THE DIFFERENTIAL ACTION OF CHEMICAL AGENTS, ESPECIALLY POLYMYXIN‐B, ON CERTAIN ALGAE, BACTERIA AND FUNGI

Abstract

Galloway, R. A., and R. W. Krauss (U. Maryland, College Park.) The differential action of chemical agents, especially polymyxin‐B, on certain algae, bacteria and fungi. Amer. Jour. Bot. 46(1): 40‐49. Illus. 1959.—Representatives from each of the major groups of compounds exhibiting toxicity toward microorganisms were screened to determine their relative effect on 2 green algae, Scenedesmus obliquas and Chlorella pyrenoidosa, 1 blue green alga, Anabaena variabilis, 4 species of bacteria in the genera Flavobacterium, Achromobacter, and Pseudomonas, and the fungus Aspergillus sydowii. The objective was the determination of the differential toxicity shown by chemical agents against these microorganisms. Polymyxin‐B sulfate proved to have a high degree of selectivity which warranted detailed examination of its action. Manometric studies were made of the effects of this compound on rates of photosynthesis and respiration. The rate of photosynthesis in Scenedesmus was only slightly diminished by 640 p.p.m. polymyxin‐B, but a rapid reduction in rate to a very low level was observed in Chlorella. The endogenous respiration rate in Scenedesmus was more than doubled. The rate of respiration on glucose, pyruvate, fumarate, and acetate remained unchanged except for a slight transient rise at a low pH or in the absence of magnesium. The effect of 640 p.p.m. of polymyxin‐B on photosynthesis of Chlorella and on respiration, whether endogenous or on any of the substrates mentioned above, was a rapid, permanent reduction to a low level. Similar reduction in rate of respiration at 160 p.p.m. was observed in the bacteria and fungus, when these organisms were utilizing lactose, pyruvate, or fumarate as substrates. Two of the bacteria were exceptions in that no reduction occurred when they were respiring lactose. Inhibition of glucose phosphorylation was not found in the algae. Therefore some system other than an alternative phosphorylation must account for resistance to polymyxin‐B.