Metabolism of sugars by genetically diverse species of oral Leptotrichia

Abstract

SUMMARY Leptotrichia buccalis ATCC 14201 is a Gram-negative, anaerobic rod-shaped bacterium resident in oral biofilm at the tooth surface. The sequenced genome of this organism reveals three contiguous genes at loci: Lebu_1525,1526 and 1527. The translation products of these genes exhibit significant homology with phospho-α-glucosidase (Pagl), a regulatory protein (GntR) and a phosphoenol pyruvate-dependent sugar transport protein (EIICB), respectively. In non-oral bacterial species, these genes comprise the sim operon that facilitates sucrose isomer metabolism. Growth studies showed that L. buccalis fermented a wide variety of carbohydrates, including four of the five isomers of sucrose. Growth on the isomeric disaccharides elicited expression of a 50kDa polypeptide comparable in size to that encoded by Lebu_1525. The latter gene was cloned, and the expressed protein was purified to homogeneity from Escherichia coli TOP 10 cells. In the presence of two cofactors, NAD+ and Mn2+ ion, the enzyme readily hydrolyzed p-nitrophenyl-α-glucopyranoside 6-phosphate (pNPαG6P), a chromogenic analog of the phosphorylated isomers of sucrose. By comparative sequence alignment, immuno-reactivity and signature motifs, the enzyme can be assigned to the phospho-α-glucosidase (Pagl) clade of Family 4 of the glycosyl hydrolase super family. We suggest that the products of Lebu_1527 and 1525, catalyze the phosphorylative translocation and hydrolysis of sucrose isomers in L. buccalis, respectively. Four genetically diverse, but 16S rDNA related species of Leptotrichia have recently been described: L. goodfellowii, L. hofstadii, L. shahii and L. wadei. The phenotypic traits of these new species, with respect to carbohydrate utilization, have also been determined.

Microbiomes of Site-Specific Dental Plaques from Children with Different Caries Status

“…498 also showed a consistently increased frequency from health to disease states. Leptotrichia has high saccharolytic potential, is able to ferment a large variety of monoand disaccharides to lactic acid (49), and is well adapted to thrive under conditions that are conducive to caries formation. Certain Leptotrichia species were shown to be negatively associated with elevated urease activity in plaques, which is correlated with dental health, and therefore positively associated with caries (50).…”

Urease and Dental Plaque Microbial Profiles in Children

“…The only bacteria that were inversely associated with urease activity but positively associated with caries activity were various species of the genera Leptotrichia . These bacteria are becoming of interest as potential cariogenic pathogens, because of their high saccharolytic potential, and their ability to ferment a large variety of mono- and disaccharides to lactic acid [ 28 ]. The observation that these bacteria can be positively associated with caries and negatively associated with urease levels encourage the further exploration of their role in the development of dental caries and their potential use as caries risk indicators in children.…”

Leptotrichia species in human infections II

“…Among the many microbial species residing in oral biofilms (plaque) at the tooth surface [104], mutans streptococci have long been recognized as primary contributors in the etiology of dental caries [104]. The pathogenicity of organisms such as Streptococcus mutans and S. sobrinus is attributable in part to (i) the capacity of these species to produce extracellular glucan(s) from dietary sucrose that facilitate microbial adherence to the tooth surface, and (ii) the fermentation of sucrose to lactic acid – the causative agent in the demineralization of tooth enamel [104].…”

“…The pathogenicity of organisms such as Streptococcus mutans and S. sobrinus is attributable in part to (i) the capacity of these species to produce extracellular glucan(s) from dietary sucrose that facilitate microbial adherence to the tooth surface, and (ii) the fermentation of sucrose to lactic acid – the causative agent in the demineralization of tooth enamel [104]. There is supporting evidence that the genus Leptotrichia is highly saccharolytic [1–3,11,104–106], implying that it ferments a wide variety of mono- and disaccharides to lactic acid similar to S. mutans . This property may implicate the participation of Leptotrichia species in tooth decay [1–3,11].…”