Molecular Mechanisms Underlying Mucosal Attachment and Colonization by \u3ci\u3eClostridioides difficile\u3c/i\u3e

Clostridioides difficile is a Gram-positive, spore-forming, anaerobic bacterium which causes gastrointestinal disease and is a leading cause of nosocomial infections. Although infection typically occurs following antibiotic therapy, in recent years there has been an increase in infections which are not preceded by antibiotic use. Additionally, community-associated infections and rates of disease recurrence have increased. While it is understood that a healthy gastrointestinal microbiota provides protection against infection, the molecular mechanisms which underly C. difficile\u27s ability to colonize and persist in the gut are mostly unknown. Building on work from others that suggests C. difficile associates with the outer mucus layer during infection, we utilized an in vitro mucus layer model to probe attachment and colonization mechanisms. Using gene-interruption mutants of the major subunits of type IV pili and flagella, two extracellular appendages implicated in adhesion, we observed that the presence of flagella facilitates initial mucus attachment. Adhesion was variable across multiple strains of C. difficile and was also dependent on the source of mucin derivation. When mucin glycans were modified by mucin-degrading bacteria, C. difficile attachment decreased in our model. Collectively, our findings suggest that adherence to mucin likely influences C. difficile\u27s ability to colonize and may offer novel strategies for future therapeutics once the underlying mechanisms are better understood. Advisor: Kurt H. Piepenbrin

High Performance Imagery : The Use of Prose Poetry in James Welch\u27s Riding the Earthboy 40 and Winter in the Blood

James Welch\u27s combining of poetry and prose has given him a unique language with which to record his impression of life. In addition, welch has an excellent sense of reality that gives life to his writing. His rendition of lonely rural Montana is valid for much of interior America, and he is a master at tracing the implications of life in similar situations for all people who live with distance and harshness. one of the qualities I respect most about Riding the Earthboy 40, Winter in the Blood, and The Death of Jim Loney is that they communicate movingly about a dark situation without apologizing, or lapsing into what James Welch has termed “an easy romanticism.” The writing has a gritty, hard quality tempered by the use of a sophisticated, ready humor that pops up to entertain as well as teach. In his essay “The Art of Fiction,” Henry James said “A novel is in its broadest definition a personal, a direct impression of life: which is greater or less according to the intensity of the impression.” James Welch\u27s reality is intrinsically intense, but it is made more so by his unique perception as well as his poetic way of writing about it. The closeness of the relationship between life and the way James Welch writes about it makes his work valid as history and also gives it more artistic value. Welch\u27s technique of using literature as a spiritual history can serve as a guideline. A literary artist\u27s discoveries can become our own--in a sense they can become ROOTS for small town and rural dwellers. Combine this with skillful craftsmanship that artfully describes the rural environment and that closely defines its people, and the result is highly readable writing that contains a variety of recognizable human experiences

Explorations in engagement for humans and robots

This paper explores the concept of engagement, the process by which individuals in an interaction start, maintain and end their perceived connection to one another. The paper reports on one aspect of engagement among human interactors--the effect of tracking faces during an interaction. It also describes the architecture of a robot that can participate in conversational, collaborative interactions with engagement gestures. Finally, the paper reports on findings of experiments with human participants who interacted with a robot when it either performed or did not perform engagement gestures. Results of the human-robot studies indicate that people become engaged with robots: they direct their attention to the robot more often in interactions where engagement gestures are present, and they find interactions more appropriate when engagement gestures are present than when they are not.Comment: 31 pages, 5 figures, 3 table

Models of Plans to Support Communication: An Initial Report

Agents collaborating to achieve a goal bring to their joint activity different beliefs about ways in which to achieve the goal and the actions necessary for doing so. Thus, a model of collaboration must provide a way of representing and distinguishing among agents’ beliefs and of stating the ways in which the intentions of different agents contribute to achieving their goal. Furthermore, in collaborative activity, collaboration occurs in the planning process itself. Thus, rather than modelling plan recognition, per se, what must be modelled is the augmentation of beliefs about the actions of multiple agents and their intentions. In this paper, we modify and expand the SharedPlan model of collaborative behavior (Grosz and Sidner 1990). We present an algorithm for updating an agent’s beliefs about a partial SharedPlan and describe an initial implementation of this algorithm in the domain of network management.Engineering and Applied Science

Type IV Pilus-Mediated Inhibition of \u3ci\u3eAcinetobacter baumannii\u3c/i\u3e Biofilm Formation by Phenothiazine Compounds

Infections by pathogenic Acinetobacter species represent a significant burden on the health care system, despite their relative rarity, due to the difficulty of treating infections through oral antibiotics. Multidrug resistance is commonly observed in clinical Acinetobacter infections and multiple molecular mechanisms have been identified for this resistance, including multidrug efflux pumps, carbapenemase enzymes, and the formation of bacterial biofilm in persistent infections. Phenothiazine compounds have been identified as a potential inhibitor of type IV pilus production in multiple Gram-negative bacterial species. Here, we report the ability of two phenothiazines to inhibit type IV pilus-dependent surface (twitching) motility and biofilm formation in multiple Acinetobacter species. Biofilm formation was inhibited in both static and continuous flow models at micromolar concentrations without significant cytotoxicity, suggesting that type IV pilus biogenesis was the primary molecular target for these compounds. These results suggest that phenothiazines may be useful lead compounds for the development of biofilm dispersal agents against Gram-negative bacterial infections

Recognition of extracellular DNA by type IV pili promotes biofilm formation by \u3ci\u3eClostridioides difficile\u3c/i\u3e

Clostridioides difficile is a Gram-positive bacillus, which is a frequent cause of gastrointestinal infections triggered by the depletion of the gut microbiome. Because of the frequent recurrence of these infections after antibiotic treatment, mechanisms of C. difficile persistence and recurrence, including biofilm formation, are of increasing interest. Previously, our group and others found that type IV pili, filamentous helical appendages polymerized from protein subunits, promoted microcolony and biofilm formation in C. difficile. In Gram-negative bacteria, the ability of type IV pili to mediate bacterial self-association has been explained through interactions between the pili of adjacent cells, but type IV pili from several Gram-negative species are also required for natural competence through DNA uptake. Here, we report the ability of two C. difficile pilin subunits, PilJ and PilW, to bind to DNA in vitro, as well as the defects in biofilm formation in the pilJ and pilW gene-interruption mutants. Additionally, we have resolved the X-ray crystal structure of PilW, which we use to model possible structural mechanisms for the formation of C. difficile biofilm through interactions between type IV pili and the DNA of the extracellular matrix. Taken together, our results provide further insight into the relationship between type IV pilus function and biofilm formation in C. difficile and, more broadly, suggest that DNA recognition by type IV pili and related structures may have functional importance beyond DNA uptake for natural competence