Isoprene accounts for about half of total biogenic volatile organic compound emissions globally, and as a climate active gas it plays a significant and varied role in atmospheric chemistry. Terrestrial plants are the largest source of isoprene, with willow (Salix) making up one of the most active groups of isoprene producing trees. Bacteria act as a biological sink for isoprene and those bacteria associated with high isoprene-emitting trees may provide further insight into its biodegradation. A DNA-SIP experiment incubating willow (Salix fragilis) leaves with 13C-labelled isoprene revealed an abundance of Comamonadaceae, Methylobacterium, Mycobacterium and Polaromonas in the isoprene degrading community when analysed by 16S rRNA gene amplicon sequencing. Metagenomic analysis of 13C-enriched samples confirmed the abundance of Comamonadaceae, Acidovorax, Polaromonas, Variovorax and Ramlibacter. Mycobacterium and Methylobacterium were also identified after metagenomic analysis and a Mycobacterium metagenome-assembled genome (MAG) was recovered. This contained two complete isoprene degradation metabolic gene clusters, along with a propane monooxygenase gene cluster. Analysis of the abundance of the alpha subunit of the isoprene monooxygenase, isoA, in unenriched DNA samples revealed that isoprene degraders associated with willow leaves are abundant, making up nearly 0.2% of the natural bacterial community. Analysis of the isoprene degrading community associated with willow leaves using DNA-SIP and focused metagenomics techniques enabled recovery of the genome of an active isoprene-degrading Mycobacterium species and provided valuable insight into bacteria involved in degradation of isoprene on the leaves of a key species of isoprene-emitting tree in the northern hemisphere.

中文翻译：

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与脆弱柳叶缘相关的异戊二烯降解细菌，这是北半球高异戊二烯排放的柳树

异戊二烯约占全球生物源挥发性有机化合物排放总量的一半，作为一种气候活跃的气体，它在大气化学中发挥着重要而多样的作用。陆生植物是异戊二烯的最大来源，柳树（Salix）是最活跃的异戊二烯生产树群之一。细菌充当异戊二烯的生物汇，那些与高异戊二烯排放树相关的细菌可以进一步了解其生物降解。通过 16S rRNA 基因扩增子测序分析，将柳树 (Salix fragilis) 叶与 13C 标记的异戊二烯一起孵育的 DNA-SIP 实验显示，异戊二烯降解群落中存在大量的毛单胞菌科、甲基杆菌、分枝杆菌和极性单胞菌。富含 13C 的样本的宏基因组分析证实了 Comamonadaceae，嗜酸菌属、极化单胞菌属、Variovorax 属和 Ramlibacter。宏基因组分析后还鉴定了分枝杆菌和甲基杆菌，并回收了分枝杆菌宏基因组组装基因组 (MAG)。这包含两个完整的异戊二烯降解代谢基因簇，以及一个丙烷单加氧酶基因簇。对未富集 DNA 样品中异戊二烯单加氧酶 isoA α 亚基的丰度分析表明，与柳叶相关的异戊二烯降解物含量丰富，占天然细菌群落的近 0.2%。