KatG is the primary detoxifier of hydrogen peroxide produced by aerobic metabolism in Bradyrhizobium japonicum.
نویسندگان
چکیده
Bacteria are exposed to reactive oxygen species from the environment and from those generated by aerobic metabolism. Catalases are heme proteins that detoxify H(2)O(2), and many bacteria contain more than one catalase enzyme. Also, the nonheme peroxidase alkyl hydroperoxide reductase (Ahp) is the major scavenger of endogenous H(2)O(2) in Escherichia coli. Here, we show that aerobically grown Bradyrhizobium japonicum cells express a single catalase activity. Four genes encoding putative catalases in the B. japonicum genome were identified, including a katG homolog encoding a catalase-peroxidase. Deletion of the katG gene resulted in loss of catalase activity in cell extracts and of exogenous H(2)O(2) consumption by whole cells. The katG strain had a severe aerobic growth phenotype but showed improved growth in the absence of O(2). By contrast, a B. japonicum ahpCD mutant grew well aerobically and consumed H(2)O(2) at wild-type rates. A heme-deficient hemA mutant expressed about one-third of the KatG activity as the wild type but grew well aerobically and scavenged low concentrations of exogenous H(2)O(2). However, cells of the hemA strain were deficient in consumption of high concentrations of H(2)O(2) and were very sensitive to killing by short exposure to H(2)O(2). In addition, KatG activity did not decrease as a result of mutation of the gene encoding the transcriptional activator OxyR. We conclude that aerobic metabolism produces toxic levels of H(2)O(2) in B. japonicum, which is detoxified primarily by KatG. Furthermore, the katG level sufficient for detoxification does not require OxyR.
منابع مشابه
The Effect of Eight Weeks of Aerobic Exercise and Vitamin-D Supplementation on Osteocalcine and Alkaline Pphosphatase in Rats Poisoned with H2O2
Background and Objectives: Osteoporosis is one of the bone diseases that various factors such as oxidative stress have a role in creating it. The current research aimed to examine the synchronous effect of aerobic physical exercise and Vitamin D supplementation on osteocalcine and alkaline phosphatase in rats poisoned by H2O2. Materials & Methods: Sixty adult male Wistar rats were randomly di...
متن کاملGene Probe Designing for Evaluation of the Diversity of Bradyrhizobium japonicum Isolates
Many researchers consider the use of different probes for hybridization assays as suitable for studying the genetic diversity of nitrogen fixing bacteria. In this study for asessing genetic diversity among Bradyrhizobium japonicum isolates, two different probes (sucA and topA) chosen from the chromosomal genome of Bradyrhizobium strain USDA 110 were designed, evaluated by DNAMAN software and im...
متن کاملBradyrhizobium japonicum mutants defective in cyclic beta-glucan synthesis show enhanced sensitivity to plant defense responses.
Susceptibility of the nitrogen-fixing soybean symbiont Bradyrhizobium japonicum to inducible plant defense metabolites such as phytoalexin and H2O2, was investigated. On the wild-type strain USDA 110 the soybean phytoalexin, glyceollin, showed bacteriostatic activity. Viable bacteria isolated from intact nodules were adapted to glyceollin. H2O2 in physiological concentrations did not affect wil...
متن کاملThe effect of eight weeks of aerobic exercise and coriander seed extract on oxidative stress and cellular energy indices of heart tissue in male rats poisoned with hydrogen peroxide
Introduction: The aim of this research was to investigate the effect of eight weeks of aerobic training and coriander seed extract with two doses of 5 and 10 mg on oxidative stress markers and cardiac muscle ATP levels of rats poisoned with hydrogen peroxide. Methods: 42 healthy adult male rats were randomly divided into 7 groups. During one week, the groups were poisoned intraperitoneally by ...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- Journal of bacteriology
دوره 186 23 شماره
صفحات -
تاریخ انتشار 2004