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Comparing the cariogenic species Streptococcus sobrinus and S. mutans on whole genome level.

Conrads G, de Soet JJ, Song L, Henne K, Sztajer H, Wagner-Döbler I, Zeng AP - J Oral Microbiol (2014)

Bottom Line: It lacks the central competence genes comC, comS, and comR.There are more genes coding for glucosyltransferases and a novel energy production pathway formed by lactate oxidase, which is not found in S. mutans.Both species show considerable differences in the regulation of fructan catabolism.

View Article: PubMed Central - PubMed

Affiliation: Division of Oral Microbiology and Immunology, Department of Operative and Preventive Dentistry & Periodontology, RWTH Aachen University Hospital, Aachen, Germany; gconrads@ukaachen.de.

ABSTRACT

Background: Two closely related species of mutans streptococci, namely Streptococcus mutans and Streptococcus sobrinus, are associated with dental caries in humans. Their acidogenic and aciduric capacity is directly associated with the cariogenic potential of these bacteria. To survive acidic and temporarily harsh conditions in the human oral cavity with hundreds of other microbial co-colonizers as competitors, both species have developed numerous mechanisms for adaptation.

Objectives: The recently published novel genome information for both species is used to elucidate genetic similarities but especially differences and to discuss the impact on cariogenicity of the corresponding phenotypic properties including adhesion, carbohydrate uptake and fermentation, acid tolerance, signaling by two component systems, competence, and oxidative stress resistance.

Conclusions: S. sobrinus can down-regulate the SpaA-mediated adherence to the pellicle. It has a smaller number of two-component signaling systems and bacteriocin-related genes than S. mutans, but all or even more immunity proteins. It lacks the central competence genes comC, comS, and comR. There are more genes coding for glucosyltransferases and a novel energy production pathway formed by lactate oxidase, which is not found in S. mutans. Both species show considerable differences in the regulation of fructan catabolism. However, both S. mutans and S. sobrinus share most of these traits and should therefore be considered as equally virulent with regard to dental caries.

No MeSH data available.


Related in: MedlinePlus

Central metabolism pathways of mutans streptococci. The orange lines represent enzyme reactions conserved across the mutans streptococci strains compared in our recent study (31), whereas the blue lines represent enzyme reactions specifically present (solid line) or absent (dashed line) in S. sobrinus DSM 20742. Red crosses: the corresponding enzymes were not present in any strain investigated.
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Figure 0001: Central metabolism pathways of mutans streptococci. The orange lines represent enzyme reactions conserved across the mutans streptococci strains compared in our recent study (31), whereas the blue lines represent enzyme reactions specifically present (solid line) or absent (dashed line) in S. sobrinus DSM 20742. Red crosses: the corresponding enzymes were not present in any strain investigated.

Mentions: Due to their key roles in carbohydrates metabolism and energy production, glycolysis/gluconeogenesis, TCA cycle and pyruvate metabolism pathways are generally considered to be highly conserved among oral bacteria. Interestingly, between other MS and S. sobrinus, differences in the central carbon metabolic pathways were found by our group (31) and shown in Fig. 1. Facultative anaerobes such as lactic acid bacteria including Streptococcus lack cytochrome oxidases of a respiratory chain and ATP required for survival and growth is generated by substrate level phosphorylation in the glycolysis pathway almost exclusively (36). Interestingly, two L-lactate oxidases (with similarity between 65 and 73% to lactate oxidases of lactobacilli) are found to be conserved in S. sobrinus (so far confirmed for strains AC153, DSM 20742, TCI-107) but are absent in all S. mutans strains. These two enzymes catalyze the reaction of L-Lactate+O2→Pyruvate+H2O2 and/or D-Lactate+O2→Pyruvate+H2O2. Indeed, three strains of S. sobrinus have been shown to produce hydrogen peroxide in vitro (37). It has been reported that in S. pneumoniae concerted action of lactate oxidase and pyruvate oxidase forms a novel energy-generation pathway by converting lactate acid to acetic acid under aerobic growth conditions (38). Because there is no pyruvate oxidase identified in S. sobrinus DSM 20742, the function of the lactate oxidases in S. sobrinus DSM 20742 should be different to that of S. pneumoniae. By a close examination we hypothesize that lactate oxidase, together with pyruvate dehydrogenase, phosphate acetyl transferase and acetate kinase, could form a novel energy production pathway to convert lactate acid to acetate and simultaneously produce one additional ATP, as depicted. By doing so, the lactate oxidases of S. sobrinus DSM 20742 could also play a role in consuming lactate to regulate pH, which would be an advantage for S. sobrinus in resistance to acid stress. In addition, this pathway could replenish Acetyl-CoA, an important intermediate for the biosynthesis of fatty acids and amino acids. Furthermore, lactate oxidase and lactate dehydrogenase could form a local NAD+ regeneration system, which would be certainly advantageous to S. sobrinus DSM 20742 under aerobic growth conditions. Favored by possessing the lactate oxidases, S. sobrinus has the potential ability of producing H2O2 to kill not only competitors (oxygen sensitive S. mutans, oral anaerobes) but also macrophages (39), and defend its ecological niche. In contrast to the unique harboring of lactate oxidases in S. sobrinus DSM 20742, citrate lyase (EC 4.1.3.6), which catalyzes the cleavage of citrate into oxaloacetate and acetate, and oxaloacetate decarboxylase (EC 4.1.1.3), catalyzing the irreversible decarboxylation of oxaloacetate to pyruvate and CO2, are not found in S. sobrinus DSM 20742, as shown in Fig. 1 by the blue dotted lines. The absence of citrate lyase and oxaloacetate decarboxylase implies that S. sobrinus DSM 20742 might lack the ability in anaerobic utilization of citrate as a substrate. The disadvantages of S. sobrinus DSM 20742 in citrate utilization could be offset by the novel energy production pathway from lactate to acetate, as proposed above.


Comparing the cariogenic species Streptococcus sobrinus and S. mutans on whole genome level.

Conrads G, de Soet JJ, Song L, Henne K, Sztajer H, Wagner-Döbler I, Zeng AP - J Oral Microbiol (2014)

Central metabolism pathways of mutans streptococci. The orange lines represent enzyme reactions conserved across the mutans streptococci strains compared in our recent study (31), whereas the blue lines represent enzyme reactions specifically present (solid line) or absent (dashed line) in S. sobrinus DSM 20742. Red crosses: the corresponding enzymes were not present in any strain investigated.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4256546&req=5

Figure 0001: Central metabolism pathways of mutans streptococci. The orange lines represent enzyme reactions conserved across the mutans streptococci strains compared in our recent study (31), whereas the blue lines represent enzyme reactions specifically present (solid line) or absent (dashed line) in S. sobrinus DSM 20742. Red crosses: the corresponding enzymes were not present in any strain investigated.
Mentions: Due to their key roles in carbohydrates metabolism and energy production, glycolysis/gluconeogenesis, TCA cycle and pyruvate metabolism pathways are generally considered to be highly conserved among oral bacteria. Interestingly, between other MS and S. sobrinus, differences in the central carbon metabolic pathways were found by our group (31) and shown in Fig. 1. Facultative anaerobes such as lactic acid bacteria including Streptococcus lack cytochrome oxidases of a respiratory chain and ATP required for survival and growth is generated by substrate level phosphorylation in the glycolysis pathway almost exclusively (36). Interestingly, two L-lactate oxidases (with similarity between 65 and 73% to lactate oxidases of lactobacilli) are found to be conserved in S. sobrinus (so far confirmed for strains AC153, DSM 20742, TCI-107) but are absent in all S. mutans strains. These two enzymes catalyze the reaction of L-Lactate+O2→Pyruvate+H2O2 and/or D-Lactate+O2→Pyruvate+H2O2. Indeed, three strains of S. sobrinus have been shown to produce hydrogen peroxide in vitro (37). It has been reported that in S. pneumoniae concerted action of lactate oxidase and pyruvate oxidase forms a novel energy-generation pathway by converting lactate acid to acetic acid under aerobic growth conditions (38). Because there is no pyruvate oxidase identified in S. sobrinus DSM 20742, the function of the lactate oxidases in S. sobrinus DSM 20742 should be different to that of S. pneumoniae. By a close examination we hypothesize that lactate oxidase, together with pyruvate dehydrogenase, phosphate acetyl transferase and acetate kinase, could form a novel energy production pathway to convert lactate acid to acetate and simultaneously produce one additional ATP, as depicted. By doing so, the lactate oxidases of S. sobrinus DSM 20742 could also play a role in consuming lactate to regulate pH, which would be an advantage for S. sobrinus in resistance to acid stress. In addition, this pathway could replenish Acetyl-CoA, an important intermediate for the biosynthesis of fatty acids and amino acids. Furthermore, lactate oxidase and lactate dehydrogenase could form a local NAD+ regeneration system, which would be certainly advantageous to S. sobrinus DSM 20742 under aerobic growth conditions. Favored by possessing the lactate oxidases, S. sobrinus has the potential ability of producing H2O2 to kill not only competitors (oxygen sensitive S. mutans, oral anaerobes) but also macrophages (39), and defend its ecological niche. In contrast to the unique harboring of lactate oxidases in S. sobrinus DSM 20742, citrate lyase (EC 4.1.3.6), which catalyzes the cleavage of citrate into oxaloacetate and acetate, and oxaloacetate decarboxylase (EC 4.1.1.3), catalyzing the irreversible decarboxylation of oxaloacetate to pyruvate and CO2, are not found in S. sobrinus DSM 20742, as shown in Fig. 1 by the blue dotted lines. The absence of citrate lyase and oxaloacetate decarboxylase implies that S. sobrinus DSM 20742 might lack the ability in anaerobic utilization of citrate as a substrate. The disadvantages of S. sobrinus DSM 20742 in citrate utilization could be offset by the novel energy production pathway from lactate to acetate, as proposed above.

Bottom Line: It lacks the central competence genes comC, comS, and comR.There are more genes coding for glucosyltransferases and a novel energy production pathway formed by lactate oxidase, which is not found in S. mutans.Both species show considerable differences in the regulation of fructan catabolism.

View Article: PubMed Central - PubMed

Affiliation: Division of Oral Microbiology and Immunology, Department of Operative and Preventive Dentistry & Periodontology, RWTH Aachen University Hospital, Aachen, Germany; gconrads@ukaachen.de.

ABSTRACT

Background: Two closely related species of mutans streptococci, namely Streptococcus mutans and Streptococcus sobrinus, are associated with dental caries in humans. Their acidogenic and aciduric capacity is directly associated with the cariogenic potential of these bacteria. To survive acidic and temporarily harsh conditions in the human oral cavity with hundreds of other microbial co-colonizers as competitors, both species have developed numerous mechanisms for adaptation.

Objectives: The recently published novel genome information for both species is used to elucidate genetic similarities but especially differences and to discuss the impact on cariogenicity of the corresponding phenotypic properties including adhesion, carbohydrate uptake and fermentation, acid tolerance, signaling by two component systems, competence, and oxidative stress resistance.

Conclusions: S. sobrinus can down-regulate the SpaA-mediated adherence to the pellicle. It has a smaller number of two-component signaling systems and bacteriocin-related genes than S. mutans, but all or even more immunity proteins. It lacks the central competence genes comC, comS, and comR. There are more genes coding for glucosyltransferases and a novel energy production pathway formed by lactate oxidase, which is not found in S. mutans. Both species show considerable differences in the regulation of fructan catabolism. However, both S. mutans and S. sobrinus share most of these traits and should therefore be considered as equally virulent with regard to dental caries.

No MeSH data available.


Related in: MedlinePlus