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Molecular rearrangement of lactose plasmid DNA associated with high‐frequency transfer and cell aggregation in Lactococcus Iactis 712
Author(s) -
Gasson Michael J.,
Swindell Simon,
Maeda Sumio,
Dodd Helen M.
Publication year - 1992
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.1992.tb01776.x
Subject(s) - plasmid , biology , lactose , dna , genetics , transposition (logic) , microbiology and biotechnology , biochemistry , linguistics , philosophy
Summary High‐frequency conjugation of the lactose plasmid pLP712 is associated with a constitutive cell aggregation phenotype and is facilitated by cointegration with a sex factor. Analysis of 23 independently derived enlarged lactose plasmids revealed that the sex factor DNA present in cointegrates varied in size. This suggested that more than simple cointegration with a sex factor plasmid was involved. Further analysis led to the discovery of a chromosomally located sex factor that could excise and be lost or exist as labile plasmid DNA. Cointegration with this sex factor was shown to be promoted by transposition of a copy of ISSI present on the lactose plasmid, and models are presented to account for the complex and variable structures of the resulting enlarged lactose plasmids.