- Volume 108, Issue 2, 1978

Urealytic activity of the cytoplasmic fraction of Ureaplasma urealyticum prepared by digitonin lysis was assayed in a simple buffer system (HEPES plus EDTA) by measuring the release of 14CO2 from [14C]urea. The K m of this preparation agreed with our previous observations of the same activity measured in a more complex reaction mixture. The substrate concentration at which maximum velocity occurred was approximately 20 mm. The activity was sensitive to heavy metals and inhibitors which react with sulphydryl groups such as N-ethylmaleimide and p-chloromercuribenzoate. It was not inhibited by Ca2+ or Mg2+ or by the reaction products, ammonia and carbon dioxide.

Esterases of 62 Serratia marcescens, S. liquefaciens, S. plymuthica and S. marinorubra strains were analysed by horizontal slab electrophoresis in polyacrylamide-agarose gel. Five principal bands hydrolysed β-naphthyl acetate but differed in their range of activity towards other substrates and in their sensitivity to di-isofluoropropyl phosphate. Additional bands were detected in some strains of S. marcescens and S. marinorubra. The comparative distribution of bands showed that the four Serratia species were characterized by distinct electrophoretic patterns of their esterases. Serratia marcescens, S. liquefaciens and S. plymuthica appeared to be more closely related to one another than to S. marinorubra. In the case of S. plymuthica and S. marinorubra, congruence was found between biovars and esterase patterns. The numerous electrophoretypes observed within Serratia species might provide useful epidemiological markers.