Diversity of energy-yielding substrates and metabolism in avian mycoplasmas.

The metabolism of organic substrates and production of H2O2, a potential pathogenicity factor, were studied in the type strains of fourteen avian Mycoplasma species, and in low-passage isolates of M. gallinarum, M. gallisepticum, M. iners and M. pullorum. Substrates were added to cell suspensions in Ringer or saline solution and oxygen uptake and/or change in pH monitored. The fermentative species could be sub-divided according to whether O2 uptake did (M. anatis, M. columborale, M. gallisepticum, M. imitans and M. iowae) or did not (M. gallinaceum, M. gallopavonis and M. pullorum) accompany glucose metabolism and the five non-fermentative, arginine-hydrolysing strains according to whether organic acids (lactate, 2-oxobutyrate, pyruvate) were (M. columbinasale, M. columbinum and M. gallinarum) or were not (M. iners and M. meleagridis) oxidized, Lysed cells of strains which consumed O2 during glucose or organic acid metabolism had relatively high NADH oxidase activity (170-950 nmol min-1 mg cell protein-1) and produced 0.02-0.36 mol H2O2 per mol O2 consumed during NADH oxidation. In contrast, strains which did not oxidize organic acids or consume O2 during glucose or organic acid metabolism possessed low NADH oxidase activity (< or = 20 nmol min-1 mg cell protein-1). All arginine-hydrolysing species showed a high affinity (Km value 1-3 microM) towards arginine. The fermentative species similarly showed a high affinity (Km value 2-5 microM) towards glucose, but used only a small number of additional sugars at detectable rates. All M. pullorum strains metabolized sucrose (Km < or = 3 microM). The type-strains of M. gallisepticum and M. imitans were biochemically similar and had high affinities for fructose and mannose. A number of low-passage avain isolates, but none of the type strains, metabolized glycerol and, in lysed cells, oxidized L-alpha-glycerophosphate (GP) with the production of 1 mol H2O2 per mol GP.