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Metabolism of sugars by genetically diverse species of oral Leptotrichia.

ABSTRACT: 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, Lebu_1526 and Lebu_1527. The translation products of these genes exhibit significant homology with phospho-?-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 50-kDa 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 TOP10 cells. In the presence of two cofactors, NAD(+) and Mn(2+) ions, the enzyme readily hydrolyzed p-nitrophenyl-?-glucopyranoside 6-phosphate (pNP?G6P), a chromogenic analogue of the phosphorylated isomers of sucrose. By comparative sequence alignment, immunoreactivity and signature motifs, the enzyme can be assigned to the phospho-?-glucosidase (Pagl) clade of Family 4 of the glycosyl hydrolase super family. We suggest that the products of Lebu_1527 and Lebu_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.

SUBMITTER: Thompson J

PROVIDER: S-EPMC3257818 | biostudies-literature | 2012 Feb

REPOSITORIES: biostudies-literature

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Metabolism of sugars by genetically diverse species of oral Leptotrichia.

Thompson J J Pikis A A

Molecular oral microbiology 20111004 1

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, Lebu_1526 and Lebu_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 ge ...[more]

PMID: 22230464

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Project description:Mice have been frequently used to study the adverse effects of inorganic arsenic (iAs) exposure in laboratory settings. Like humans, mice metabolize iAs to monomethyl-As (MAs) and dimethyl-As (DMAs) metabolites. However, mice metabolize iAs more efficiently than humans, which may explain why some of the effects of iAs reported in humans have been difficult to reproduce in mice. In the present study, we searched for mouse strains in which iAs metabolism resembles that in humans. We examined iAs metabolism in male mice from 12 genetically diverse Collaborative Cross (CC) strains that were exposed to arsenite in drinking water (0.1 or 50 ppm) for 2 weeks. Concentrations of iAs and its metabolites were measured in urine and livers. Significant differences in total As concentration and in proportions of total As represented by iAs, MAs, and DMAs were observed between the strains. These differences were more pronounced in livers, particularly in mice exposed to 50 ppm iAs. In livers, large variations among the strains were found in percentage of iAs (15-48%), MAs (11-29%), and DMAs (29-66%). In contrast, DMAs represented 96-99% of total As in urine in all strains regardless of exposure. Notably, the percentages of As species in urine did not correlate with total As concentration in liver, suggesting that the urinary profiles were not representative of the internal exposure. In livers of mice exposed to 50 ppm, but not to 0.1 ppm iAs, As3mt expression correlated with percent of iAs and DMAs. No correlations were found between As3mt expression and the proportions of As species in urine regardless of exposure level. Although we did not find yet a CC strain in which proportions of As species in urine would match those reported in humans (typically 10-30% iAs, 10-20% MAs, 60-70% DMAs), CC strains characterized by low %DMAs in livers after exposure to 50 ppm iAs (suggesting inefficient iAs methylation) could be better models for studies aiming to reproduce effects of iAs described in humans.

Project description:Background:In the context of sustainable development, yeast are one class of microorganisms foreseen for the production of oil from diverse renewable feedstocks, in particular those that do not compete with the food supply. However, their use in bulk production, such as for the production of biodiesel, is still not cost effective, partly due to the possible poor use of desired substrates or poor robustness in the practical bioconversion process. We investigated the natural capacity of Blastobotrys adeninivorans, a yeast already used in biotechnology, to store lipids under different conditions. Results:The genotyping of seven strains showed the species to actually be composed of two different groups, one that (including the well-known strain LS3) could be reassigned to Blastobotrys raffinosifermentans. We showed that, under nitrogen limitation, strains of both species can synthesize lipids to over 20% of their dry-cell weight during shake-flask cultivation in glucose or xylose medium for 96 h. In addition, organic acids were excreted into the medium. LS3, our best lipid-producing strain, could also accumulate lipids from exogenous oleic acid, up to 38.1?±?1.6% of its dry-cell weight, and synthesize lipids from various sugar substrates, up to 36.6?±?0.5% when growing in cellobiose. Both species, represented by LS3 and CBS 8244T, could grow with little filamentation in the lipogenic medium from 28 to 45 °C and reached lipid titers ranging from 1.76?±?0.28 to 3.08?±?0.49 g/L in flasks. Under these conditions, the maximum bioconversion yield (Y FA/S?=?0.093?±?0.017) was obtained with LS3 at 37 °C. The presence of genes for predicted subunits of an ATP citrate lyase in the genome of LS3 reinforces its oleaginous character. Conclusions:Blastobotrys adeninivorans and B. raffinosifermentans, which are known to be xerotolerant and genetically-tractable, are promising biotechnological yeasts of the Saccharomycotina that could be further developed through genetic engineering for the production of microbial oil. To our knowledge, this is the first report of efficient lipid storage in yeast when cultivated at a temperature above 40 °C. This paves the way to help reducing costs through consolidated bioprocessing.

Dataset Information

Metabolism of sugars by genetically diverse species of oral Leptotrichia.

Publications

Metabolism of sugars by genetically diverse species of oral Leptotrichia.

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