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Biomedical subjects

G Dunny

Publications and source records attributed to G Dunny.

6 recordsLinked to original sources
PubMed2000

A sensitive method to detect initiation of growth in Streptococcus gordonii using ribosomal RNA operon-reporter gene fusions.

A system for studying the early growth response of Streptococcus gordonii to environmental stimuli has been developed. A reporter gene, encoding alpha-amylase, has been integrated into an rRNA operon to monitor changes in cellular physiology associated with the initiation of growth. Two such strains with single integrants have been characterized during the transition from lag phase to exponential growth. Synthesis of the reporter is correlated to growth initiation in both strains, and the reporter enzyme is detectable with sufficient sensitivity. Comparison of the expression profiles of the two rrn operons containing the reporter gene suggests that they are differentially expressed over the course of growth.

Artificial Gene Fusion↗
PubMed1998

Retrohoming of a bacterial group II intron: mobility via complete reverse splicing, independent of homologous DNA recombination.

The mobile group II intron of Lactococcus lactis, Ll.LtrB, provides the opportunity to analyze the homing pathway in genetically tractable bacterial systems. Here, we show that Ll.LtrB mobility occurs by an RNA-based retrohoming mechanism in both Escherichia coli and L. lactis. Surprisingly, retrohoming occurs efficiently in the absence of RecA function, with a relaxed requirement for flanking exon homology and without coconversion of exon markers. These results lead to a model for bacterial retrohoming in which the intron integrates into recipient DNA by complete reverse splicing and serves as the template for cDNA synthesis. The retrohoming reaction is completed in unprecedented fashion by a DNA repair event that is independent of homologous recombination between the alleles. Thus, Ll.LtrB has many features of retrotransposons, with practical and evolutionary implications.

Bacterial Proteins↗
PubMed1995

Novel insertion sequence-like element IS982 in lactococci.

A novel insertion sequence-like (IS) element, designated IS982, was found on the lactose plasmid, pSK11L, from Lactococcus lactis subsp. cremoris SK11 and was located between the origin of replication and the oligopeptide transport gene cluster. The 1003-base pair (bp) IS982 was flanked by 18-bp perfect inverted repeats. IS982 contained an open reading frame encoding a putative transposase of 296 amino acids. An almost identical IS-like element (99% DNA sequence identity) was cloned and partially sequenced from the chromosome of Lactococcus lactis subsp. cremoris Wg2 with 17-bp perfect inverted repeats. Southern analysis indicated that in 12 lactococcal strains examined, IS982 was present with copy numbers ranging from 1 to at least 20. IS982 displayed sequence homology to the putative IS element RSBst-alpha from Bacillus stearothermophilus CU21, IS982 and RSBst-alpha were not related to other known insertion sequences and may represent a new family of IS elements.

Amino Acid Sequence↗
PubMed1986

Monoclonal antibodies to cell surface antigens involved in sex pheromone induced mating in Streptococcus faecalis.

Hybridoma cell lines producing monoclonal antibodies to Streptococcus faecalis cell surface antigens were constructed. Some of the antibodies isolated were directed against surface components involved in pheromone-induced mating. This paper describes the use of the monoclonal antibodies to identify antigenically related surface components detected by immunoprecipitation and Western blotting, their use in pheromone response assays, and their use as functional inhibitors in mating experiments.

Antibodies, Monoclonal↗
PubMed1982

Genetic and physiological analysis of conjugation in Streptococcus faecalis.

In an effort to elucidate the mechanisms of conjugal plasmid transfer in Streptococcus faecalis, a genetic analysis of the sex pheromone-dependent tetracycline resistance plasmid pCF-10 was initiated. Rare transconjugants obtained from short matings with wild-type donors not exposed to sex pheromones were screened for increased donor potential in a subsequent mating. From this screening, a mutant plasmid, designated pCF-11, whose transfer functions are expressed in the absence of pheromone induction was isolated. Cells carrying pCF-11 spontaneously clump when grown in broth culture but do not excrete sex pheromones active against wild-type donors. In the course of initial experiments, it was observed that physiological conditions could affect plasmid transfer frequency. Therefore, a set of standardized optimal mating conditions was defined. The experiments carried out to determine these conditions revealed that a transient increase in transfer frequency of about 2 order of magnitude occurred in early-exponential-phase donor cells. This peak of activity is independent of sex pheromone response, since it was observed with induced or uninduced donor cells carrying either pCF-11 or pCF-10.

Conjugation, Genetic↗