Galactose Metabolism by
            <i>Streptococcus mutans</i>

Abranches, Jacqueline; Chen, Yi-Ywan M.; Burne, Robert A.

doi:10.1128/aem.70.10.6047-6052.2004

Cited by 53 publications

(56 citation statements)

References 24 publications

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“…Additionally, the incorporation of galactose intermediates into glycolysis through the tagatose pathway (involving the lacC and lacD genes) was also enhanced. For efficient utilization of galactose in S. mutans, a combined function of both tagatose and Leloir pathways is required (Abranches et al, 2004). In this respect, the gene encoding the galactose-1-phosphate uridyl transferase (spr1667) of the Leloir pathway was up-regulated in the pneumococcal ATR.…”

Section: Discussionmentioning

confidence: 86%

Transcriptional analysis of the acid tolerance response in Streptococcus pneumoniae

et al. 2005

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Streptococcus pneumoniae, one of the major causes of morbidity and mortality in humans, faces a range of potentially acidic conditions in the middle and late stages of growth in vitro, in diverse human fluids during the infection process, and in biofilms present in the nasopharynx of carriers. S. pneumoniae was shown to develop a weak acid tolerance response (ATR), where cells previously exposed to sublethal pHs (5?8-6?6) showed an increased survival rate of up to one order of magnitude after challenge at the lethal pH (4?4, survival rate of 10 "4 ).Moreover, the survival after challenge of stationary phase cells at pH 4?4 was three orders of magnitude higher than that of cells taken from the exponential phase, due to the production of lactic acid during growth and increasing acidification of the growth medium until stationary phase. Global expression analysis after short-term (5, 15 and 30 min, the adaptation phase) and long-term (the maintenance phase) acidic shock (pH 6?0) was performed by microarray experiments, and the results were validated by real-time RT-PCR. Out of a total of 126 genes responding to acidification, 59 and 37 were specific to the adaptation phase and maintenance phase, respectively, and 30 were common to both periods. In the adaptation phase, both up-and down-regulation of gene transcripts was observed (38 and 21 genes, respectively), whereas in the maintenance phase most of the affected genes were down-regulated (34 out of 37). Genes involved in protein fate (including those involved in the protection of the protein native structure) and transport (including transporters of manganese and iron) were overrepresented among the genes affected by acidification, 8?7 and 24?6 % of the acid-responsive genes compared to 2?8 % and 9?6 % of the genome complement, respectively. Cross-regulation with the response to oxidative and osmotic stress was observed. Potential regulatory motifs involved in the ATR were identified in the promoter regions of some of the regulated genes.

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Section: Discussionmentioning

confidence: 86%

Transcriptional analysis of the acid tolerance response in Streptococcus pneumoniae

et al. 2005

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“…The first enzyme of the Leloir pathway, galactokinase, catalyzes the phosphorylation of galactose to galactose-1-phosphate. Inactivation of the galactokinase gene completely abolished the growth of S. mutans in galactose (3,5). Therefore, the primary galactose uptake might not be mediated by a PTS.…”

Section: Fig 3 Differential Transcription Of Genes For Pts Eii and mentioning

confidence: 96%

Global Transcriptional Analysis of Streptococcus mutans Sugar Transporters Using Microarrays

2007

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The transport of carbohydrates by Streptococcus mutans is accomplished by the phosphoenolpyruvatephosphotransferase system (PTS) and ATP-binding cassette (ABC) transporters. To undertake a global transcriptional analysis of all S. mutans sugar transporters simultaneously, we used a whole-genome expression microarray. Global transcription profiles of S. mutans UA159 were determined for several monosaccharides (glucose, fructose, galactose, and mannose), disaccharides (sucrose, lactose, maltose, and trehalose), a ␤-glucoside (cellobiose), oligosaccharides (raffinose, stachyose, and maltotriose), and a sugar alcohol (mannitol). The results revealed that PTSs were responsible for transport of monosaccharides, disaccharides, ␤-glucosides, and sugar alcohol. Six PTSs were transcribed only if a specific sugar was present in the growth medium; thus, they were regulated at the transcriptional level. These included transporters for fructose, lactose, cellobiose, and trehalose and two transporters for mannitol. Three PTSs were repressed under all conditions tested. Interestingly, five PTSs were always highly expressed regardless of the sugar source used, presumably suggesting their availability for immediate uptake of most common dietary sugars (glucose, fructose, maltose, and sucrose). The ABC transporters were found to be specific for oligosaccharides, raffinose, stachyose, and isomaltosaccharides. Compared to the PTSs, the ABC transporters showed higher transcription under several tested conditions, suggesting that they might be transporting multiple substrates.Numerous studies have implicated Streptococcus mutans as the principal causative agent of human dental caries. It is well known that host diet is important for S. mutans cariogenicity, and sugar metabolism of this bacterium plays a key role in the formation of caries. S. mutans is able to metabolize a wide range of carbohydrates that may originate from dietary sources or from host macromolecules. If the diet is rich in sugars, especially sucrose, the end product of sugar metabolism is mostly lactic acid that can lead to demineralization of tooth enamel. Therefore, sugar transport and metabolism by this bacterium are directly related to the onset and development of dental caries.In bacteria, sugar substrates are taken up by ATP-binding cassette (ABC) transporters, galactoside-pentose hexuronide (GPH) translocators, and, most commonly, phosphoenolpyruvate-sugar phosphotransferase systems (PTSs). The bacterial PTSs are responsible for the binding, transmembrane transport, and phosphorylation of numerous sugar substrates. These systems are also involved in the regulation of a variety of metabolic and transcriptional processes (29, 37). The PTS consists of two nonspecific energy-coupling components, enzyme I (EI) and a heat-stable protein (HPr), as well as several sugarspecific multiprotein permeases known as EII. In most cases, EIIA and EIIB are located in the cytoplasm, while EIIC acts as a membrane channel (37). Fourteen PTS systems have been found in S. mutans UA1...

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“…Repression of the gal operon is mediated by GalR, which is believed to have its DNA-binding activity to an operator site(s) located in the galR-galK intergenic region modified by intracellular galactose (8). A more recent study by our group suggested that the Leloir and tagatose-6-phosphate pathways are both important for the utilization of galactose and that the transcript levels of the galK and lac genes were elevated during growth on galactose (3).…”

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confidence: 99%

“…Inactivation of the galK gene was shown to severely impair the ability of S. mutans to grow with galactose as the sole carbohydrate (3). Of note, some galactose-containing carbohydrates appear to be transported by the multiple sugar metabolism (msm) system (41), the permease responsible for transporting galactose has not yet been identified (3).…”

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confidence: 99%

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Utilization of Lactose and Galactose by Streptococcus mutans : Transport, Toxicity, and Carbon Catabolite Repression

2010

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Abundant in milk and other dairy products, lactose is considered to have an important role in oral microbial ecology and can contribute to caries development in both adults and young children. To better understand the metabolism of lactose and galactose by Streptococcus mutans, the major etiological agent of human tooth decay, a genetic analysis of the tagatose-6-phosphate (lac) and Leloir (gal) pathways was performed in strain UA159. Deletion of each gene in the lac operon caused various alterations in expression of a P lacA -cat promoter fusion and defects in growth on either lactose (lacA, lacB, lacF, lacE, and lacG), galactose (lacA, lacB, lacD, and lacG) or both sugars (lacA, lacB, and lacG). Failure to grow in the presence of galactose or lactose by certain lac mutants appeared to arise from the accumulation of intermediates of galactose metabolism, particularly galatose-6-phosphate. The glucose-and lactose-PTS permeases, EII Man and EII Lac , respectively, were shown to be the only effective transporters of galactose in S. mutans. Furthermore, disruption of manL, encoding EIIAB Man , led to increased resistance to glucose-mediated CCR when lactose was used to induce the lac operon, but resulted in reduced lac gene expression in cells growing on galactose. Collectively, the results reveal a remarkably high degree of complexity in the regulation of lactose/galactose catabolism.Lactose, a ␤1,4-linked disaccharide of ␤-D-galactose and ␣/␤-D-glucose, is commonly found in the dairy-rich diets of most industrialized nations. Lactose is rapidly fermented by streptococci, including the cariogenic oral bacterium Streptococcus mutans (21), as well as by a variety of industrially important lactic acid bacteria (LAB) (19). Multiple pathways have been identified in bacteria for the utilization of lactose encountered in the environment. For example, Streptococcus salivarius strain 25975 (26) secretes a ␤-galactosidase that hydrolyzes extracellular lactose into galactose and glucose, although it is more common for lactose to be transported before cleavage (18). Most efficiently, and almost exclusively in Gram-positive bacteria, lactose is internalized by the phosphoenolpyruvate (PEP)-dependent sugar-phosphotransferase system (PTS), yielding lactose-6-phosphate (Lac-6-P) (36). The Lac-6-P is hydrolyzed to glucose and galactose-6-phosphate (Gal-6-P) by a cytoplasmic phospho-␤-galactosidase (LacG), and the Gal-6-P can be catabolized by the tagatose-6-phosphate pathway (18) (Fig. 1). Many bacteria, including Escherichia coli, Lactococcus lactis strain 7962, and S. salivarius strain 57.I, can internalize lactose through non-PTS transporters. Intracellular lactose is cleaved by a ␤-galactosidase enzyme and the D-galactose can directly enter the Leloir pathway ( Fig. 1) (18, 20).S. mutans has a functional lactose-specific PTS (14, 26) encoded by the lacF (EIIA) and lacE (EIIBC) genes (40). A phospho-␤-galactosidase (lacG) and the enzymes of the tagatose-6-phosphate pathway (Fig. 1B), including the two subunits of the heteromeri...

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Galactose Metabolism by Streptococcus mutans

Cited by 53 publications

References 24 publications

Transcriptional analysis of the acid tolerance response in Streptococcus pneumoniae

Transcriptional analysis of the acid tolerance response in Streptococcus pneumoniae

Global Transcriptional Analysis of Streptococcus mutans Sugar Transporters Using Microarrays

Utilization of Lactose and Galactose by Streptococcus mutans : Transport, Toxicity, and Carbon Catabolite Repression

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