Is nitrate reduction to nitrite possible in glucose-amended alkaline saline soil under aerobic conditions?

A phylogenetic analysis of the archaeal community in the soil of the former Lake Texcoco showed that some of the clones identified were affiliated to Archeae that reduce nitrate (NO3−) to nitrite (NO2−) and NO2− to unknown products under aerobic conditions. Previous research suggested that this indeed might occur when an easily decomposable C-substrate is available, but little is known about the factors that control the possible processes involved. The sandy clay loam soil with pH 10 and electrolytic conductivity 56 dS m−1 was spiked with 1000 mg glucose-C kg−1 soil (GLUCOSE pre-treatment), 200 mg NO3−-N kg−1 soil (NITRATE pre-treatment), or left unamended (CONTROL pre-treatment) and conditioned for eight days. Pre-treated soil was then added with 1000 mg glucose-C kg−1 soil and 200 mg NO3−-N kg−1 soil and amended with ammonium (NH4+) (AMM treatment) and l-glutamine (GLUT treatment), acetylene (C2H2) (ACE treatment), oxygen (O2) (OXI treatment), left untreated (CON treatment) or sterilized. No abiotic factors affected concentrations of NH4+, NO2− or NO3−. In the CONTROL pre-treatment, concentration of NO3− decreased 170 mg N kg−1 soil within 72 h, in the GLUCOSE pre-treatment with 182 mg N kg−1 soil within 2 h and in the NITRATE pre-treatment with 272 mg N kg−1 soil within 168 h. Mean concentration of NO2− was 3.2 mg N kg−1 soil in unamended soil, 5.7 mg N kg−1 soil in the CONTROL pre-treatment, but >20 mg kg−1 soil in the GLUCOSE pre-treatment and ≥40 mg kg−1 in the NITRATE pre-treatment. The application of NO3− and glucose increased the mean concentration of NH4+ compared to the unamended soil independently of pre-treatment. It was found that microorganisms in the alkaline saline soil of the former Lake Texcoco can reduce concentrations of NO3− while releasing NO2− under aerobic conditions when an easy decomposable substrate is available without it being directly related to microbial activity and this being more outspoken when glucose or nitrate were previously added.