Cell-bound and extracellular phosphatase activities of cyanobacterial isolates

Fifty cyanobacterial strains (10 genera) were tested in batch culture for their ability to use organic phosphorus compounds (1 mg liter(-1) P) as their sole P source. Two monoesters, Na2-beta-glycerophosphate and rho-nitrophenyl phosphate (rhoNPP), supported growth of all strains, and the diester bis-rho-nitrophenyl phosphate (bis-rho) and herring sperm DNA supported almost all strains. ATP was either a very favorable or poor P source and failed to support growth of nine strains, seven of which were Rivulariaceae with trichomes ending in a hair or long tapered region. Phytic acid was in general the least favorable P source. P-limited cultures grown initially with inorganic phosphate to conditions of P limitation were also tested for cell-bound and extracellular phosphomonoesterase (PMEase) and phosphodiesterase (PDEase) activities at two pH values (7.6, 10.3) using rhoNPP and bis-rhoNPP as substrates. Cell-bound PMEase was inducible in all strains and cell-bound PDEase in most strains. Most showed extracellular PMEase, but not extracellular PDEase. The highest values (micrometer rhoNPP or bis-rhoNPP hydrolyzed mg dry weight(-1) hour(-1) all occurred in strains of Gloeotrichia as follows: cell-bound PMEase at pH 7.6, 2.7 micromolar in strain D602; cell-bound PMEase at pH 10.3, 5.2 micromolar in D602; extracellular PMEase at pH 7.6, 0.73 micromolar in D281; extracellular PMEase at pH 10.3, 6.6 micromolar in D281; cell-bound PDEase at 7.6, 0.40 micromolar in D613; cell-bound PDEase at pH 10.3, 1.0 micromolar in D613. The results were compared to see if they indicated possible relationships between phosphatase activity and taxonomic or ecological grouping. The following differences were significant (P less than 0.05). Rivulariaceae produced higher yields than filamentous non-Rivulariaceae with beta-glycerophosphate, rhoNPP, and DNA. Rivulariaceae with the ability to form hairs in culture showed poorer growth in ATP than non-hair-forming Rivulariaceae, but were more effective at utilizing phytic acid. Strains from calcareous environments had higher PMEase activity at pH 10.3 than strains from noncalcareous environments (P less than 0.01).