Bleaching euglena gracilis with antihistamines and streptomycin-type antibiotics

Summary Kanamycin, paromomycin, and neomycin, like streptomycin, permanently bleach Euglena gracilis. This effect, along with general toxicity, is opposed by Mg, histidine or a combination of pantothenate, nicotinic acid, and threonine. Such opposition is thought to be peripheral effects centered on uptake and transport.Certain antihistamines, notably tripelennamine, methapyrilene, and pyrilamine induce permanent bleaching. Diphenylhydramine and phenindamine induced temporary bleaching. Doxylamine, antazoline, pyrathiazine, pheniramine, prophenpyridamine, and promethazine did not bleach when tested up to inhibitory concentrations.Bleaching by streptomycin+heat was additive, not synergistic.The evidence at hand for the mode of action of ultraviolet irradiation, streptomycin antibiotics, and erythromycin suggests, as a working hypothesis, that the common factor may be interference with nucleic acid metabolism; the common factor in bleaching by antibiotics may be simultaneous provision of a molecular grouping favoring uptake and transport of the active moiety, which in turn may be rare sugars interfering with ribose and desoxyribose in the photosynthetic apparatus.New antibiotics of the streptomycin family might well be screened for bleaching activity as a possible index of damage to the 8th cranial nerve, for so far the correlation is excellent for this class of antibiotic.This paper is dedicated to Professor Dr. E. G. Pringsheim on the occasion of his 80th birthday.