Omics Analyses for Hyper Glucose-Tolerance Using Acetic Acid Bacteria

Acetic acid bacteria (AAB), forming a divergent phylogenetic group within alpha-proteobacteria, are characterized by their abilities to transform alcohols and sugars into the corresponding organic acids. The capabilities have been historically used for vinegar fermentation from ethanol. Whereas, natural habitats of AAB are widespread niches accumulating sugars, e.g. fruits, flowers and soils near fruit plants. Among AAB, two phylogenetically closed species, Tanticharoenia sakaeratensis and Asaia bogorensis, show a distinctive ability to grow in media containing 30% glucose. Interestingly, both of AAB could not multiply in media containing even 2% of salt, which gives lower osmotic pressure than glucose 30%. It indicates that osmotic tolerance of the AAB is not for general substances but specific to sugars, and that the AAB must include mechanisms for the hyper glucose tolerance. To clarify mechanisms for the hyper glucose-tolerance, comparative omics analyses, including genome DNA sequencing, transcriptome and proteome analyses, were performed. The results illustrated that the two AAB altered expressions of similar genes and systems under different conditions with low and high glucose concentrations.  In both AAB gene expressions for glycolysis and pentose phosphate pathways decreased, and ones for antioxidant enzymes (such as superoxide dismutase (SOD) and peroxidase) and cytochrome o ubiquinol oxidase increased.  On the contrary, the omics analyses indicated a variety uniqueness of each bacterium. For instance, under high glucose conditions, T. sakaeratensis repressed a main energy metabolism including NADH dehydrogenase (complex I) and induced gene expression of pyruvate decarboxylase, whereas A. bogorensis promoted expressions of more stress responsible genes involved in anti-oxidation, such as DNA starvation/stationary phase protection protein (Dps) and osmotically inducible peroxiredoxin OsmC. Because the complex I is a main superoxide producer, T. sakaeratensis needs less antioxidant enzymes than A. bogorensis. We herein propose that enzymes managing oxidative stresses are engaged in overcoming the high glucose stress, and the acquisitions of the glucose tolerance systems in the two AAB were evolutionally independent.

  This work was financially supported by the Advanced Low Carbon Technology Research and Development Program (ALCA), and a Grant-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology of Japan (KAKEN-HI: 22510222).