Do tree microbiomes clean up urban air pollution?

概述一氧化碳（CO）是大气中普遍存在的痕量气体，由自然过程产生。它也是燃烧过程产生的一种重要的人为空气污染物。作为一种有毒气体，它加剧了空气污染造成的过早死亡和发病的沉重负担。微生物在从大气中去除CO中起着至关重要的作用，并且先前已被鉴定为土壤微生物群落的丰富成员（Cordero等人，2019，King and Weber，2007）.令人惊讶的是，我们最近发现在树木的叶圈中也发现了CO降解细菌（Palmer等人，2021），它被定义为树木的地上部分，构成了巨大的微生物栖息地。我们发现，从两个常见的英国树种，山楂和冬青叶洗涤，有可能降解CO，表明CO降解微生物的存在。我们确定了广泛的多样性的候选CO-氧化细菌在叶际社区使用培养独立的微生物群落分析方法，使用16 S rRNA作为分类标记和编码一氧化碳脱氢酶大亚基（CODH，由coxL编码）的基因作为功能标记。环境叶际宏基因组的数据挖掘表明，含有CO氧化基因的细菌可以构成叶际微生物群落的25%。这些发现表明，具有降解CO潜力的叶际微生物群可以在全球CO循环中驱动一个重要的和以前未实现的汇（Palmer等人，2021年）。该项目将以这些发现为基础，旨在更广泛地降解包括树木和苔藓在内的地上栖息地中的微生物。您将评估这些栖息地中相关的CO降解细菌的丰度和活性，测试CO降解的潜力，并评估CO降解细菌是否在原位活跃。这将为地上栖息地中CO降解细菌的分布提供基本的新见解，并促进我们对CO地球化学循环的理解。它还可能为叶际微生物群如何影响空气质量，空气质量如何影响微生物活性的机制理解奠定基础，并可能为树种的明智选择提供基础，这些树种可以最大限度地提高微生物生态系统服务，以减轻城市地区的空气污染。

Overview Carbon monoxide (CO) is a ubiquitous trace gas in the atmosphere that is produced by natural processes. It is also a significant anthropogenic air pollutant produced by combustion processes. As a toxic gas, it contributes to the high burden of premature mortality and morbidity caused by air pollution. Microorganisms play a crucial role in the removal of CO from the atmosphere and have previously been identified as abundant members of soil microbial communities (Cordero et al., 2019, King and Weber, 2007). Surprisingly, we recently found that CO-degrading bacteria are also found in the phyllosphere of trees (Palmer et al., 2021), which is defined as the above ground parts of trees and constitutes a huge microbial habitat. We showed that leaf washings from two common UK tree species, hawthorn and holly, had the potential to degrade CO, indicating the presence of CO-degrading microorganisms. We identified a wide diversity of candidate CO-oxidising bacteria in the phyllosphere community using cultivation independent approaches of microbial community analysis using 16S rRNA as a taxonomic marker and the gene encoding the large subunit of the carbon monoxide dehydrogenase (CODH, encoded by coxL) as a functional marker. Data mining of environmental phyllosphere metagenomes suggests that the bacteria containing genes for CO oxidation could constitute up to 25% of the phyllosphere microbial community. These findings suggest that phyllosphere microbiota with the potential to degrade CO could drive a significant and previously unrealised sink in the global CO cycle (Palmer et al., 2021). This project will build on those findings and aim to characterise CO degrading microorganisms more widely in above ground habitats including trees and mosses. You will assess the abundance and activity of CO-degrading bacteria associated in these habitats, test the potential for CO degradation and assess whether CO-degrading bacteria are active in situ. This will provide fundamental new insights into the distribution of CO-degrading bacteria in above ground habitats and advance our understanding of the CO biogeochemical cycle. It may also lay the foundation for a mechanistic understanding of how phyllosphere microbiota may affect air quality, how air quality affects microbial activity, and it will potentially provide a basis for informed selection of tree species that could maximise microbial ecosystem services for mitigation of air pollution in urban areas.