Transfer and Occurrence of Large Mercury Resistance Plasmids in River Epilithon

Abstract

In situ mating experiments were done in the River Taff, South Wales, United Kingdom, by using a natural mercury resistance plasmid (pQM1) isolated from a mixture of epilithic bacteria in vitro. The river temperature from March to November was found to influence transfer frequencies strongly (6.8 x 10-9 to 1.5 X 10-2 per recipient). A linear relationship existed between loglo transfer frequency and river temperature (6 to 21°C), a 2.6°C change in temperature giving a 10-fold change in transfer frequency. In vitro experiments showed that pQM1 transferred most efficiently between fluorescent pseudomonads and that one epilithic isolate (Pseudomonasfluorescens) was an efficient donor in situ. Experiments with a P. putida recipient showed that intact epilithic bacterial communities could transfer mercury resistance plasmids in situ at frequencies of up to 3.75 x 10-6 per recipient. Nineteen of the large (>250-kilobase) plasmids isolated by transfer into P. putida were studied in detail and grouped into seven types by restriction digests. Mercury resistance and UV resistance were found to be common linked phenotypes in 19 of the 23 plasmids tested.

Mangrove microniches determine the structural and functional diversity of enriched petroleum hydrocarbon-degrading consortia

“…It is assumed that horizontal gene transfer by mobile genetic elements plays an important role in the acclimation of bacterial populations to environmental contamination (Bale et al, 1988;Rasmussen & Sørensen, 1998;Wilson et al, 2003). However, in spite of its potential ecological importance, a limited number of studies have addressed plasmid diversity in coastal environments (Sobecky, 1999;Beeson et al, 2002), and no reports exist thus far that specifically focus on mangrove ecosystems.…”

Mobilization of a recombinant nonconjugative plasmid at the interface between wastewater and the marine coastal environment

“…The effects of temperature on the mobilizing ability of several plasmids has been reported by others [4,9,28]. Bale et al [29] reported a linear relationship between log10 transfer frequency and river temperature, and that a 2.6°C change in temperature could induce a 10-fold change in transfer frequency. These results are in contrast with our findings, except for the strain SE200D83; we noted that most of the mobilizing frequencies were higher at 20°C than at 15°C, as with l/ibrio harveyi isolated from both the fresh and marine environment.…”

Comparison of the plasmid types obtained by two distantly related recipients in biparental exogenous plasmid isolations from soil

“…Considering the BHR character of 12 out of 16 plasmids, factors other than limitations in host range must have caused the large di¡erence in plasmid types obtained in the two recipients. Previous plate mating studies have shown that plasmid transfer frequencies depend on the donor-recipient pair used in the mating experiments [6,20,21]. The number of transconjugants in such a single donor-recipient mating is a function of both the conjugation events and outgrowth of cells that have received the plasmid.…”