14 research outputs found
Co-regulation of β-lactam resistance, alginate production and quorum sensing in Pseudomonas aeruginosa
Development of β-lactam resistance, production of alginate and modulation of virulence factor expression that alters host immune responses are the hallmarks of chronic Pseudomonas aeruginosa infection in cystic fibrosis patients. In this study, we propose that a co-regulatory network exists between these mechanisms. We compared the promoter activities of ampR, algT/U, lasR, lasI, rhlR, rhlI and lasA genes, representing the β-lactam antibiotic resistance master regulatory gene, the alginate switch operon, the las and rhl quorum-sensing (QS) genes, and the LasA staphylolytic protease, respectively. Four isogenic P. aeruginosa strains, the prototypic Alg− PAO1, Alg− PAOampR, the mucoid Alg+ PAOmucA22 (Alg+ PDO300) and Alg+ PAOmucA22ampR (Alg+ PDOampR) were used. We found that in the presence of AmpR regulator and β-lactam antibiotic, the extracytoplasmic function sigma factor AlgT/U positively regulated PampR, whereas AmpR negatively regulated PalgT/U. On the basis of this finding we suggest the presence of a negative feedback loop to limit algT/U expression. In addition, the functional AlgT/U caused a significant decrease in the expression of QS genes, whereas loss of ampR only resulted in increased PlasI and PlasR transcription. The upregulation of the las QS system is likely to be responsible for the increased lasA promoter and the LasA protease activities in Alg− PAOampR and Alg+ PDOampR. The enhanced expression of virulence factors in the ampR strains correlated with a higher rate of Caenorhabditis elegans paralysis. Hence, this study shows that the loss of ampR results in increased virulence, and is indicative of the existence of a co-regulatory network between β-lactam resistance, alginate production, QS and virulence factor production, with AmpR playing a central role
Attitude and Divergence in Business Students: An Examination of Personality Differences in Business and Non-Business Students
Many studies have reported that
economics and business students
have been more apt to act in selfinterested
ways when compared to
their counterparts in other academic
fields. It is our contention that past
studies have not shed light on the
underlying psychological differences
which might be leading to
this difference in behavior. We put
forth evidence that certain business
majors are correlated with a marked
increase in levels of narcissism and
decreased levels of empathy, as
measured by psychological personality
tests.Many studies have reported that
economics and business students
have been more apt to act in selfinterested
ways when compared to
their counterparts in other academic
fields. It is our contention that past
studies have not shed light on the
underlying psychological differences
which might be leading to
this difference in behavior. We put
forth evidence that certain business
majors are correlated with a marked
increase in levels of narcissism and
decreased levels of empathy, as
measured by psychological personality
tests