Institute of Biochemistry and Physiology of Plants and Microorganisms, Russian Academy of Sciences (IBPPM RAS), 13 Prospekt Entuziastov, Saratov 410049, Russia.
Microbiol Res. 2014 Jan 20;169(1):99-105. doi: 10.1016/j.micres.2013.03.002. Epub 2013 Mar 30.
Plant-growth-promoting rhizobacteria exert beneficial effects on plants through their capacity for nitrogen fixation, phytohormone production, phosphate solubilization, and improvement of the water and mineral status of plants. We suggested that these bacteria may also have the potential to express degradative activity toward glyphosate, a commonly used organophosphorus herbicide. In this study, 10 strains resistant to a 10 mM concentration of glyphosate were isolated from the rhizoplane of various plants. Five of these strains--Alcaligenes sp. K1, Comamonas sp. K4, Azomonas sp. K5, Pseudomonas sp. K3, and Enterobacter cloacae K7--possessed a number of associative traits, including fixation of atmospheric nitrogen, solubilization of phosphates, and synthesis of the phytohormone indole-3-acetic acid. One strain, E. cloacae K7, could utilize glyphosate as a source of P. Gas-liquid chromatography showed that E. cloacae growth correlated with a decline in herbicide content in the culture medium (40% of the initial 5mM content), with no glyphosate accumulating inside the cells. Thin-layer chromatography analysis of the intermediate metabolites of glyphosate degradation found that E. cloacae K7 had a C-P lyase activity and degraded glyphosate to give sarcosine, which was then oxidized to glycine. In addition, strain K7 colonized the roots of common sunflower (Helianthus annuus L.) and sugar sorghum (Sorghum saccharatum Pers.), promoting the growth and development of sunflower seedlings. Our findings extend current knowledge of glyphosate-degrading rhizosphere bacteria and may be useful for developing a biotechnology for the cleanup and restoration of glyphosate-polluted soils.
植物促生根际细菌通过固氮、产生植物激素、溶解磷酸盐以及改善植物的水分和矿物质状况对植物产生有益影响。我们认为，这些细菌也可能具有表达对草甘膦（一种常用的有机磷除草剂）降解活性的潜力。在这项研究中，从各种植物的根际分离出 10 株对 10mM 浓度草甘膦具有抗性的菌株。其中 5 株，即 Alcaligenes sp. K1、Comamonas sp. K4、Azomonas sp. K5、Pseudomonas sp. K3 和 Enterobacter cloacae K7，具有一些共生特征，包括固定大气氮、溶解磷酸盐和合成植物激素吲哚-3-乙酸。其中一株，E. cloacae K7，可以利用草甘膦作为磷源。气液色谱显示，E. cloacae 的生长与培养基中除草剂含量的下降相关（初始 5mM 含量的 40%），细胞内没有草甘膦积累。草甘膦降解中间代谢产物的薄层层析分析发现，E. cloacae K7 具有 C-P 裂合酶活性，并将草甘膦降解为肌氨酸，然后将肌氨酸氧化为甘氨酸。此外，菌株 K7 定殖于普通向日葵（Helianthus annuus L.）和糖高粱（Sorghum saccharatum Pers.）的根际，促进了向日葵幼苗的生长和发育。我们的发现扩展了对草甘膦降解根际细菌的现有认识，可能有助于开发用于清理和修复草甘膦污染土壤的生物技术。
