Alkane constitutes major fractions of crude oils, and its microbial aerobic degradation dominantly follows the terminal oxidation and the sub-terminal pathways. However, the latter one received much less attention, especially since the related genes were yet to be fully defined. Here, we isolated a bacterium designated Acinetobacter sp. strain NyZ410, capable of growing on alkanes with a range of chain lengths and derived sub-terminal oxidation products. From its genome, a secondary alcohol degradation gene cluster (sad) was identified to be likely involved in converting the aliphatic secondary alcohols (the sub-terminal oxidation products of alkanes) to the corresponding primary alcohols by removing two-carbon unit. On this cluster, sadC encoded an alcohol dehydrogenase converting the aliphatic secondary alcohols to the corresponding ketones; sadD encoded a Baeyer–Villiger monooxygenase catalysing the conversion of the aliphatic ketones to the corresponding esters; SadA and SadB are two esterases hydrolyzing aliphatic esters to the primary alcohols and acetic acids. Bioinformatics analyses indicated that the sad cluster was widely distributed in the genomes of probable alkane degraders, apparently coexisting (64%) with the signature enzymes AlkM and AlmA for alkane terminal oxidation in 350 bacterial genomes. It suggests that the alkane sub-terminal oxidation may be more ubiquitous than previously thought.

中文翻译：

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烷烃利用者中末端氧化的悲伤基因簇的广泛分布

烷烃构成原油的主要馏分，其微生物有氧降解主要遵循末端氧化和次末端途径。然而，后者受到的关注要少得多，特别是因为相关基因尚未完全确定。在这里，我们分离出一种名为不动杆菌属的细菌。菌株 NyZ410，能够在具有一系列链长和衍生的亚末端氧化产物的烷烃上生长。从它的基因组来看，一个二级酒精降解基因簇（ sad) 被确定可能参与通过去除双碳单元将脂肪族仲醇（烷烃的次末端氧化产物）转化为相应的伯醇。在这个簇上，sadC编码了一种醇脱氢酶，可将脂肪族仲醇转化为相应的酮；sadD编码 Baeyer-Villiger 单加氧酶，催化脂肪酮转化为相应的酯；SadA 和 SadB 是两种酯酶，可将脂族酯水解为伯醇和乙酸。生物信息学分析表明，悲伤簇广泛分布在可能的烷烃降解物的基因组中，显然与 350 个细菌基因组中用于烷烃末端氧化的标志性酶 AlkM 和 AlmA 共存 (64%)。这表明烷烃亚末端氧化可能比以前认为的更普遍。