Characterization of the two nonidentical ArgR regulators of Tetragenococcus halophilus and their regulatory effects on a
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APPLIED GENETICS AND MOLECULAR BIOTECHNOLOGY
Characterization of the two nonidentical ArgR regulators of Tetragenococcus halophilus and their regulatory effects on arginine metabolism Jieting Lin 1,2,3 & Xiaotong Luo 1,2 & Michael G. Gänzle 3 & Lixin Luo 1,2 Received: 15 May 2020 / Revised: 6 August 2020 / Accepted: 26 August 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The halophilic lactic acid bacterium Tetragenococcus halophilus has been widely used in high-salinity fermentation processes of food. Previous studies have indicated that the catabolism of arginine may contribute to the osmotic stress adaptation of T. halophilus. Unusually, in the chromosome of T. halophilus, preceding the arginine deiminase (ADI) operon, locate two cotranscribed genes, both encoding an ArgR regulator; similar structure was rarely found and the roles of the regulators have not been demonstrated. In the current study, regulatory roles of these two nonidentical ArgR regulators on the arginine metabolism of T. halophilus were investigated. The results show that these two regulators play different roles in arginine metabolism, ArgR1 acts as a negative regulator of the ADI pathway by binding to the promoter sequences and repressing the transcription of genes, and the addition of arginine or hyper-osmotic stress conditions can abolish the ArgR1 repression, whereas ArgR2 negatively regulates the genes involved in arginine biosynthesis. Our study found that despite the commonly known roles of the ArgR regulators as the activator of arginine catabolism and the repressor of arginine biosynthesis, which are found in most studied bacteria possessed one ArgR regulator, the two nonidentical ArgR regulators of T. halophilus both act as repressors, and the repression by which is regulated when sensing changes of environments. By revealing the regulation of arginine metabolism, the current study provides molecular insights and potential tools for future applications of halophiles in biotechnology. Key points • The expression of the ADI pathway of T. halophilus is regulated by carbon sources and osmotic stress. • The arginine metabolism process of T. halophilus is fine-tuned by the two ArgR regulators. • The ADI pathway may contribute to the osmotic stress adaptation by generating more energy and accumulating citrulline which acts as compatible solute. Keywords Tetragenococcus halophilus . ADI pathway . ArgR regulator . Osmotic stress Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00253-020-10868-6) contains supplementary material, which is available to authorized users. * Lixin Luo [email protected] 1
School of Biology and Biological Engineering, South China University of Technology, Guangzhou 510006, People’s Republic of China
2
Guangdong Provincial Key Laboratory of Fermentation and Enzyme Engineering, South China University of Technology, Guangzhou 510006, People’s Republic of China
3
Department of Agricultural, Food and Nutritional Science, University of Alber
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