Synthesis of Adenylate Nucleotides by Mollicutes (Mycoplasmas)

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Abstract
Cultures of Acholeplasma laidlawii B, A. morum, Mycoplasma bovis, M. arginini, M. fermentans and M. gallisepticum, representing 4 metabolic groups, were sampled at intervals over 40-50 h and assayed for the numbers of colony-forming units (c.f.u.), changes in pH and glucose concentration, and concentrations of ATP, ADP, AMP, lactate and pyruvate. The adenylate energy charge (ECA), the mean generation time and the number of nmol of ATP/mg dry weight were calculated for cultures in the mid-exponential growth phase. The maximum cell concentrations ranged from 0.2 .times. 1010 to 5.0 .times. 1010 c.f.u. ml-1. Doubling times ranged from 0.34 to 3.29 h. The fermentative nonarginine-requiring A. laidlawii B, A. morum and M. gallisepticum and the fermentative arginine-requiring M. fermentans utilized glucose and produced lactate and pyruvate. The nonfermentative nonarginine-requiring M. bovis neither utilized glucose nor produced lactate or pyruvate. The nonfermentative arginine-requiring M. arginini utilized glucose but did not produce lactate or pyruvate. At mid-exponential growth phase, the average ECA of A. laidlawii B was 0.90, a value similar to that reported for Spiroplasma citri and other bacteria. The average ECA of A. morum and the 4 Mycoplasma spp. was 0.70. In A. laidlawii B at mid-exponential growth phase, ATP accounted for 97% of the total adenylate nucleotide pool. At the same stage of growth, the average cellular ATP concentration of the other Mollicutes was significantly lower, ranging from 45-63% (P < 0.01). Excluding A. laidlawii B, the Mollicutes were relatively energy deficient during their mid-exponential growth phase. The diminished metabolic capacity may be related to the association of Mollicutes with living cells and perhaps to the cytopathic effects of these microorganisms.