Levoglucosan is produced in the pyrolysis of cellulose and starch, including from bushfires or the burning of biofuels, and is deposited from the atmosphere across the surface of the earth. We describe two levoglucosan degrading Paenarthrobacter spp. (Paenarthrobacter nitrojuajacolis LG01 and Paenarthrobacter histidinolovorans LG02) that were isolated from soil by metabolic enrichment using levoglucosan as the sole carbon source. Genome sequencing and proteomics analysis revealed the expression of a series of genes encoding known levoglucosan degrading enzymes, levoglucosan dehydrogenase (LGDH, LgdA), 3-keto-levoglucosan β -eliminase (LgdB1) and glucose 3-dehydrogenase (LgdC), along with an ABC transporter cassette and an associated solute binding protein. However, no homologues of 3-ketoglucose dehydratase (LgdB2) were evident, while the expressed genes contained a range of putative sugar phosphate isomerases/xylose isomerases with weak similarity to LgdB2. Sequence similarity network analysis of genome neighbours of LgdA revealed that homologues of LgdB1 and LgdC are generally conserved in a range of bacteria in the phyla Firmicutes, Actinobacteria and Proteobacteria. One group of sugar phosphate isomerase/xylose isomerase homologues (named LgdB3) was identified with limited distribution that is mutually exclusive with LgdB2, and we propose that they may fulfil a similar function. LgdB1, LgdB2 and LgdB3 adopt similar predicted 3D folds, suggesting overlapping function in processing intermediates in LG metabolism. Our findings highlight diversity within the LGDH pathway, through which bacteria utilize levoglucosan as a nutrient source.

左旋葡聚糖是在纤维素和淀粉的热解过程中产生的，包括丛林大火或生物燃料的燃烧，并从地球表面的大气中沉积下来。我们描述了两种左旋葡聚糖降解类杆菌属。（Paenarthrobacter nitrojuajacolis LG01 和Paenarthrobacter histidinolovoransLG02) 是通过使用左旋葡聚糖作为唯一碳源的代谢富集从土壤中分离出来的。基因组测序和蛋白质组学分析揭示了一系列编码已知左旋葡聚糖降解酶、左旋葡聚糖脱氢酶 (LGDH、LgdA)、3-酮基-左旋葡聚糖 β-消除酶 (LgdB1) 和葡萄糖 3-脱氢酶 (LgdC) 的基因的表达，以及ABC 转运蛋白盒和相关的溶质结合蛋白。然而，没有明显的 3-酮葡萄糖脱水酶 (LgdB2) 同系物，而表达的基因包含一系列与 LgdB2 具有弱相似性的假定糖磷酸异构酶/木糖异构酶。LgdA 基因组邻居的序列相似性网络分析表明，LgdB1 和 LgdC 的同源物通常在厚壁菌门、放线菌门和变形菌门的一系列细菌中是保守的。一组糖磷酸异构酶/木糖异构酶同源物（命名为 LgdB3）被鉴定为具有与 LgdB2 互斥的有限分布，我们认为它们可能具有相似的功能。LgdB1、LgdB2 和 LgdB3 采用相似的预测 3D 折叠，表明在 LG 代谢的加工中间体中具有重叠功能。我们的研究结果突出了 LGDH 通路的多样性，细菌通过该通路利用左旋葡聚糖作为营养来源。