Carbon catabolism and synthesis of macromolecules during spore germination of Microsporum gypseum

Abstract

Either d- or l-leucine (10(-3)m) and unsaturated long-chain fatty acids such as oleic, linoleic, and arachidonic (10(-4)m) significantly stimulated macroconidia germination of Microsporum gypseum. Saturated long-chain fatty acids did not affect germination, whereas saturated short-chain fatty acids such as caprylic, hexanoic, and butyric were completely inhibitory. Germination was followed by an increase in endogenous respiration and a decrease in dry weight of approximately 5% at 4 hr. Endogenous fatty acids and soluble carbohydrates were utilized significantly during germination. Tritiated leucine, uridine, and thymidine were incorporated respectively into protein, ribonucleic acid (RNA), and deoxyribonucleic acid (DNA) fractions within the first 5 min of germination. Incorporation of oleic-1-C(14) into RNA and protein was significantly increased after germ tube development. Net synthesis of RNA and protein started prior to germ tube protrusion. Increase in DNA could be detected only later. A significant increase in RNA and protein during the 4th hr of germination was correlated with vegetative development. Inhibition of respiration and incorporation of leucine-H(3) and uridine-H(3) into corresponding macromolecules by dl-fluorophenylalanine and phenethyl alcohol started before germ tube appearance. Griseofulvin significantly inhibited incorporation of uridine-H(3) and thymidine-H(3), but not of leucine-H(3). This inhibition occurred only after initial vegetative development. In contrast to the two other inhibitors, which substantially inhibited germination, griseofulvin only slightly retarded the period of germination and did not affect respiration.