Induction of alpha-glucosidase in Mycoplasma laidlawii A

Abstract

The object of the study was to find if regulation of gene expression, found so vital to bacteria, exists in the mycoplasma which are noted for their small size, limited biosynthetic ability and small genomes. Glucose grown cells transferred to maltose media exhibit a lag before turbidity or 14C-amino acid incorporation into protein begins to increase. The lag is not observed for glucose grown cells transferred to media containing glucose and maltose or when maltose grown cells are transferred to media containing glucose or maltose. When growth begins the specific activity of a previously unreported alpha-glucosidase increases in the culture transferred to maltose until enzyme levels become 10 fold higher than that measured in the glucose control in which the specific activity was constant. The specific activity stops increasing if chloramphenicol is added. The "differential rate of synthesis" is 10 fold higher in the culture transferred to maltose than in the glucose control. The pH optimum of the alpha-glucosidase is 6080 The specific activity of a previously unreported phosphatase (pH optimum = 6.7, one band in disc electrophoresis at pH 5.5, 7.0, 801, 8.5) is the same and constant in either the glucose or maltose cultures. The presence of glucose, either added with or before maltose, does not interfere with the induction. Partially constitutive mutants were isolated. In one case it was found that a 2 fold increase in basal level of alpha-glucosidase eliminated the lag. Alpha-glucosidase activity paralleled maltose splitting activity (the former being measured by p-nitrophenyl-alpha-glucoside splitting, the latter by enzymatic measurement of glucose released from maltose). The interpretation is that M. laidlwaii A must adapt to maltose metabolism. The adaptation corresponds to the induction of alpha-glucosidase by maltose. The induction is under specific genetic control. There is no "glucose effect" in this system. Maltose metabolism is mediated, at least in part, by alpha-glucosidase in this organism.