Cloning of malic acid assimilating activity from Leuconostoc oenos in E. coli.

High molecular weight DNA was extracted from a malo-lactic fermenting strain of Leuconostoc oenos by a specifically designed lysis procedure, restricted, and ligated into Escherichia coli cloning vector pTR 262, which allows for positive selection for inserts. Malic acid assimilating activity was directly selected for using a host blocked in malic acid utilization. Transformants grew on malate minimal medium but were genetically unstable and contained plasmid DNA that was altered through recA independent events. Analogous results were obtained from a test system using prototrophic transformants of a proline auxotrophic host.