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K O'Hanlon

Publications and source records attributed to K O'Hanlon.

7 recordsLinked to original sources
PubMed2001

An analysis of bacteriocins produced by lactic acid bacteria isolated from malted barley.

AIMS: The aim of this study was to perform a detailed characterization of bacteriocins produced by lactic acid bacteria (LAB) isolated from malted barley. METHODS AND RESULTS: Bacteriocin activities produced by eight LAB, isolated from various types of malted barley, were purified to homogeneity by ammonium sulphate precipitation, cation exchange, hydrophobic interaction and reverse-phase liquid chromatography. Molecular mass analysis and N-terminal amino acid sequencing of the purified bacteriocins showed that four non-identical Lactobacillus sakei strains produced sakacin P, while four Leuconostoc mesenteroides strains were shown to produce bacteriocins highly similar or identical to leucocin A, leucocin C or mesenterocin Y105. Two of these bacteriocin-producing strains, Lb. sakei 5 and Leuc. mesenteroides 6, were shown to produce more than one bacteriocin. Lactobacillus sakei 5 produced sakacin P as well as two novel bacteriocins, which were termed sakacin 5X and sakacin 5T. The inhibitory spectrum of each purified bacteriocin was analysed and demonstrated that sakacin 5X was capable of inhibiting the widest range of beer spoilage organisms. CONCLUSION: All bacteriocins purified in this study were class II bacteriocins. Two of the bacteriocins have not been described previously in the literature while the remaining purified bacteriocins have been isolated from environments other than malted barley. SIGNIFICANCE AND IMPACT OF THE STUDY: This study represents a thorough analysis of bacteriocin-producing LAB from malt and demonstrates, for the first time, the variety of previously identified and novel inhibitory peptides produced by isolates from this environment. It also highlights the potential of these LAB cultures to be used as biological controlling agents in the brewing industry.

Amino Acid Sequence↗
PubMed1999

Isolation of rifampin-resistant mutants of Listeria monocytogenes and their characterization by rpoB gene sequencing, temperature sensitivity for growth, and interaction with an epithelial cell line.

The sequence of the rpoB gene from Listeria monocytogenes was determined. Rifampin-resistant (Rif(r)) mutants arising from L. monocytogenes cultures exposed to rifampin were isolated, and by partial sequencing of their rpoB genes, seven different point mutations affecting five different amino acids (473Asp-->Asn or Gly, 479Gly-->Asp, 483His-->Tyr or Leu, 528Ile-->Phe, and 530Ser-->Tyr), which led to MICs of 0.5 to 100 microg/ml for the organisms, were determined. These mutants showed various deficiencies for growth at 42 degrees C, with only one being comparable to the wild-type strain. The interaction of these Rif(r) mutants with human Caco-2 cells was examined by using an immunofluorescence technique. Three mutants failed to interact, while three showed a reduced interaction compared to that of the wild type. It is believed that these pleiotropic phenotypes have arisen as a result of mutations within the DNA-dependent RNA polymerase holoenzyme.

Antibiotics, Antitubercular↗
PubMed1999

Applied proteomics--analyzing protein structure and function for drug discovery. 27-28 January 1999, London, UK.

This two-day meeting, attended by approximately 60 delegates, was aimed at researchers in the proteomics field. The proteome is defined as the entire protein content of the cell. Proteomics is the analysis of the end-product of gene expression and all regulations governing gene expression are taken into account, ie, transcriptional and translational. The three stages involved in proteomic analysis are: a separation phase, ie, two dimensional (2D) gel electrophoresis; a characterization phase, ie, mass spectrometry; and, a data analysis phase, ie, bioinformatics.

Journal Article↗
PubMed1996

Analysis of the beta' subunit of DNA-dependent RNA polymerase does not support the hypothesis inferred from 16S rRNA analysis that Oenococcus oeni (formerly Leuconostoc oenos) is a tachytelic (fast-evolving) bacterium.

rRNA sequencing has shown that leuconostocs comprise three distinct phylogenetic lineages which have been designated separate genera (viz., the genera Leuconostoc sensu stricto, Oenococcus, and Weissella). In addition, the 16S rRNA line formed by Oenococcus oeni (formerly Leuconostoc oenos) is exceptionally long; this fact, together with variations in the compositions of conserved positions in the 16S rRNA, has led to the hypothesis (D. Yang and C. R. Woese, Syst. Appl. Microbiol. 12:145-149, 1989) that this organism is a fast-evolving bacterium. Previous evidence that the leuconostocs should be divided into three genera and that O. oeni is an example of tachytelic evolution has come solely from rRNA analyses. In this study we seqenced the rpoC gene encoding the beta' subunit of DNA-dependent RNA polymerase of leuconostocs and performed a comparative phylogenetic analysis. The subdivision of the leuconostocs into three distinct lineages was confirmed by the rpoC gene data, but no evidence that indicated that O. oeni is evolving at an extraordinary rate was found. If O. oeni is truly tachytelic, then fast-evolving phenomena would be expected to occur throughout the whole genome, including this independent molecular chronometer.

Amino Acid Sequence↗