ABSTRACT
The effects of optimal sources and concentrations of major nutrients (supplying N, S, P, K+, Na+, Ca2+, Mg2+, and inorganic carbon) and organic buffers on growth and secondary metabolite accumulation in Scytonema ocellatum strain FF-66-3 were determined. Nitrate, phosphate, magnesium, and sulfur had no specific stimulatory or inhibitory effects on scytophycin accumulation within the range of concentrations that supported optimal growth. Calcium concentrations greater than those required for growth (0.1 mM) stimulated scytophycin accumulation. Sodium carbonate concentrations in excess of 0.25 mM strongly inhibited growth. Ammonium (2.5 mM) inhibited both growth and product formation. 3-[N-Morpholino]propanesulfonic acid at 3-5 mM effectively controlled pH and facilitated both growth and product formation.
Subject(s)
Anti-Bacterial Agents/biosynthesis , Cyanobacteria/metabolism , Pyrans/metabolism , Calcium/pharmacology , Cyanobacteria/growth & development , Macrolides , Magnesium/pharmacology , Nitrogen/metabolism , Phosphates/pharmacology , Potassium/pharmacology , Sodium/pharmacologyABSTRACT
Nonaxenic clones prepared from the cyanobacterium Syctonema ocellatum Lyngbye ex Bornet et Flahault strain FF-66-3 exhibited a high degree of heterogeneity with respect to tolytoxin titer. Thirty-four of 114 clones (29.8%) isolated by fragmentation of Scytonema filaments did not produce detectable amounts of tolytoxin in culture. One clone (designated SO127) produced approximately twice as much tolytoxin as the parental culture and continued to produce tolytoxin after repeated subculture. Three axenic clones were prepared from SO127 by a combination of antibiotic treatment and mechanical separation. Although axenic cultures yielded slightly greater biomass, tolytoxin content did not significantly differ between axenic and nonaxenic cultures, indicating that bacteria do not play a role in tolytoxin biosynthesis. Bacterial cultures derived from S. ocellatum did not produce detectable amounts of tolytoxin.
