title: Effects of the Bradyrhizobium japonicum waaL (rfaL) Gene on Hydrophobicity, Motility, Stress Tolerance, and Symbiotic Relationship with Soybeans.
abstract: We cloned and sequenced the waaL (rfaL) gene from Bradyrhizobium japonicum, which infects soybean and forms nitrogen-fixing nodules on soybean roots. waaL has been extensively studied in the lipopolysaccharide (LPS) biosynthesis of enteric bacteria, but little is known about its function in (brady)rhizobial LPS architecture. To characterize its role as O-antigen ligase in the LPS biosynthesis pathway, we constructed a waaL knock-out mutant and its complemented strain named JS015 and CS015, respectively. LPS analysis showed that an LPS structure of JS015 is deficient in O-antigen as compared to that of the wild type and complemented strain CS015, suggesting that WaaL ligates the O-antigen to lipid A-core oligosaccharide to form a complete LPS. JS015 also revealed increased cell surface hydrophobicity, but it showed decreased motility in soft agar plates. In addition to the alteration in cell surface properties, disruption of the waaL gene caused increased sensitivity of JS015 to hydrogen peroxide, osmotic pressure, and novobiocin. Specifically, plant tests revealed that JS015 failed to nodulate the host plant soybean, indicating that the rhizobial waaL gene is responsible for the establishment of a symbiotic relationship between soybean and B. japonicum.
authors.affiliation: Department of Biological Engineering, Inha University, Incheon 402-751, Korea. dynaroo@naver.com.
authors.forename: Jun-Gu
authors.initials: JG
authors.lastname: Noh
authors.affiliation: Department of Biological Engineering, Inha University, Incheon 402-751, Korea. haneul7760@hanmail.net.
authors.forename: Han-Eul
authors.initials: HE
authors.lastname: Jeon
authors.affiliation: Department of Biological Engineering, Inha University, Incheon 402-751, Korea. sjaeseon@inha.ac.kr.
authors.forename: Jae-Seong
authors.initials: JS
authors.lastname: So
authors.affiliation: Department of Biology, University of Texas, Arlington, TX 76019, USA. wschang@uta.edu.|Division of Biotechnology, College of Environmental and Bioresource Sciences, Chonbuk National University, Iksan 570-752, Korea. wschang@uta.edu.
authors.forename: Woo-Suk
authors.initials: WS
authors.lastname: Chang
mesh_terms: D000222:Adaptation, Physiological / Q000187:drug effects; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D020369:Bradyrhizobium / Q000187:drug effects / Q000235:genetics* / Q000502:physiology; D002462:Cell Membrane / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005407:Flagella / Q000378:metabolism / Q000648:ultrastructure; D005798:Genes, Bacterial; D057927:Hydrophobic and Hydrophilic Interactions; D008070:Lipopolysaccharides / Q000378:metabolism; D008969:Molecular Sequence Data; D009068:Movement; D009154:Mutation; D009675:Novobiocin / Q000633:toxicity; D019081:O Antigens; D009997:Osmotic Pressure / Q000187:drug effects; D018384:Oxidative Stress / Q000187:drug effects; D055170:Plant Root Nodulation / Q000187:drug effects / Q000235:genetics; D053204:Root Nodules, Plant / Q000187:drug effects / Q000382:microbiology; D013025:Glycine max / Q000187:drug effects / Q000382:microbiology*; D013312:Stress, Physiological / Q000187:drug effects / Q000235:genetics; D013559:Symbiosis / Q000187:drug effects
chemical_list: D001426:Bacterial Proteins; D008070:Lipopolysaccharides; D019081:O Antigens; D009675:Novobiocin
keywords: O-antigen ligase; lipopolysaccharide (LPS); rfaL; soybean symbiont Bradyrhizobium japonicum; stress responses; symbiotic nitrogen fixation; waaL