[Survival ability of genetically engineered strains of Escherichia coli. 1. Physiological characterization and the effect of different physiochemical conditions].

Two genetically engineered E. coli strains L+ and CAG+ possessing the ability to produce the enzyme Pro-urokinase and showing additionally ampicillin resistance, and wild-strains L- and CAG-, were characterized using 328 physiological tests. Their test profiles were compared with those of 30 clinical and nonclinical E. coli isolates. This biotyping made a differentiation and recognition of the genetically manipulated strains possible. It also allowed distinguishing them from the other tested isolates. The genetically engineered strains showed a narrower activity spectrum compared with their wild-strains. However, based on differentiating characteristics, all strains could be clearly biochemically identified as E. coli. Under different laboratory test conditions (organic load, pH, salt content, temperature), the E. coli strains showed no striking features or peculiarities with respect to their survival compared to data from literature. However, low pH (pH less than 5), high salt content (greater than 7%) as well as low (less than 8 degrees C) and high (greater than 37 degrees C) incubation temperatures clearly reduced their ability to survive. Apart from a few exceptions (e.g. survival of strain L+ at 44 degrees C and pH 7 with high cell densities), the survival of the genetically engineered strains corresponded to that of the control and wild-strains. Both CAG strains, especially the genetically manipulated strain CAG+, showed in many cases reduced viability compared with the other strains.