Figure 5

The growth phenotype conferred by WT NhaA when expressed in a host strain that does not synthesize cardiolipin and by alanine replacement mutants R203A or R204A or R203A-R204A expressed in a strain synthesizing cardiolipin. (a) Cells of BKT12/pAXH3, pI^Q, a mutant host that does not synthesize cardiolipin, bearing a plasmid combination expressing NhaA, were grown on non-selective agar plates (LBK) and on the indicated selective agar media for 48 hr at 37 °C as described in the Materials and Methods section. TA16/pAXH3 expressing WT-NhaA served as a positive control, and EP432/pBR322 served as a negative control. (b) Cells (OD₆₀₀ 0.5) of NhaA mutants, R203A, R204A and R203A-R204A in EP432 were tested for Na⁺/Li⁺ growth sensitivity as described in (a). EP432/pBR322 and EP432/pAXH3 served as negative and positive controls, respectively. (b) The experiments were conducted three times with identical results.