The effect of osmolarity, temperature and anaerobiosis on the expressi
on of Escherichia coil alpha-haemolysin was investigated. Low osmolari
ty of the culture medium, growth at high temperature (37 degrees C)and
anaerobiosis increase haemolysin production in E. coli cells harbouri
ng the haemolytic plasmid pHly152 as well as in haemolytic strains iso
lated from urinary-tract infections.