Abstract
Many pleiotropically carbohydrate-negative mutants lacking components of the phosphoenolpyruvate: sugar phosphotransf erase system (PEP. PTS or simply PTS), i. e., pleiotropic PTS mutants, of Vibrio parahaemolyticus were isolated by the methyl-α-D-glucoside screening method described previously (J. Bacteriol. 119: 632-634, 1974). As expected from the selecting procedure, all the mutants isolated were deficient in the utilization of glucose as the carbon and energy source. Their patterns of pleiotropy for the utilization of the other eight carbohydrates, however, were strikingly different from one another. Some of the metabolic defects of the mutants could be overcome by supplementing cyclic adenosine 3', 5'-monophosphate (cAMP) to the medium. Therefore, such metabolic defects might be due not to any defect in the PTSmediated phosphorylation of carbohydrates, but to an insufficient supply of cAMP to induce certain enzymes involved in metabolism of the sugars. A similar finding has been reported. in PTS-mutants of Escherichia coli. On the other hand, the pleiotropic patterns of the V. parahaemolyticus mutants were still heterogeneous even in the presence of exogenous cAMP. Therefore, at least three different types, B, C, and D, of mutants were recognized. Mutants, of type B were defective in the utilization of five carbohydrates, glucose, trehalose, fructose, mannose, and mannitol, whereas mutants of type D could utilize fructose normally, and mutants of type C were lacking only in the utilization of glucose and trehalose when cAMP was present in the medium. A possible interpretation for this phenomenon is that the PEP·PTS of the organism has at least three protein components, which are common to the PTS-mediated phosphorylation reaction for more than two carbohydrates.
