FIG. 2.

Testing the cation dependency of the citrate transporters CitH and TctABC of C. glutamicum by using the growth of E. coli on citrate as the indicator. E. coli MG1655 transformed with pXMJ19-citH (•), pXMJ19-tctCBA (▪), or pXMJ19 (▴) was grown in a 500-ml Erlenmeyer flask containing 50 ml of M9 minimal medium supplemented with 1 g/liter Casamino Acids, 50 mM sodium citrate, and none or one of the following salts: 5 mM CaCl₂, 5 mM MgCl₂, 5 mM ZnCl₂, 5 mM NiCl₂, and 5 mM SrCl₂. The cultures were incubated at 37°C on a rotary shaker at 120 rpm. The growth curves shown here are representative of those from three independent growth experiments with comparable results.