Further studies on the mode of action of 2, 4-dichlorophenoxyacetic acid on Azotobacter vinelandii as related to magnesium and phosphate.

The vital roles played by metallic ions in the metabolic activities of bacteria are well known. One such ion, magnesium, has been reported to be quite versatile in its relation to the cell. It has been demonstrated to hold a prominent position in oxidative activities which generate high energy phosphate bonds (Goucher and Kocholaty, 1954). It has been implicated in the puzzling phenomenon of cell permeability and transport mechanisms (Goucher et al., 1955), and has been proved to occupy a prominent position in cellular growth and division (Webb, 1953). One of the areas of cellular activity shown to be magnesium dependent is in the adaptive response of Azotobacter vinelandii to the oxidation of certain substrates (Goucher et al., 1955). Previous work (Johnson and Colmer, 1957) with 2,4-dichlorophenoxyacetic acid (2,4-D) and A. vinelandii indicated that the herbicide and magnesium ion had a relationship in the observed toxicity of 2,4-D for the organism. This report gives the results of studies made with A. vinelandii in its magnesium dependent adaptive response to certain substrates as further emphasis to the hypothesis that the mode of action of 2,4-D for the cell is intimately related to its chelation of essential ions.