Extracellular vesicles produced by Bifidobacterium longum export mucin-binding proteins

Keita Nishiyama, Takashi Takaki, Makoto Sugiyama, Itsuko Fukuda, Maho Aiso, Takao Mukai, Toshitaka Odamaki, Jin zhong Xiao, Ro Osawa, Nobuhiko Okada

Research output: Contribution to journalArticle

Abstract

Extracellular proteins are important factors in host-microbe interactions; however, the specific factors that enable bifidobacterial adhesion and survival in the gastrointestinal (GI) tract are not fully characterized. Here, we discovered that Bifidobacterium longum NCC2705 cultured in bacterium-free supernatants of human fecal fermentation broth released a myriad of particles into the extracellular environment. The aim of this study was to characterize the physiological properties of these extracellular particles. The particles, approximately 50 to 80 nm in diameter, had high protein and double-stranded DNA contents, suggesting that they were extracellular vesicles (EVs). A proteomic analysis showed that the EVs primarily consisted of cytoplasmic proteins with crucial functions in essential cellular processes. We identified several mucin-binding proteins by performing a biomolecular interaction analysis of phosphoketolase, GroEL, elongation factor Tu (EF-Tu), phosphoglycerate kinase, transaldolase (Tal), and heat shock protein 20 (Hsp20). The recombinant GroEL and Tal proteins showed high binding affinities to mucin. Furthermore, the immobilization of these proteins on microbeads affected the permanence of the microbeads in the murine GI tract. These results suggest that bifidobacterial exposure conditions that mimic the intestine stimulate B. longum EV production. The resulting EVs exported several cytoplasmic proteins that may have promoted B. longum adhesion. This study improved our understanding of the Bifidobacterium colonization strategy in the intestinal microbiome. IMPORTANCE Bifidobacterium is a natural inhabitant of the human gastrointestinal (GI) tract. Morphological observations revealed that extracellular appendages of bifidobacteria in complex microbial communities are important for understanding its adaptations to the GI tract environment. We identified dynamic extracellular vesicle (EV) production by Bifidobacterium longum in bacterium-free fecal fermentation broth that was strongly suggestive of differing bifidobacterial extracellular appendages in the GI tract. In addition, export of the adhesive moonlighting proteins mediated by EVs may promote bifidobacterial colonization. This study provides new insight into the roles of EVs in bifidobacterial colonization processes as these bacteria adapt to the GI environment.

Original languageEnglish
Article numbere01464-20
JournalApplied and Environmental Microbiology
Volume86
Issue number19
DOIs
Publication statusPublished - 2020 Oct

Keywords

  • Adhesion
  • Bifidobacterium
  • Colonization
  • Extracellular vesicle
  • Fecal fermentation
  • Symbiosis

ASJC Scopus subject areas

  • Biotechnology
  • Food Science
  • Applied Microbiology and Biotechnology
  • Ecology

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