Differential response of N 2 O emissions, N 2 O-producing and N 2 O-reducing bacteria to varying tetracycline doses in fertilized soil.

Tetracyclines are the most widely used antibiotics worldwide. Their presence in soils could affect nutrient cycling, but our knowledge regarding how they affect soil microbial communities involved in greenhouse gas emissions is limited. The objective of the current study was to evaluate how tetracycline is affecting NO emissions and the abundance of denitrifiers in fertilized soil. For this purpose, soil mesocosms were treated with only NHNO (100 mg/kg) or NHNO (100 mg/kg) plus three different doses of tetracycline (0.1, 0.5 and 2 mg/kg). Soils that did not receive tetracycline or NHNO were used as controls. Nitrous oxide fluxes were monitored daily for 16 days. The total bacterial (16S rRNA), the abundance of NO-reducing and -producing bacteria were quantified by qPCR at the end of the experiment. The application of NHNO caused a significant increase of NO emissions and AOB abundance but did not affect the abundance of denitrifiers and AOA compared to control soils. Different doses of tetracycline in fertilized soils did not mitigate these NO emissions; instead, higher cumulative emissions were noticed in soils treated with the lowest dose. In these soils the total bacterial abundance was higher compared to soils received higher tetracycline concentration. The abundances of the NO-producing and NO-reducing communities were also differently affected by the addition of tetracycline, which was dose-dependent. Higher doses of tetracycline favored NO-reducers within the total bacterial community, which could be important for mitigating NO emissions in the long term.