AUTHOR=Sun Chenglong , Guo Yunxue , Tang Kaihao , Wen Zhongling , Li Baiyuan , Zeng Zhenshun , Wang Xiaoxue 

TITLE=MqsR/MqsA Toxin/Antitoxin System Regulates Persistence and Biofilm Formation in Pseudomonas putida KT2440

JOURNAL=Frontiers in Microbiology

VOLUME=8

YEAR=2017

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2017.00840

DOI=10.3389/fmicb.2017.00840

ISSN=1664-302X

ABSTRACT=<p>Bacterial toxin/antitoxin (TA) systems have received increasing attention due to their prevalence, diverse structures, and important physiological functions. In this study, we identified and characterized a type II TA system in a soil bacterium <italic>Pseudomonas putida</italic> KT2440. This TA system belongs to the MqsR/MqsA family. We found that PP_4205 (MqsR) greatly inhibits cell growth in <italic>P. putida</italic> KT2440 and <italic>Escherichia coli</italic>, the antitoxin PP_4204 (MqsA) neutralizes the toxicity of the toxin MqsR, and the two genes encoding them are co-transcribed. MqsR and MqsA interact with each other directly <italic>in vivo</italic> and MqsA is a negative regulator of the TA operon through binding to the promoter. Consistent with the MqsR/MqsA pair in <italic>E. coli</italic>, the binding of the toxin MqsR to MqsA inhibits the DNA binding ability of MqsA in <italic>P. putida</italic> KT2440. Disruption of the <italic>mqsA</italic> gene which induces <italic>mqsR</italic> expression increases persister cell formation 53-fold, while overexpressing <italic>mqsA</italic> which represses <italic>mqsR</italic> expression reduces persister cell formation 220-fold, suggesting an important role of MqsR in persistence in <italic>P. putida</italic> KT2440. Furthermore, both MqsR and MqsA promote biofilm formation. As a DNA binding protein, MqsA can also negatively regulate an ECF sigma factor AlgU and a universal stress protein PP_3288. Thus, we revealed an important regulatory role of MqsR/MqsA in persistence and biofilm formation in <italic>P. putida</italic> KT2440.</p>