Micorobial Genome

  Acetic acid bacteira (AAB) are a widely divergent group within the alpha-proteobacteria and are isolated from a variety of natural habitats such as fruits, flowers and fermented foods; they are rarely found in soil and insect guts. AAB incompletely oxidize a variety of sugars and alcohols, and accumulate large amounts of the corresponding oxidation products in their environments or culture media. These traits of AAB, known as oxidative fermentation, are utilized in many industrial production processes, such as the manufacture of vinegar and L-sorbose. In industrial production, AAB play a crucial role in the quantity, taste, nutrition and hygienic quality of the products, making the reliability of strains indispensable with respect to functional properties and robustness of growth.

  Acetobacter strains, which are the most popular AAB for the production of vinegar in many countries, have shown noticeable physiological instabilities, the characteristics of which were reported in at least two different contexts, specifically temporal acclimation and heritable mutation. As an example of temporal acclimation (or physiological adaptation), Acetobacter strains may gradually acquire resistance against higher concentrations of acetic acid when properly adapted, but they rapidly lose the acquired phenotype when maintained without acetate. This is why new tanks for fermentation are continuously inoculated with AAB from old tanks, but not with a preserved seed AAB strain in traditional vinegar production. Very little is known about the genetic properties of these instabilities, but phenotypic modifications by transposon insertion were reported in ethanol oxidation and acetic acid resistance,  and cellulose formation.