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In addition to its role as carbon and energy source, fructose metabolism was reported to affect other cellular processes, such as biofilm formation by streptococci and bacterial pathogenicity in plants. Fructose genes encoding a 1-phosphofructokinase and a phosphotransferase system (PTS) fructose-specific enzyme IIABC component reside commonly in a gene cluster with a DeoR family regulator in various gram-positive bacteria. We present a comprehensive study of fructose metabolism in Lactococcus lactis, including a systematic study of fru mutants, global messenger analysis, and a molecular characterization of its regulation. The fru operon is regulated at the transcriptional level by both FruR and CcpA and at the metabolic level by inducer exclusion. The FruR effector is fructose-1-phosphate (F1P), as shown by combined analysis of transcription and measurements of the intracellular F1P pools in mutants either unable to produce this metabolite or accumulating it. The regulation of the fru operon by FruR requires four adjacent 10-bp direct repeats. The well-conserved organization of the fru promoter region in various low-GC gram-positive bacteria, including CRE boxes as well as the newly defined FruR motif, suggests that the regulation scheme defined in L. lactis could be applied to these bacteria. Transcriptome profiling of fruR and fruC mutants revealed that the effect of F1P and FruR regulation is limited to the fru operon in L. lactis. This result is enforced by the fact that no other targets for FruR were found in the available low-GC gram-positive bacteria genomes, suggesting that additional phenotypical effects due to fructose metabolism do not rely directly on FruR control, but rather on metabolism.

The sequencing of the serotype-specific, 5.9-kb region II of Haemophilus influenzae type a capsulation locus has been undertaken. The sequence was found to have four open reading frames named acs1 to acs4. Acs1 is 96% similar to H. influenzae type b Orf1 having CDP-ribitol pyrophosphorylase activity. Acs1 was further cloned and over expressed in Escherichia coli to find out if it is a bifunctional enzyme. Results indicate that E. coli cells with acs1 have ribitol 5-phosphate dehydrogenase and CDP-ribitol pyrophosphorylase activities.

Studies show that two specific mutations result in approximately 40% of alleles for glycogen-storage diseases. Through cloning a cDNA that encoded a putative glucose-6-phosphate translocase, researchers determined the mutations that resulted in disease alleles. These findings could indicate that glucose-6-phosphate and inorganic phosphate are transported by the same transporter in microsomes.

The biochemical basis fo glucose-induced inhibition of malolactic fermentation in Leuconostoc oenos was examined. The study made use of in vivo and in vitro nuclear magnetic resonance spectroscopy and manometric techniques. Results revealed that inhibition of malolactic activity of glucose by L. oenos suggest that activity of the acetaldehyde dehydrogenase is low compared to those of NAD(P)H-forming enzymes in the early stages of glucose metabolism.

Erythritol is formed from glucose 6-phosphate by Leuconostoc oenos during the isomerization of glucose 6-phosphate to fructose 6-phosphate by a phosphoglucose isomerase. The production of erythritol is regulated by anaerobiosis, and an increase in the concentration of hexo 6-phosphate is eventually observed in the erythritol-producing bacteria, in the absence of oxygen.

An investigation by 13/C nuclear magnetic resonance analysis on the metabolism of glucose by nongrowing cells of Leuconostoc oenos GM revealed the production of erythritol and glycerol. Elucidation of the pathway of erythritol production using 13/C-labelled glucose showed that the synthesis resulted from the reduction and dephosphorylation of the C-4 moiety of fructose-6-phosphate. Different conditions of aeration affected the metabolism of glucose.

Lactobacillus brevis and L. buchneri produce a 1,3-propanediol:NAD+ oxidoreductase which has properties similar to that of the corresponding Kleibsiella pneumoniae enzyme. Characterization of this enzyme showed that it is an octameric protein with molecular mass of 330 kDa, and requires manganous or ferrous ions for activity. It differs from the K pneuminiae enzyme in that it can dehydrogenate glycerol at a significant rate.In addition to glycerol, the enzyme is < 10% active with ethanol and 1,3- propanediol. These properties are markedly different from those of a L.reuteri 1,3-propanediol dehydrogenase.

The sugar-glycerol cofermentation process in Lactobacillus brevis and L. buchneri was analyzed. The presence of glycerol induced biphasic growth rates, resulting in increased growth yields. This could be attributed to the presence of 1,3-propanediol, an intermediate in glycerol metabolism, which channeled intermediate metabolites towards NADH-producing reactions. This additional NADH allows lactate to be scavenged for ATP generation, producing acetate via pyruvate. The conversion of lactate to pyruvate probably involves NAD-independent lactate dehydrogenases, which are induced under conditions of reduced intracellular NADH levels.