50 research outputs found

    Adaptable Functionality of Transcriptional Feedback in Bacterial Two-Component Systems

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    A widespread mechanism of bacterial signaling occurs through two-component systems, comprised of a sensor histidine kinase (SHK) and a transcriptional response regulator (RR). The SHK activates RR by phosphorylation. The most common two-component system structure involves expression from a single operon, the transcription of which is activated by its own phosphorylated RR. The role of this feedback is poorly understood, but it has been associated with an overshooting kinetic response and with fast recovery of previous interrupted signaling events in different systems. Mathematical models show that overshoot is only attainable with negative feedback that also improves response time. Our models also predict that fast recovery of previous interrupted signaling depends on high accumulation of SHK and RR, which is more likely in a positive feedback regime. We use Monte Carlo sampling of the parameter space to explore the range of attainable model behaviors. The model predicts that the effective feedback sign can change from negative to positive depending on the signal level. Variations in two-component system architectures and parameters may therefore have evolved to optimize responses in different bacterial lifestyles. We propose a conceptual model where low signal conditions result in a responsive system with effectively negative feedback while high signal conditions with positive feedback favor persistence of system output

    Xylella fastidiosa gene expression analysis by DNA microarrays

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    Xylella fastidiosa genome sequencing has generated valuable data by identifying genes acting either on metabolic pathways or in associated pathogenicity and virulence. Based on available information on these genes, new strategies for studying their expression patterns, such as microarray technology, were employed. A total of 2,600 primer pairs were synthesized and then used to generate fragments using the PCR technique. The arrays were hybridized against cDNAs labeled during reverse transcription reactions and which were obtained from bacteria grown under two different conditions (liquid XDM2 and liquid BCYE). All data were statistically analyzed to verify which genes were differentially expressed. In addition to exploring conditions for X. fastidiosa genome-wide transcriptome analysis, the present work observed the differential expression of several classes of genes (energy, protein, amino acid and nucleotide metabolism, transport, degradation of substances, toxins and hypothetical proteins, among others). The understanding of expressed genes in these two different media will be useful in comprehending the metabolic characteristics of X. fastidiosa, and in evaluating how important certain genes are for the functioning and survival of these bacteria in plants

    Development and validation of the Online Histrionic Personality Scale (OHPS) using the DSM-5 criteria for Histrionic Personality Disorder

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    The present study evaluated personality presentation in online environments in terms of histrionic personality. The aim of the study was to develop the Online Histrionic Personality Scale (OHPS). The OHPS was developed using the diagnostic criteria for histrionic personality disorder (HPD) in the DSM-5 and assesses histrionic behavior in online environments. The present study comprised 381 university students (219 females and 162 males) from four different samples. The validity of the OHPS was investigated utilizing exploratory factor analysis (EFA), confirmatory factor analysis (CFA), and criterion validity. As a result of the EFA, a single-factor structure with an eigenvalue of 3.850 was found and accounted for 48.12% of the total variance. This one-dimensional structure was tested with CFA in two different samples. CFA results show that OHPS had an acceptable fit. The criterion validity of the OHPS was examined with the Desire for Being Liked Scale (DBLS) and the Histrionic Personality Belief subscale of the Personality Belief Questionnaire-Short Form (PBQ-STF). Analysis showed that the OHPS was significantly associated with desire for being liked (r = .65, p < .01) and histrionic personality beliefs (r = .70, p < .01). The reliability of the OHPS was evaluated with Cronbach’s α internal consistency reliability coefficient and corrected item total correlation coefficient in three different samples. The Cronbach α internal consistency coefficients of the OHPS were .84 (EFA sample), .88 (CFA sample), and .88 (criterion validity sample). Corrected item total correlation coefficients of OHPS ranged from .53 to .62 in the EFA sample, .47 to .78 in the CFA sample, and .52 to .76 in the criterion validity sample. The distribution of data was examined with floor and ceiling effects in three different samples. Finally, the standard error of measurement (SEM) was calculated in three different samples. There were no floor and ceiling effects in the data, and the SEM values were within acceptable limits. When validity and reliability analyses of the OHPS are considered as a whole, it is concluded that the OHPS is a valid and reliable scale that assesses online histrionic personality among university students

    Feminist identity among Latina adolescents

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    Self-presentation and gender on MySpace

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