title: Purine biosynthesis, biofilm formation, and persistence of an insect-microbe gut symbiosis.
abstract: The Riptortus-Burkholderia symbiotic system is an experimental model system for studying the molecular mechanisms of an insect-microbe gut symbiosis. When the symbiotic midgut of Riptortus pedestris was investigated by light and transmission electron microscopy, the lumens of the midgut crypts that harbor colonizing Burkholderia symbionts were occupied by an extracellular matrix consisting of polysaccharides. This observation prompted us to search for symbiont genes involved in the induction of biofilm formation and to examine whether the biofilms are necessary for the symbiont to establish a successful symbiotic association with the host. To answer these questions, we focused on purN and purT, which independently catalyze the same step of bacterial purine biosynthesis. When we disrupted purN and purT in the Burkholderia symbiont, the ΔpurN and ΔpurT mutants grew normally, and only the ΔpurT mutant failed to form biofilms. Notably, the ΔpurT mutant exhibited a significantly lower level of cyclic-di-GMP (c-di-GMP) than the wild type and the ΔpurN mutant, suggesting involvement of the secondary messenger c-di-GMP in the defect of biofilm formation in the ΔpurT mutant, which might operate via impaired purine biosynthesis. The host insects infected with the ΔpurT mutant exhibited a lower infection density, slower growth, and lighter body weight than the host insects infected with the wild type and the ΔpurN mutant. These results show that the function of purT of the gut symbiont is important for the persistence of the insect gut symbiont, suggesting the intricate biological relevance of purine biosynthesis, biofilm formation, and symbiosis.
authors.affiliation: Global Research Laboratory, Pusan National University, Pusan, South Korea.
authors.forename: Jiyeun Kate
authors.initials: JK
authors.lastname: Kim
authors.affiliation: Global Research Laboratory, Pusan National University, Pusan, South Korea.
authors.forename: Jeong Yun
authors.initials: JY
authors.lastname: Kwon
authors.affiliation: College of Pharmacy, Pusan National University, Pusan, South Korea.
authors.forename: Soo Kyoung
authors.initials: SK
authors.lastname: Kim
authors.affiliation: Global Research Laboratory, Pusan National University, Pusan, South Korea.
authors.forename: Sang Heum
authors.initials: SH
authors.lastname: Han
authors.affiliation: Global Research Laboratory, Pusan National University, Pusan, South Korea.
authors.forename: Yeo Jin
authors.initials: YJ
authors.lastname: Won
authors.affiliation: College of Pharmacy, Pusan National University, Pusan, South Korea.
authors.forename: Joon Hee
authors.initials: JH
authors.lastname: Lee
authors.affiliation: Global Research Laboratory, Pusan National University, Pusan, South Korea.
authors.forename: Chan-Hee
authors.initials: CH
authors.lastname: Kim
authors.affiliation: Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan.
authors.forename: Takema
authors.initials: T
authors.lastname: Fukatsu
authors.affiliation: Global Research Laboratory, Pusan National University, Pusan, South Korea brlee@pusan.ac.kr.
authors.forename: Bok Luel
authors.initials: BL
authors.lastname: Lee
mesh_terms: D000818:Animals; D018441:Biofilms; D019117:Burkholderia / Q000235:genetics / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism; D004926:Escherichia coli / Q000254:growth & development; D041981:Gastrointestinal Tract / Q000382:microbiology*; D005798:Genes, Bacterial; D020062:Heteroptera / Q000382:microbiology*; D046529:Microscopy, Electron, Transmission; D009154:Mutation; D011134:Polysaccharides / Q000378:metabolism; D011687:Purines / Q000096:biosynthesis*; D013559:Symbiosis
chemical_list: D011134:Polysaccharides; D011687:Purines; D006152:Cyclic GMP; C030985:purine