Comparative study of I and II clade isolates: insights into their responses to environmental variables and soil fertilization types.

INTRODUCTION

Soil nitrous oxide (NO) emissions are a major contributor to global warming and climate change. Microbial NO reduction via the gene-classified into clade I and clade II-is the only known biological sink for NO.

METHODS

In this study, we isolated two NO-reducing bacterial strains: an sp. harboring clade I (I) and a sp. harboring clade II (II). We evaluated their performance under different environmental conditions and their effects on NO emissions from agricultural soils subjected to varying fertilization strategies.

RESULTS

Pure culture experiments revealed that growth and NO-reducing activity in both strains were significantly influenced by pH, oxygen concentration, nitrate levels, and carbon source. Notably, the II strain demonstrated broader environmental adaptability and higher NO-reduction efficiency across a range of conditions. In soil microcosm experiments, NO emissions were strongly affected by fertilization type, with mixed organic-inorganic treatments producing the highest emissions. Inoculation with the II strain significantly reduced NO emissions in soils receiving inorganic or combined fertilizers. In contrast, the I strain tended to increase emissions, except under the mixed fertilization regime.

DISCUSSION

These findings highlight the importance of selecting NO-reducing microbial strains based on their functional capacity and environmental tolerance. This work advances the development of targeted microbial strategies for mitigating NO emissions, supporting more sustainable and climate-resilient agricultural practices.