Variation of Microbial Rhizosphere Communities in Response to Crop Species, Soil Origin, and Inoculation with Sinorhizobium meliloti L33

• Published in: Microbial ecology 2000-07, Vol.40 (1), p.43-56
• Main Authors: Miethling, R, Wieland, G, Backhaus, H, Tebbe, C.C
• Format: Article
• Language: English
• Subjects: Acid soils; Agricultural soils; Agrology; Agronomy. Soil science and plant productions; Alfalfa; Animal, plant and microbial ecology; bacteria; Biochemistry and biology; Biological and medical sciences; Chemical, physicochemical, biochemical and biological properties; community structure; crop rotation; denaturing gradient gel electrophoresis; Economic plant physiology; Fatty acids; Fundamental and applied biological sciences. Psychology; greenhouses; Medicago sativa; microbial communities; Microbial ecology; Microbiology; Physics, chemistry, biochemistry and biology of agricultural and forest soils; polymerase chain reaction; Rhizosphere; ribosomal RNA; roots; Rye; Secale cereale; Sinorhizobium meliloti; soil; Soil bacteria; Soil inoculation; Soil microorganisms; Soil science; Symbiosis (nodules, symbiotic nitrogen fixation, mycorrhiza...); Various environments (extraatmospheric space, air, water)
• ISSN: 0095-3628; 1432-184X
• DOI: 10.1007/s002480000021

A greenhouse study with soil–plant microcosms was conducted in order to compare the effect of crop species, soil origin, and a bacterial inoculant on the establishment of microbial communities colonizing plant roots. Two crop species, alfalfa (Medicago sativa) and rye (Secale cereale), were grown separately in two soils collected from agricultural fields at different locations and with differing histories of leguminous crop rotation. A subset of microcosms was inoculated at 10⁶ cfu g⁻¹ soil with the luciferase marker gene-tagged Sinorhizobium meliloti strain L33, a symbiotic partner of M. sativa. Microbial consortia were collected from the rhizospheres of alfalfa after 10 weeks of incubation and from rye after 11 weeks. S. meliloti L33 populations were one to two orders of magnitude higher in the rhizospheres of alfalfa than of rye. In soil with previous alfalfa cultivation, 80% of the alfalfa nodules were colonized by indigenous bacteria, while in the other soil alfalfa was colonized almost exclusively (>90%) with S. meliloti L33. Three community-level targeting approaches were used to characterize the variation of the extracted microbial rhizosphere consortia: (1) Community level physiological profiles (CLPP), (2) fatty acid methyl ester analysis (FAME), and (3) diversity of PCR amplified 16S rRNA target sequences from directly extracted ribosomes, determined by temperature gradient gel electrophoresis (TGGE). All approaches identified the crop species as the major determinant of microbial community characteristics. Consistently, the influence of soil was of minor importance, while a modification of the alfalfa-associated microbial community structure after inoculation with S. meliloti L33 was only consistently observed by using TGGE.