2026-03-05 タフツ大学
A new imaging approach used microscopic glowing tags to reveal gene activity in individual C. diff cells in gut tissue samples from infected mice. Image: Nicholas DiBenedetto, CC by NonCommercial-NoDerivatives 4.0 International
＜関連情報＞
- https://now.tufts.edu/2026/03/05/targeting-dangerous-gut-infection
- https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.3003610
- https://www.nature.com/articles/s41467-026-68411-6
- https://www.nature.com/articles/s41467-023-43595-3
CspC:CspAヘテロ二量体は、クロストリディオイデス・ディフィシル胞子の発芽中に発芽および共発芽シグナルを伝達する The CspC:CspA heterodimer transduces germinant and co-germinant signals during Clostridioides difficile spore germination
Morgan E. McNellis,Gonzalo González-Del Pino,Juan A. Serrano-Jiménez,Emily R. Forster,Anca Ioana Stoica,Ekaterina E. Heldwein,Aimee Shen
PLOS Biology Published: February 2, 2026
DOI:https://doi.org/10.1371/journal.pbio.3003610
Abstract
The clinically significant pathogen Clostridioides difficile lacks the transmembrane nutrient germinant receptors conserved in almost all spore-forming bacteria. Instead, C. difficile initiates spore germination using a unique mechanism that requires two signals: a bile acid germinant and a co-germinant, which can be either an amino acid or a divalent cation. While two soluble pseudoproteases, CspC and CspA, were initially identified as the germinant and co-germinant receptors, respectively, in C. difficile, we previously identified residues in an unstructured region of CspC that regulate the sensitivity of C. difficile spores to both signals. However, the mechanism by which CspC transduces these signals remained unclear. Here, we demonstrate that CspC forms a stable complex with CspA and determine the crystal structure of the CspC:CspA heterodimer. The structure reveals extensive interactions along the binding interface, including direct interactions between the unstructured region of CspC and CspA. Using structure-function analyses, we identify CspC:CspA interactions that regulate the sensitivity of C. difficile spores to germinant signals and show that CspA regulates the response of C. difficile to not only co-germinant but also germinant signals. While we show that CspA can form a homodimer and determine its crystal structure, CspA homodimerization appears unimportant for C. difficile spore germination. Collectively, our analyses establish the CspC:CspA heterodimer, rather than its individual constituents, as a critical signaling node for sensing both germinant and co-germinant signals. They also suggest a new mechanistic model for how C. difficile transduces germinant signals, which could guide the development of therapeutics against this important pathogen.
腸管感染中のクロストリディオイデス・ディフィシルの表現型の異質性と単一細胞形態のin situ可視化 In situ visualization of Clostridioides difficile phenotypic heterogeneity and single-cell morphology during gut infection
Nicholas V. DiBenedetto,M. Lauren Donnelly-Morell,Carol A. Kumamoto & Aimee Shen
Nature Communications Published:14 January 2026
DOI:https://doi.org/10.1038/s41467-026-68411-6
Abstract
Phenotypic heterogeneity refers to the ability of clonal populations of the same species to display distinct phenotypes despite experiencing the same environment. Bacteria exhibit phenotypic heterogeneity across diverse cellular processes, which can provide competitive fitness advantages both within the host and against surrounding microbiota. However, visualizing phenotypic heterogeneity at single-cell resolution within dense microbial communities is technically challenging. Here, we present a method for visualizing this heterogeneity by combining spectrally compatible reporters to track the spatial distribution of gene expression in individual bacterial cells in the mammalian gut. Using toxin gene expression in Clostridioides difficile as a model for visualizing phenotypic heterogeneity, we demonstrate that, while C. difficile primarily occupies the lumen, a subpopulation of C. difficile associates with the colonic epithelium independent of toxin production. We further show that heterogeneity in C. difficile toxin gene expression is independent of location in the gut and that a toxin gene overexpressing mutant unexpectedly forms filamentous cells during the acute phase of infection. Thus, our reporter system provides quantitative, single-cell resolution of bacterial behavior within the intact gut environment and establishes a broadly applicable platform for investigating phenotypic heterogeneity in dense microbial communities.
クロストリディオイデス・ディフィシルにおけるペプチドグリカン合成の解析により明らかになった胞子形成細菌の分裂機構の多様化 Diversification of division mechanisms in endospore-forming bacteria revealed by analyses of peptidoglycan synthesis in Clostridioides difficile
Shailab Shrestha,Najwa Taib,Simonetta Gribaldo & Aimee Shen
Nature Communications Published:02 December 2023
DOI:https://doi.org/10.1038/s41467-023-43595-3
Abstract
The bacterial enzymes FtsW and FtsI, encoded in the highly conserved dcw gene cluster, are considered to be universally essential for the synthesis of septal peptidoglycan (PG) during cell division. Here, we show that the pathogen Clostridioides difficile lacks a canonical FtsW/FtsI pair, and its dcw-encoded PG synthases have undergone a specialization to fulfill sporulation-specific roles, including synthesizing septal PG during the sporulation-specific mode of cell division. Although these enzymes are directly regulated by canonical divisome components during this process, dcw-encoded PG synthases and their divisome regulators are dispensable for cell division during normal growth. Instead, C. difficile uses a bifunctional class A penicillin-binding protein as the core divisome PG synthase, revealing a previously unreported role for this class of enzymes. Our findings support that the emergence of endosporulation in the Firmicutes phylum facilitated the functional repurposing of cell division factors. Moreover, they indicate that C. difficile, and likely other clostridia, assemble a distinct divisome that therefore may represent a unique target for therapeutic interventions.
