title: Intraspecific variation in Burkholderia caledonica: Europe vs. Africa and soil vs. endophytic isolates.
abstract: The best-known interaction between bacteria and plants is the Rhizobium-legume symbiosis, but other bacteria-plant interactions exist, such as between Burkholderia and Rubiaceae (coffee family). A number of bacterial endophytes in Rubiaceae are closely related to the soil bacterium Burkholderia caledonica. This intriguing observation is explored by investigating isolates from different geographic regions (Western Europe vs. sub-Saharan Africa) and from different niches (free-living bacteria in soil vs. endophytic bacteria in host plants). The multilocus sequence analysis shows five clades, of which clade 1 with two basal isolates deviates from the rest and is therefore not considered further. All other isolates belong to the species B. caledonica, but two genetically different groups are identified. Group A holds only European isolates and group B holds isolates from Africa, with the exception of one European isolate. Although the European and African isolates are considered one species, some degree of genetic differentiation is evident. Endophytic isolates of B. caledonica are found in certain members of African Rubiaceae, but only in group B. Within this group, the endophytes cannot be distinguished from the soil isolates, which indicates a possible exchange of bacteria between soil and host plant.
authors.affiliation: Plant Conservation and Population Biology, KU Leuven, 3001 Leuven, Belgium. Electronic address: brecht.verstraete@bio.kuleuven.be.
authors.forename: Brecht
authors.initials: B
authors.lastname: Verstraete
authors.affiliation: Laboratory of Microbiology, Ghent University, 9000 Ghent, Belgium.
authors.forename: Charlotte
authors.initials: C
authors.lastname: Peeters
authors.affiliation: H.G.W.J. Schweickerdt Herbarium, University of Pretoria, 0083 Hatfield, South Africa.
authors.forename: Braam
authors.initials: B
authors.lastname: van Wyk
authors.affiliation: Plant Conservation and Population Biology, KU Leuven, 3001 Leuven, Belgium; Naturalis Biodiversity Center, Leiden University, 2300 RA Leiden, The Netherlands.
authors.forename: Erik
authors.initials: E
authors.lastname: Smets
authors.affiliation: Plant Conservation and Population Biology, KU Leuven, 3001 Leuven, Belgium; National Botanic Garden of Belgium, 1860 Meise, Belgium.
authors.forename: Steven
authors.initials: S
authors.lastname: Dessein
authors.affiliation: Laboratory of Microbiology, Ghent University, 9000 Ghent, Belgium.
authors.forename: Peter
authors.initials: P
authors.lastname: Vandamme
mesh_terms: D017954:Africa South of the Sahara; D019117:Burkholderia / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D060026:Endophytes / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification; D005060:Europe; D014644:Genetic Variation; D008969:Molecular Sequence Data; D058885:Multilocus Sequence Typing; D058974:Phylogeography; D019666:Rubiaceae / Q000382:microbiology*; D012988:Soil Microbiology
chemical_list: D004269:DNA, Bacterial
keywords: Biogeography; Burkholderia caledonica; Endophyte; Rhizosphere; Rubiaceae; Soil