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Plasmid

Title:		A phase variation event that activates conjugation functions encoded by the Enterococcus faecalis plasmid pAD1
Author(s):		Pontius LT; Clewell DB;
Address:		"Department of Microbiology and Immunology, School of Medicine, University of Michigan, Ann Arbor 48109"
Journal Title:		Plasmid
Year:		1991
Volume:		26
Issue:		3
Page Number:		172 - 185
DOI:		10.1016/0147-619x(91)90041-t
ISSN/ISBN:		0147-619X (Print) 0147-619X (Linking)
Abstract:		"Enterococcus faecalis cells carrying the conjugative plasmid pAD1 undergo several related changes when induced by the sex pheromone cAD1. Included are the production of novel surface proteins, the formation of cellular aggregates in broth cultures, the ability to transfer the plasmid at high frequency in broth matings, and the change from a soft to a 'dry' colony morphology. Spontaneous, constitutively dry colony (Dryc) variants of E. faecalis (pAD1) were found to arise at a frequency of 10(-4)-10(-2). Dryc phase variants constitutively expressed aggregation and plasmid transfer functions typically expressed only under cAD1-inducing conditions. Reversion of Dryc variants to a cAD1-inducible phenotype (Dry+) occurred at a similar frequency. Tn917-lac mutagenesis of regions of pAD1 previously shown to be involved in plasmid transfer revealed that in Dry+ cells these regions were transcribed only when the inducer, cAD1, was present. In Dryc variants the regions were transcribed constitutively. A pAD1 miniplasmid containing determinants regulating cAD1 inducible plasmid transfer and a cAD1-inducible lacZ transcriptional fusion displayed phase variation in LacZ expression at a rate similar to the Dry+/Dryc phase variation. These results suggest that the site of mutation(s) resulting in the Dryc phenotype is within the regulation-related region of pAD1. Complementation tests showed that this region, when supplied in trans, complemented the Dryc phenotype. Phase variation affecting mating functions represents an alternative (pheromone independent) method of regulating pAD1 transfer"
Keywords:		"*Conjugation, Genetic DNA Restriction Enzymes DNA Transposable Elements DNA, Bacterial Enterococcus faecalis/*genetics Gene Expression Regulation, Bacterial Genetic Complementation Test Genetic Markers Mutagenesis Oligopeptides/genetics *Plasmids;"
Notes:		"MedlinePontius, L T Clewell, D B eng AI10318/AI/NIAID NIH HHS/ GM33956/GM/NIGMS NIH HHS/ Research Support, U.S. Gov't, P.H.S. 1991/11/01 Plasmid. 1991 Nov; 26(3):172-85. doi: 10.1016/0147-619x(91)90041-t"