語   出版者・発行元：Plos One  

Staphylococcus epidermidis is a commensal bacterium in humans. To persist in the bacterial flora of the host, some bacteria produce antibacterial factors such as the antimicrobial peptides known as bacteriocins. In this study, we tried to isolate bacteriocin-producing S. epidermidis strains. Among 150 S. epidermidis isolates from the oral cavities of 287 volunteers, we detected two bacteriocin-producing strains, KSE56 and KSE650. Complete genome sequences of the two strains confirmed that they carried the epidermin-harboring plasmid pEpi56 and the nukacin IVK45-like-harboring plasmid pNuk650. The amino acid sequence of epidermin from KSE56 was identical to the previously reported sequence, but the epidermin synthesis-related genes were partially different. The prepeptide amino acid sequences of nukacin KSE650 and nukacin IVK45 showed one mismatch, but both mature peptides were entirely similar. pNuk650 was larger and had an additional seven ORFs compared to pIVK45. We then investigated the antibacterial activity of the two strains against several skin and oral bacteria and found their different activity patterns. In conclusion, we report the complete sequences of 2 plasmids coding for bacteriocins from S. epidermidis, which were partially different from those previously reported. Furthermore, this is the first report to show the complete sequence of an epidermin-carrying plasmid, pEpi56.

DOI： 10.1371/journal.pone.0258283

Scopus

PubMed

記述言語：日本語   出版者・発行元：Scientific Reports  

Streptococcus mutans produces bacteriocins that show antibacterial activity against several bacteria. However, comprehensive analysis of these bacteriocins has not been well done. In this study, we isolated 125 S. mutans strains from volunteers and determined their whole genome sequence. Based on the genome analysis, the distribution of each bacteriocin gene (mutacins I-IV, K8 and Smb) was investigated. We found 17, 5, and 2 strains showing 100% matches with mutacin I, mutacin II and mutacin III, respectively. Five mutacin III-positive strains had 2 mismatches compared to mature mutacin III. In 67 mutacin IV-positive strains, 38 strains showed 100% match with mutacin IV, while 29 strains showed some variations. In 23 mutacin K8- and 32 mutacin Smb-positive strains, all except one mutacin K8-positive strain showed 100% match with the mature peptides. Among 125 strains, 84 (65.1%), 26 (20.2%), and 5 (3.9%) strains were positive for one, two and three bacteriocin genes, respectively. Then, the antibacterial activity against oral streptococci and other oral bacterial species was investigated by using bacteriocin gene single-positive strains. Each bacteriocin gene-positive strain showed a different pattern of antibacterial activity. These results speculate that individual S. mutans strains may affect the bacterial composition of dental plaques.

DOI： 10.1038/s41598-021-92370-1

Scopus

PubMed

記述言語：日本語   出版者・発行元：Japanese Dental Science Review  

Small regulatory RNAs (sRNAs) belong to a family of non-coding RNAs, and many of which regulate expression of genes via interaction with mRNA. The recent popularity of high-throughput next generation sequencers have presented abundant sRNA-related data, including sRNAs of several different oral bacterial species. Some sRNA candidates have been validated in terms of their expression and interaction with target mRNAs. Since the oral cavity is an environment constantly exposed to various stimuli, such as fluctuations in temperature and pH, and osmotic pressure, as well as changes in nutrient availability, oral bacteria require rapid control of gene expression for adaptation to such diverse conditions, while regulation via interactions of sRNAs with mRNA provides advantages for rapid adaptation. This review summarizes methods effective for identification and validation of sRNAs, as well as sRNAs identified to be associated with oral bacterial species, including cariogenic and periodontal pathogens, together with their confirmed and putative target genes.

DOI： 10.1016/j.jdsr.2021.09.004

Scopus

PubMed

記述言語：英語   出版者・発行元：John Wiley & Sons Australia, Ltd  

様々な条件下でAggregatibacter actinomycetemcomitansの病原性因子の発現を調べた。好気培養のAGM培地中のA.actinomycetemcomitans HK1651株(HK1651株)と比べて、仔ウシ血清(CS)含有AAGMと鉄制限AAGM培地中のHK1651株の増殖は大幅に遅延した。CS含有AAGMと鉄制限AAGM培地中のomp100、omp64、aae、emaA、cdtA発現は有意に上昇した。寒天培地上のomp100、omp64、aae、emaA、cdtA発現レベルは液体培地中より有意に高かった。AAGM培地中のHK1651株のomp29、omp16/18(IDH 781株を除く)、lktA発現は他の供試株より有意に高く、CS含有AAGM培地中のomp29とomp16/18発現は有意に高かった。HK1651における発現とは対照的に、CS含有AAGM培地中の他の株におけるomp100の発現は上昇しなかった。RNA-seq解析により、CS含有AAGM培地中で多くの鉄獲得に関与する遺伝子が特定された。好気条件下のAAGM培地中のバイオフィルム形成と比べて、CS含有AAGMと唾液含有AAGM培地中のバイオフィルム形成は低下した。CS含有AAGM培地中でHK1651株はFusobacterium nucleatumと強く共凝集した。

記述言語：日本語   出版者・発行元：Microbiology and Immunology  

Aggregatibacter actinomycetemcomitans is a facultative anaerobic Gram-negative bacterium associated with periodontal diseases, especially aggressive periodontitis. The virulence factors of this pathogen, including adhesins, exotoxins, and endotoxin, have been extensively studied. However, little is known about their gene expression mode in the host. Herein, we investigated whether culture conditions reflecting in vivo environments, including serum and saliva, alter expression levels of virulence genes in the strain HK1651, a JP2 clone. Under aerobic conditions, addition of calf serum (CS) into a general medium induced high expression of two outer membrane proteins (omp100 and omp64). The high expression of omp100 and omp64 was also induced by an iron-limited medium. RNA-seq analysis showed that the gene expressions of several factors involved in iron acquisition were increased in the CS-containing medium. When HK1651 was grown on agar plates, genes encoding many virulence factors, including the Omps, cytolethal distending toxin, and leukotoxin, were differentially expressed. Then, we investigated their expression in five other A. actinomycetemcomitans strains grown in general and CS-containing media. The expression pattern of virulence factors varied among strains. Compared with the other five strains, HK1561 showed high expression of omp29 regardless of the CS addition, while the gene expression of leukotoxin in HK1651 was higher only in the medium without CS. HK1651 showed reduced biofilm in both CS- and saliva-containing media. Coaggregation with Fusobacterium nucleatum was remarkably enhanced using HK1651 grown in the CS-containing medium. Our results indicate that the expression of virulence factors is altered by adaptation to different conditions during infection.

DOI： 10.1111/1348-0421.12864

Scopus

PubMed

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

開催年月日： 2016年8月

記述言語：英語   会議種別：ポスター発表  

開催年月日： 2016年3月

記述言語：英語   会議種別：ポスター発表  

開催年月日： 2015年9月

記述言語：英語   会議種別：ポスター発表  

開催年月日： 2015年3月

記述言語：日本語  

開催地：岐阜  

国内学会

開催年月日： 2014年3月

記述言語：日本語  

開催地：東京  

国内学会

開催年月日： 2013年3月

記述言語：英語   会議種別：口頭発表（一般）  

開催年月日： 2012年8月

記述言語：日本語   会議種別：口頭発表（一般）  

開催年月日： 2012年3月

記述言語：日本語  

開催地：長崎  

国内学会

開催年月日： 2010年8月

記述言語：日本語   会議種別：口頭発表（一般）  

開催年月日： 2010年3月

記述言語：日本語  

開催地：横浜  

国内学会

開催年月日： 2009年10月

記述言語：日本語   会議種別：口頭発表（一般）  

開催年月日： 2009年3月

記述言語：日本語  

開催地：名古屋国際会議場  

国内学会

開催年月日： 2008年9月

記述言語：英語  

開催地：兵庫  

国際学会

開催年月日： 2008年3月

記述言語：日本語  

開催地：京都  

国内学会

記述言語：英語  

記述言語：日本語  

記述言語：日本語  

記述言語：日本語  

記述言語：日本語  

記述言語：日本語  

記述言語：英語  

記述言語：日本語  

記述言語：日本語