RESUMO
The genome of Streptococcus mutans UA159 contains two phospho-beta-glucosidase genes, bglA and celA, which occur in operon-like arrangements along with genes for components of phosphotransferase transport systems and a third phospho-beta-glucosidase encoded by the arb gene, which does not have its own associated transport system but relies on uptake by the bgl or cel systems. Targeted inactivation of each of the phospho-beta-glucosidase genes revealed that bglA is involved in aesculin hydrolysis, celA is essential for utilisation of cellobiose, amygdalin, gentobiose and salicin, and arb is required for utilisation of arbutin. Inactivation of genes for the phosphotransferase systems revealed an overlap of specificity for transport of beta-glucosides and also indicated that further, unidentified transport systems exist. The cel and arb genes are subject to catabolite repression by glucose, but the regM gene is not essential for catabolite repression. Screening a collection of isolates of S. mutans revealed strains with deletions affecting the msm, bgl and/or cel operons. The phenotypes of these strains could largely be explained on the basis of the results obtained from the knockout mutants of S. mutans UA159 but also indicated the existence of other pathways apparently absent from UA159. The extensive genetic and phenotypic variation found in beta-glucoside metabolism indicates that there may be extensive heterogeneity in the species.
Assuntos
Deleção de Genes , Variação Genética/genética , Genoma Bacteriano/genética , Glucosídeos/metabolismo , Streptococcus mutans/genética , Amigdalina/genética , Arbutina/genética , Proteínas de Bactérias/genética , Álcoois Benzílicos/metabolismo , Celobiose/genética , Celulase/genética , Esculina/metabolismo , Inativação Gênica , Glucosídeos/genética , Humanos , Hidrólise , Mutação/genética , Óperon/genética , Fenótipo , Sistema Fosfotransferase de Açúcar do Fosfoenolpiruvato/genética , beta-Glucosidase/genéticaRESUMO
Many isolates of Streptococcus mutans lack the ability to ferment melibiose and other sugars. We previously reported that this was commonly due to a chromosomal deletion and, in the present study, sequence information from the S. mutans genome project was used to design PCR primers to explore the nature and extent of the deletion. In all melibiose-negative strains examined, there was an incomplete insertion element, ISSmu3, in place of the 18-kb stretch of chromosome encoding the msm and GAL operons. Strains that were also unable to utilise beta-glucosides were found to have a separate 4 kb deletion in the BGL regulon that is proposed to be due to homologous recombination between two short stretches of identical sequence. The evidence is consistent with all the melibiose-negative strains examined being derived from a common ancestor.
Assuntos
Deleção Cromossômica , Cromossomos Bacterianos/genética , Elementos de DNA Transponíveis/genética , Streptococcus mutans/genética , DNA Bacteriano/genética , Fermentação/genética , Galactose/genética , Galactose/metabolismo , Genoma Bacteriano , Glucosídeos/metabolismo , Humanos , Melibiose/metabolismo , Óperon/genética , Regulon/genética , Análise de Sequência de DNA , Streptococcus mutans/classificação , beta-Glucosidase/genéticaRESUMO
Five strains of Stomatococcus mucilaginosus were investigated to determine whether the organism produces a lipoteichoic acid or a lipoglycan. Crude phenol extracts were purified by hydrophobic interaction chromatography and shown to contain lipoglycan. The major carbohydrate component present was mannose, indicating that the macroamphiphile is a lipomannan. The fatty acid composition of the lipoglycan was similar to that of stomatococcal whole cells. These data provide additional chemotaxonomic evidence supporting the suprageneric classification of the genus Stomatococcus within a group of actinomycete genera that also includes the genus Micrococcus.
Assuntos
Lipopolissacarídeos/análise , Manose/análise , Micrococcaceae/química , Ácidos Graxos/análise , Lipopolissacarídeos/química , Micrococcaceae/classificação , Ácidos Teicoicos/análiseRESUMO
A competitive ELISA is described for the measurement of lipoteichoic acid. The assay was used to determine the wall associated lipoteichoic acid of Streptococcus sanguis which was found to represent only 2-4% of the phenol extractable content. Extracellular lipoteichoic acid was detected even after exhaustive cell washing. This material was not the result of de novo synthesis because membrane de-polarization had no effect on the amount detected. Since extracellular lipoteichoic acid interfered with the measurement of cell surface antigen, cells were fixed with glutaraldehyde prior to assay. Lipoteichoic acid was demonstrated on the surface of fixed cells which did not leak antigen. The relevance of fixation used in antigen location studies by electron microscopy of immune-labelled cells is discussed.
