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Phosphate distribution and transport in mycoplasma
Canadian Journal of Biochemistry and Cell Biology = Revue Canadienne De Biochimie Et Biologie Cellulaire
|November 1, 1984
Summary
Mycoplasma capricolum utilizes two energy-dependent transport systems to uptake phosphate, accumulating it against concentration gradients. These systems show distinct affinities and are modulated by external phosphate levels and metabolizable substrates.
Area of Science:
- Microbiology
- Cellular Physiology
- Biochemistry
Background:
- Phosphate is crucial for nucleic acids and polyphosphates in Mycoplasma capricolum, comprising 75% of cellular phosphate.
- Resting cells primarily contain orthophosphate in the cold acid-soluble fraction.
- Metabolizing cells show increased phosphate esters and reduced orthophosphate levels.
Purpose of the Study:
- To investigate the phosphate uptake mechanisms in Mycoplasma capricolum.
- To characterize the kinetics and regulation of phosphate transport systems.
- To understand the role of energy and external phosphate concentrations on phosphate influx.
Main Methods:
- Analysis of cellular phosphate fractions (nucleic acids, polyphosphates, cold acid-soluble).
- Measurement of orthophosphate and phosphate ester concentrations in resting and metabolizing cells.
- Characterization of phosphate transport kinetics (Km values) under varying conditions.
- Assessment of arsenate inhibition on phosphate influx.
Main Results:
- Phosphate is actively transported into cells against its concentration gradient via orthophosphate entry.
- Two distinct energy-stimulated transport systems with high (Km = 12.8 microM) and low (Km = 1.1 mM) affinities were identified in phosphate-poor media.
- External phosphate addition (30 mM) altered the kinetic properties of both transport systems.
- Arsenate inhibition of phosphate influx was restricted to the energy-dependent component.
Conclusions:
- Mycoplasma capricolum employs sophisticated, energy-dependent mechanisms for phosphate acquisition.
- The identified transport systems exhibit adaptability to environmental phosphate availability.
- Understanding these systems is key to comprehending microbial phosphate metabolism and response to inhibitors.