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Glucose metabolism in Legionella pneumophila was studied by focusing on the Entner-Doudorotf (ED) pathway with a combined genetic and biochemical approach. The bacterium utilized exogenous glucose for synthesis of acid-insoluble cell components but manifested no discernible increase in the growth rate. Assays with permeabilized cell preparations revealed the activities of three enzymes involved in the pathway, i.e., glucokinase, phosphogluconate dehydratase, and 2-dehydro-3-deoxy-phosphogluconate aidolase, presumed to be encoded by the glk, edd, and eda genes, respectively. Gene-disrupted mutants for the three genes and the ywt G gene encoding a putative sugar transporter were devoid of the ability to metabolize exogenous glucose, indicating that the pathway is almost exclusively responsible for glucose metabolism and that the ywt G gene product is the glucose transporter. It was also established that these four genes formed part of an operon in which the gene order was edd-glk-eda-ywtG, as predicted by genomic information. Intriguingly, while the mutants exhibited no appreciable change in growth characteristics in vitro, they were defective in multiplication within eukaryotic cells, strongly indicating that the ED pathway must be functional for the intracellular growth of the bacterium to occur. Curiously, while the deficient glucose metabolism of the ywtG mutant was successfully complemented by the ywt [G.sup.+] gene supplied in trans via plasmid, its defect in intracellular growth was not. However, the latter defect was also manifested in wild-type cells when a plasmid carrying the mutant ywtG gene was introduced. This phenomenon, resembling so-called dominant negativity, awaits further investigation. doi: 10.1128/JB.01535-09

Streptococcus pneumoniae was shown to possess lactate oxidase in addition to well-documented pyruvate oxidase. The activities of both [H.sub.2][O.sub.2]-forming oxidases in wild-type cultures were detectable even in the early exponential phase of growth and attained the highest levels in the early stationary phase. For each of these oxidases, a defective mutant was constructed and compared to the parent regarding the dynamics of pyruvate and lactate in aerobic cultures. The results obtained indicated that the energy-yielding metabolism in the wild type could be best described by the following scheme. (i) As long as glucose is available, approximately one-fourth of the pyruvate formed is converted to acetate by the sequential action of pyruvate oxidase and acetate kinase with acquisition of additional ATP; (ii) the rest of the pyruvate is reduced by lactate dehydrogenase to form lactate, with partial achievement of redox balance; (iii) the lactate is oxidized by lactate oxidase back to pyruvate, which is converted to acetate as described above; and (iv) the sequential reactions mentioned above continue to occur as long as lactate is present. As predicted by this model, exogenously added lactate was shown to increase the final growth yield in the presence of both oxidases.

Streptococcus pyogenes strains can be divided into two classes, one capable and the other incapable of producing [H.sub.2][O.sub.2] (M. Saito, S. Ohga, M. Endoh, H. Nakayama, Y. Mizunoe, T. Hara, and S. Yoshida, Microbiology 147:2469-2477, 2001). In the present study, this dichotomy was shown to parallel the presence or absence of [H.sub.2][O.sub.2]-producing lactate oxidase activity in permeabilized cells. Both lactate oxidase activity and [H.sub.2][O.sub.2] production under aerobic conditions were detectable only after glucose in the medium was exhausted. Thus, the glucose-repressible lactate oxidase is likely responsible for [H.sub.2][O.sub.2] production in S. pyogenes. Of the other two potential [H.sub.2][O.sub.2]-producing enzymes of this bacterium, NADH and [alpha]-glycerophosphate oxidase, only the former exhibited low but significant activity in either class of strains. This activity was independent of the growth phase, suggesting that the protein may serve in vivo as a subunit of the [H.sub.2][O.sub.2]-scavenging enzyme NAD(P)H-linked alkylhydroperoxide reductase. The activity of lactate oxidase was associated with the membrane while that of NADH oxidase was in the soluble fraction, findings consistent with their respective physiological roles, i.e., the production and scavenging of [H.sub.2][O.sub.2]. Analyses of fermentation end products revealed that the concentration of lactate initially increased with time and decreased on glucose exhaustion, while that of acetate increased during the culture. These results suggest that the lactate oxidase activity of [H.sub.2][O.sub.2]-producing cells oxidizes lactate to pyruvate, which is in turn converted to acetate. This latter process proceeds presumably via acetyl coenzyme A and acetyl phosphate with formation of extra ATP.

Accumulation of hydrogen peroxide (H2O2) in non-H2O2-producing Streptococcus pyogenes strains, during the late exponential phase, results in the loss of cell viability but can be prevented by catalase, suggesting that H2O2 is the cause of lethality. Furthermore non-H2O2-producing strains exhibit resistance to phagocyte killing in chronic granulomatous disease patients.

Purification, mutant studies and gene cloning relative to ferritin from the obligate anaerobe Porphyromonas gingivalis, an obligate anaerobe, are discussed. The organism cane store heme on its cell surface, which gives black pigmentation of colonies on blood agar plates. Not much is known about its intracellular iron storage. P. gingivalis ferritin was found to comprise non-heme iron.

Stable L-forms of bacteria are resistant to serum but unstable L-forms, influenced by penicillin are sensitive to serum inhibition in Staphylococcus aureus. The inhibitory effect of serum on wall-less forms of bacteria is a factor to be considered during cultivation of bacterial forms.