The Physiology of Astrephomene gubernaculifera¹

SYNOPSIS. A comparative physiologic study of 4‐ and 7‐chromosome strains of Astrephomene gubernaculifera was done. The vitamins p ‐aminobenzoic acid, nicotinamide, biotin, thiamin HCl and vitamin B 12 were tested for their ability to support growth. Only vitamin B 12 was required for active growth altho the presence of thiamin HCl was necessary to produce structurally typical colonies. Astrephomene will not grow in the absence of an exogenous source of carbon. Of the 36 carbon sources tested, only pyruvate, butyrate, succinate and acetate permitted active growth. Sodium acetate was the best. Strains grew within the initial pH range of 5.0–7.5. At pH values above 8.0 growth declined rapidly. When media were buffered with TES (N‐tris [hydroxymethyl]methyl‐2‐aminoethane‐sulfonic acid) at an initial pH of 6.8 growth was enhanced. The organism grew at 15–40 C. Growth in the dark was slightly less than that in the light.