title: Evidence for a plant-associated natural habitat for Cronobacter spp.
abstract: Cronobacter (Enterobacter sakazakii) species are responsible for rare cases of necrotising enterocolitis and bacteraemia in infants, as well as cases of meningitis with high case fatality rates in neonates and immunocompromised infants. Some physiological features, such as the production of a yellow pigment, the formation of a gum-like extracellular polysaccharide and the ability to persist in a desiccated state, suggest an environmental niche for these organisms. To date, the natural habitat of Cronobacter spp. remains unknown. In this report, the isolation and characterisation of two Cronobacter sakazakii strains from plant roots is described. Also, the root colonisation behaviour of Cronobacter strains originating from clinical and plant sources is assessed. The nine strains investigated showed features often found in plant-associated and rhizosphere microorganisms, including solubilisation of mineral phosphate and production of indole acetic acid. Siderophore production was observed for all except one strain. In addition, the capability to endophytically colonise tomato and maize roots was demonstrated for several strains, either by fluorescence in situ hybridisation, using fluorescently labelled oligonucleotide probes, or by using strains tagged with green fluorescent protein and confocal laser scanning microscopy. The results provide evidence that plants may be the natural habitat of Cronobacter spp.
authors.affiliation: Helmholtz Zentrum München, German Research Centre for Environmental Health (GmbH), Department Microbe-Plant Interactions, Ingolstaedter Landstrasse, Neuherberg, Germany. michael.schmid@helmholtz-muenchen.de
authors.forename: Michael
authors.initials: M
authors.lastname: Schmid
authors.forename: Carol
authors.initials: C
authors.lastname: Iversen
authors.forename: Iti
authors.initials: I
authors.lastname: Gontia
authors.forename: Roger
authors.initials: R
authors.lastname: Stephan
authors.forename: Andreas
authors.initials: A
authors.lastname: Hofmann
authors.forename: Anton
authors.initials: A
authors.lastname: Hartmann
authors.forename: Bhavanath
authors.initials: B
authors.lastname: Jha
authors.forename: Leo
authors.initials: L
authors.lastname: Eberl
authors.forename: Kathrin
authors.initials: K
authors.lastname: Riedel
authors.forename: Angelika
authors.initials: A
authors.lastname: Lehner
mesh_terms: D016000:Cluster Analysis; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D004755:Enterobacteriaceae / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification*; D017404:In Situ Hybridization, Fluorescence; D007210:Indoleacetic Acids / Q000378:metabolism; D018551:Solanum lycopersicum / Q000382:microbiology; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D010710:Phosphates / Q000378:metabolism; D010802:Phylogeny; D018517:Plant Roots / Q000382:microbiology*; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D017262:Siderophores / Q000096:biosynthesis; D003313:Zea mays / Q000382:microbiology
chemical_list: D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D007210:Indoleacetic Acids; D010710:Phosphates; D012336:RNA, Ribosomal, 16S; D017262:Siderophores; C030737:indoleacetic acid