Exocellular phosphatidylethanolamine production and multiple-metal tolerance in Pseudomonas fluorescens

Abstract Pseudomonas fluorescens appeared to circumvent the challenge imposed by millimolar amounts of metals (5 mM Al³⁺, 5 mM Fe³⁺, 2 mM Ca²⁺, 1 mM Ga³⁺ and 3 mM Zn²⁺) by the formation of phosphatidylethanolamine. This lipid moiety constituted an important organic component of an insoluble gelatinous residue in which most of the test metals were immobilized at stationary phase of growth. Ultracentrifugation and dialysis experiments showed that the metals were associated with phosphatidylethanolamine from early stages of growth. Transmission electron microscopy revealed metal rich bodies in the cytoplasm prior to their secretion in the spent fluid. These results demonstrate a role of phosphatidylethanolamine in multiple-metal homeostasis.