Plants and phytoplankton are natural sources of the volatile organic compounds (VOCs) acetone and isoprene, which are reactive and can alter atmospheric chemistry. In earlier research we reported that, when co-cultured with a diatom, the marine bacterium Pelagibacter (strain HTCC1062; ‘SAR11 clade’) reduced the concentration of compounds tentatively identified as acetone and isoprene. In this study, experiments with Pelagibacter monocultures confirmed that these cells are capable of metabolizing acetone and isoprene at rates similar to bacterial communities in seawater and high enough to consume substantial fractions of the total marine acetone and isoprene budgets if extrapolated to global SAR11 populations. Homologues of an acetone/cyclohexanone monooxygenase were identified in the HTCC1062 genome and in the genomes of a wide variety of other abundant marine taxa, and were expressed at substantial levels (c. 10⁻⁴ of transcripts) across TARA oceans metatranscriptomes from ocean surface samples. The HTCC1062 genome lacks the canonical isoprene degradation pathway, suggesting an unknown alternative biochemical pathway is used by these cells for isoprene uptake. Fosmidomycin, an inhibitor of bacterial isoprenoid biosynthesis, blocked HTCC1062 growth, but the cells were rescued when isoprene was added to the culture, indicating SAR11 cells may be capable of synthesizing isoprenoid compounds from exogenous isoprene.

中文翻译：

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海洋异养细菌 Pelagibacter HTCC1062 (SAR11) 对主要大气挥发性有机化合物的代谢

植物和浮游植物是挥发性有机化合物 (VOC) 丙酮和异戊二烯的天然来源，它们具有反应性，可以改变大气化学。在早期的研究中，我们报告说，当与硅藻共培养时，海洋细菌Pelagibacter（菌株 HTCC1062；'SAR11 clade'）降低了初步鉴定为丙酮和异戊二烯的化合物的浓度。在这项研究中，用Pelagibacter进行的实验单一培养证实，这些细胞能够以与海水中的细菌群落相似的速率代谢丙酮和异戊二烯，并且如果外推到全球 SAR11 种群，则足以消耗总海洋丙酮和异戊二烯预算的很大一部分。丙酮/环己酮单加氧酶的同源物在 HTCC1062 基因组和多种其他丰富的海洋类群的基因组中被鉴定，并在相当大的水平上表达 ( c . 10 ^-4来自海洋表面样本的 TARA 海洋元转录组。HTCC1062 基因组缺乏典型的异戊二烯降解途径，表明这些细胞使用未知的替代生化途径来摄取异戊二烯。Fosmidomycin 是一种细菌类异戊二烯生物合成的抑制剂，可阻断 HTCC1062 的生长，但在将异戊二烯添加到培养物中时细胞得以拯救，这表明 SAR11 细胞可能能够从外源性异戊二烯合成类异戊二烯化合物。