ERP143698 PRJEB58631 dcba2efb-b8e5-49db-ac74-57fea5dad2db Inhibition of Nitrous Oxide Reduction in Forest Soil Microcosms by Different Forms of Methanobactin Copper plays a critical role in controlling greenhouse gas emissions as it is a key component of both the particulate methane monooxygenase and nitrous oxide reductase. To collect copper, several alphaproteobacterial methanotrophs produce and excrete a small modified peptide (< 1,300 Da) - methanobactin (MB) – that has an extremely high affinity for copper. As MB is secreted by methanotrophs for copper collection, it is possible that such activity may limit the ability of microbes (e.g., denitrifiers) to take up copper, thereby decreasing their activity, as well as also affecting overall microbial community composition. Here we show that different forms of MB - one from Methylosinus trichosporium OB3b (MB-OB3b) and another from Methylocystis sp. strain SB2 (MB-SB2) affected nitrous oxide (N2O) accumulation as well caused significant shifts in microbial community composition in three different sets of forest soil microcosms. Such effects, however, were mediated by the amount of copper in the soils, with microcosms constructed from soils with the lowest amount of copper showing the strongest response to the presence of either form of MB. In addition, the presence of MB-SB2 had a stronger effect, likely due to its higher affinity for copper. Finally, it was also found that the presence of either form of MB affected the accumulation of nitrite in all three forest soils, and that the addition of MB affected the presence of genes encoding for either a copper-dependent nitrite reductase (nirK) vs. an iron-containing form (nirS). These data indicate the methanotrophic-mediated production of strong copper chelating agents can significantly impact not only methane consumption, but also multiple steps of the denitrification arm of the nitrogen cycle as well as have broad effects on microbial community composition of forest soils. undefined Copper plays a critical role in controlling greenhouse gas emissions as it is a key component of both the particulate methane monooxygenase and nitrous oxide reductase. To collect copper, several alphaproteobacterial methanotrophs produce and excrete a small modified peptide (< 1,300 Da) - methanobactin (MB) – that has an extremely high affinity for copper. As MB is secreted by methanotrophs for copper collection, it is possible that such activity may limit the ability of microbes (e.g., denitrifiers) to take up copper, thereby decreasing their activity, as well as also affecting overall microbial community composition. Here we show that different forms of MB - one from Methylosinus trichosporium OB3b (MB-OB3b) and another from Methylocystis sp. strain SB2 (MB-SB2) affected nitrous oxide (N2O) accumulation as well caused significant shifts in microbial community composition in three different sets of forest soil microcosms. Such effects, however, were mediated by the amount of copper in the soils, with microcosms constructed from soils with the lowest amount of copper showing the strongest response to the presence of either form of MB. In addition, the presence of MB-SB2 had a stronger effect, likely due to its higher affinity for copper. Finally, it was also found that the presence of either form of MB affected the accumulation of nitrite in all three forest soils, and that the addition of MB affected the presence of genes encoding for either a copper-dependent nitrite reductase (nirK) vs. an iron-containing form (nirS). These data indicate the methanotrophic-mediated production of strong copper chelating agents can significantly impact not only methane consumption, but also multiple steps of the denitrification arm of the nitrogen cycle as well as have broad effects on microbial community composition of forest soils. ENA-FIRST-PUBLIC 2022-12-22 ENA-LAST-UPDATE 2023-01-03