Dynamic succession patterns and interactions of phyllospheric microorganisms during NO exposure.

The phyllosphere plays a role in alleviating air pollution, potentially leveraging the native microorganisms for further enhancement. It remains unclear how phyllospheric microorganisms respond to nitrogen oxide (NO) pollution and participate in abatement. Here, we exposed Schefflera octophylla to NO to reveal microbial succession patterns and interactions in the phyllosphere. During exposure, phyllospheric ammonium (NH-N) significantly increased, with different alpha diversity changes between bacteria and fungi. Community successions enclosed core taxa with relatively excellent tolerance, represented by bacterial genera (Norcardiodes, Aeromicrobium) and fungal genera (Talaromyces, Acremonium). The exposure eliminated specific pathogens (e.g., Zymoseptoria) and benefitted plant growth-promoting populations (e.g., Talaromyces, Exiguobacterium), which might favor plant disease control, improve plant health and thus buffer NO pollution. Cooccurrence networks revealed more negative correlations among bacteria and closer linkages among fungi during exposure. Our results also showed a functional shift from the predominance of pathotrophs to saprotrophs. Our study identified microbial successions and interactions during NO pollution and thus enlightened prospective taxa and potential roles of phyllospheric microorganisms in NO remediation.