Molecular characterization and structural instability of the industrially important composite metabolic plasmid pLP712

The widely used plasmid-free Lactococcus lactis strain MG1363 was derived from the industrial dairy starter strain NCDO712. This strain carries a 55.39 kb plasmid encoding genes for lactose catabolism and a serine proteinase involved in casein degradation. We report the DNA sequencing and annotation...

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Bibliographic Details
Published in:	Microbiology (New York) Vol. 158; no. Pt 12; pp. 2936 - 2945
Main Authors:	WEGMANN, Udo, OVERWEG, Karin, JEANSON, Sophie, GASCON, Mike, SHEARMAN, Claire
Format:	Journal Article
Language:	English
Published:	Reading Society for General Microbiology 01-12-2012 MAIK Nauka/Interperiodica
Subjects:	Biological and medical sciences Conjugation, Genetic DNA, Bacterial - chemistry DNA, Bacterial - genetics Evolution, Molecular Food and Nutrition Food engineering Fundamental and applied biological sciences. Psychology Gene Transfer, Horizontal Genomic Instability Industrial Microbiology Lactococcus lactis - genetics Lactococcus lactis - isolation & purification Life Sciences Metabolic Networks and Pathways - genetics Microbiology Microbiology and Parasitology Molecular Sequence Data Plasmids Recombination, Genetic Sequence Analysis, DNA Sequence Homology Transformation, Genetic Plasmid serine fermented foods caséine lactococcus lactis milk sugar milk plasmid protéinase bacterial genes casein gène lactose lactococcus aliment fermenté gène bactérien lait analyse moléculaire milk industry plasmide fermentation metabolism industrie laitière catabolisme
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Summary:	The widely used plasmid-free Lactococcus lactis strain MG1363 was derived from the industrial dairy starter strain NCDO712. This strain carries a 55.39 kb plasmid encoding genes for lactose catabolism and a serine proteinase involved in casein degradation. We report the DNA sequencing and annotation of pLP712, which revealed additional metabolic genes, including peptidase F, d-lactate dehydrogenase and α-keto acid dehydrogenase (E3 complex). Comparison of pLP712 with other large lactococcal lactose and/or proteinase plasmids from L. lactis subsp. cremoris SK11 (pSK11L, pSK11P) and the plant strain L. lactis NCDO1867 (pGdh442) revealed their close relationship. The plasmid appears to have evolved through a series of genetic events as a composite of pGdh442, pSK11L and pSK11P. We describe in detail a scenario by which the metabolic genes relevant to the growth of its host in a milk environment have been unified on one replicon, reflecting the evolution of L. lactis as it changed its biological niche from plants to dairy environments. The extensive structural instability of pLP712 allows easy isolation of derivative plasmids lacking genes for casein degradation and/or lactose catabolism. Plasmid pLP712 is transferable by transduction and conjugation, and both of these processes result in significant molecular rearrangements. We report the detailed molecular analysis of insertion sequence element-mediated genetic rearrangements within pLP712 and several different mechanisms, including homologous recombination and adjacent deletion. Analysis of the integration of the lactose operon into the chromosome highlights the fluidity of the MG1363 integration hotspot and the potential for frequent movement of genes between plasmids and chromosomes in Lactococcus.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	1350-0872 0026-2617 1465-2080 1608-3237
DOI:	10.1099/mic.0.062554-0