title: Soil amoebae rapidly change bacterial community composition in the rhizosphere of Arabidopsis thaliana.
abstract: We constructed an experimental model system to study the effects of grazing by a common soil amoeba, Acanthamoeba castellanii, on the composition of bacterial communities in the rhizosphere of Arabidopsis thaliana. Amoebae showed distinct grazing preferences for specific bacterial taxa, which were rapidly replaced by grazing tolerant taxa in a highly reproducible way. The relative proportion of active bacteria increased although bacterial abundance was strongly decreased by amoebae. Specific bacterial taxa had disappeared already two days after inoculation of amoebae. The decrease in numbers was most pronounced in Betaproteobacteria and Firmicutes. In contrast, Actinobacteria, Nitrospira, Verrucomicrobia and Planctomycetes increased. Although other groups, such as betaproteobacterial ammonia oxidizers and Gammaproteobacteria did not change in abundance, denaturing gradient gel electrophoresis with specific primers for pseudomonads (Gammaproteobacteria) revealed both specific changes in community composition as well as shifts in functional genes (gacA) involved in bacterial defence responses. The resulting positive feedback on plant growth in the amoeba treatment confirms that bacterial grazers play a dominant role in structuring bacteria-plant interactions. This is the first detailed study documenting how rapidly protozoan grazers induce shifts in rhizosphere bacterial community composition.
authors.affiliation: Technische Universität Darmstadt, Institut für Zoologie, Darmstadt, Germany.
authors.forename: Katja
authors.initials: K
authors.lastname: Rosenberg
authors.forename: Joanne
authors.initials: J
authors.lastname: Bertaux
authors.forename: Kristin
authors.initials: K
authors.lastname: Krome
authors.forename: Anton
authors.initials: A
authors.lastname: Hartmann
authors.forename: Stefan
authors.initials: S
authors.lastname: Scheu
authors.forename: Michael
authors.initials: M
authors.lastname: Bonkowski
mesh_terms: D048248:Acanthamoeba castellanii / Q000502:physiology*; D000818:Animals; D017360:Arabidopsis / Q000254:growth & development / Q000382:microbiology*; D001419:Bacteria / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification; D044822:Biodiversity; D016172:DNA Fingerprinting; D004269:DNA, Bacterial / Q000235:genetics; D004275:DNA, Ribosomal / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel; D017404:In Situ Hybridization, Fluorescence; D009691:Nucleic Acid Denaturation; D018517:Plant Roots / Q000382:microbiology*; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012988:Soil Microbiology
chemical_list: D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D012336:RNA, Ribosomal, 16S