Impact of co-introduction of soluble potassium and nitrogen on methanotrophs

• Potassium (K) promotes the abundance of Type I methanotroph Methylomonas . • The abundance of Methylocaldum is related to the transformation of NO 3 – -N. • K and NO 3 – -N promote Type I methanotroph diversity. • K-N intake could increase community diversity and cause methanotrophs to exhibit a clustering effect. • K may stimulate adenosine synthesis to energize the sMMO in Methylomonas . Aerobic methane (CH 4 ) oxidation in paddy fields is a critical process for mitigating fugitive CH 4 emissions. Potassium (K) fertilizer is commonly used to increase crop yields and quality in paddy fields, often in combination with nitrogen (N) fertilizer. However, the impact of the significant input of K and N on methanotrophs is unclear. This study employed zeolite-adsorbed K and N to examine their influence on methanotrophic activity. Control groups with non-adsorbed (R) and experimental groups with K alone (K0), and combined with nitrate (NO 3 – -N) (K1) or ammonium (NH 4 + -N) (K2) were established. Incubations were conducted over six cycles with a 15 % volume ratio of CH 4 and oxygen. Results showed that both K and NO 3 – -N enhanced the abundance of Type I methanotrophs, with K particularly increasing the abundance of Methylomonas and NO 3 – -N primarily promoting the growth of Methylocaldum . Metabolomic analysis indicates K inhibits the synthesis of bioactive and reductive phenols, ketones, sesquiterpenoids, and unsaturated fatty acids. This effect was suggesting that K more readily entering the periplasmic space to stimulate adenosine synthesis, thereby energizing the soluble methane monooxygenase (sMMO) enzyme unique to Methylomonas . N contributes to energy metabolism by integrating into nitrogenous precursors, supporting community vitality. This study provides insights into the adaptation of methanotrophs in ecological niche differentiation and the co-introduction of K and N fertilizer management strategies to alleviate CH 4 emissions.