CLONING, SEQUENCING AND EXPRESSION OF STRESS GENES FROM THE ETHANOL-PRODUCING BACTERIUM ZYMOMONAS-MOBILIS - THE GROESL OPERON

Zymomonas mobilis is unique among bacteria in its ability to produce h igh levels of ethanol (EtOH) during fermentation. Elevated EtOH concen tration, like elevated temperature, is a microbial stress and a univer sal inducer of stress proteins. For Z. mobilis, exposure to high level s of EtOH represents a natural stress. By using a simple strategy whic h combines the genetic tools of Escherichia coli and Bacillus subtilis , we have cloned genes encoding two of the most abundant stress protei ns in Z. mobilis, GroES and GroEL. Both genes were expressed at high l evels in E. coli. Despite the unique environment (EtOH concentrations of above 10%) in which the translated products from these genes functi on in Z. mobilis, the amino-acid sequences encoded were remarkably sim ilar to their homologues from bacteria which are not known to accumula te EtOH. Two small regions were observed, however, which appear more s imilar to Saccharomyces cerevisiae hsp60 (groEL homologue) than to E. coli or the concensus. These may be related to EtOH tolerance.