title: Active invasion of bacteria into living fungal cells.
abstract: The rice seedling blight fungus Rhizopus microsporus and its endosymbiont Burkholderia rhizoxinica form an unusual, highly specific alliance to produce the highly potent antimitotic phytotoxin rhizoxin. Yet, it has remained a riddle how bacteria invade the fungal cells. Genome mining for potential symbiosis factors and functional analyses revealed that a type 2 secretion system (T2SS) of the bacterial endosymbiont is required for the formation of the endosymbiosis. Comparative proteome analyses show that the T2SS releases chitinolytic enzymes (chitinase, chitosanase) and chitin-binding proteins. The genes responsible for chitinolytic proteins and T2SS components are highly expressed during infection. Through targeted gene knock-outs, sporulation assays and microscopic investigations we found that chitinase is essential for bacteria to enter hyphae. Unprecedented snapshots of the traceless bacterial intrusion were obtained using cryo-electron microscopy. Beyond unveiling the pivotal role of chitinolytic enzymes in the active invasion of a fungus by bacteria, these findings grant unprecedented insight into the fungal cell wall penetration and symbiosis formation.
authors.affiliation: Department of Biomolecular Chemistry, Leibniz Institute for Natural Product Research and Infection Biology, Jena, Germany.
authors.forename: Nadine
authors.initials: N
authors.lastname: Moebius
authors.affiliation: Department of Biomolecular Chemistry, Leibniz Institute for Natural Product Research and Infection Biology, Jena, Germany.
authors.forename: Zerrin
authors.initials: Z
authors.lastname: Üzüm
authors.affiliation: CBS-KNAW Fungal Biodiversity Centre, Utrecht, Netherlands.
authors.forename: Jan
authors.initials: J
authors.lastname: Dijksterhuis
authors.affiliation: Department of Biomolecular Chemistry, Leibniz Institute for Natural Product Research and Infection Biology, Jena, Germany.
authors.forename: Gerald
authors.initials: G
authors.lastname: Lackner
authors.affiliation: Department of Biomolecular Chemistry, Leibniz Institute for Natural Product Research and Infection Biology, Jena, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Hertweck
mesh_terms: D019117:Burkholderia / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D002688:Chitinases / Q000378:metabolism; D020285:Cryoelectron Microscopy; D015180:Electrophoresis, Gel, Two-Dimensional; D054884:Host-Pathogen Interactions; D025301:Hyphae / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D018942:Macrolides / Q000378:metabolism*; D018613:Microscopy, Confocal; D008855:Microscopy, Electron, Scanning; D009154:Mutation; D012275:Oryza / Q000382:microbiology; D010935:Plant Diseases / Q000382:microbiology; D020543:Proteome / Q000378:metabolism; D040901:Proteomics / Q000379:methods; D012233:Rhizopus / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013559:Symbiosis
chemical_list: D018942:Macrolides; D020543:Proteome; C041443:rhizoxin; D002688:Chitinases
keywords: Burkholderia; Rhizopus; infectious disease; microbiology; symbiosis