Genomic diversity of Lactobacillus salivarius

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dc.contributor.advisor O'Toole, Paul W. en
dc.contributor.advisor van Sinderen, Douwe en Raftis, Emma J. 2016-09-29T09:00:48Z 2016-09-29T09:00:48Z 2015 2015
dc.identifier.citation Raftis, E. J. 2015. Genomic diversity of Lactobacillus salivarius. PhD Thesis, University College Cork. en
dc.identifier.endpage 258 en
dc.description.abstract Lactobacillus salivarius is unusual among the lactobacilli due to its multireplicon genome architecture. The circular megaplasmids harboured by L. salivarius strains encode strain-specific traits for intestinal survival and probiotic activity. L. salivarius strains are increasingly being exploited for their probiotic properties in humans and animals. In terms of probiotic strain selection, it is important to have an understanding of the level of genomic diversity present in this species. Comparative genomic hybridization (CGH) and multilocus sequence typing (MLST) were employed to assess the level of genomic diversity in L. salivarius. The wellcharacterised probiotic strains L. salivarius UCC118 was employed as a genetic reference strain. The group of test strains were chosen to reflect the range of habitats from which L. salivarius strains are frequently recovered, including human, animal, and environmental sources. Strains of L. salivarius were found to be genetically diverse when compared to the UCC118 genome. The most conserved strains were human GIT isolates, while the greatest level of divergence were identified in animal associated isolates. MLST produced a better separation of the test strains according to their isolation origins, than that produced by CGHbased strain clustering. The exopolysaccharide (EPS) associated genes of L. salivarius strains were found to be highly divergent. The EPS-producing phenotype was found to be carbonsource dependent and inversely related to a strain's ability to produce a biofilm. The genome of the porcine isolate L. salivarius JCM1046 was shown by sequencing to harbour four extrachromosomal replicons, a circular megaplasmid (pMP1046A), a putative chromid (pMP1046B), a linear megaplasmid (pLMP1046) and a smaller circular plasmid (pCTN1046) which contains an integrated Tn916-like element (Tn6224), which carries the tetracycline resistance gene tetM. pLMP1046 represents the first sequence of a linear plasmid in a Lactobacillus species. Dissemination of antibiotic resistance genes among species with food or probiotic-association is undesirable, and the identification of Tn6224-like elements in this species has implications for strain selection for probiotic applications. In summary, this thesis used a comparative genomics approach to examine the level of genotypic diversity in L. salivarius, a species which contains probiotic strains. The genome sequence of strain JCM1046 provides additional insight into the spectrum of extrachromosomal replicons present in this species. en
dc.description.sponsorship Science Foundation Ireland (Research Frontiers Programme award to P.W.O. 05/RFP/GEN047 and by a Centre for Science, Engineering and Technology award to the Alimentary Pharmabiotic Centre) en
dc.format.mimetype application/pdf en
dc.language.iso en en
dc.publisher University College Cork en
dc.rights © 2015, Emma J. Raftis. en
dc.rights.uri en
dc.subject Comparative genomics en
dc.subject Lactobacillus salivarius en
dc.subject Megaplasmid en
dc.title Genomic diversity of Lactobacillus salivarius en
dc.type Doctoral thesis en
dc.type.qualificationlevel Doctoral en
dc.type.qualificationname PhD (Science) en
dc.internal.availability Full text available en No embargo required en
dc.description.version Accepted Version
dc.contributor.funder Science Foundation Ireland en
dc.description.status Not peer reviewed en Microbiology en
dc.check.type No Embargo Required
dc.check.reason No embargo required en
dc.check.opt-out Not applicable en
dc.thesis.opt-out false
dc.check.embargoformat Not applicable en
dc.internal.conferring Summer 2015 en

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© 2015, Emma J. Raftis. Except where otherwise noted, this item's license is described as © 2015, Emma J. Raftis.
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