Environmentally co-occurring mercury resistance plasmids are genetically and phenotypically diverse and confer variable context-dependent fitness effects

TY - JOUR

T1 - Environmentally co-occurring mercury resistance plasmids are genetically and phenotypically diverse and confer variable context-dependent fitness effects

AU - Hall, James P J

AU - Harrison, Ellie

AU - Lilley, Andrew K

AU - Paterson, Steve

AU - Spiers, Andrew J

AU - Brockhurst, Michael A

N1 - This article is protected by copyright. All rights reserved.

PY - 2015

Y1 - 2015

N2 - Plasmids are important mobile elements that can facilitate genetic exchange and local adaptation within microbial communities. We compared the sequences of four co-occurring pQBR-family environmental mercury resistance plasmids and measured their effects on competitive fitness of a Pseudomonas fluorescens SBW25 host, which was isolated at the same field site. Fitness effects of carriage differed between plasmids and were strongly context dependent, varying with medium, plasmid status of competitor and levels of environmental mercury. The plasmids also varied widely in their rates of conjugation and segregational loss. We found that few of the plasmid-borne accessory genes could be ascribed functions, although we identified a putative chemotaxis operon, a type IV pilus-encoding cluster, and a region encoding putative arylsulfatase enzymes, which were conserved across geographically distant isolates. One plasmid, pQBR55, conferred the ability to catabolise sucrose. Transposons, including the mercury resistance Tn5042, appeared to have been acquired by the different pQBR plasmids by recombination, indicating an important role for horizontal gene transfer in the recent evolution of pQBR plasmids. Our findings demonstrate extensive genetic and phenotypic diversity amongst co-occurring members of a plasmid community and suggest a role for environmental heterogeneity in the maintenance of plasmid diversity.

AB - Plasmids are important mobile elements that can facilitate genetic exchange and local adaptation within microbial communities. We compared the sequences of four co-occurring pQBR-family environmental mercury resistance plasmids and measured their effects on competitive fitness of a Pseudomonas fluorescens SBW25 host, which was isolated at the same field site. Fitness effects of carriage differed between plasmids and were strongly context dependent, varying with medium, plasmid status of competitor and levels of environmental mercury. The plasmids also varied widely in their rates of conjugation and segregational loss. We found that few of the plasmid-borne accessory genes could be ascribed functions, although we identified a putative chemotaxis operon, a type IV pilus-encoding cluster, and a region encoding putative arylsulfatase enzymes, which were conserved across geographically distant isolates. One plasmid, pQBR55, conferred the ability to catabolise sucrose. Transposons, including the mercury resistance Tn5042, appeared to have been acquired by the different pQBR plasmids by recombination, indicating an important role for horizontal gene transfer in the recent evolution of pQBR plasmids. Our findings demonstrate extensive genetic and phenotypic diversity amongst co-occurring members of a plasmid community and suggest a role for environmental heterogeneity in the maintenance of plasmid diversity.

U2 - 10.1111/1462-2920.12901

DO - 10.1111/1462-2920.12901

M3 - Article

C2 - 25969927

SN - 1462-2912

JO - Environmental Microbiology

JF - Environmental Microbiology

ER -