Regulation of phosphate accumulation in the unicellular cyanobacterium Synechococcus.

The phosphorus contents of acid-soluble pools, lipid, ribonucleic acid, and acid-insoluble polyphosphate were lowered in Synechococcus in proportion to the reduction in growth rate in phosphate-limited but not in nitrate-limited continuous culture. Phosphorus in these cell fractions was lost proportionately during progressive phosphate starvation of batch cultures. Acid-insoluble polyphosphate was always present in all cultural conditions to about 10% of total cell phosphorus and did not turn over during balanced exponential growth. Extensive polyphosphate formation occurred transiently when phosphate was given to cells which had been phosphate limited. This material was broken down after 8 h even in the presence of excess external orthophosphate, and its phosphorus was transferred into other cell fractions, notably ribonucleic acid. Phosphate uptake kinetics indicated an invariant apparent K(m) of about 0.5 muM, but V(max) was 40 to 50 times greater in cells from phosphate-limited cultures than in cells from nitrate-limited or balanced batch cultures. Over 90% of the phosphate taken up within the first 30 s at 15 degrees C was recovered as orthophosphate. The uptake process is highly specific, since neither phosphate entry nor growth was affected by a 100-fold excess of arsenate. The activity of polyphosphate synthetase in cell extracts increased at least 20-fold during phosphate starvation or in phosphate-restricted growth, but polyphosphatase activity was little changed by different growth conditions. The findings suggest that derepression of the phosphate transport and polyphosphate-synthesizing systems as well as alkaline phosphatase occurs in phosphate shortage, but that the breakdown of polyphosphate in this organism is regulated by modulation of existing enzyme activity.
AuthorsJ F Grillo, J Gibson
JournalJournal of bacteriology (J Bacteriol) Vol. 140 Issue 2 Pg. 508-17 (Nov 1979) ISSN: 0021-9193 [Print] UNITED STATES
PMID227842 (Publication Type: Journal Article, Research Support, U.S. Gov't, Non-P.H.S.)
Chemical References
  • Phosphates
  • Plant Proteins
  • Polyphosphates
  • RNA
  • Phosphotransferases
  • Phosphoric Monoester Hydrolases
  • Biological Transport
  • Cyanobacteria (metabolism)
  • Kinetics
  • Phosphates (metabolism)
  • Phosphoric Monoester Hydrolases (metabolism)
  • Phosphotransferases (metabolism)
  • Plant Proteins (biosynthesis)
  • Polyphosphates (metabolism)
  • RNA (metabolism)

Join CureHunter, for free Research Interface BASIC access!

Take advantage of free CureHunter research engine access to explore the best drug and treatment options for any disease. Find out why thousands of doctors, pharma researchers and patient activists around the world use CureHunter every day.
Realize the full power of the drug-disease research network!

Choose Username:
Verify Password: