| Title | Characterization of MocR, a GntR-like transcriptional regulator, in Bradyrhizobium japonicum: its impact on motility, biofilm formation, and soybean nodulation |
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| Author | May Nyan Taw1, Hae-In Lee1, Sang-Ho Lee2, and Woo-Suk Chang1,3* |
| Address | 1Department of Biology, University of Texas at Arlington, Arlington, Texas 76019, USA, 2Fusion Technology R&D Division, Korea Institute of Industrial Technology, Ansan 426-910, Republic of Korea, 3Division of Biotechnology, College of Environmental and Bioresource Sciences, Chonbuk National University, Iksan 570-752, Republic of Korea |
| Bibliography | Journal of Microbiology, 53(8),518-525, 2015, |
| DOI | 10.1007/s12275-015-5313-z |
| Key Words | GntR transcriptional regulator, MocR, Bradyrhizobium japonicum, motility, biofilm, symbiotic nitrogen fixation |
| Abstract | Bradyrhizobium japonicum is a Gram-negative soil bacterium that can fix nitrogen into ammonia by developing a symbiotic relationship with the soybean plant. MocR proteins make up a subfamily of GntR superfamily, one of the most widely distributed and prolific groups of the helix-turn-helix transcription factors. In this study, we constructed a mutant strain for mocR (blr6977) to investigate its role in cellular processes and symbiosis in B. japonicum. Although growth rate and morphology of the mutant were indistinguishable from those of the wild type, the mutant showed significant differences in motility and attachment (i.e., biofilm formation) from the wild type. The mutant displayed a decrease in biofilm formation, but was more motile than the wild type. The inactivation of mocR did not affect the number of nodules on soybean roots, but caused delayed nodulation. Delayed nodulation intrigued us to study competitiveness of the mutant infecting soybeans. The mutant was less competitive than the wild type, indicating that delayed nodulation might be due to competitiveness. Gene expressions of other MocR subfamily members were also compared between the wild type and mutant strains. None of the mocR-like genes examined in this study were differentially expressed between both strains. |