title: Effects of selected root exudate components on soil bacterial communities.
abstract: Low-molecular-weight organic compounds in root exudates play a key role in plant-microorganism interactions by influencing the structure and function of soil microbial communities. Model exudate solutions, based on organic acids (OAs) (quinic, lactic, maleic acids) and sugars (glucose, sucrose, fructose), previously identified in the rhizosphere of Pinus radiata, were applied to soil microcosms. Root exudate compound solutions stimulated soil dehydrogenase activity and the addition of OAs increased soil pH. The structure of active bacterial communities, based on reverse-transcribed 16S rRNA gene PCR, was assessed by denaturing gradient gel electrophoresis and PhyloChip microarrays. Bacterial taxon richness was greater in all treatments than that in control soil, with a wide range of taxa (88-1043) responding positively to exudate solutions and fewer (<24) responding negatively. OAs caused significantly greater increases than sugars in the detectable richness of the soil bacterial community and larger shifts of dominant taxa. The greater response of bacteria to OAs may be due to the higher amounts of added carbon, solubilization of soil organic matter or shifts in soil pH. Our results indicate that OAs play a significant role in shaping soil bacterial communities and this may therefore have a significant impact on plant growth.
authors.affiliation: Bio-Protection Research Centre, Lincoln University, Lincoln, Christchurch, New Zealand.
authors.forename: Shengjing
authors.initials: S
authors.lastname: Shi
authors.forename: Alan E
authors.initials: AE
authors.lastname: Richardson
authors.forename: Maureen
authors.initials: M
authors.lastname: O'Callaghan
authors.forename: Kristen M
authors.initials: KM
authors.lastname: DeAngelis
authors.forename: Eirian E
authors.initials: EE
authors.lastname: Jones
authors.forename: Alison
authors.initials: A
authors.lastname: Stewart
authors.forename: Mary K
authors.initials: MK
authors.lastname: Firestone
authors.forename: Leo M
authors.initials: LM
authors.lastname: Condron
mesh_terms: D001419:Bacteria / Q000145:classification / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism*; D004269:DNA, Bacterial / Q000235:genetics; D008969:Molecular Sequence Data; D009930:Organic Chemicals / Q000032:analysis / Q000378:metabolism; D010802:Phylogeny; D028223:Pinus / Q000737:chemistry / Q000378:metabolism / Q000382:microbiology; D053147:Plant Exudates / Q000032:analysis / Q000378:metabolism*; D018517:Plant Roots / Q000737:chemistry / Q000378:metabolism* / Q000382:microbiology*; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D058441:Rhizosphere; D012987:Soil / Q000032:analysis; D012988:Soil Microbiology
chemical_list: D004269:DNA, Bacterial; D009930:Organic Chemicals; D053147:Plant Exudates; D012336:RNA, Ribosomal, 16S; D012987:Soil