Carbon monoxide (CO) is both a ubiquitous atmospheric trace gas and an air pollutant. While aerobic CO-degrading microorganisms in soils and oceans are estimated to remove ~370 Tg of CO per year, the presence of CO-degrading microorganisms in above-ground habitats, such as the phyllosphere, and their potential role in CO cycling remains unknown. CO-degradation by leaf washes of two common British trees, Ilex aquifolium and Crataegus monogyna, demonstrated CO uptake in all samples investigated. Based on the analyses of taxonomic and functional genes, diverse communities of candidate CO-oxidizing taxa were identified, including members of Rhizobiales and Burkholderiales which were abundant in the phyllosphere at the time of sampling. Based on predicted genomes of phyllosphere community members, an estimated 21% of phyllosphere bacteria contained CoxL, the large subunit of CO-dehydrogenase. In support of this, data mining of publicly available phyllosphere metagenomes for genes encoding CO-dehydrogenase subunits demonstrated that, on average, 25% of phyllosphere bacteria contained CO-dehydrogenase gene homologues. A CO-oxidizing Phyllobacteriaceae strain was also isolated from phyllosphere samples which contains genes encoding both CO-dehydrogenase as well as a ribulose-1,5-bisphosphate carboxylase-oxygenase. These results suggest that the phyllosphere supports diverse and potentially abundant CO-oxidizing bacteria, which are a potential sink for atmospheric CO.

中文翻译：

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树的叶球是多种 CO 氧化细菌的栖息地

一氧化碳 (CO) 既是一种普遍存在的大气痕量气体，又是一种空气污染物。虽然土壤和海洋中的好氧 CO 降解微生物估计每年可去除约 370 Tg 的 CO，但在地上栖息地（如植物圈）中存在 CO 降解微生物及其在 CO 循环中的潜在作用仍然未知。两种常见英国树木、冬青和单核山楂的叶片冲洗对 CO 的降解，证明了所有研究样品中的 CO 吸收。基于对分类学和功能基因的分析，确定了候选 CO 氧化类群的不同群落，包括采样时叶际中丰富的根瘤菌目和伯克霍尔德菌目成员。根据预测的叶际群落成员基因组，估计 21% 的叶际细菌含有 CoxL，即 CO-脱氢酶的大亚基。为了支持这一点，对编码 CO-脱氢酶亚基的基因公开可用的叶际宏基因组的数据挖掘表明，平均 25% 的叶际细菌含有 CO-脱氢酶基因同源物。还从包含编码 CO-脱氢酶和核酮糖-1 的基因的叶际样品中分离出一种 CO-氧化性叶杆菌科菌株，5-二磷酸羧化酶-加氧酶。这些结果表明，植物圈支持多种可能丰富的 CO 氧化细菌，它们是大气 CO 的潜在汇。