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1. Flagellin is essential for initial attachment to mucosal surfaces by Clostridioides difficile

   https://doi.org/10.1128/spectrum.02120-23  

   Sidner, Ben; Lerma, Armando; Biswas, Baishakhi; Do, Thi Van; Yu, Yafan; Ronish, Leslie A.; McCullough, Hugh; Auchtung, Jennifer M.; Piepenbrink, Kurt H. (December 2023, Microbiology Spectrum)

   Atack, John M. (Ed.)

   ABSTRACT Mucins are glycoproteins which can be found in host cell membranes and as a gelatinous surface formed from secreted mucins. Mucosal surfaces in mammals form a barrier to invasive microbes, particularly bacteria, but are a point of attachment for others.Clostridioides difficileis an anaerobic bacterium, which colonizes the mammalian gastrointestinal (GI) tract and is a common cause of acute GI inflammation leading to a variety of negative outcomes. AlthoughC. difficiletoxicity stems from secreted toxins, colonization is a prerequisite forC. difficiledisease. WhileC. difficileis known to associate with the mucous layer and underlying epithelium, the mechanisms underlying these interactions that facilitate colonization are less well understood. To understand the molecular mechanisms by whichC. difficileinteracts with mucins, we usedex vivomucosal surfaces to test the ability ofC. difficileto bind to mucins from different mammalian tissues. We found significant differences inC. difficileadhesion based upon the source of mucins, with highest levels of binding observed to mucins purified from the human colonic adenocarcinoma line LS174T and lowest levels of binding to porcine gastric mucin. We also observed defects in adhesion by mutants deficient in flagella but not type IV pili. These results imply that interactions between host mucins andC. difficileflagella facilitate the initial host attachment ofC. difficileto host cells and secreted mucus. IMPORTANCEClostridioides difficileis one of the leading causes of hospital-acquired infections worldwide and presents challenges in treatment due to recurrent gastrointestinal disease after treatment with antimicrobials. The mechanisms by whichC. difficilecolonizes the gut represent a key gap in knowledge, including its association with host cells and mucosa. Our results show the importance of flagellin for specific adhesion to mucosal hydrogels and can help to explain prior observations of adhesive defects in flagellin and pilin mutants. 

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2. The role of mucosal barriers in disease progression and transmission

   https://doi.org/10.1016/j.addr.2023.115008  

   Bustos, Nicole A; Ribbeck, Katharina; Wagner, Caroline E (September 2023, Advanced Drug Delivery Reviews)

   Mucus is a biological hydrogel that coats and protects all non-keratinized wet epithelial surfaces. Mucins, the primary structural components of mucus, are critical components of the gel layer that protect against invading pathogens. For communicable diseases, pathogen-mucin interactions contribute to the pathogen’s fate and the potential for disease progression in-host, as well as the potential for onward transmission. We begin by reviewing in-host mucus filtering mechanisms, including size filtering and interaction filtering, which regulate the permeability of mucus barriers to all molecules including pathogens. Next, we discuss the role of mucins in communicable diseases at the point of transmission (i.e. how the encapsulation of pathogens in emitted mucosal droplets externally to hosts may modulate pathogen infectivity and viability). Overall, mucosal barriers modulate both host susceptibility as well as the dynamics of population-level disease transmission. The study of mucins and their use in models and experimental systems are therefore crucial for understanding the mechanistic biophysical principles underlying disease transmission and the early stages of host infection. 

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3. Microrheology of gel-forming airway mucins isolated from porcine trachea

   https://doi.org/10.1039/D4SM01343C  

   Engle, Elizabeth M; Yang, Sydney; Boboltz, Allison; Kumar, Sahana; Stern, Alexa; Duncan, Gregg A (June 2025, Soft Matter)

   A method to extract gel-forming mucins from pig trachea is developed. These airway mucins form viscous gels resembling human airway mucus, making them a useful model for lung disease research. 

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4. Herbivore kairomones affect germination speed, seedling growth, and herbivory

   https://doi.org/10.1007/s00442-024-05621-z  

   Pellegrini, Brooke_A; Pintado, Lina_S; Souza, Paige_N; Bhavanam, Santhi_P; Orians, Colin_M; Orrock, John_L; Preisser, Evan_L (September 2024, Oecologia)

   Abstract Seeds and seedlings are particularly vulnerable to herbivory. Unlike mature plants, which can wait until herbivory is experienced to induce defense, seeds and seedlings face mortality if they wait. Slug mucus functions as a kairomone, a non-attack-related substance emitted by consumers that is detected by a prey species (in this case, plants). While snail mucus has been shown to induce defense in seedlings, it is not widely confirmed whether slugs have the same effect and whether seeds can also detect and react to such herbivore cues. We investigated how exposure toArion subfuscusmucus affected growth and defense inBrassica nigraseeds and seedlings. Seeds exposed to slug mucus germinated 5% faster than control (water only) seeds, but the resulting seedlings weighed 16% less than control seedlings. To test whether this difference results from herbivore-exposed plants allocating energy from growth to defense, we conducted choice bioassays assessing slug preference for control seedlings versus seedlings that were either (A) exposed to mucus only as a seed; or (B) exposed to mucus as a seed and seedling. While slugs did not differentiate between control seedlings and ones exposed to herbivore cues only as a seed, they ate 88% less biomass of seedlings exposed to mucus as both seeds and seedlings. These results suggest that slug mucus induces changes in plant traits related to defense and growth/competitive ability. Future research should determine the chemical mechanisms of this induced defense. 

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5. Comparative mucomic analysis of three functionally distinct Cornu aspersum Secretions

   https://doi.org/10.1038/s41467-023-41094-z  

   Cerullo, Antonio_R; McDermott, Maxwell_B; Pepi, Lauren_E; Liu, Zhi-Lun; Barry, Diariou; Zhang, Sheng; Yang, Xu; Chen, Xi; Azadi, Parastoo; Holford, Mande; et al (September 2023, Nature Communications)

   Abstract Every animal secretes mucus, placing them among the most diverse biological materials. Mucus hydrogels are complex mixtures of water, ions, carbohydrates, and proteins. Uncertainty surrounding their composition and how interactions between components contribute to mucus function complicates efforts to exploit their properties. There is substantial interest in commercializing mucus from the garden snail,Cornu aspersum, for skincare, drug delivery, tissue engineering, and composite materials.C. aspersumsecretes three mucus—one shielding the animal from environmental threats, one adhesive mucus from the pedal surface of the foot, and another pedal mucus that is lubricating. It remains a mystery how compositional differences account for their substantially different properties. Here, we characterize mucus proteins, glycosylation, ion content, and mechanical properties that could be used to provide insight into structure-function relationships through an integrative “mucomics” approach. We identify macromolecular components of these hydrogels, including a previously unreported protein class termed Conserved Anterior Mollusk Proteins (CAMPs). Revealing differences betweenC. aspersummucus shows how considering structure at all levels can inform the design of mucus-inspired materials. 

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