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High‐frequency electroporation of whole Corynebacterium glutamicum cells without enzymatic pretreatment was achieved. Under optimized conditions concerning growth stage, washing of cells, cell concentration and pulse parameters transformation efficiencies of far more than 107 transformants per μg pWST4B plasmid DNA were reached. Using electroporation, linearised and subsequently religated plasmid as well as chimeric ligase reaction products were directly introduced into C. glutamicum with reasonable efficiencies. Electrotransformation efficiency was reduced about 105‐fold for plasmid DNA cycled through E. coli JM83. Restriction deficient mutants of C. glutamicum were isolated which could be efficiently transformed with foreign DNA.

The modulation of the intracellular glucocorticoidal effect on surfactant synthesis of the fetal lung by the metabolic capacity of 11ß-hydroxysteroid dehydrogenase (11ß-HSD) could be an important factor in lung maturation. The kinetic properties of microsomal 11ß-HSD of the rat lung are characterized with respect to product inhibition, substrate specificity, effect of electrolytes or trace elements, and the dependence of the oxidase reductase (OR) ratio on incubation conditions. With NADP^+ product inhibition of the reductase was demonstrated. The most common trace elements and electrolytes exhibited no effect on the activity of 11ß-HSD. It is shown that the OR ratio was strongly dependent on assay conditions. With optimal assay conditions oxidase activity exceeds reductase activity in adult and fetal rat lung microsomes (OR ratio >1). Thus, glucocorticoids are mainly metabolized to their inactive forms. The enzyme activity in the adult is about 10 times higher than in the fetal lung. The low enzyme activity in fetal lungs could be the reason why the glucocorticoidal effects on surfactant synthesis are not suppressed despite the predominance of oxidase activity.