Tn5041-like transposons: molecular diversity, evolutionary relationships and distribution of distinct variants in environmental bacteria.
A detailed study on the geographic distribution, molecular diversity and evolutionary relationships of 24 closely related variants of the Tn5041 transposon found among 182 mercury resistant environmental Gram-negative strains from the IMG-Hg Reference Collection is reported here. RFLP analysis, followed by the determination of partial DNA sequences, identified 14 distinct types of these transposons, which differed from each other by 1-7 single-event DNA polymorphisms. No polymorphisms were detected at the right arm of the transposons except an insertion of a new mobile DNA element carrying a mer operon (named the mer2 cassette) within the Tn5041 mer operon. According to the model presented here, the insertion occurred via homologous recombination with a circular form of the mer2 cassette. A total of 8 point mutations, 1 internal deletion, 2 end-involving deletions, 3 mosaic regions and 2 insertions were detected at the left arm of the transposons. The insertions were a transposon closely related to Tn21 but lacking the integron and a new group II intron (named INT5041C). Inspection of the geographic distribution of the Tn5041 variants suggested that at least three long-distance waves of dissemination of these variants had occurred, accompanied by homologous recombination between different Tn5041 lineages. Movements of circular DNAs by homologous recombination as a source of mosaic genes and new mer genes, and formation of unusual mosaics ending or beginning at the Tn5041 att site are discussed.
Kholodii
G
G
Institute of Molecular Genetics, Russian Academy of Sciences, Moscow 123182, Russia1.
Gorlenko
Zh
Z
Institute of Molecular Genetics, Russian Academy of Sciences, Moscow 123182, Russia1.
Mindlin
S
S
Institute of Molecular Genetics, Russian Academy of Sciences, Moscow 123182, Russia1.
Hobman
J
J
School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK2.
Nikiforov
V
V
Institute of Molecular Genetics, Russian Academy of Sciences, Moscow 123182, Russia1.
D001419:Bacteria / Q000235:genetics*; D004251:DNA Transposable Elements / Q000235:genetics*; D004270:DNA, Circular; D004777:Environment; D019143:Evolution, Molecular; D005656:Fungal Proteins / Q000235:genetics; D014644:Genetic Variation; D032023:Integrons / Q000235:genetics; D007438:Introns; D008969:Molecular Sequence Data; D012150:Polymorphism, Restriction Fragment Length; D011995:Recombination, Genetic; D029701:Saccharomyces cerevisiae Proteins
D004251:DNA Transposable Elements; D004270:DNA, Circular; D005656:Fungal Proteins; C071054:REC107 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins