Urban wetlands, although often overlooked, are hotspots for CH ₄ cycling. However, the understanding of anaerobic CH ₄ oxidation and microbial responses to different electron acceptors in urban wetlands remains limited. Here, we employed DNA-stable isotope probing (SIP) and metagenomic techniques to identify the core CH ₄ -oxidizing microbial groups in the presence of NO ₃ ^- , SO ₄ ^2- , or ferrihydrite (Fe(III)) in anoxic urban-lake sediments. The addition of NO ₃ ^- to sediment microcosms promoted CH ₄ oxidation, whereas SO ₄ ^2- and Fe(III) had minimal or inhibitory effects on CH ₄ oxidation rates in anoxic microcosms. The SIP-identified methanotrophs in response to the addition of CH ₄ comprised the Marine Benthic Group D (MBG-D), “ Candidatus Methylomirabilis Sh765B-TzT-35 and Z114MB74,” and the putatively aerobic methanotrophs Methylobacter and Methylocystis . The presence of NO ₃ ^- further enriched Methylocaldum , Methylomonas , ‘ Ca . Methylomirabilis Sh765B-TzT-35 and Z114MB74’, Methylococcaceae , and Methylospira . In contrast, SO ₄ ^2- and Fe(III) amendments notably shifted the dominant methanotrophs through the significant labeling of Methylocystis . Furthermore, metagenomic analysis of ¹³ C-labeled DNA showed enrichment of genes for oxidation of CH ₄ and its intermediates, as well as the reduction of NO ₃ ^- , SO ₄ ^2- , Fe(III), and fermentation. These results underscore the activity of NO ₃ ^- -dependent CH ₄ -oxidizing microorganisms and highlight their potential metabolic versatility in highly anthropogenically influenced urban wetlands. IMPORTANCE: Urban wetlands are critical ecosystems for CH ₄ cycling but are increasingly impacted by complex pollutants from urban development, such as nitrates, sulfates, and Fe(III) from industrial runoff, atmospheric deposition, and wastewater discharge. This study reveals how these pollutants act as electron acceptors, modulating microbial metabolic pathways and reshaping methanotrophic communities under anoxic conditions. By uncovering the microbial mechanisms driving CH₄ oxidation in urban wetland sediments, our findings provide a deeper understanding of how anthropogenic pollution alters biogeochemical cycles. These insights are crucial for developing targeted strategies to mitigate CH₄ emissions and improve greenhouse gas control in rapidly urbanizing regions.

Females and males of dioecious plants have evolved sex-specific characteristics in terms of their morphological and physiological properties. However, the differentiation of phyllosphere microbiota in dioecious plants remains largely unexplored. Here, the diversity and composition of female and male Populus cathayana phyllosphere bacterial and fungal communities were investigated using 16S rRNA/ITS1 gene–based MiSeq sequencing. The divergences of bacterial and fungal community compositions occurred between females and males. Both females and males had their unique phyllosphere bacterial and fungal microbiota, such as bacterial Gemmata spp. (5.41%) and fungal Pringsheimia spp. (0.03%) in females and bacterial Chitinophaga spp. (0.009%) and fungal Phaeococcomyces spp. (0.02%) in males. Significant differences in the relative abundance of phyla Proteobacteria and Planctomycetes bacteria and phyla Ascomycota and Basidiomycota fungi (P < 0.05) were also found between females and males. Some bacterial species of genera Spirosoma and Amnibacterium and fungal genera Venturia, Suillus, and Elmerina spp. were significantly enriched in males (P < 0.05). In contrast, levels of fungal genera Phoma and Aureobasidium spp. were significantly higher in females than in males (P < 0.05). The mineral, inorganic, and organic nutrients content contributed differently to the divergence of female and male phyllosphere microbial communities, with 87.08 and 45.17% of the variations being explained for bacterial and fungal communities, respectively. These results highlight the sexual discrimination of phyllosphere microbes on the dioecious plants and provide hints on the potential host-associated species in phyllosphere environments. [ ] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY 4.0 International license .