Two strains, 20D3 and 20D31, were analysed for the presence of plasmids. Agarose gel electrophoresis of crude lysates of these strains indicated that 20D3 carried three plasmids with molecular sizes of 88 kb, 216 kb and 260 kb while 20D31 contained five plasmids with molecular sizes of 7·8 kb, 28 kb, 105 kb, 180 kb and 260 kb. Strain 20D31 proved to be sensitive to phage GU5, suggesting that at least one of its plasmids coded for a derepressed transfer system. Curing and mobilization experiments indicated that the GU5 sensitivity was determined by the 28 kb plasmid, which was conjugative and belonged to the IncN group. Both strains lost yellow pigmentation and thiamin prototrophy when grown at elevated temperature (39 °C) or in the presence of nalidixic acid or SDS. The irreversible loss of both traits was ascribed to the curing of the 260 kb plasmid. Yellow pigmentation was due to the production of carotenoids.


Article metrics loading...

Loading full text...

Full text loading...


Most cited this month Most Cited RSS feed

This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error