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United States Department of Agriculture

Agricultural Research Service

Title: ISOLATION, IDENTIFICATION, AND CHARACTERIZATION OF SOIL AGGREGATING BACTERIA IN SOIL MICROAGGREGATES

Authors
item Caesar, Thecan
item Caesar, Anthony
item Sainju, Upendra

Submitted to: American Society of Agronomy Meetings
Publication Type: Abstract Only
Publication Acceptance Date: July 15, 2004
Publication Date: N/A

Interpretive Summary: A technique combining spiral plating and substrate utilization analysis (Biolog GN microplates) was developed to identify bacteria in microaggregates (less than 250 microns) from a no-till continuous barley cropping system. Bacteria were extracted in MgSO4 buffer in the presence of glass beads for 16 hours on a shaker at 150 rpm. They were diluted using spiral plating and the five most predominant bacterial isolates were picked from the most diluted portion of the spiral and purified. An aggregating test was performed using soil particles (less than 50 microns) amended with bacteria from the phylogenetic groups isolated from the microaggregates. Members of the genus Pantoea (P. diffusa and P. stewartii) and Serratia (S. marcescens) from the Enterobacteriaceae, and Pseudomonas (P. putida, P. fluorescens biotype F and P. aeruginosa) from the Pseudomonadeae were very efficient in aggregating and stabilizing soil particles. In contrast, the gram-positive non-sporing rods in the genus Kurthia and three Coryneform bacteria (genus Arthrobacter, Brevibacterium, and Microbacterium) did not aggregate soil. Fluorescently labeled lectins were used in combination with epifluorescence microscopy and confocal laser scanning microscopy to allow the visualization and characterization of carbohydrate-containing extracellular polymeric substances (EPS) produced by the soil aggregating bacteria.

Technical Abstract: A technique combining spiral plating and substrate utilization analysis (Biolog GN microplates) was developed to identify bacteria in microaggregates (less than 250 microns) from a no-till continuous barley cropping system. Bacteria were extracted in MgSO4 buffer in the presence of glass beads for 16 hours on a shaker at 150 rpm. They were diluted using spiral plating and the five most predominant bacterial isolates were picked from the most diluted portion of the spiral and purified. An aggregating test was performed using soil particles (less than 50 microns) amended with bacteria from the phylogenetic groups isolated from the microaggregates. Members of the genus Pantoea (P. diffusa and P. stewartii) and Serratia (S. marcescens) from the Enterobacteriaceae, and Pseudomonas (P. putida, P. fluorescens biotype F and P. aeruginosa) from the Pseudomonadeae were very efficient in aggregating and stabilizing soil particles. In contrast, the gram-positive non-sporing rods in the genus Kurthia and three Coryneform bacteria (genus Arthrobacter, Brevibacterium, and Microbacterium) did not aggregate soil. Fluorescently labeled lectins were used in combination with epifluorescence microscopy and confocal laser scanning microscopy to allow the visualization and characterization of carbohydrate-containing extracellular polymeric substances (EPS) produced by the soil aggregating bacteria.

Last Modified: 7/22/2014