Aluminum Elicits Exocellular Phosphatidylethanolamine Production in Pseudomonas fluorescens

Abstract

Pseudomonas fluorescens ATCC 13525 was found to grow in a minimal mineral medium supplemented with millimolar amounts of aluminum, a known environmental toxicant. During the stationary phase of growth, the trivalent metal was localized in a phosphatidylethanolamine (PE)-containing residue. The concentration of PE in pellets ranged from 1.7 to 13.9 mg ml of culture ؊1 in media supplemented with 1 to 30 mM aluminum. Although the gelatinous residue was observed during the stationary phase of growth, ultracentrifugation and dialysis experiments revealed that PE was produced from earlier stages of incubation and was associated with aluminum. A sharp diminution in the levels of PE and aluminum in the spent fluid was concomitant with the formation of the insoluble deposit. The aluminum content of the soluble cellular fraction increased during growth and reached an optimum of 1.85 mM of test metal at 45 h in cultures with 15 mM aluminum. Further incubation, however, led to a marked decrease in the cellular aluminum content, and during the stationary phase of growth, only trace amounts of the trivalent metal were detected in this fraction. When 45-h cells were incubated in fresh citrate medium, most of the intracellular aluminum was secreted in the spent fluid and citrate was rapidly consumed. Aluminum efflux was also observed in cultures in which D-glucose was substituted for citrate. However, no efflux of this trivalent metal was evident in media devoid of either citrate or D-glucose. Scanning electron microscopic studies and X-ray energy-dispersive analyses of the dialyzed supernatant aided in the visualization of nodule-like aluminum-and phosphorus-rich bodies associated with thread-like carbon-, oxygen-, and phosphorus-containing structures. Transmission electron microscopic and electron energy loss spectroscopic analyses revealed the presence of aluminum within bacteria after 45 h of incubation. Cells harvested after aluminum insolubilization did not shown aluminum inclusions. This aluminum-tolerant microbe may have potential application in bioremediation processes.

Metabolomic and proteomic changes induced by growth inhibitory concentrations of copper in the biofilm-forming marine bacteriumPseudoalteromonas lipolytica

“…The augmentation of PEs production induced by metal stress (aluminium) has already been observed in Pseudomonas fluorescens. 41 In this study, the authors suggested that the bacteria elaborated exocellular PEs in order to help the immobilization of aluminium. A similar hypothesis could be formulated for P. lipolytica TC8 with Cu.…”

Metabolic manipulation by Pseudomonas fluorescens: a powerful stratagem against oxidative and metal stress

“…These characteristics have been tailored naturally in order to render P. fluorescens suitable for bioremediation, in pathogen control and as biofertilizers. This propensity to survive a plethora of adverse conditions makes this bacterium an ideal candidate to study metabolic reconfigurations responsive to abiotic stress [21][22][23]. In this mini-review, the metabolic networks that enable P. fluorescens to fend oxidative/nitrosative stress and to detoxify metal pollutants are discussed.…”

Metabolic adaptation and oxaloacetate homeostasis in P. fluorescens exposed to aluminum toxicity

“…Enhanced expression of isocitrate lyase (ICL) enables the organism to generate glyoxylate that is subsequently converted into oxalate [8]. Phosphatidyl ethanolamine (PE) also appears to play a pivotal role in this detoxification strategy [9]. However, if the phosphate level is decreased 100-fold, P. fluorescens produces a polycarboxylate-citrate derivative as an aluminophore, an aluminum sequestering molecule [10,11].…”