scholarly journals Galactose Metabolism by Streptococcus mutans

2004 ◽  
Vol 70 (10) ◽  
pp. 6047-6052 ◽  
Author(s):  
Jacqueline Abranches ◽  
Yi-Ywan M. Chen ◽  
Robert A. Burne
Keyword(s):  
Streptococcus Mutans ◽  
Wild Type Strain ◽  
Sugar Metabolism ◽  
Growth Defect ◽  
Wild Type ◽  
Phosphotransferase System ◽  
Galactose Metabolism ◽  
Gene Encoding ◽  
Leloir Pathway ◽  
In The Wild

ABSTRACT The galK gene, encoding galactokinase of the Leloir pathway, was insertionally inactivated in Streptococcus mutans UA159. The galK knockout strain displayed only marginal growth on galactose, but growth on glucose or lactose was not affected. In strain UA159, the sugar phosphotransferase system (PTS) for lactose and the PTS for galactose were induced by growth in lactose and galactose, although galactose PTS activity was very low, suggesting that S. mutans does not have a galactose-specific PTS and that the lactose PTS may transport galactose, albeit poorly. To determine if the galactose growth defect of the galK mutant could be overcome by enhancing lactose PTS activity, the gene encoding a putative repressor of the operon for lactose PTS and phospho-β-galactosidase, lacR, was insertionally inactivated. A galK and lacR mutant still could not grow on galactose, although the strain had constitutively elevated lactose PTS activity. The glucose PTS activity of lacR mutants grown in glucose was lower than in the wild-type strain, revealing an influence of LacR or the lactose PTS on the regulation of the glucose PTS. Mutation of the lacA gene of the tagatose pathway caused impaired growth in lactose and galactose, suggesting that galactose can only be efficiently utilized when both the Leloir and tagatose pathways are functional. A mutation of the permease in the multiple sugar metabolism operon did not affect growth on galactose. Thus, the galactose permease of S. mutans is not present in the gal, lac, or msm operons.

scholarly journals Expression and function of the cdgD gene, encoding a CHASE–PAS-DGC-EAL domain protein, in Azospirillum brasilense

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
José Francisco Cruz-Pérez ◽  
Roxana Lara-Oueilhe ◽  
Cynthia Marcos-Jiménez ◽  
Ricardo Cuatlayotl-Olarte ◽  
María Luisa Xiqui-Vázquez ◽  
...  
Keyword(s):  
Azospirillum Brasilense ◽  
Type Strain ◽  
Wild Type Strain ◽  
Soil Conditions ◽  
Wild Type ◽  
Gene Encoding ◽  
Wheat Roots ◽  
Genes Encoding ◽  
In The Wild ◽  
Plant Growth Promoting

AbstractThe plant growth-promoting bacterium Azospirillum brasilense contains several genes encoding proteins involved in the biosynthesis and degradation of the second messenger cyclic-di-GMP, which may control key bacterial functions, such as biofilm formation and motility. Here, we analysed the function and expression of the cdgD gene, encoding a multidomain protein that includes GGDEF-EAL domains and CHASE and PAS domains. An insertional cdgD gene mutant was constructed, and analysis of biofilm and extracellular polymeric substance production, as well as the motility phenotype indicated that cdgD encoded a functional diguanylate protein. These results were correlated with a reduced overall cellular concentration of cyclic-di-GMP in the mutant over 48 h compared with that observed in the wild-type strain, which was recovered in the complemented strain. In addition, cdgD gene expression was measured in cells growing under planktonic or biofilm conditions, and differential expression was observed when KNO3 or NH4Cl was added to the minimal medium as a nitrogen source. The transcriptional fusion of the cdgD promoter with the gene encoding the autofluorescent mCherry protein indicated that the cdgD gene was expressed both under abiotic conditions and in association with wheat roots. Reduced colonization of wheat roots was observed for the mutant compared with the wild-type strain grown in the same soil conditions. The Azospirillum-plant association begins with the motility of the bacterium towards the plant rhizosphere followed by the adsorption and adherence of these bacteria to plant roots. Therefore, it is important to study the genes that contribute to this initial interaction of the bacterium with its host plant.

scholarly journals Towards Enhanced Galactose Utilization by Lactococcus lactis

2010 ◽  
Vol 76 (21) ◽  
pp. 7048-7060 ◽  
Author(s):  
Ana R. Neves ◽  
Wietske A. Pool ◽  
Ana Solopova ◽  
Jan Kok ◽  
Helena Santos ◽  
...  
Keyword(s):  
Lactococcus Lactis ◽  
Poor Quality ◽  
Genetically Engineered ◽  
Phosphotransferase System ◽  
Galactose Metabolism ◽  
Gene Encoding ◽  
Leloir Pathway ◽  
Lactose Fermentation ◽  
Consumption Rates ◽  
Galactose Utilization

ABSTRACT Accumulation of galactose in dairy products due to partial lactose fermentation by lactic acid bacteria yields poor-quality products and precludes their consumption by individuals suffering from galactosemia. This study aimed at extending our knowledge of galactose metabolism in Lactococcus lactis, with the final goal of tailoring strains for enhanced galactose consumption. We used directed genetically engineered strains to examine galactose utilization in strain NZ9000 via the chromosomal Leloir pathway (gal genes) or the plasmid-encoded tagatose 6-phosphate (Tag6P) pathway (lac genes). Galactokinase (GalK), but not galactose permease (GalP), is essential for growth on galactose. This finding led to the discovery of an alternative route, comprising a galactose phosphotransferase system (PTS) and a phosphatase, for galactose dissimilation in NZ9000. Introduction of the Tag6P pathway in a galPMK mutant restored the ability to metabolize galactose but did not sustain growth on this sugar. The latter strain was used to prove that lacFE, encoding the lactose PTS, is necessary for galactose metabolism, thus implicating this transporter in galactose uptake. Both PTS transporters have a low affinity for galactose, while GalP displays a high affinity for the sugar. Furthermore, the GalP/Leloir route supported the highest galactose consumption rate. To further increase this rate, we overexpressed galPMKT, but this led to a substantial accumulation of α-galactose 1-phosphate and α-glucose 1-phosphate, pointing to a bottleneck at the level of α-phosphoglucomutase. Overexpression of a gene encoding α-phosphoglucomutase alone or in combination with gal genes yielded strains with galactose consumption rates enhanced up to 50% relative to that of NZ9000. Approaches to further improve galactose metabolism are discussed.

The LicT protein acts as both a positive and a negative regulator of loci within the bgl regulon of Streptococcus mutans

Microbiology ◽  
2003 ◽  
Vol 149 (5) ◽  
pp. 1333-1340 ◽  
Author(s):  
Christopher K. Cote ◽  
Allen L. Honeyman
Keyword(s):  
Streptococcus Mutans ◽  
Dna Sequence ◽  
Transcriptional Activity ◽  
Wild Type Strain ◽  
Negative Regulator ◽  
Wild Type ◽  
Phosphotransferase System ◽  
Reading Frame ◽  
Genomic Dna Sequence ◽  
Transcriptional Fusions

An open reading frame (ORF) that would encode a putative antiterminator protein (LicT) of the BglG family was identified in the genomic DNA sequence of Streptococcus mutans. A DNA sequence that would encode a potential ribonucleic antiterminator (RAT) site in the mRNA at which the putative antitermination protein LicT would bind was located immediately downstream from this ORF. These putative antitermination components are upstream of a glucose-independent β-glucoside-utilization system that is responsible for aesculin utilization by S. mutans NG8 in the presence of glucose. It was hypothesized that these putative regulatory components were an important mechanism that was involved with the controlled expression of the S. mutans bglP locus. A strain of S. mutans containing a licT : : Ω-Kan2 insertional mutation was created. This strain could not hydrolyse aesculin in the presence of glucose. The transcriptional activity associated with other genes from the bgl regulon was determined in the licT : : Ω-Kan2 genetic background using lacZ transcriptional fusions and β-galactosidase assays to determine the effect of LicT on these loci. The LicT protein had no significant effect on the expression of the bglC promoter, a regulator of the bglA locus. However, it is essential for the optimal expression of bglP. These data correlate with the phenotype observed on aesculin plates for the S. mutans wild-type strain NG8 and the licT : : Ω-Kan2 strain. Thus, the glucose-independent β-glucoside-specific phosphotransferase system (PTS) regulon in S. mutans relies on LicT for BglP expression and, in turn, aesculin transport in the presence of glucose. Interestingly, LicT also seems to negatively regulate the expression of the bglA promoter region. In addition, the presence of the S. mutans licT gene has been shown to be able to activate a cryptic β-glucoside-specific operon found in Escherichia coli.

scholarly journals Role of Unsaturated Fatty Acid Biosynthesis in Virulence of Streptococcus mutans

2007 ◽  
Vol 75 (3) ◽  
pp. 1537-1539 ◽  
Author(s):  
Elizabeth M. Fozo ◽  
Kathy Scott-Anne ◽  
Hyun Koo ◽  
Robert G. Quivey
Keyword(s):  
Fatty Acids ◽  
Streptococcus Mutans ◽  
Type Strain ◽  
Wild Type Strain ◽  
Fatty Acid Biosynthesis ◽  
Wild Type ◽  
Acid Biosynthesis ◽  
Carious Lesions ◽  
In The Wild

ABSTRACT An insertionally inactivated fabM strain of Streptococcus mutans does not produce unsaturated membrane fatty acids and is acid sensitive (E. M. Fozo and R. G. Quivey, Jr., J. Bacteriol. 186:4152-4158, 2004). In this study, the strain was shown to be poorly transmissible from host to host. Animals directly infected with the fabM strain exhibited fewer and less severe carious lesions than those observed in the wild-type strain.

scholarly journals Phenotypic Consequences Resulting from a Methionine-to-Valine Substitution at Position 48 in the HPr Protein of Streptococcus salivarius

1999 ◽  
Vol 181 (22) ◽  
pp. 6914-6921 ◽  
Author(s):  
Pascale Plamondon ◽  
Denis Brochu ◽  
Suzanne Thomas ◽  
Julie Fradette ◽  
Lucie Gauthier ◽  
...  
Keyword(s):  
Type Strain ◽  
Wild Type Strain ◽  
Minor Effect ◽  
Streptococcus Salivarius ◽  
Wild Type ◽  
Phosphotransferase System ◽  
Gene Encoding ◽  
Regulatory Molecule ◽  
Dependent Protein ◽  
A Minor

ABSTRACT In gram-positive bacteria, the HPr protein of the phosphoenolpyruvate:sugar phosphotransferase system (PTS) can be phosphorylated on a histidine residue at position 15 (His15) by enzyme I (EI) of the PTS and on a serine residue at position 46 (Ser46) by an ATP-dependent protein kinase (His∼P and Ser-P, respectively). We have isolated fromStreptococcus salivarius ATCC 25975, by independent selection from separate cultures, two spontaneous mutants (Ga3.78 and Ga3.14) that possess a missense mutation in ptsH (the gene encoding HPr) replacing the methionine at position 48 by a valine. The mutation did not prevent the phosphorylation of HPr at His15 by EI nor the phosphorylation at Ser46 by the ATP-dependent HPr kinase. The levels of HPr(Ser-P) in glucose-grown cells of the parental and mutant Ga3.78 were virtually the same. However, mutant cells growing on glucose produced two- to threefold less HPr(Ser-P)(His∼P) than the wild-type strain, while the levels of free HPr and HPr(His∼P) were increased 18- and 3-fold, respectively. The mutants grew as well as the wild-type strain on PTS sugars (glucose, fructose, and mannose) and on the non-PTS sugars lactose and melibiose. However, the growth rate of both mutants on galactose, also a non-PTS sugar, decreased rapidly with time. The M48V substitution had only a minor effect on the repression of α-galactosidase, β-galactosidase, and galactokinase by glucose, but this mutation abolished diauxie by rendering cells unable to prevent the catabolism of a non-PTS sugar (lactose, galactose, and melibiose) when glucose was available. The results suggested that the capacity of the wild-type cells to preferentially metabolize glucose over non-PTS sugars resulted mainly from inhibition of the catabolism of these secondary energy sources via a HPr-dependent mechanism. This mechanism was activated following glucose but not lactose metabolism, and it did not involve HPr(Ser-P) as the only regulatory molecule.

scholarly journals Screen for Leukotoxin Mutants in Aggregatibacter actinomycetemcomitans: Genes of the Phosphotransferase System Are Required for Leukotoxin Biosynthesis

2008 ◽  
Vol 76 (8) ◽  
pp. 3561-3568 ◽  
Author(s):  
Maria P. Isaza ◽  
Matthew S. Duncan ◽  
Jeffrey B. Kaplan ◽  
Scott C. Kachlany
Keyword(s):  
Type Strain ◽  
Wild Type Strain ◽  
Aggressive Periodontitis ◽  
Pcr Analysis ◽  
Growth Media ◽  
Wild Type ◽  
Camp Production ◽  
Phosphotransferase System ◽  
In The Wild ◽  
Transposon Insertions

ABSTRACT Aggregatibacter (formerly Actinobacillus) actinomycetemcomitans is a pathogen that causes localized aggressive periodontitis and extraoral infections including infective endocarditis. Recently, we reported that A. actinomycetemcomitans is beta-hemolytic on certain growth media due to the production of leukotoxin (LtxA). Based on this observation and our ability to generate random transposon insertions in A. actinomycetemcomitans, we developed and carried out a rapid screen for LtxA mutants. Using PCR, we mapped several of the mutations to genes that are known or predicted to be required for LtxA production, including ltxA, ltxB, ltxD, and tdeA. In addition, we identified an insertion in a gene previously not recognized to be involved in LtxA biosynthesis, ptsH. ptsH encodes the protein HPr, a phosphocarrier protein that is part of the sugar phosphotransferase system. HPr results in the phosphorylation of other proteins and ultimately in the activation of adenylate cyclase and cyclic AMP (cAMP) production. The ptsH mutant showed only partial hemolysis on blood agar and did not produce LtxA. The phenotype was complemented by supplying wild-type ptsH in trans, and real-time PCR analysis showed that the ptsH mutant produced approximately 10-fold less ltxA mRNA than the wild-type strain. The levels of cAMP in the ptsH mutant were significantly lower than in the wild-type strain, and LtxA production could be restored by adding exogenous cAMP to the culture.

scholarly journals Interference of Components of the Phosphoenolpyruvate Phosphotransferase System with the Central Virulence Gene Regulator PrfA of Listeria monocytogenes

2006 ◽  
Vol 189 (2) ◽  
pp. 473-490 ◽  
Author(s):  
Sonja Mertins ◽  
Biju Joseph ◽  
Monika Goetz ◽  
Regina Ecke ◽  
Gerald Seidel ◽  
...  
Keyword(s):  
Listeria Monocytogenes ◽  
Type Strain ◽  
Virulence Genes ◽  
Wild Type Strain ◽  
Virulence Gene ◽  
Wild Type ◽  
Phosphotransferase System ◽  
In The Wild ◽  
The Common ◽  
Transcript Profiles

ABSTRACT Analysis of Listeria monocytogenes ptsH, hprK, and ccpA mutants defective in carbon catabolite repression (CCR) control revealed significant alterations in the expression of PrfA-dependent genes. The hprK mutant showed high up-regulation of PrfA-dependent virulence genes upon growth in glucose-containing medium whereas expression of these genes was even slightly down-regulated in the ccpA mutant compared to the wild-type strain. The ptsH mutant could only grow in a rich culture medium, and here the PrfA-dependent genes were up-regulated as in the hprK mutant. As expected, HPr-Ser-P was not produced in the hprK and ptsH mutants and synthesized at a similar level in the ccpA mutant as in the wild-type strain. However, no direct correlation was found between the level of HPr-Ser-P or HPr-His-P and PrfA activity when L. monocytogenes was grown in minimal medium with different phosphotransferase system (PTS) carbohydrates. Comparison of the transcript profiles of the hprK and ccpA mutants with that of the wild-type strain indicates that the up-regulation of the PrfA-dependent virulence genes in the hprK mutant correlates with the down-regulation of genes known to be controlled by the efficiency of PTS-mediated glucose transport. Furthermore, growth in the presence of the non-PTS substrate glycerol results in high PrfA activity. These data suggest that it is not the component(s) of the CCR or the common PTS pathway but, rather, the component(s) of subsequent steps that seem to be involved in the modulation of PrfA activity.

scholarly journals A Pleiotropic Regulator, Frp, Affects Exopolysaccharide Synthesis, Biofilm Formation, and Competence Development in Streptococcus mutans

2006 ◽  
Vol 74 (8) ◽  
pp. 4581-4589 ◽  
Author(s):  
Bing Wang ◽  
Howard K. Kuramitsu
Keyword(s):  
Streptococcus Mutans ◽  
Biofilm Formation ◽  
Wild Type Strain ◽  
Transformation Efficiency ◽  
Competence Development ◽  
Wild Type ◽  
Cellular Functions ◽  
In The Wild ◽  
Pleiotropic Regulator

ABSTRACT Exopolysaccharide synthesis, biofilm formation, and competence are important physiologic functions and virulence factors for Streptococcus mutans. In this study, we report the role of Frp, a transcriptional regulator, on the regulation of these traits crucial to pathogenesis. An Frp-deficient mutant showed decreased transcription of several genes important in virulence, including those encoding fructosyltransferase (Ftf), glucosyltransferase B (GtfB), and GtfC, by reverse transcription and quantitative real-time PCR. Expression of Ftf was decreased in the frp mutant, as assessed by Western blotting as well as by the activity assays. Frp deficiency also inhibited the production of GtfB in the presence of glucose and sucrose as well as the production of GtfC in the presence of glucose. As a consequence of the effects on GtfB and -C, sucrose-induced biofilm formation was decreased in the frp mutant. The expression of competence mediated by the competence-signaling peptide (CSP) system, as assessed by comC gene transcription, was attenuated in the frp mutant. As a result, the transformation efficiency was decreased in the frp mutant but was partially restored by adding synthetic CSP. Transcription of the frp gene was significantly increased in the frp mutant under all conditions tested, indicating that frp transcription is autoregulated. Furthermore, complementation of the frp gene in the frp mutant restored transcription of the affected genes to levels similar to those in the wild-type strain. These results suggest that Frp is a novel pleiotropic effector of multiple cellular functions and is involved in the modulation of exopolysaccharide synthesis, sucrose-dependent biofilm formation, and competence development.

scholarly journals Involvement of the SppA1 Peptidase in Acclimation to Saturating Light Intensities in Synechocystis sp. Strain PCC 6803

2004 ◽  
Vol 186 (12) ◽  
pp. 3991-3999 ◽  
Author(s):  
E. Pojidaeva ◽  
V. Zinchenko ◽  
S. V. Shestakov ◽  
A. Sokolenko
Keyword(s):  
Light Intensity ◽  
Wild Type Strain ◽  
Wild Type ◽  
Additional Mechanism ◽  
Gene Encoding ◽  
Light Intensities ◽  
In The Wild ◽  
Pcc 6803

ABSTRACT The sll1703 gene, encoding an Arabidopsis homologue of the thylakoid membrane-associated SppA peptidase, was inactivated by interposon mutagenesis in Synechocystis sp. strain PCC 6803. Upon acclimation from a light intensity of 50 to 150 μE m−2 s−1, the mutant preserved most of its phycobilisome content, whereas the wild-type strain developed a bleaching phenotype due to the loss of about 40% of its phycobiliproteins. Using in vivo and in vitro experiments, we demonstrate that the ΔsppA1 strain does not undergo the cleavage of the LR 33 and LCM 99 linker proteins that develops in the wild type exposed to increasing light intensities. We conclude that a major contribution to light acclimation under a moderate light regime in cyanobacteria originates from an SppA1-mediated cleavage of phycobilisome linker proteins. Together with changes in gene expression of the major phycobiliproteins, it contributes an additional mechanism aimed at reducing the content in phycobilisome antennae upon acclimation to a higher light intensity.

scholarly journals Characterization of Streptococcus mutans Strains Deficient in EIIABMan of the Sugar Phosphotransferase System

2003 ◽  
Vol 69 (8) ◽  
pp. 4760-4769 ◽  
Author(s):  
Jacqueline Abranches ◽  
Yi-Ywan M. Chen ◽  
Robert A. Burne
Keyword(s):  
Streptococcus Mutans ◽  
Type Strain ◽  
Wild Type Strain ◽  
Sugar Transport ◽  
Fold Increase ◽  
Sugar Uptake ◽  
Uptake System ◽  
Oral Streptococci ◽  
Wild Type ◽  
Phosphotransferase System

ABSTRACT The phosphoenolpyruvate:sugar phosphotransferase system (PTS) is the major sugar uptake system in oral streptococci. The role of EIIABMan (encoded by manL) in gene regulation and sugar transport was investigated in Streptococcus mutans UA159. The manL knockout strain, JAM1, grew more slowly than the wild-type strain in glucose but grew faster in mannose and did not display diauxic growth, indicating that EIIABMan is involved in sugar uptake and in carbohydrate catabolite repression. PTS assays of JAM1, and of strains lacking the inducible (fruI) and constitutive (fruCD) EII fructose, revealed that S. mutans EIIABMan transported mannose and glucose and provided evidence that there was also a mannose-inducible or glucose-repressible mannose PTS. Additionally, there appears to be a fructose PTS that is different than FruI and FruCD. To determine whether EIIABMan controlled expression of the known virulence genes, glucosyltransferases (gtfBC) and fructosyltransferase (ftf) promoter fusions of these genes were established in the wild-type and EIIABMan-deficient strains. In the manL mutant, the level of chloramphenicol acetyltransferase activity expressed from the gtfBC promoter was up to threefold lower than that seen with the wild-type strain at pH 6 and 7, indicating that EIIABMan is required for optimal expression of gtfBC. No significant differences were observed between the mutant and the wild-type background in ftf regulation, with the exception that under glucose-limiting conditions at pH 7, the mutant exhibited a 2.1-fold increase in ftf expression. Two-dimensional gel analysis of batch-grown cells of the EIIABMan-deficient strain indicated that the expression of at least 38 proteins was altered compared to that seen with the wild-type strain, revealing that EIIABMan has a pleiotropic effect on gene expression.

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