Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Record number 538089
Title Dynamics in copy numbers of five plasmids of a dairy Lactococcus lactis strain under dairy-related conditions including near-zero growth rates
Author(s) Mastrigt, Oscar van; Lommers, Marcel M.A.N.; Vries, Yorick C. de; Abee, Tjakko; Smid, Eddy J.
Source Applied and Environmental Microbiology 84 (2018)11. - ISSN 0099-2240
Department(s) Food Microbiology Laboratory
Publication type Refereed Article in a scientific journal
Publication year 2018
Keyword(s) Plasmid copy number - Replication - Retentostat - Rolling circle - Segregational stability - Theta

Lactic acid bacteria can carry multiple plasmids affecting their performance in dairy fermentations. The expression of plasmid-borne genes and the activity of the corresponding proteins are severely affected by changes in the numbers of plasmid copies. We studied the impact of growth rate on the dynamics of plasmid copy numbers at high growth rates in chemostat cultures and down to nearzero growth rates in retentostat cultures. Five plasmids of the dairy strain Lactococcus lactis FM03-V1 were selected, and these varied in size (3 to 39 kb), in replication mechanism (theta or rolling circle), and in putative (dairy-associated) functions. The copy numbers ranged from 1.5 to 40.5, and the copy number of theta-type replicating plasmids was negatively correlated to the plasmid size. Despite the extremely wide range of growth rates (0.0003 h-1 to 0.6 h-1), the copy numbers of the five plasmids were stable and only slightly increased at near-zero growth rates, showing that the plasmid replication rate was strictly controlled. One low-copy-number plasmid, carrying a large exopolysaccharide gene cluster, was segregationally unstable during retentostat cultivations, reflected in a complete loss of the plasmid in one of the retentostat cultures. The copy number of the five plasmids was also hardly affected by varying the pH value, nutrient limitation, or the presence of citrate (maximum 2.2-fold), signifying the stability in copy number of the plasmids.

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