Microevolution of the mexT and lasR Reinforces the Bias of Quorum Sensing System in Laboratory Strains of Pseudomonas aeruginosa PAO1

The Pseudomonas aeruginosa strain PAO1 has routinely been used as a laboratory model for quorum sensing (QS). However, the microevolution of P. aeruginosa laboratory strains resulting in genetic and phenotypic variations have caused inconsistencies in QS research. To investigate the underlying causes of these variations, we analyzed 5 Pseudomonas aeruginosa PAO1 sublines from our laboratory using a combination of phenotypic characterization, high throughput genome sequencing, and bioinformatic analysis. The major phenotypic variations among the sublines spanned across the levels of QS signals and virulence factors such as pyocyanin and elastase. Furthermore, the sublines exhibited distinct variations in motility and biofilm formation. Most of the phenotypic variations were mapped to mutations in the lasR and mexT, which are key components of the QS circuit. By introducing these mutations in the subline PAO1-E, which is devoid of such mutations, we confirmed their influence on QS, virulence, motility, and biofilm formation. The findings further highlight a possible divergent regulatory mechanism between the LasR and MexT in the P. aeruginosa. The results of our study reveal the effects of microevolution on the reproducibility of most research data from QS studies and further highlight mexT as a key component of the QS circuit of P. aeruginosa

A further exploitation of the attenuated-total-reflection technique to measure the complex second hyperpolarizability for the quadratic electro-optic effect of a linear conjugated polymer

By using the technique of the attenuated total reflection, the complex second hyperpolarizability for the quadratic electro-optic effect of a linear conjugated polymer is determined at the wavelength of the absorption edge by employing the data measured from different guided wave resonance dips. The values and the signs of the real and imaginary parts of the second hyperpolarizability are simultaneously obtained without employing the Kramers-Kronig transformation

Authenticity in college English textbooks - An intercultural perspective

10.1177/003368820203300203RELC Journal33258-8