Acetic Acid Bacteria Taxonomy from Early Descriptions to Molecular Techniques

The exploitation of acetic acid bacteria (AAB) has a long history in fermentation processes and now represents an emerging field in biotechnological applications, especially with regard to the biosynthesis of useful chemicals with a potentially high economic value and, in food science, through the standardization of micro- biological processes for the manufacture of both vinegar and other fermented beverages. Historically, AAB were recognized as ‘vinegar bacteria’ because the first stud- ies were done on vinegar, and later on wine and beer spoilage. In fact, vinegar AAB are a subset of a larger AAB group, which includes bacteria that interact with flowers, fruits, the rhizosphere of plants, and even human beings (Table 3.1). It is generally recognized that AAB are fastidious microorganisms, which means that many of them are difficult to grow on laboratory media. Many efforts have been made to isolate and culture colonies of AAB. Several media have been suggested and tried, but none of them appears to satisfy the growth requirements of AAB. This has hindered the application of cultivation-based techniques to the study of AAB and, consequently, their taxonomic classification. However, the recent dis- covery of new culture-independent methods has opened up new horizons for the systematic study of AAB.