Adaptation of Xanthobacter autotrophicus GJ10 to bromoacetate due to activation and mobilization of the haloacetate dehalogenase gene by insertion element IS1247.
Monobromoacetate (MBA) is toxic for the 1,2-dichloroethane-degrading bacterium Xanthobacter autotrophicus GJ10 at concentrations higher than 5 mM. Mutants which are able to grow on higher concentrations of MBA were isolated and found to overexpress haloacid dehalogenase, which is encoded by the dhlB gene. In mutant GJ10M50, a DNA fragment (designated IS1247) had copied itself from a position on the chromosome that was not linked to the dhlB region to a site immediately upstream of dhlB, resulting in a 1,672-bp insertion. IS1247 was found to encode an open reading frame corresponding to 464 amino acids which showed similarity to putative transposases from two other insertion elements. In most of the other MBA-resistant mutants of GJ10, IS1247 was also present in one more copy than in the wild type, which had two copies located within 20 kb. After insertion to a site proximal to dhlB, IS1247 was able to transpose itself together with the dhlB gene to a plasmid, without the requirement of a second insertion element being present downstream of dhlB. The results show that IS1247 causes bromoacetate resistance by overexpression and mobilization of the haloacid dehalogenase gene, which mimics steps during the evolution of a catabolic transposon and plasmid during adaptation to a toxic growth substrate.
van der Ploeg
J
J
Department of Biochemistry, Groningen Biomolecular Sciences and Biotechnology, University of Groningen, The Netherlands.
Willemsen
M
M
van Hall
G
G
Janssen
D B
DB
D000085:Acetates / Q000378:metabolism / Q000494:pharmacology*; D000222:Adaptation, Physiological; D000595:Amino Acid Sequence; D001483:Base Sequence; D001673:Biodegradation, Environmental; D004251:DNA Transposable Elements / Q000235:genetics*; D004352:Drug Resistance, Microbial; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial / Q000235:genetics; D006088:Gram-Negative Aerobic Bacteria / Q000187:drug effects / Q000235:genetics*; D006219:Halogens / Q000378:metabolism; D006867:Hydrolases / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation; D009713:Nucleotidyltransferases / Q000235:genetics; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics; D015183:Restriction Mapping; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D019895:Transposases
D000085:Acetates; D004251:DNA Transposable Elements; D006219:Halogens; C016274:bromoacetate; D009713:Nucleotidyltransferases; D019895:Transposases; D006867:Hydrolases; C034507:2-haloacid dehalogenase; C023098:haloacetate dehalogenase