FIG 7.

Vanillin-dependent changes in metal homeostasis. (A) Inductively coupled plasma mass spectrometry (ICP-MS) analysis of intracellular metal content of E. coli BW25113 in response to growth with 10 mM vanillin. (B) RT-PCR showing expression of copA in response to 10 mM vanillin relative to expression in untreated cells (control). Expression levels are normalized to the rrsA housekeeping gene. (C) Comparison of levels of growth in LB plus 10 mM vanillin at 6 h after inoculation (OD₆₀₀) of BW25113 wild-type parent and isogenic copA deletion strain from the Keio collection. A value of 100% corresponds to an OD₆₀₀ of 0.49 ± 0.04. (D) Cell density after 24 h growth of E. coli BW25113 in minimal medium alone (dark colored bars) or with 10 mM vanillin (light colored bars). Either no additional metal ions were added (None) or 5 μM copper II sulfate (+ Cu), 200 μM iron (II) sulfate (+ Fe), or 200 μM Mn (II) sulfate (+ Mn) was added. In each panel, the data shown represent means plus standard deviations of results from three independent cultures. *, P = 0.01 to 0.05; **, P = 0.001 to 0.01; ***, P < 0.001; ****, P < 0.0001 (Student's t test).