Root mucilage from Pea and its utilization by rhizosphere bacteria as a sole carbon source

• Published in: Molecular plant-microbe interactions Vol. 14; no. 6; pp. 775 - 784
• Main Authors: KNEE, Emma M, GONG, Fang-Chen, GAO, Mensheng, TEPLITSKL, Max, JONES, Angela R, FOXWORTHY, Angel, MORT, Andrew J, BAUER, Wolfgang D
• Format: Journal Article
• Language: English
• Published: St Paul, MN APS Press 01.06.2001; The American Phytopathological Society
• Subjects: Agronomy. Soil science and plant productions; Amino Acids - chemistry; Amino Acids - metabolism; Animal, plant and microbial ecology; Biochemistry and biology; Biological and medical sciences; Burkholderia cepacia; Burkholderia cepacia - growth & development; Burkholderia cepacia - metabolism; Carbohydrate Metabolism; Carbohydrates - chemistry; Carbon - metabolism; Chemical, physicochemical, biochemical and biological properties; Flavonoids - pharmacology; Fundamental and applied biological sciences. Psychology; glycanase; Microbial ecology; Microbiology; naringenin; Physics, chemistry, biochemistry and biology of agricultural and forest soils; Pisum sativum - metabolism; Pisum sativum - microbiology; Plant Root Cap - chemistry; Plant Root Cap - metabolism; Plant Root Cap - microbiology; Proteoglycans - chemistry; Proteoglycans - metabolism; Pseudomonas fluorescens; Pseudomonas fluorescens - growth & development; Pseudomonas fluorescens - metabolism; Rhizobium leguminosarum; Rhizobium leguminosarum - growth & development; Rhizobium leguminosarum - metabolism; Soil; Soil science; Symbiosis; symbiotic plasmid; Pseudomonadales; Symbionte; Nutrition; Growth; Use; Pseudomonas fluorescens; Rhizobium leguminosarum; Grain legume; Rhizosphere; Leguminosae; Dicotyledones; Pisum sativum; Angiospermae; Bacteria; Pseudomonadaceae; Spermatophyta; Associated microflora; Rhizobiaceae; Mucilage; Polysaccharide
• ISSN: 0894-0282; 1943-7706
• DOI: 10.1094/mpmi.2001.14.6.775

Plant roots secrete a complex polysaccharide mucilage that may provide a significant source of carbon for microbes that colonize the rhizosphere. High molecular weight mucilage was separated by high-pressure liquid chromatography gel filtration from low molecular weight components of pea root exudate. Purified pea root mucilage generally was similar in sugar and glycosidic linkage composition to mucilage from cowpea, wheat, rice, and maize, but appeared to contain an unusually high amount of material that was similar to arabinogalactan protein. Purified pea mucilage was used as the sole carbon source for growth of several pea rhizosphere bacteria, including Rhizobium leguminosarum 8401 and 4292, Burkholderia cepacia AMMD, and Pseudomonas fluorescens PRA25. These species grew on mucilage to cell densities of three- to 25-fold higher than controls with no added carbon source, with cell densities of 1 to 15% of those obtained on an equal weight of glucose. Micromolar concentrations of nod gene-inducing flavonoids specifically stimulated mucilage-dependent growth of R. leguminosarum 8401 to levels almost equaling the glucose controls. R. leguminosarum 8401 was able to hydrolyze p-nitrophenyl glycosides of various sugars and partially utilize a number of purified plant polysaccharides as sole carbon sources, indicating that R. leguminosarum 8401 can make an unexpected variety of carbohydrases, in accordance with its ability to extensively utilize pea root mucilage.