This review consists of three major sections. The first and largest section reviews the protein constituents and known properties of the phosphotransferase systems present in well-studied Gram-positive bacteria. These bacteria include species of the following genera: (1) Staphylococcus, (2) Streptococcus, (3) Bacillus, (4) Lactobacillus, (5) Clostridium, (6) Arthrobacter, and (7) Brochothrix. The properties of the different systems are compared. The second major section deals with the regulation of carbohydrate uptake. There are four parts: (1) inhibition by intracellular sugar phosphates in Staphylococcus aureus, (2) PTS-mediated regulation of glycerol uptake in Bacillus subtilis, (3) competition for phospho-HPr in Streptococcus mutans, and (4) the possible involvement of protein kinases in the regulation of sugar uptake via the phosphotransferase system. The third section deals with the phenomenon of inducer expulsion. The first part is concerned with the physiological characterization of the phenomenon; then the consequences of unregulated uptake and expulsion, a futile cycle of energy expenditure, are considered. Finally, the biochemistry of the protein kinase and the protein phosphate phosphatase system, which appears to regulate sugar transport via the phosphotransferase system, is defined. The review, therefore, concentrates on the phosphotransferase system, its functions in carbohydrate transport and phosphorylation, the mechanisms of its regulation, and the mechanism by which it participates in the regulation of other physiological processes in the bacterial cell.

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Fusobacterium nucleatum is a Gram-negative anaerobic rod-shaped bacterium frequently isolated from human dental plaque. It is capable of the desulfuration of cysteine and methionine, resulting in the formation of sulfide and thiol volatiles, respectively. Intact cells, as well as cell-free extracts produced by French pressure cell lysis of F. nucleatum, hydrolyzed radiolabeled cysteine to produce sulfide, pyruvic acid, and ammonia. The hydrolysis products of radiolabeled methionine were a volatile thiol, ketobutyrate, and ammonia. Both activities were associated with the cytoplasmic component, not the membrane. The desulfuration mechanisms are heat-labile, inhibited by the presence of excess substrate, and rates are dependent upon substrate concentration. These dissimilar pathways by F. nucleatum can account in part for the presence of sulfur-containing volatile products that occur in the mouth.

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