Abstract
Actinomyces (Streptomyces) roseoflavus var. roseofungini which yields secondary nocardioform colonies when grown on synthetic medium with D-
fructose as sole carbon and energy source ("fructose effect") was employed as test organism in screening for conditions and compounds which enhance or retard the fructose effect.
The results of alterations in cultivation conditions point to the importance of fructose being metabolized for its effect to be observed. The effective individual compounds tested were tentatively grouped as follows: (1) Strongly inhibitory in high concentrations for the growth of actinomycete while retarding emergence of secondary colonies against the background of weak growth in moderate or low concentrations (most antibiotics and some enzyme inhibitors, phenol, indole, anthranillic acid, indolyl-acetic acid, sodium hydrosulphite, iron salts). (2) Non-inhibitory for growth (occasional stimulation noted), retarding emergence of secondary colonies, a) Active in low concentrations (mannitol, tyrosine, shikimate, oxalate, alanine, valine, norvaline, leucine). b) Active in high concentrations (glucose, galactose, glycerol, ascorbate, citrate, lactate, several amino acids). (3) Non-inhibitory for growth with slight tendency to enhance emergence of secondary colonies (fumarate, malate, succinate, phenylalanine, sodium chloride). Compounds of group 3 neither individually nor in combinations were able to substitute fructose in its capacity to elicit secondary growth. Some treatments (increase in incubation temperature, addition of methionine) tended to increase the relative number of secondary colonies of diminished size.
The results are discussed in relation to the possibility that emergence of secondary colonies is due to some "abnormalities" in fructose metabolism, leading to production of metabolites which induce and/or select particular type of mutants. Among effective additives some (mannitol) probably affect the fructose metabolism itself, while others "cure" the lesions due to its "peculiarity" or improve the efficiency of fructose utilization.
