TY - JOUR
T1 - Broad-Host-Range Plasmids from Agricultural Soils Have IncP-1 Backbones with Diverse Accessory Genes
AU - Sen, D
AU - Van der Auwera, GA
AU - Rogers, LM
AU - Thomas, Christopher
AU - Brown, CJ
AU - Top, EM
PY - 2011/11/1
Y1 - 2011/11/1
N2 - Broad-host-range plasmids are known to spread genes between distinct phylogenetic groups of bacteria. These genes often code for resistances to antibiotics and heavy metals or degradation of pollutants. Although some broad-host-range plasmids have been extensively studied, their evolutionary history and genetic diversity remain largely unknown. The goal of this study was to analyze and compare the genomes of 12 broad-host-range plasmids that were previously isolated from Norwegian soils by exogenous plasmid isolation and that encode mercury resistance. Complete nucleotide sequencing followed by phylogenetic analyses based on the relaxase gene traI showed that all the plasmids belong to one of two subgroups (beta and epsilon) of the well-studied incompatibility group IncP-1. A diverse array of accessory genes was found to be involved in resistance to antimicrobials (streptomycin, spectinomycin, and sulfonamides), degradation of herbicides (2,4-dichlorophenoxyacetic acid and 2,4-dichlorophenoxypropionic acid), and a putative new catabolic pathway. Intramolecular transposition of insertion sequences followed by deletion was found to contribute to the diversity of some of these plasmids. The previous observation that the insertion sites of a Tn501-related element are identical in four IncP-1 beta plasmids (pJP4, pB10, R906, and R772) was further extended to three more IncP-1 beta plasmids (pAKD15, pAKD18, and pAKD29). We proposed a hypothesis for the evolution of these Tn501-bearing IncP-1 beta plasmids that predicts recent diversification followed by worldwide spread. Our study increases the available collection of complete IncP-1 plasmid genome sequences by 50% and will aid future studies to enhance our understanding of the evolution and function of this important plasmid family.
AB - Broad-host-range plasmids are known to spread genes between distinct phylogenetic groups of bacteria. These genes often code for resistances to antibiotics and heavy metals or degradation of pollutants. Although some broad-host-range plasmids have been extensively studied, their evolutionary history and genetic diversity remain largely unknown. The goal of this study was to analyze and compare the genomes of 12 broad-host-range plasmids that were previously isolated from Norwegian soils by exogenous plasmid isolation and that encode mercury resistance. Complete nucleotide sequencing followed by phylogenetic analyses based on the relaxase gene traI showed that all the plasmids belong to one of two subgroups (beta and epsilon) of the well-studied incompatibility group IncP-1. A diverse array of accessory genes was found to be involved in resistance to antimicrobials (streptomycin, spectinomycin, and sulfonamides), degradation of herbicides (2,4-dichlorophenoxyacetic acid and 2,4-dichlorophenoxypropionic acid), and a putative new catabolic pathway. Intramolecular transposition of insertion sequences followed by deletion was found to contribute to the diversity of some of these plasmids. The previous observation that the insertion sites of a Tn501-related element are identical in four IncP-1 beta plasmids (pJP4, pB10, R906, and R772) was further extended to three more IncP-1 beta plasmids (pAKD15, pAKD18, and pAKD29). We proposed a hypothesis for the evolution of these Tn501-bearing IncP-1 beta plasmids that predicts recent diversification followed by worldwide spread. Our study increases the available collection of complete IncP-1 plasmid genome sequences by 50% and will aid future studies to enhance our understanding of the evolution and function of this important plasmid family.
U2 - 10.1128/AEM.05439-11
DO - 10.1128/AEM.05439-11
M3 - Article
C2 - 21948829
SN - 0099-2240
VL - 77
SP - 7975
EP - 7983
JO - Applied and Environmental Microbiology
JF - Applied and Environmental Microbiology
IS - 22
ER -