Involvement of lactose enzyme II of the phosphotransferase system in rapid expulsion of free galactosides from Streptococcus pyogenes

Reizer, Jonathan; Saier, Milton H.

doi:10.1128/jb.156.1.236-242.1983

Cited by 45 publications

(19 citation statements)

References 35 publications

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“…As mentioned earlier, this stimulation of xtl expulsion was abolished by metabolic inhibitors, such as IAA, and no stimulation of expulsion occurred in the presence of nonmetabolizable sugar analogs (e.g., 2-DG or 6-deoxyglucose [data not shown]). A striking parallel exists between the dephosphorylation and accelerated expulsion of the nonmetabolizable pentitol from L. casei and the previously described expulsion of the nonmetabolizable hexose-6-phosphate (methyl-3-D-thiogalactopyranoside-6-phosphate) from cells of lactic acid bacteria (12,13,17). Studies by Reizer et al (11) and Thompson and Saier (17) suggest that energy (possibly ATP) and certain glycolytic intermediate products are involved in the increased rate of dephosphorylation and expulsion of thiomethylglucoside-6-phosphate in Streptococcus pyogenes and S. lactis, respectively.…”

Section: Resultssupporting

confidence: 55%

Futile xylitol cycle in Lactobacillus casei

Hausman¹,

Thompson²,

London³

1984

J Bacteriol

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A futile xylitol cycle appears to be responsible for xylitol-mediated inhibition of growth of Lactobacillus casei CI-16 at the expense of ribitol. The gratuitously induced xylitol-specific phosphoenolpyruvate-dependent phosphotransferase accumulates the pentitol as xylitol-5-phosphate, a phosphatase cleaves the latter, and an export system expels the xylitol. Operation of the cycle rapidly dissipates the ribitol-5-phosphate pool (and ultimately the energy supply of the cell), thereby producing bacteriostasis.Those strains of Lactobacillus casei capable of growing at the expense of ribitol (rtl) are sensitive to xylitol (xtl) when the former is used as a source of energy (7). Previous studies have shown that growth at the expense of rtl results in the coincidental induction of an xtl-specific phosphoenolpyruvate (PEP)-dependent phosphotransferase system (PTS). The xtl PTS transports xtl into the cell to form xylitol-5phosphate (xtl-5-P); however, the absence of an xtl-5-P dehydrogenase prevents the further metabolism of this intermediate, and it accumulates in the cell (7). Depending upon its external concentration, xtl can either completely inhibit growth (at >5 mM) or merely increase the generation time of the organism (at <2 mM). Although much is known about the metabolic events that occur during the xtl-mediated inhibition of L. casei, the actual mechanism responsible for producing the bacteriostatic effects is unknown. Thompson and Chassy (15) demonstrated that the inhibition of growth by 2-deoxy-D-glucose (2-DG) in cultures of Streptococcus lactis 133 growing on lactose or sucrose was due to the initiation and maintenance of a futile cycle. The 2-DG cycle catalyzed the import and export of the nonmetabolizable hexose at the expense of the energy reserves (PEP) of the cells, thereby inhibiting growth.In this report, we demonstrate that the bacteriostatic effects of xtl are probably due to the futile cycling of the nonmetabolizable pentitol which (like the 2-DG-mediated inhibition) dissipates the energy reserves of L. casei Cl-16. MATERIALS AND METHODSCultivation and maintenance of L. casei CI-16. L. casei Cl-16 was obtained from the private collection of M. Rogosa, National Institute of Dental Research, Bethesda, Md. The organism was maintained and stored in fortified litmus milk medium (9). Lactobacillus-carrying medium (5) was used for all growth experiments and to prepare washed suspensions for resting-cell studies. All substrates were filter sterilized, and the microorganism was growth at 37°C in static culture.Growth experiments. The fate of the metabolic intermediate products of rtl before and after the addition of xtl was monitored by periodic sampling of an exponential-phase culture. Replicate sterile screw-capped test tubes were filled with 15 ml of filter-sterilized lactobacillus-carrying medium containing 30 mM [1-'4C]rtl (specific activity, 1 pCi/p.mol) * Corresponding author. and was adjusted to a density of 100 to 110 Klett units (660nm filter) with a washed-cell suspension harvested from a mi...

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Section: Resultssupporting

confidence: 55%

Futile xylitol cycle in Lactobacillus casei

Hausman¹,

Thompson²,

London³

1984

J Bacteriol

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“…Given the stress conditions (low a w and/or low pH), it is possible that the extracellular galactose found in the present study might have originated from dephosphorylation of galactose 6-phosphate and subsequent excretion from the cells, a known mechanism of detoxification in lactococci (2,40,48,49). In comparison, Streptococcus thermophilus (25,44) and homofermentative lactobacilli (24) excrete nonutilizable galactose resulting from lactose hydrolysis.…”

Section: Discussionmentioning

confidence: 86%

Influence of Reduced Water Activity on Lactose Metabolism byLactococcus lactissubsp.cremorisat Different pH Values

Liu

Asmundson

Gopal³

et al. 1998

Appl Environ Microbiol

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The influence of reduced water activity (aw) on lactose metabolism by Lactococcus lactis subsp.cremoris 2254 and 2272 was studied at different pH values. In control incubations (aw, 0.99) with nongrowing cells in pH-controlled phosphate buffer, the levels of carbon recovered asl-(+)-lactate were 92% at pH 6.1 and 5.3 and 78% at pH 4.5. However, the levels of recovery decreased to ∼50% at all pH values tested when the aw was 0.88 (with glycerol as the humectant). When growing cells in broth controlled at pH 6.3 were used, a reduction in the aw from 0.99 to 0.96 resulted in a decrease in the level of lactose carbon recovered asl-(+)-lactate from 100 to 71%. Low levels ofl-(+)-lactate carbon recovery (<50%) were also observed with cells resuspended in pH-uncontrolled reconstituted skim milk at aw values of 0.99 and 0.87 and in young cheese curds. The missing lactose carbon could not be accounted for by acetate, ethanol, formate, acetaldehyde, or pyruvate. Attempts were made to determine where the missing lactose carbon was diverted to under the stress conditions used. Some of the missing lactose carbon was recovered as galactose (0.1 to 2.5 mM) in culture supernatants. Decreasing either the aw or the pH resulted in increased galactose accumulation by nongrowing cells; adjusting both environmental factors together potentiated the effect. The sensitivities of the two lactococcal strains tested were different; strain 2272 was more prone to accumulate galactose under stress conditions. A methyl pentose(s) and additional galactose were found in acid-hydrolyzed supernatants from cultures containing both growing and nongrowing cells, indicating that a saccharide(s) rich in these components was formed by lactococci under low-aw and low-pH stress conditions.

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“…We also note that the substrate specificity of this antiporter places it in a special position with regard to more general aspects of bacterial transport. For example; given a 2:1 stoichiometry (see above), the anion exchange in S. lactis 7962 could perform the same net task attributed in other streptococci to sequential operation of an intracellulat phosphatase and an enzyme II-mediated extrusion of free sugar (18,19,28). This striking parallel between anion exchange anid inducer expulsion does suggest that phosphate/sugar 6-phosphate antiport might share features with two important mechanisms of sugar transfer in bacteria-phosphotransferase group transtocation and cation-linked sugar symport.…”

Section: Discussionmentioning

confidence: 97%

Phosphate/hexose 6-phosphate antiport in Streptococcus lactis

Maloney¹,

Ambudkar

Thomas

et al. 1984

J Bacteriol

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After growth in appropriate media, resting cells of Streptococcus lactis 7962 showed a rapid exchange between external and internal pools of inorganic phosphate. This exchange was not found in other strains of S. lactis (ML3, 133, or K1) or in Streptococcus faecalis. Phosphate exchange in S. lactis 7962 did not require other anions or cations in the assay medium, nor was phosphate influx affected by the membrane potential and pH gradient formed during glycolysis. Thus, the exchange reaction was independent of known ionic drivers (H+, Na+, OH-, etc.). Experiments testing inhibitions of phosphate entry suggested that alternative substrates for exchange included arsenate, as well as the 6-phosphates of glucose, 2-deoxyglucose, fructose, mannose, or glucosamine, and direct studies with 2-deoxyglucose 6-phosphate verified that resting cells could accumulate this sugar phosphate to levels expected for exchange with internal phosphate. Two other observations supported the idea of an exchange between phosphate and sugar phosphate. First, early addition of the heterologous substrate blocked entry of the test compound, whereas later addition caused efflux of preaccumulated material. Second, expression of phosphate exchange and 2-deoxyglucose 6phosphate transport varied in parallel. Both activities were found at high levels after growth in medium supplemented with rhamnose or arabinose, at intermediate levels with addition of galactose, and at low levels after growth with glucose, fructose, or mannose. We conclude that these findings describe a novel anion antiporter that mediates the exchange of phosphate (arsenate) and sugar 6-phosphates. Current descriptions of secondary, ion-linked active transport in bacteria give many examples of the coupling between a driving cation and driven solute (for reviews, see references 4, 15, and 20). If the solute is anionic, or if it carries no net charge, one usually finds that an accumulation is supported by a symport (cotransport) reaction. If, on the other hand, a driven solute is cationic, the coupled event is commonly one of antiport (countertransport, exchange). In keeping with the

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Involvement of lactose enzyme II of the phosphotransferase system in rapid expulsion of free galactosides from Streptococcus pyogenes

Cited by 45 publications

References 35 publications

Futile xylitol cycle in Lactobacillus casei

Futile xylitol cycle in Lactobacillus casei

Influence of Reduced Water Activity on Lactose Metabolism byLactococcus lactissubsp.cremorisat Different pH Values

Phosphate/hexose 6-phosphate antiport in Streptococcus lactis

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