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Cellular response to a multiple-metal stress in Pseudomonas fluorescens
1Department of Chemistry and Biochemistry, Laurentian University, Sudbury, Ontario, Canada. vappanna@nickel.laurentian.ca
Journal of Biotechnology
|July 18, 1996
Summary
Pseudomonas fluorescens utilizes citrate in the presence of high metal concentrations, with metals binding to phosphatidylethanolamine (PE) and forming exocellular residues, impacting cellular yield.
Area of Science:
- Microbiology
- Biochemistry
- Environmental Science
Background:
- Pseudomonas fluorescens is a bacterium known for its metabolic versatility.
- Metal contamination can affect microbial growth and cellular processes.
- Understanding metal-microbe interactions is crucial for environmental remediation and biotechnology.
Purpose of the Study:
- To investigate the growth of Pseudomonas fluorescens in a medium supplemented with millimolar concentrations of aluminum, iron, zinc, calcium, and gallium.
- To elucidate the mechanisms of metal uptake, binding, and sequestration by P. fluorescens.
- To identify the cellular components involved in metal interaction.
Main Methods:
- Culturing P. fluorescens in a minimal mineral medium with specified metal ions and citrate as the carbon source.
- Monitoring growth rate and cellular yield.
- Utilizing ultracentrifugation and dialysis to analyze metal localization.
- Employing transmission electron microscopy (TEM) and scanning electron microscopy (SEM) for ultrastructural analysis.
- Chemical analysis of exocellular residues.
Main Results:
- P. fluorescens grew in the presence of high metal concentrations, albeit with reduced growth rate and cellular yield.
- Citrate was completely utilized.
- Metals were found to associate with phosphatidylethanolamine (PE) from early growth stages.
- Metals were immobilized in an exocellular lipid-rich residue at the stationary phase.
- TEM and SEM revealed metal-rich bodies within the cytoplasm and associated with elongated structures.
Conclusions:
- Pseudomonas fluorescens can tolerate and metabolize citrate in the presence of significant metal concentrations.
- Phosphatidylethanolamine (PE) plays a role in metal binding and sequestration.
- The formation of exocellular metal-rich residues is a key mechanism for metal detoxification in P. fluorescens.
- Metal stress influences bacterial physiology, leading to altered metal distribution within the cell and exocellular environment.