TY - JOUR
T1 - Novel insight into the genetic context of the cadAB genes from a 4-chloro-2-methylphenoxyacetic acid-degrading Sphingomonas
AU - Nielsen, Tue Kjærgaard
AU - Xu, Zhuofei
AU - Gozdereliler, Erkin
AU - Aamand, Jens
AU - Hansen, Lars H.
AU - Sørensen, Sebastian R.
PY - 2013
Y1 - 2013
N2 - The 2-methyl-4-chlorophenoxyacetic (MCPA) acid-degrader Sphingomonas sp. ERG5 has recently been isolated from MCPA-degrading bacterial communities. Using Illumina-sequencing, the 5.7 Mb genome of this isolate was sequenced in this study, revealing the 138 kbp plasmid pCADAB1 harboring the 32.5 kbp composite transposon Tn6228 which contains genes encoding proteins for the removal of 2,4-dichlorophenoxyacetic acid (2,4-D) and MCPA, as well as the regulation of this pathway. Transposon Tn6228 was confirmed by PCR to be situated on the plasmid and also exist in a circular intermediate state - typical of IS3 elements. The canonical tfdA alpha-gene of group III 2,4-D degraders, encoding the first step in degradation of 2,4-D and related compounds, was not present in the chromosomal contigs. However, the alternative cadAB genes, also providing the initial degradation step, were found in Tn6228, along with the 2,4-D-degradation-associated genes tfdBCDEFKR and cadR. Putative reductase and ferredoxin genes cadCD of Rieske non-heme iron oxygenases were also present in close proximity to cadAB, suggesting that these might have an unknown role in the initial degradation reaction. Parts of the composite transposon contain sequence displaying high similarity to previously analyzed 2,4-D degradation genes, suggesting rapid dissemination and high conservation of the chlorinated-phenoxyacetic acid (PAA)-degradation genotype among the sphingomonads.
AB - The 2-methyl-4-chlorophenoxyacetic (MCPA) acid-degrader Sphingomonas sp. ERG5 has recently been isolated from MCPA-degrading bacterial communities. Using Illumina-sequencing, the 5.7 Mb genome of this isolate was sequenced in this study, revealing the 138 kbp plasmid pCADAB1 harboring the 32.5 kbp composite transposon Tn6228 which contains genes encoding proteins for the removal of 2,4-dichlorophenoxyacetic acid (2,4-D) and MCPA, as well as the regulation of this pathway. Transposon Tn6228 was confirmed by PCR to be situated on the plasmid and also exist in a circular intermediate state - typical of IS3 elements. The canonical tfdA alpha-gene of group III 2,4-D degraders, encoding the first step in degradation of 2,4-D and related compounds, was not present in the chromosomal contigs. However, the alternative cadAB genes, also providing the initial degradation step, were found in Tn6228, along with the 2,4-D-degradation-associated genes tfdBCDEFKR and cadR. Putative reductase and ferredoxin genes cadCD of Rieske non-heme iron oxygenases were also present in close proximity to cadAB, suggesting that these might have an unknown role in the initial degradation reaction. Parts of the composite transposon contain sequence displaying high similarity to previously analyzed 2,4-D degradation genes, suggesting rapid dissemination and high conservation of the chlorinated-phenoxyacetic acid (PAA)-degradation genotype among the sphingomonads.
U2 - 10.1371/journal.pone.0083346
DO - 10.1371/journal.pone.0083346
M3 - Journal article
C2 - 24391756
VL - 8
JO - PLoS ONE
JF - PLoS ONE
SN - 1932-6203
IS - 12
M1 - e83346
ER -