Isolation and characterization of a glyphosate-degrading rhizosphere strain, Enterobacter cloacae K7

Abstract

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.

ISOLATION AND CHARACTERIZATION OF A MOLYBDENUM-REDUCING AND GLYPHOSATE-DEGRADING Klebsiella oxytoca STRAIN SAW-5 IN SOILS FROM SARAWAK

“…None of the pesticides could support molybdenum reduction, however, the bacterium could grow on glyphosate (Figure 2d). Numerous glyphosatedegrading bacteria has been isolated and include Enterobacter cloacae (Kryuchkova et al, 2014), Ochrobactrum spp. (Hadi et al, 2013), Pseudomonas fluorescens (Zboinska et al, 1992), Agrobacterium radiobacter (McAuliffe et al, 1990), Pseudomonas sp.…”

“…Removal of glyphosate from soils is best carried out by bioremediation often employing glyphosate-degrading bacteria as the low con-centration of glyphosate in polluted soils make other form of remediation such as chemical and physical more expensive and unpractical. Examples of glyphosate-degrading bacterium reported include Enterobacter cloacae (Kryuchkova et al, 2014), Ochrobactrum spp. (Hadi et al, 2013), Pseudomonas fluorescens (Zboinska et al, 1992).…”

Assessment of the resistance of four nitrogen-fixing Bacteria to glyphosate

“…Whereas, numerous studies have shown microorganisms can degrade that glyphosate. Several potential glyphosate degrading microorganisms have been isolated from organophosphates contaminated soils such as Enterobacter cloacae (Kryuchkova et al, 2014), Geobacillus caldoxylosilyticus (Obojska et al, 2002), Pseudomonas spp. (Dick and Quinn, 1995), Rhizobium sp.…”

Glyphosate biodegradation and potential soil bioremediation by Bacillus subtilis strain Bs-15

“…Bacteria are perhaps the most versatile and diversified organisms with regard to their nutritional requirements (Leckie, 2005). The development of an affordable and environmentally friendly bioremediation method using glyphosate-degrading bacteria is a promising approach for cleansing and restoring soils contaminated with this herbicide (Kryuchkova et al, 2014).…”

“…Although plant growth promotion rhizobacteria are commonly used to promote plant growth and control plant diseases, their potential use in bioremediation has also been explored (Narasimhan et al, 2003;Huang et al, 2005). Several studies have been conducted to isolate pure bacterial strains with degrading capability for potential uses such as the removal of glyphosate from soil and bioremediation of glyphosate-contaminated soils (Ermakova et al, 2008;Ahire et al, 2012;Kryuchkova et al, 2014).…”