Nitrifying bacteria and archaea withstanding glyphosate in fertilized soil microcosms

ALLEGRINI, MARCO; GOMEZ, ELENA V; ZABALOY, MARÍA CELINA; SCHUSTER, KONRAD; TEBBE, DENNIS

APPLIED SOIL ECOLOGY

ELSEVIER SCIENCE BV

Año: 2017 vol. 117 p. 88 - 95

0929-1393

The use of glyphosate has been continually increasing world-wide. Microbes involved in the soil nitrogen cycle, particularly the ammonia-oxidizing bacteria and archaea (AOB, AOA) that perform the rate-limiting step in nitrification, i.e. the oxidation of ammonia to nitrite, are recognized to be sensitive to pesticide application. However, knowledge about the effects of glyphosate on these microorganisms is limited, and no reports exist about the impacts of simultaneous application of this herbicide and N fertilization, particularly with culture-independent approaches. The aim of this study was to assess the non-target effect of glyphosate on overall microbial activity and nitrification activity, as well as the dynamics of nitrifying populations, in a soil with the addition of N fertilizer. Microcosms were prepared with the amendments: Fertilizer [(NH4)2PO4, 335 mg kg-1 soil], Glyphosate+Fertilizer [G+F, 150 mg kg-1 soil plus dose ofF], or Control [CT, water]. Triplicate microcosms were destructively sampled over 1 month and analyzed for nitrate production (N−NO3). Soil DNA was extracted and copies of 16S rRNA and bacterial and archaeal amoA genes were measured by quantitative PCR, while AOB community structure was analyzed by denaturant gradient gel electrophoresis (DGGE). Results showed a significant interaction (P