Fig 6.

Deletion of colR results in loss of Zn²⁺-induced pEtN modification of P. aeruginosa lipid A. A) Lipid A was isolated from ³²P-labeled cells grown in LB broth and separated by TLC. While pEtN modification of lipid A is detectable for PA14 + 1mM ZnSO₄, no such modification occurs in PA14ΔcolR in response to Zn²⁺. Modification is restored in the complemented mutant. B) Relative gene expression of eptA_Pa and arnT in response to Zn²⁺ in the ΔcolR mutant or complemented mutant. Transcription of eptA_Pa in the presence of 1mM ZnSO₄ is induced >4-fold in a ColR-dependent manner. An approximately 10-fold decrease in arnT transcription in the presence of 1mM ZnSO₄ is also dependent on ColR. Ratios were standardized relative to expression of the housekeeping control gene, clpX. C) and D). MALDI-TOF MS analysis of lipid A prepared from cells grown in LB broth. C) No pEtN modification is detected in the PA14ΔcolR mutant grown in LB + 1mM ZnSO₄. D) Complementation of PA14ΔcolR with pcolR_nprom restores the Zn²⁺-dependent pEtN addition to the lipid A. The fractions most representative of pEtN modification are shown.