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Open Access Highly Accessed Research article

Complete genome sequence and comparative analysis of Acetobacter pasteurianus 386B, a strain well-adapted to the cocoa bean fermentation ecosystem

Koen Illeghems, Luc De Vuyst and Stefan Weckx*

Author Affiliations

Research Group of Industrial Microbiology and Food Biotechnology (IMDO), Faculty of Sciences and Bio-engineering Sciences, Vrije Universiteit Brussel, Pleinlaan 2, Brussels B-1050, Belgium

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BMC Genomics 2013, 14:526  doi:10.1186/1471-2164-14-526

Published: 1 August 2013

Abstract

Background

Acetobacter pasteurianus 386B, an acetic acid bacterium originating from a spontaneous cocoa bean heap fermentation, proved to be an ideal functional starter culture for coca bean fermentations. It is able to dominate the fermentation process, thereby resisting high acetic acid concentrations and temperatures. However, the molecular mechanisms underlying its metabolic capabilities and niche adaptations are unknown. In this study, whole-genome sequencing and comparative genome analysis was used to investigate this strain’s mechanisms to dominate the cocoa bean fermentation process.

Results

The genome sequence of A. pasteurianus 386B is composed of a 2.8-Mb chromosome and seven plasmids. The annotation of 2875 protein-coding sequences revealed important characteristics, including several metabolic pathways, the occurrence of strain-specific genes such as an endopolygalacturonase, and the presence of mechanisms involved in tolerance towards various stress conditions. Furthermore, the low number of transposases in the genome and the absence of complete phage genomes indicate that this strain might be more genetically stable compared with other A. pasteurianus strains, which is an important advantage for the use of this strain as a functional starter culture. Comparative genome analysis with other members of the Acetobacteraceae confirmed the functional properties of A. pasteurianus 386B, such as its thermotolerant nature and unique genetic composition.

Conclusions

Genome analysis of A. pasteurianus 386B provided detailed insights into the underlying mechanisms of its metabolic features, niche adaptations, and tolerance towards stress conditions. Combination of these data with previous experimental knowledge enabled an integrated, global overview of the functional characteristics of this strain. This knowledge will enable improved fermentation strategies and selection of appropriate acetic acid bacteria strains as functional starter culture for cocoa bean fermentation processes.

Keywords:
Acetobacter pasteurianus; Cocoa bean fermentation; 454 pyrosequencing