Abstract
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.
Highlights
Vinegar is a centuries-old fermented condiment, which is produced by raw materials such as fruit, rice, grains, and cocoa
A. pasteurianus strain Ab3 is a Gram-negative, rod-shaped, acid-tolerant and acid forming strain isolated from the traditional Chinese rice vinegar (Meiguichu) fermentation process
The numerous phage genomes, insertion sequences and transposases might cause the genomic instability of Ab3, which is consistent with results published on A. pasteurianus IFO 3283–01 [25]
Summary
Vinegar is a centuries-old fermented condiment, which is produced by raw materials such as fruit, rice, grains, and cocoa. A variety of vinegars with special flavors have been populated in different regions of the world. In Italy, grape must is used as the raw material for naturally fermented Balsamic vinegar [1]. For the kome-kurozu vinegar manufactured in Japan, rice koji (moldy steamed rice grain) is used to strengthen the rice saccharification process [2]. Two types of traditional Chinese vinegar, i.e., Shanxi-aged vinegar and Zhenjiang-scented vinegar, are produced by a solid-state cultivation process using various grains as the raw material. Big-Qu and Small-Qu, are inoculated into the grains as starters[3]. A. pasteurianus is regarded as the dominant species in the acetic acid fermentation stage. PLOS ONE | DOI:10.1371/journal.pone.0162172 September 9, 2016
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