Li-Hua Li1,2, Yung-Luen Shih3,4,5, Jing-Yun Huang6,7, Chao-Jung Wu7, Yi-Wei Huang7, Hsin-Hui Huang7, Yu-Chieh Tsai7, Tsuey-Ching Yang8. 1. Department of Pathology and Laboratory Medicine, Taipei Veterans General Hospital, Taipei, Taiwan. 2. Program of Medical Biotechnology, Taipei Medical University, Taipei, Taiwan. 3. Department of Pathology and Laboratory Medicine, Shin Kong Wu Ho-Su Memorial Hospital, Taipei, Taiwan. 4. School of Medical Laboratory Science and Biotechnology, Taipei Medical University, Taipei, Taiwan. 5. School of Medicine, College of Medicine, Fu-Jen Catholic University, New Taipei City, Taiwan. 6. Department of Laboratory Medicine, Chang-Gung Memorial Hospital, LinKou, Taiwan. 7. Department of Biotechnology and Laboratory Science in Medicine, National Yang-Ming University, Taipei, Taiwan. 8. Department of Biotechnology and Laboratory Science in Medicine, National Yang-Ming University, Taipei, Taiwan. tcyang@ym.edu.tw.
Abstract
BACKGROUND: Aerobically-grown bacteria can be challenged by hydrogen peroxide stress from endogenous aerobic metabolism and exogenously generated reactive oxygen species. Catalase (Kat), alkyl hydroperoxidase (Ahp), and glutathione peroxidase (Gpx) systems are major adaptive responses to H2O2 stress in bacteria. Stenotrophomonas maltophilia is a ubiquitous Gram-negative bacterium equipped with four Kats (KatA1, KatA2, KatMn, and KatE), one Ahp (AhpCF), and three Gpxs (Gpx1, Gpx2, and Gpx3). Here, we systematically investigated how the eight H2O2 scavenging genes differentially contribute to the low-micromolar levels of H2O2 generated from aerobic metabolism and high-millimolar levels of H2O2 from exogenous sources. METHODS: Gene expression was assessed and quantified by reverse transcription-PCR (RT-PCR) and real time quantitative PCR (qRT-PCR), respectively. The contribution of these enzymes to H2O2 stress was assessed using mutant construction and functional investigation. RESULTS: Of the eight genes, katA2, ahpCF, and gpx3 were intrinsically expressed in response to low-micromolar levels of H2O2 from aerobic metabolism, and the expression of katA2 and ahpCF was regulated by OxyR. AhpCF and KatA2 were responsible for alleviating aerobic growth-mediated low concentration H2O2 stress and AhpCF played a critical role for stationary-phase cells. KatA2 was upregulated to compensate for AhpCF in the case of ahpCF inactivation. After exposure to millimolar levels of H2O2, katA2 and ahpCF were upregulated in an OxyR-dependent manner. KatA2 was the critical enzyme for dealing with high concentration H2O2. Loss-of-function of KatA2 increased bacterial susceptibility to high concentration H2O2. CONCLUSIONS: AhpCF and KatA2 are key enzymes protecting S. maltophilia from hydrogen peroxide stress.
BACKGROUND: Aerobically-grown bacteria can be challenged by hydrogen peroxide stress from endogenous aerobic metabolism and exogenously generated reactive oxygen species. Catalase (Kat), alkyl hydroperoxidase (Ahp), and glutathione peroxidase (Gpx) systems are major adaptive responses to H2O2 stress in bacteria. Stenotrophomonas maltophilia is a ubiquitous Gram-negative bacterium equipped with four Kats (KatA1, KatA2, KatMn, and KatE), one Ahp (AhpCF), and three Gpxs (Gpx1, Gpx2, and Gpx3). Here, we systematically investigated how the eight H2O2 scavenging genes differentially contribute to the low-micromolar levels of H2O2 generated from aerobic metabolism and high-millimolar levels of H2O2 from exogenous sources. METHODS: Gene expression was assessed and quantified by reverse transcription-PCR (RT-PCR) and real time quantitative PCR (qRT-PCR), respectively. The contribution of these enzymes to H2O2 stress was assessed using mutant construction and functional investigation. RESULTS: Of the eight genes, katA2, ahpCF, and gpx3 were intrinsically expressed in response to low-micromolar levels of H2O2 from aerobic metabolism, and the expression of katA2 and ahpCF was regulated by OxyR. AhpCF and KatA2 were responsible for alleviating aerobic growth-mediated low concentration H2O2 stress and AhpCF played a critical role for stationary-phase cells. KatA2 was upregulated to compensate for AhpCF in the case of ahpCF inactivation. After exposure to millimolar levels of H2O2, katA2 and ahpCF were upregulated in an OxyR-dependent manner. KatA2 was the critical enzyme for dealing with high concentration H2O2. Loss-of-function of KatA2 increased bacterial susceptibility to high concentration H2O2. CONCLUSIONS: AhpCF and KatA2 are key enzymes protecting S. maltophilia from hydrogen peroxide stress.
Authors: Pâmela B Vilela; Rondon P Mendonça Neto; Maria Clara V M Starling; Alessandra da S Martins; Giovanna F F Pires; Felipe A R Souza; Camila C Amorim Journal: Sci Total Environ Date: 2021-08-12 Impact factor: 7.963