REGULATION OF SUGAR TRANSPORT AND METABOLISM IN LACTIC ACID BACTERIA

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Two new amino acids have been discovered, isolated and purified from cells of Streptococcus lactis: N(5)-(1-carboxyethyl)ornithine and N(6)-(1-carboxyethyl) lysine. Confirmation of structure has been obtained by 1-H and 13-C nuclear magnetic resonance spectroscopy (NMR), mass spectroscopy and by chemical synthesis. Probable routes of in vivo synthesis of the two novel compounds, have been elucidated by radiotracer procedures and by thin-layer fluorography. The first detailed studies of sugar transport by the oral anaerobic microorganisms Peptostreptococcus anaerobius (Gram-positive) and Fusobacterium nucleatum (Gram-negative) have been conducted. Glucose transport by these bacteria is dependent upon the presence of specific amino acids in the extracellular environment. The biochemical basis for this unique amino acid dependency, and the modes of energy coupling to sugar accumulation have been established. The specificity of the glucose carrier in F. nucleatum has been determined by use of structural glucose analogs, and glycogen has been found to represent the major product of glucose uptake by the cell. These findings, obtained by use of [14-C]glucose and chemical analysis, have been elegantly confirmed by ultrastructural and morphological studies involving electron- and phase-contrast microscopy.