osaB is essential for osmoadaptation. Cultures were incubated for 7 d at 30°C. (i) S. lividans strains grown on R2YE containing 10.3% sucrose: (A) 1326, (B) AB101 containing pPM927, (C) AB101 containing pAB04, (D) AB101, (E) X0236; (ii) S. coelicolor strains grown on R2YE containing 10.3% sucrose: (A) M145, (B) AB201, (C) AB001 containing pPM927, (D) AB001 containing pAB04, (E) AB001; (iii) the same S. coelicolor strains grown on MS containing 25 mM KCl; and (iv) grown on MS with no supplementary osmolyte.