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Structural basis for adaptation of lactobacilli to gastrointestinal mucus
Author(s) -
Etzold Sabrina,
Kober Olivia I.,
MacKenzie Donald A.,
Tailford Louise E.,
Gunning A. Patrick,
Walshaw John,
Hemmings Andrew M.,
Juge Nathalie
Publication year - 2014
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/1462-2920.12377
Subject(s) - mucus , biology , mucin , bacterial adhesin , microbiology and biotechnology , bacteria , gastrointestinal tract , tropism , genetics , biochemistry , gene , escherichia coli , ecology , virus
Summary The mucus layer covering the gastrointestinal ( GI ) epithelium is critical in selecting and maintaining homeostatic interactions with our gut bacteria. However, the underpinning mechanisms of these interactions are not understood. Here, we provide structural and functional insights into the canonical mucus‐binding protein ( MUB ), a multi‐repeat cell‐surface adhesin found in L actobacillus inhabitants of the GI tract. X ‐ray crystallography together with small‐angle X ‐ray scattering demonstrated a ‘beads on a string’ arrangement of repeats, generating 174 nm long protein fibrils, as shown by atomic force microscopy. Each repeat consists of tandemly arranged Ig‐ and mucin‐binding protein ( MucBP ) modules. The binding of full‐length MUB was confined to mucus via multiple interactions involving terminal sialylated mucin glycans. While individual MUB domains showed structural similarity to fimbrial proteins from G ram‐positive pathogens, the particular organization of MUB provides a structural explanation for the mechanisms in which lactobacilli have adapted to their host niche by maximizing interactions with the mucus receptors, potentiating the retention of bacteria within the mucus layer. Together, this study reveals functional and structural features which may affect tropism of microbes across mucus and along the GI tract, providing unique insights into the mechanisms adopted by commensals and probiotics to adapt to the mucosal environment.