The Influence of Interpersonal Communication Variables on Group Attraction and Group Communication Satisfaction.

This investigation explored the effects of the interpersonal communication concepts of willingness to communicate, self-monitoring, and loneliness on the group outcomes of group attraction and group communication satisfaction. Using the Willingness to Communicate Scale (McCroskey, & Richmond, 1990), Lennox and Wolfe\u27s (1984) Revised Self-monitoring Scale, the Revised UCLA Loneliness Scale (Russell, Peplau, & Cutrona, 1980), an adaptation of Byrne\u27s (1969) original Interpersonal Judgment Scale, and an adaptation of Hecht\u27s (1978) Communication Satisfaction Inventory, communication dispositions were analyzed in relationship to group attraction and group communication satisfaction. Consistent with expectations, the results show that loneliness mediated reported group communication satisfaction. Individuals who view themselves as lonely are less satisfied with group communication. Inconsistent with expectations, results show that willingness to communicate is not associated with group attraction or group communication satisfaction. Surprisingly, the results show that the self-monitoring dimension of ability to modify self-presentation is negatively associated with group attraction; but the self-monitoring dimension of sensitivity to expressive behavior is not associated with either group outcome. Additionally, non-U.S. citizens are less attracted to their groups than U.S. citizens. Further, there was a significant increase in group attraction after the subjects engaged in group exercises that focused on communication. No matter what communication orientation, individuals like their groups more after communicating together in group exercises. Finally, the implications of these findings for future research and application are discussed

Comparative Global Gene Expression Profiles of Wild-Type Yersinia pestis CO92 and Its Braun Lipoprotein Mutant at Flea and Human Body Temperatures

Braun/murein lipoprotein (Lpp) is involved in inflammatory responses and septic shock. We previously characterized a Δlpp mutant of Yersinia pestis CO92 and found that this mutant was defective in surviving in macrophages and was attenuated in a mouse inhalation model of plague when compared to the highly virulent wild-type (WT) bacterium. We performed global transcriptional profiling of WT Y. pestis and its Δlpp mutant using microarrays. The organisms were cultured at 26 and 37 degrees Celsius to simulate the flea vector and mammalian host environments, respectively. Our data revealed vastly different effects of lpp mutation on the transcriptomes of Y. pestis grown at 37 versus 26°C. While the absence of Lpp resulted mainly in the downregulation of metabolic genes at 26°C, the Y. pestis Δlpp mutant cultured at 37°C exhibited profound alterations in stress response and virulence genes, compared to WT bacteria. We investigated one of the stress-related genes (htrA) downregulated in the Δlpp mutant relative to WT Y. pestis. Indeed, complementation of the Δlpp mutant with the htrA gene restored intracellular survival of the Y. pestis Δlpp mutant. Our results support a role for Lpp in Y. pestis adaptation to the host environment, possibly via transcriptional activation of htrA

Protection Afforded by Fluoroquinolones in Animal Models of Respiratory Infections with Bacillus anthracis, Yersinia pestis, and Francisella tularensis

Successful treatment of inhalation anthrax, pneumonic plague and tularemia can be achieved with fluoroquinolone antibiotics, such as ciprofloxacin and levofloxacin, and initiation of treatment is most effective when administered as soon as possible following exposure. Bacillus anthracis Ames, Yersinia pestis CO92, and Francisella tularensis SCHU S4 have equivalent susceptibility in vitro to ciprofloxacin and levofloxacin (minimal inhibitory concentration is 0.03 μg/ml); however, limited information is available regarding in vivo susceptibility of these infectious agents to the fluoroquinolone antibiotics in small animal models. Mice, guinea pig, and rabbit models have been developed to evaluate the protective efficacy of antibiotic therapy against these life-threatening infections. Our results indicated that doses of ciprofloxacin and levofloxacin required to protect mice against inhalation anthrax were approximately 18-fold higher than the doses of levofloxacin required to protect against pneumonic plague and tularemia. Further, the critical period following aerosol exposure of mice to either B. anthracis spores or Y. pestis was 24 h, while mice challenged with F. tularensis could be effectively protected when treatment was delayed for as long as 72 h postchallenge. In addition, it was apparent that prolonged antibiotic treatment was important in the effective treatment of inhalation anthrax in mice, but short-term treatment of mice with pneumonic plague or tularemia infections were usually successful. These results provide effective antibiotic dosages in mice, guinea pigs, and rabbits and lay the foundation for the development and evaluation of combinational treatment modalities

Lst1p and Exp1p act in parallel pathways to export the plasma membrane H⁺-ATPase from the ER in S. cerevisiae

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Biology, 2004.Includes bibliographical references.Efficient transport of proteins to the correct intracellular compartment is critical for maintaining the functional integrity of the cell. Proteins destined for export from the ER are sorted from ER resident proteins and packaged into vesicles coated with the COPII protein complex. To facilitate our study of the mechanisms of protein sorting, we have selected Pma1p, the plasma membrane H+ ATPase of S. cerevisiae, as a model cargo protein. We found that efficient trafficking of Pma1p to the cell surface requires Lst1p, one of two yeast homologs of the COPII component Sec24p. We initially isolated LSTJ as one of a series of genes whose mutant alleles are lethal in combination with mutant alleles of the COPII gene SEC13. Strains deleted for LSTJ exhibit phenotypes attributable to a defect in Pma1p localization, including sensitivity to growth on acidic medium (pH 3.0) and decreased proton pumping activity. Pma1p accumulates in the ER of Ist1A strains, while other cargo molecules such as invertase and CPY are transported with wildtype kinetics. Like Sec24p, Lst1p specifically binds the COPII component Sec23p. Thus, we propose that Lst1p is an alternative COPII component that selectively exports Pma1p from the ER. We isolated EXP1 (ER-export of Pma1p) as a low-copy suppressor of the lethality displayed by Ist1-] sec13-1 double mutants. Expression of EXP1 from a centromeric plasmid suppresses the sensitivity of IstlA strains to growth on acidic medium and restores plasma membrane localization of Pma1p. Unlike stlA strains, exp1 strains grow normally under acidic conditions.(cont.) However, stl A explA double mutants are inviable and display severe Pma1p-trafficking defects. EXP1 encodes a 17 KD Type III integral membrane that cofractionates with ER in wild type cells and with the Golgi in sec21-1 mutants, indicating that Exp1p normally cycles between the Golgi and ER. Bacterially purified Exp1p fusion proteins interact with Sec23/24p in vitro. We have identified specific deletions of the cytosolic domain of EXP1 that fail to complement the lethality of a 1st1Aexp1A double mutant and to bind the Sec23/24p subcomplex. We also demonstrated that these deletion mutants fail to cycle between the Golgi and the ER. Based on these findings, we propose that Exp1p acts to enhance the Sec24p-mediated export of Pma1p from the ER. The identification here of two parallel pathways for Pma1p export from the ER provides new insight into the molecular mechanisms driving the selective uptake of secretory cargo proteins into budding COPII vesicles.by Michelle Crotwell Kirtley.Ph.D

Immunomodulatory and Protective Roles of Quorum-Sensing Signaling Molecules N-Acyl Homoserine Lactones during Infection of Mice with Aeromonas hydrophila ▿ †

Aeromonas hydrophila leads to both intestinal and extraintestinal infections in animals and humans, and the underlying mechanisms leading to mortality are largely unknown. By using a septicemic mouse model of infection, we showed that animals challenged with A. hydrophila die because of kidney and liver damage, hypoglycemia, and thrombocytopenia. Pretreatment of animals with quorum-sensing-associated signaling molecules N-acyl homoserine lactones (AHLs), such as butanoyl and hexanoyl homoserine lactones (C4- and C6-HSLs), as well as N-3-oxododecanoyl (3-oxo-C12)-HSL, prevented clinical sequelae, resulting in increased survivability of mice. Since little is known as to how different AHLs modulate the immune response during infection, we treated mice with the above AHLs prior to lethal A. hydrophila infection. When we compared results in such animals to those in controls, the treated animals exhibited a significantly reduced bacterial load in the blood and other mouse organs, as well as various levels of cytokines/chemokines. Importantly, neutrophil numbers were significantly elevated in the blood of C6-HSL-treated mice compared to those in animals given phosphate-buffered saline and then infected with the bacteria. These findings coincided with the fact that neutropenic animals were more susceptible to A. hydrophila infection than normal mice. Our data suggested that neutrophils quickly cleared bacteria by either phagocytosis or possibly another mechanism(s) during infection. In a parallel study, we indeed showed that other predominant immune cells inflicted during A. hydrophila infections, such as murine macrophages, when they were pretreated with AHLs, rapidly phagocytosed bacteria, whereas untreated cells phagocytosed fewer bacteria. This study is the first to report that AHL pretreatment modulates the innate immune response in mice and enhances their survivability during A. hydrophila infection

Role of Primary Human Alveolar Epithelial Cells in Host Defense against Francisella tularensis Infection▿

Francisella tularensis, an intracellular pathogen, is highly virulent when inhaled. Alveolar epithelial type I (ATI) and type II (ATII) cells line the majority of the alveolar surface and respond to inhaled pathogenic bacteria via cytokine secretion. We hypothesized that these cells contribute to the lung innate immune response to F. tularensis. Results demonstrated that the live vaccine strain (LVS) contacted ATI and ATII cells by 2 h following intranasal inoculation of mice. In culture, primary human ATI or ATII cells, grown on transwell filters, were stimulated on the apical (AP) surface with virulent F. tularensis Schu 4 or LVS. Basolateral (BL) conditioned medium (CM), collected 6 and 24 h later, was added to the BL surfaces of transwell cultures of primary human pulmonary microvasculature endothelial cells (HPMEC) prior to the addition of polymorphonuclear leukocytes (PMNs) or dendritic cells (DCs) to the AP surface. HPMEC responded to S4- or LVS-stimulated ATII, but not ATI, CM as evidenced by PMN and DC migration. Analysis of the AP and BL ATII CM revealed that both F. tularensis strains induced various levels of a variety of cytokines via NF-κB activation. ATII cells pretreated with an NF-κB inhibitor prior to F. tularensis stimulation substantially decreased interleukin-8 secretion, which did not occur through Toll-like receptor 2, 2/6, 4, or 5 stimulation. These data indicate a crucial role for ATII cells in the innate immune response to F. tularensis

New Insights into Autoinducer-2 Signaling as a Virulence Regulator in a Mouse Model of Pneumonic Plague

ABSTRACT The Enterobacteriaceae family members, including the infamous Yersinia pestis, the causative agent of plague, have a highly conserved interbacterial signaling system that is mediated by the autoinducer-2 (AI-2) quorum-sensing molecule. The AI-2 system is implicated in regulating various bacterial virulence genes in diverse environmental niches. Deletion of the gene encoding the synthetic enzyme for the AI-2 substrate, luxS, leads to either no significant change or, paradoxically, an increase in in vivo bacterial virulence. We showed that deletion of the rbsA and lsrA genes, components of ABC transport systems that interact with AI-2, synergistically disrupted AI-2 signaling patterns and resulted in a more-than-50-fold decrease in Y. pestis strain CO92 virulence in a stringent pneumonic plague mouse model. Deletion of luxS or lsrK (encoding AI-2 kinase) from the ΔrbsA ΔlsrA background strain or complementation of the ΔrbsA ΔlsrA mutant with the corresponding gene(s) reverted the virulence phenotype to that of the wild-type Y. pestis CO92. Furthermore, the administration of synthetic AI-2 in mice infected with the ΔrbsA ΔlsrA ΔluxS mutant strain attenuated this triple mutant to a virulence phenotype similar to that of the ΔrbsA ΔlsrA strain in a pneumonic plague model. Conversely, the administration of AI-2 to mice infected with the ΔrbsA ΔlsrA ΔluxS ΔlsrK mutant did not rescue animals from lethality, indicating the importance of the AI-2–LsrK axis in regulating bacterial virulence. By performing high-throughput RNA sequencing, the potential role of some AI-2-signaling-regulated genes that modulated bacterial virulence was determined. We anticipate that the characterization of AI-2 signaling in Y. pestis will lead to reexamination of AI-2 systems in other pathogens and that AI-2 signaling may represent a broad-spectrum therapeutic target to combat antibiotic-resistant bacteria, which represent a global crisis of the 21st century. IMPORTANCE Yersinia pestis is the bacterial agent that causes the highly fatal disease plague. The organism represents a significant concern because of its potential use as a bioterror agent, beyond the several thousand naturally occurring human infection cases occurring globally each year. While there has been development of effective antibiotics, the narrow therapeutic window and challenges posed by the existence of antibiotic-resistant strains represent serious concerns. We sought to identify novel virulence factors that could potentially be incorporated into an attenuated vaccine platform or be targeted by novel therapeutics. We show here that a highly conserved quorum-sensing system, autoinducer-2, significantly affected the virulence of Y. pestis in a mouse model of pneumonic plague. We also identified steps in autoinducer-2 signaling which had confounded previous studies and demonstrated the potential for intervention in the virulence mechanism(s) of autoinducer-2. Our findings may have an impact on bacterial pathogenesis research in many other organisms and could result in identifying potential broad-spectrum therapeutic targets to combat antibiotic-resistant bacteria, which represent a global crisis of the 21st century