Figure 4

Growth on solid minimal agar. Colonies of E. coli strains XL1 Blue, EP432 pUC18 (control) and EP432 pUCHelNhaD and also of H. elongata were grown on MM63 minimal agar supplied with trace elements and vitamins for two days at 37°C. First set of pictures shows growth without NaCl (< 0.01% NaCl, 2 mM) due to media component impurities) under increasing LiCl concentrations, second set of pictures is growth under different salinities in the absence of LiCl. Concentrations of NaCl and LiCl are indicated above individual bars. No growth is marked with a white X (some artifacts due to toothpick transfer are visible). LiCl tolerance is drastically reduced in EP432 and this is not clearly counteracted by the presence of pUCHelNhaD although we observed slightly larger colonies. Salt tolerance is also reduced in this organism and only poorly compensated by expression of H. elongata NhaD. The halophilic H. elongata does not grow without salt and a corresponding osmotic activity in the growth medium. Apparently LiCl has no lethal effect on H. elongata at concentrations of 150 and 300 mM in solid medium and seems to partially replace the organism's sodium requirements.