Comparative Genomics of Acetobacterpasteurianus Ab3, an Acetic Acid Producing Strain Isolated from Chinese Traditional Rice Vinegar Meiguichu

Acetobacter pasteurianus, an acetic acid resistant bacterium belonging to alpha-proteobacteria, has been widely used to produce vinegar in the food industry. To understand the mechanism of its high tolerance to acetic acid and robust ability of oxidizing ethanol to acetic acid (> 12%, w/v), we described the 3.1 Mb complete genome sequence (including 0.28 M plasmid sequence) with a G+C content of 52.4% of A. pasteurianus Ab3, which was isolated from the traditional Chinese rice vinegar (Meiguichu) fermentation process. Automatic annotation of the complete genome revealed 2,786 protein-coding genes and 73 RNA genes. The comparative genome analysis among A. pasteurianus strains revealed that A. pasteurianus Ab3 possesses many unique genes potentially involved in acetic acid resistance mechanisms. In particular, two-component systems or toxin-antitoxin systems may be the signal pathway and modulatory network in A. pasteurianus to cope with acid stress. In addition, the large numbers of unique transport systems may also be related to its acid resistance capacity and cell fitness. Our results provide new clues to understanding the underlying mechanisms of acetic acid resistance in Acetobacter species and guiding industrial strain breeding for vinegar fermentation processes.巴氏醋酸杆菌（Acetobacter pasteurianus）是一类耐乙酸的α-变形菌纲（alpha-proteobacteria）细菌，在食品工业中被广泛应用于食醋生产。为解析其高乙酸耐受性以及将乙醇氧化为乙酸（浓度＞12%，质量体积比，w/v）的强大能力的分子机制，本研究报道了从中国传统米醋（Meiguichu）发酵过程中分离得到的巴氏醋酸杆菌Ab3的完整基因组序列：其总长度为3.1 Mb，包含0.28 Mb的质粒序列，G+C含量为52.4%。对该完整基因组的自动注释结果显示，其包含2786个蛋白质编码基因与73个RNA基因。通过对不同巴氏醋酸杆菌菌株的比较基因组分析，发现Ab3菌株携带诸多可能与乙酸耐受机制相关的特有基因。具体而言，双组分调控系统（two-component systems）与毒素-抗毒素系统（toxin-antitoxin systems）可能是巴氏醋酸杆菌应对酸胁迫的信号通路与调控网络。此外，大量的特有转运系统同样可能与其乙酸耐受能力及细胞适应性相关。本研究结果为解析醋酸杆菌属菌株的乙酸耐受潜在机制，以及指导食醋发酵工业的菌株育种工作提供了全新的研究线索。