Arthrobacter pyridinolis possesses alternative transport systems for d‐fructose: a respiration‐coupled transport system whereby d‐fructose transport occurs with concomitant oxidation of l‐malate, and a phosphoenolpyruvate: d‐fructose phosphotransferase system. Studies of d‐fructose uptake by whole cells in the presence and absence of cyanide demonstrate that respiration‐coupled transport is used almost exclusively during the first half of logarithmic growth, after which it accounts for only 15–20% of d‐fructose uptake. Phosphotransferase levels are low during log phase, peak during late log, and then slowly decline. In a mutant of A. pyridinolis which requires δ‐amino‐levulinic acid for growth, the growth rate, cell cytochrome content, and activity of the respiration‐coupled transport system increased with increasing concentrations of δ‐aminolevulinic acid up to 50 μg/ml. By contrast, phosphotransferase activity was highest in cells grown on limiting δ‐aminolevulinic acid. l‐Malate, which stimulates respiration‐coupled transport, repressed the phosphotransferase system. The respiratory activity and the ability to release CO2 from internalized d‐fructose was consistently low in d‐fructose‐grown cells. A cyanide‐resistant cytochrome, tentatively identified as cytochrome d, appeared in the late exponential phase of growth. Isocitrate lyase activity, required for aerobic growth of this organism, declined markedly during the late exponential phase. Thus the phosphotransferase system is maximally induced, in this obligate aerobe, under conditions of relative anaerobiosis during which metabolism is primarily fermentative.
|Number of pages
|European Journal of Biochemistry
|Published - Mar 1979