where PEP denotes phosphoenolpyruvate; HPr, a small heat-stable protein containing histidine; and P-HPr, the phosphorylated protein. Their data indicated that I and HPr have broad functions serving a family of enzymes II, each specific for one or a few 2 We have recently demonstrated that the dissimilation of D-mannitol by Aerobacter aerogenes depends upon a phosphotransferase system similar to the one described above. In the absence of an inducible specific for D-mannitol (referred to as enzyme II in this work), A. aerogenes fails to grow on this compound.3 In the present report some of the phenotypic consequences of mutations affecting I or HPr are described. In contradistinction to the loss of II, which renders the cell incapable of utilizing a particular compound, the lack of I or HPr pleiotropically affects the metabolism of a number of polyhydric alcohols and sugars. Materials and Methods.-Bacteria: Strain 5P14, a double auxotroph of A. aerogenes 1033 (ref. 4), provided by B. Magasanik, was used as the starting cell line. Its strict requirement for arginine and guanine permitted distinction of mutant progeny from contaminating organisms. For our convenience this strain has been called strain 2002 (ref. 3) and will be referred to as such in this communication. Strain 2006, a mutant lacking II, hence unable to grow on.Dmannitol, was obtained from strain 2002 (ref. 3). Strain 2050, lacking I, and strain 2070, lacking HPr, were both isolated as D-mannitol-negative clones from populations of strain 2002 treated with ethyl methanesulfonate.5 MacConikey agar in which D-mannitol was substituted for lactose6 was used for the detection of these mutants. Strain 2051, a spontaneous revertant exhibiting normal growth rate on agar with D-mannose as carbon source, was derived from a population of cells of strain 2050 recycled in liquid medium with the same carbon source. Strain 2071 was isolated as a spontaneous revertant by directly plating 109 cells of strain 2070 on agar with D-sorbitol as carbon source. Chemicals: _-C14-D-mannitol (25 c/mole) was obtained from Nuclear-Chicago Corp.; Dmannitol, L-arabinose, D-mannose, and D-fructose from Eastman Kodak Co.; glycerol and maltose from Fisher Scientific Co.; D)-arabitol, ribitol, D-sorbitol, D-ribose, and D-galactose from Pfanstiehl Chemical Co.; i-inositol, lactose, and acid-hydrolyzed casein from Nutritional Biochemicals Corp.; D-glucose from Merck and Co.; and PEP (sodium salt) from Calbiochem.