Efficient glyphosate removal from groundwater by biogenic manganese oxides produced by Pseudomonas sagittaria

Abstract

Glyphosate, a synthetic phosphonate compound, is the active principle of glyphosate-based herbicides (GBH). These herbicides are widely distributed in the environment of most of the economically productive lands which build on their production in glyphosate-resistant genetically modified crops. Previous studies about Argentine Pampas agroecosystem revealed the presence of glyphosate in different environmental samples including waters of agricultural basins and sediments of the large Paraná River. Here, with the aim to develop new biotechnological tools based on microorganisms to remediate glyphosate contaminated environments, sand filters with adhered bacterial isolates from this region were tested in their ability to remove glyphosate from groundwater. One of the bacterial strains tested was Ochrobactrum haematophilum SR, which has high efficiency to degrade glyphosate in bacterial cultures and the other, Pseudomonas sagittaria MOB-181, that oxidizes Mn(II) and is used to eliminate this metal from groundwater. The objective of this study was to analyze if previously isolated bacteria with ability to degrade glyphosate can bind to sand and if alone or along with Mn(II) oxidizing bacteria that have proven to remove metals can bioremediate glyphosate or even improve its removal. Our results showed that both bacteria alone were able to reduce the amount of glyphosate present in groundwater samples. In the case of P. sagittaria MOB-181, the effect was seen in the presence of manganese oxides, whereas in the absence of Mn(II), this bacterium did not diminish glyphosate concentration from groundwater. While O. haematophilum SR removed 58 % of 1.5 mM glyphosate after 14 days, P. sagittaria MOB-181 producing Mn oxides showed a greater efficiency, decreasing 65 % of glyphosate at the same period of time. The combined strategy using P. sagittaria MOB-181 in the presence of Mn(II) and O. haematophilum SR did not improve the removal values obtained for the first one. Thus, we provide novel alternatives applicable for the development of glyphosate removal tools.