Abstract
Legume-nodulating rhzobia must cope with ROS not only during free-living aerobic conditions but also during establishment and maintenance of nitrogen fixing symbiosis, since host legume plant might employ ROS as defense measure against invading microorganisms. Number and enzymatic properties of catalases vary among rhizobial species. The sequence of Mesorhizobium loti MAFF303099 revealed that this organism contain two predicted catalase genes, mlr2101 and mlr6940. The latter shows homology to B. japonicum katG and locates adjacent to an oxyR-homologue mll6938. We intend to reveal how M. loti MAFF303099 use these probably distinct catalases to cope with ROS and if there is any universal strategy for utilization of anti-oxidant enzymes among rhizobia. Here, we describe effects of insertion or deletion-insertion mutagenesis and expression analysis for two M. loti .catalases
Our results indicated that mlr6940 has important role in free-living condition, whereas mlr2101 might have role(s) under no-proliferating conditions including nitrogen-fixing conditions.
