Wednesday, November 7, 2007
292-3
Biochemical, Microbiological and Molecular Characterization of Microbial Community in Rhizosphere Soil Under Long-Term Management.
Maddalena Curci1, Patrizia Ricciuti1, Carmine Crecchio1, Elena Armenise2, and Pacifico Ruggiero1. (1) Dipartimento di Biologia e Chimica Agro-forestale ed Ambientale, University of Bari, Via Amendola 165/A, Bari, I 70126, Italy, (2) Dipartimento di Scienze delle Produzioni Vegetali - University of Bari, Via Amendola 165/A, Bari, I 70126, Italy
Although it has been demonstrated that rhizosphere microbial community composition is influenced by variations in exudates caused by plant species, soil type, cropping systems and fertilization, there are, so far, few evidences whether and to what extent long-term soil management determines changes on microbial community structure and activity.
The aim of the present study was to explore the long-term effects (35 years) of different management practices on both activity and composition of rhizosphere microbial communities using a combination of biochemical, physiological and molecular techniques.
The experimental design (split-split plot) was set up in 1972 on a silty-clay soil experimental field situated in Southern Italy. Three crop rotations (a three-year crop rotation: sugar beet, wheat + catch crop, wheat; a one-year crop rotation: wheat + catch crop; wheat monoculture), two crop residue managements (burning and incorporation), and a fertilization plan (NPK fertilization or no fertilization) were compared.
Rhizosphere microbial biomass C and N, total culturable bacteria, cellulosolytics, fungi and actinomycetes, and enzymes related to the C, N, P S were determined. Analysis of variance was applied to determine their correlation with the long-term practices investigated.
Total DNA and RNA were extracted from rhizospheric soil samples through a direct method and the extracted RNA was retro-transcripted. DNA and c-DNA were amplified with two different set of primers targeting a 500 bp region of the eubacterial 16S and a 390 bp region of fungal 18S r-DNA. Fingerprints were compared by denaturing gradient gel electrophoresis. Microbial diversity was valuated by determining similarity value coefficients and clustering of electrophoretic profiles.
Microbial community metabolic profiles were evaluated inoculating extracted microbial populations in plates containing 31 different carbon sources. Functional diversity of microbial communities was evaluated by calculating Shannon’s substrate diversity index (H’), substrate richness (S) and substrate evenness (E) and cluster analysis.
The long-term managements induced significant changes in some parameters related to composition and activity of rhizosphere microbial communities. Biomass C and N detected variations induced by crop rotation, crop residue management and mineral fertilization plan, while almost all enzymes investigated changed their activities in response to the fertilization plan only. As expected, counting of cultivable microorganisms was basically not affected by all the agricultural managements. Molecular and functional diversity of microbial communities were affected by crop rotation more than by residue management and mineral fertilization.
The aim of the present study was to explore the long-term effects (35 years) of different management practices on both activity and composition of rhizosphere microbial communities using a combination of biochemical, physiological and molecular techniques.
The experimental design (split-split plot) was set up in 1972 on a silty-clay soil experimental field situated in Southern Italy. Three crop rotations (a three-year crop rotation: sugar beet, wheat + catch crop, wheat; a one-year crop rotation: wheat + catch crop; wheat monoculture), two crop residue managements (burning and incorporation), and a fertilization plan (NPK fertilization or no fertilization) were compared.
Rhizosphere microbial biomass C and N, total culturable bacteria, cellulosolytics, fungi and actinomycetes, and enzymes related to the C, N, P S were determined. Analysis of variance was applied to determine their correlation with the long-term practices investigated.
Total DNA and RNA were extracted from rhizospheric soil samples through a direct method and the extracted RNA was retro-transcripted. DNA and c-DNA were amplified with two different set of primers targeting a 500 bp region of the eubacterial 16S and a 390 bp region of fungal 18S r-DNA. Fingerprints were compared by denaturing gradient gel electrophoresis. Microbial diversity was valuated by determining similarity value coefficients and clustering of electrophoretic profiles.
Microbial community metabolic profiles were evaluated inoculating extracted microbial populations in plates containing 31 different carbon sources. Functional diversity of microbial communities was evaluated by calculating Shannon’s substrate diversity index (H’), substrate richness (S) and substrate evenness (E) and cluster analysis.
The long-term managements induced significant changes in some parameters related to composition and activity of rhizosphere microbial communities. Biomass C and N detected variations induced by crop rotation, crop residue management and mineral fertilization plan, while almost all enzymes investigated changed their activities in response to the fertilization plan only. As expected, counting of cultivable microorganisms was basically not affected by all the agricultural managements. Molecular and functional diversity of microbial communities were affected by crop rotation more than by residue management and mineral fertilization.