Wind-Tunnel Investigation of a Revised Horizontal Tail Surface for the Grumman TBF-1 Airplane

No abstract availabl

Regulation of Type IV Pili Contributes to Surface Behaviors of Historical and Epidemic Strains of Clostridium difficile

ABSTRACT The intestinal pathogen Clostridium difficile is an urgent public health threat that causes antibiotic-associated diarrhea and is a leading cause of fatal nosocomial infections in the United States. C. difficile rates of recurrence and mortality have increased in recent years due to the emergence of so-called “hypervirulent” epidemic strains. A great deal of the basic biology of C. difficile has not been characterized. Recent findings that flagellar motility, toxin synthesis, and type IV pilus (TFP) formation are regulated by cyclic diguanylate (c-di-GMP) reveal the importance of this second messenger for C. difficile gene regulation. However, the function(s) of TFP in C. difficile remains largely unknown. Here, we examine TFP-dependent phenotypes and the role of c-di-GMP in controlling TFP production in the historical 630 and epidemic R20291 strains of C. difficile . We demonstrate that TFP contribute to C. difficile biofilm formation in both strains, but with a more prominent role in R20291. Moreover, we report that R20291 is capable of TFP-dependent surface motility, which has not previously been described in C. difficile . The expression and regulation of the pilA1 pilin gene differs between R20291 and 630, which may underlie the observed differences in TFP-mediated phenotypes. The differences in pilA1 expression are attributable to greater promoter-driven transcription in R20291. In addition, R20291, but not 630, upregulates c-di-GMP levels during surface-associated growth, suggesting that the bacterium senses its substratum. The differential regulation of surface behaviors in historical and epidemic C. difficile strains may contribute to the different infection outcomes presented by these strains. IMPORTANCE How Clostridium difficile establishes and maintains colonization of the host bowel is poorly understood. Surface behaviors of C. difficile are likely relevant during infection, representing possible interactions between the bacterium and the intestinal environment. Pili mediate bacterial interactions with various surfaces and contribute to the virulence of many pathogens. We report that type IV pili (TFP) contribute to biofilm formation by C. difficile . TFP are also required for surface motility, which has not previously been demonstrated for C. difficile . Furthermore, an epidemic-associated C. difficile strain showed higher pilin gene expression and greater dependence on TFP for biofilm production and surface motility. Differences in TFP regulation and their effects on surface behaviors may contribute to increased virulence in recent epidemic strains

Loss of the V-ATPase B1 Subunit Isoform Expressed in Non-Neuronal Cells of the Mouse Olfactory Epithelium Impairs Olfactory Function

The vacuolar proton-pumping ATPase (V-ATPase) is the main mediator of intracellular organelle acidification and also regulates transmembrane proton (H+) secretion, which is necessary for an array of physiological functions fulfilled by organs such as the kidney, male reproductive tract, lung, bone, and ear. In this study we characterize expression of the V-ATPase in the main olfactory epithelium of the mouse, as well as a functional role for the V-ATPase in odor detection. We report that the V-ATPase localizes to the apical membrane microvilli of olfactory sustentacular cells and to the basolateral membrane of microvillar cells. Plasma membrane V-ATPases containing the B1 subunit isoform are not detected in olfactory sensory neurons or in the olfactory bulb. This precise localization of expression affords the opportunity to ascertain the functional relevance of V-ATPase expression upon innate, odor-evoked behaviors in B1-deficient mice. This animal model exhibits diminished innate avoidance behavior (revealed as a decrease in freezing time and an increase in the number of sniffs in the presence of trimethyl-thiazoline) and diminished innate appetitive behavior (a decrease in time spent investigating the urine of the opposite sex). We conclude that V-ATPase-mediated H+ secretion in the olfactory epithelium is required for optimal olfactory function

Continuous evaluation of corrugating medium. Project 1108-17, Report 112 : a progress report to Fourdrinier Kraft Board Institute, Inc.

"Test results on rolls of corrugating medium for the months of February and March, 1965."April 1, 1965.

Determination of the reinforcement afforded sack paper by an electrical resistance strain gage. Project 2033, progress report 8 to Multiwall Shipping Sack Paper Manufacturers

"September 8, 1959.""The Institute of Paper Chemistry, John A. Shoman, research assistant, Container Section, J. W. Gander, research aide and R. C. McKee, chief, Container Section.

Edgewise compression strength of corrugated board

"7-11-61."Project number handwritten on title page. Included in IPC/IPST Central files collection for project 1108-4

Review of 1963-1966 sack research program. Project 2033, report thirty-nine : a progress report to Multiwall Shipping Sack Paper Manufacturers Research Group

"June 21, 1966.""The Institute of Paper Chemistry, J. W. Gander, research associate, William J. Whitsitt, and R. C. McKee, chairman, Container Section.

A Nutrient-Regulated Cyclic Diguanylate Phosphodiesterase Controls Clostridium difficile Biofilm and Toxin Production during Stationary Phase

ABSTRACT The signaling molecule cyclic diguanylate (c-di-GMP) mediates physiological adaptation to extracellular stimuli in a wide range of bacteria. The complex metabolic pathways governing c-di-GMP synthesis and degradation are highly regulated, but the specific cues that impact c-di-GMP signaling are largely unknown. In the intestinal pathogen Clostridium difficile , c-di-GMP inhibits flagellar motility and toxin production and promotes pilus-dependent biofilm formation, but no specific biological functions have been ascribed to any of the individual c-di-GMP synthases or phosphodiesterases (PDEs). Here, we report the functional and biochemical characterization of a c-di-GMP PDE, PdcA, 1 of 37 confirmed or putative c-di-GMP metabolism proteins in C. difficile 630. Our studies reveal that pdcA transcription is controlled by the nutrient-regulated transcriptional regulator CodY and accordingly increases during stationary phase. In addition, PdcA PDE activity is allosterically regulated by GTP, further linking c-di-GMP levels to nutrient availability. Mutation of pdcA increased biofilm formation and reduced toxin biosynthesis without affecting swimming motility or global intracellular c-di-GMP. Analysis of the transcriptional response to pdcA mutation indicates that PdcA-dependent phenotypes manifest during stationary phase, consistent with regulation by CodY. These results demonstrate that inactivation of this single PDE gene is sufficient to impact multiple c-di-GMP-dependent phenotypes, including the production of major virulence factors, and suggest a link between c-di-GMP signaling and nutrient availability

A Nutrient-Regulated Cyclic Diguanylate Phosphodiesterase Controls Clostridium difficile Biofilm and Toxin Production During Stationary Phase

The signaling molecule cyclic diguanylate (c-di-GMP) mediates physiological adaptation to extracellular stimuli in a wide range of bacteria. The complex metabolic pathways governing c-di-GMP synthesis and degradation are highly regulated, but the specific cues that impact c-di-GMP signaling are largely unknown. In the intestinal pathogen Clostridium difficile, c-di-GMP inhibits flagellar motility and toxin production and promotes pilus-dependent biofilm formation, but no specific biological functions have been ascribed to any of the individual c-di-GMP synthases or phosphodiesterases (PDEs). Here, we report the functional and biochemical characterization of a c-di-GMP PDE, PdcA, 1 of 37 confirmed or putative c-di-GMP metabolism proteins in C. difficile 630. Our studies reveal that pdcA transcription is controlled by the nutrient-regulated transcriptional regulator CodY and accordingly increases during stationary phase. In addition, PdcA PDE activity is allosterically regulated by GTP, further linking c-di-GMP levels to nutrient availability. Mutation of pdcA increased biofilm formation and reduced toxin biosynthesis without affecting swimming motility or global intracellular c-di-GMP. Analysis of the transcriptional response to pdcA mutation indicates that PdcA-dependent phenotypes manifest during stationary phase, consistent with regulation by CodY. These results demonstrate that inactivation of this single PDE gene is sufficient to impact multiple c-di-GMP-dependent phenotypes, including the production of major virulence factors, and suggest a link between c-di-GMP signaling and nutrient availability