![]() ![]() Only relevant parts of the fusions are shown. (C) Nucleotide sequence of dltA′ -′ lacZ fusions. Upon integration, the endogenous bgaA gene is disrupted, and box, one of the two repetitive elements ( box and rupA), is deleted. The wild-type region of bgaA is shown, along with the same region after insertion of the translation probe plasmid pTP1. (B) Genetic organization of the bgaA region in S. To construct translational fusions to ′ lacZ, HindIII or BamHI may be used. Authentic amino acids of β-galactosidase are highlighted in boldface. The nucleotide sequence of the multiple cloning site is shown. (A) Genetic map of the integrative translation probe plasmid pTP1. pneumoniae contain d-alanine residues in order to protect this human pathogen against the actions of cationic antimicrobial peptides. The results of our study suggest that, as in many other low-G+C gram-positive bacteria, teichoic acids of S. In addition, mild alkaline hydrolysis of heat-inactivated whole cells released d-alanine from dltA-proficient strains, but not from dltA mutants. Subsequent phenotypic analysis showed that dltA inactivation resulted in enhanced sensitivity to the cationic antimicrobial peptides nisin and gallidermin, a phenotype fully consistent with those of dltA mutants of other gram-positive bacteria. Repair of the stop codon in dltA of R6 and insertional inactivation of dltA in D39 and Rx yielded pairs of dltA-deficient and dltA-proficient strains. pneumoniae D39, the parental strain of R6, and Rx, another derivative of D39, contained intact dltA genes. pneumoniae R6 is a dltA mutant, whereas S. Applying a novel integrative translation probe plasmid with Escherichia coli 'lacZ as a reporter, we could demonstrate that dltA translation starts at the upstream GTG. Translation of dltA could also start upstream of the annotated TTG start codon at a GTG, resulting in the premature termination of dltA translation at a stop codon. The annotation of dltA in R6 predicts a protein, d-alanine-d-alanyl carrier protein ligase (Dcl), that is shorter at the amino terminus than all other Dcl proteins. pneumoniae strains, the laboratory strain R6 and the clinical isolate TIGR4. Streptococcus pneumoniae is one of the few species within the group of low-G +C gram-positive bacteria reported to contain no d-alanine in teichoic acids, although the dltABCD operon encoding proteins responsible for d-alanylation is present in the genomes of two S. ![]()
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