Do tree microbiomes clean up urban air pollution?

一氧化碳（CO）是大气中普遍存在的微量气体，是由自然过程产生的。它也是燃烧过程中产生的一种重要的人为空气污染物。作为一种有毒气体，它造成了空气污染引起的过早死亡和发病率的沉重负担。微生物在从大气中去除CO中起着至关重要的作用，并且以前被确定为土壤微生物群落的丰富成员（Cordero等人，2019；King和Weber， 2007）。令人惊讶的是，我们最近发现，co降解细菌也存在于树木的层层圈中（Palmer et al., 2021），层层圈被定义为树木的地上部分，构成了一个巨大的微生物栖息地。我们发现，两种常见的英国树种山楂和冬青的叶片洗涤物具有降解CO的潜力，表明CO降解微生物的存在。我们使用培养独立的微生物群落分析方法，以16S rRNA作为分类标记，编码一氧化碳脱氢酶（CODH，由coxL编码）大亚基的基因作为功能标记，在层球群落中发现了广泛的候选co氧化细菌。环境层际元基因组的数据挖掘表明，含有CO氧化基因的细菌可能占层际微生物群落的25%。这些发现表明，具有降解CO潜力的层圈微生物群可以推动全球CO循环中一个重要的、以前未实现的汇（Palmer et al., 2021）。该项目将以这些发现为基础，旨在更广泛地描述包括树木和苔藓在内的地上栖息地的CO降解微生物。您将评估与这些栖息地相关的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CO降解细菌在地上栖息地的分布提供新的见解，并促进我们对CO生物地球化学循环的理解。它还可能为从机制上理解层圈微生物群如何影响空气质量、空气质量如何影响微生物活动奠定基础，并可能为知情选择树种提供基础，从而最大限度地发挥微生物生态系统服务，缓解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.