TY - JOUR

T1 - Effects of stress and other environmental factors on horizontal plasmid transfer assessed by direct quantification of discrete transfer events

AU - Johnsen, Anders R.

AU - Kroer, Niels

PY - 2007/3/1

Y1 - 2007/3/1

N2 - Selection pressure may affect the horizontal transfer of plasmids. The inability to distinguish between gene transfer and the growth of transconjugants complicates testing. We have developed a method that enables the quantification of discrete transfer events. It uses large numbers of replicate matings (192 or 384) in microtiter wells and the counting of transfer-positive and transfer-negative wells. We applied the method to study the transfer of the IncP1 plasmid pRO103 between Escherichia coli and Pseudomonas putida strains. pRO103 encodes resistance to mercury and tetracycline and partial degradation of 2,4-dichlorophenoxyacetic acid (2,4-D). The results showed positive correlation between transfer and donor metabolic activity, and an optimal temperature for transfer of 29°C. On stimulation of donor activity, the optimal temperature was decreased to 24.5°C. HgCl2 above 1.0 μg L-1 negatively affected transfer, whereas 2,4-D up to 0.3 mM had no effect. The negative effect of mercury was shown to be a result of stressing of the recipient. No effects of mercury on transfer could be detected by traditional filter mating. Thus, the method is superior to filter mating and, as the experimental design allows the manipulation of individual parameters, it is ideal for the assessment and comparison of effects of environmental factors on plasmid transfer.

AB - Selection pressure may affect the horizontal transfer of plasmids. The inability to distinguish between gene transfer and the growth of transconjugants complicates testing. We have developed a method that enables the quantification of discrete transfer events. It uses large numbers of replicate matings (192 or 384) in microtiter wells and the counting of transfer-positive and transfer-negative wells. We applied the method to study the transfer of the IncP1 plasmid pRO103 between Escherichia coli and Pseudomonas putida strains. pRO103 encodes resistance to mercury and tetracycline and partial degradation of 2,4-dichlorophenoxyacetic acid (2,4-D). The results showed positive correlation between transfer and donor metabolic activity, and an optimal temperature for transfer of 29°C. On stimulation of donor activity, the optimal temperature was decreased to 24.5°C. HgCl2 above 1.0 μg L-1 negatively affected transfer, whereas 2,4-D up to 0.3 mM had no effect. The negative effect of mercury was shown to be a result of stressing of the recipient. No effects of mercury on transfer could be detected by traditional filter mating. Thus, the method is superior to filter mating and, as the experimental design allows the manipulation of individual parameters, it is ideal for the assessment and comparison of effects of environmental factors on plasmid transfer.

KW - Conjugation

KW - Plasmid

KW - pRO103

KW - Selection

KW - Stress

UR - http://www.scopus.com/inward/record.url?scp=33847746348&partnerID=8YFLogxK

U2 - 10.1111/j.1574-6941.2006.00230.x

DO - 10.1111/j.1574-6941.2006.00230.x

M3 - Journal article

C2 - 17100984

AN - SCOPUS:33847746348

VL - 59

SP - 718

EP - 728

JO - F E M S Microbiology Ecology

JF - F E M S Microbiology Ecology

SN - 0168-6496

IS - 3

ER -