Affiliation:
1. State Key Laboratory for Diagnosis and Treatment of Infectious Diseases and Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, the First Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang, People's Republic of China
2. State Key Laboratory of Breeding Base for Zhejiang Sustainable Pest and Key Laboratory for Food Microbial Technology of Zhejiang Province, Zhejiang Academy of Agricultural Sciences, Hangzhou, Zhejiang, People's Republic of China
Abstract
ABSTRACT
Segmented filamentous bacteria (SFB) are known modulators of the mammalian immune system. Currently, the technology for investigating SFB culture
in vitro
is immature, and as a result, the mechanisms of SFB colonization and immune regulation are not yet fully elucidated. In this study, we investigated the gene diversity and host specificity of SFB flagellin genes. The
fliC1
and
fliC2
genes are relatively conserved, while the
fliC3
and
fliC4
genes are more variable, especially at the central and C-terminal regions. Host specificity analysis demonstrated that the
fliC1
genes do not cluster together based on the host organism, whereas the
fliC3
and
fliC4
genes were host specific at the nucleotide and deduced amino acid levels. SFB flagellin protein expression in the ileum mucosa and cecal contents was detected by using fluorescence
in situ
hybridization (FISH) combined with immunohistochemical (IHC) analysis, immunoblotting, and liquid chromatography-tandem mass spectrometry (LC-MS/MS). Although the purified SFB FliC3 protein originating from both mouse and rat was able to activate Toll-like receptor 5 (TLR5)-linked NF-κB signaling, no host specificity was observed. Interestingly, the patterns of interaction with mouse ileum mucosal proteins were different for mouse FliC3 (mFliC3) and rat FliC3 (rFliC3). Gene Ontology (GO) and KEGG analyses indicated that more adherence-related proteins interacted with mFliC3, while more lysosome- and proteolysis-related proteins interacted with rFliC3.
In vitro
degradation experiments indicated that the stability of rFliC3 was lower than that of mFliC3 when they were incubated with mouse ileum mucosal proteins. In summary, the gene diversity and host specificity of SFB flagellin genes were investigated, and SFB flagellin expression was detected in gut samples.
IMPORTANCE
Since SFB genomes contain only one copy of each FliC gene, the diversity of FliC is representative of SFB strain diversity. Currently, little is known regarding the diversity and specificity of members of the group of SFB. The work presented herein demonstrates that select SFB strains, exhibiting unique FliC patterns, are present in a variety of mammalian hosts. SFB
fliC
genes were found to interact with a number of unique targets, providing further evidence for SFB host selection. Together, this work represents a major advancement in identifying SFB and delineating how members of the group of SFB interact with the host. Future examination of FliC genes will likely enhance our knowledge of intestinal colonization by the gut microbiota.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
Cited by
12 articles.
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