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

Abstract

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.

CzcR Is Essential for Swimming Motility in Pseudomonas aeruginosa during Zinc Stress

“…For example, this might be caused by the different growth conditions or different compositions of the culture media ( 41 ). In addition, variations in the genetic background of the PAO1 strains could be another possible factor leading to the discrepant regulatory patterns because dramatic genetic and phenotypic diversity was reported among PAO1 sublines even from the same laboratory ( 42 ). Although CzcR was activated by Zn 2+ to repress PYO production, it was also noted that Zn 2+ could significantly induce the PYO production without the presence of CzcR.…”

Beyond Thresholds: Quorum‐Sensing as Quantitatively Varying Reaction Norms to Multiple Environmental Dimensions

“…Both the British NPAO1 and the Danish MH340 used in our study (Figure 1A) have an 8bp deletion in mexT compared to the strain used in Whiteley et al., 1999 [42] . While mexT can act as a transcription factor for other QS effectors (although not elastase directly), lack of mexT based regulation of MexEF‐OprN can also reduce expression of efflux pumps [45–49] . This 8bp deletion could therefore lead to decreased efflux‐mediated transport of the QS signal N‐(3‐oxododecanoyl)‐L‐homoserine lactone (3‐oxo‐C12), leading to increased retention of basally produced 3‐oxo‐C12 and thus higher intracellular concentrations of 3‐oxo‐C12 compared to the environment.…”

“…[42] While mexT can act as a transcription factor for other QS effectors (although not elastase directly), lack of mexT based regulation of MexEF-OprN can also reduce expression of efflux pumps. [45][46][47][48][49] This 8bp deletion could therefore lead to decreased efflux-mediated transport of the QS signal N-(3oxododecanoyl)-L-homoserine lactone (3-oxo-C12), leading to increased retention of basally produced 3-oxo-C12 and thus higher intracellular concentrations of 3-oxo-C12 compared to the environment. This internally high concentration of 3-oxo-C12 could then lead to induction of QS at lower densities compared to strains with more active effluxmediated transport of signal (like in Whiteley et al, 1999 [42] ).…”

Comprehensive Virulence Profiling and Evolutionary Analysis of Specificity Determinants inStaphylococcus aureusTwo-Component Systems

“…The analysis of site-specific selection pressure was analyzed using the method described by (24) with minor modifications. The S. aureus genomes were downloaded from the NCBI database.…”