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Mutagenesis via IS transposition in Deinococcus radiodurans
Author(s) -
Mennecier Samuel,
Servant Pascale,
Coste Geneviève,
Bailone Adriana,
Sommer Suzanne
Publication year - 2006
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2005.04936.x
Subject(s) - deinococcus radiodurans , biology , transposable element , insertion sequence , mutant , transposition (logic) , genetics , microbiology and biotechnology , point mutation , mutagenesis , dna repair , mutation frequency , dna , gene , linguistics , philosophy
Summary Analysis of the complete genome indicates that insertion sequences (ISs) are abundant in the radio‐resistant bacterium Deinococcus radiodurans . By developing a forward mutagenesis assay to detect any inactivation events in D. radiodurans , we found that in the presence of an active mismatch repair system 75% of the mutations to trimethoprim‐resistance (Tmp R ) resulted from an IS insertion into the thyA coding region. Analysis of their distribution among the spontaneous Tmp R mutants indicated that five different ISs were transpositionally active. A type II Miniature Inverted‐repeat Transposable Element (MITE), related to one of the deinococcal ISs, was also discovered as an insertion into thyA . Seven additional genomic copies of this MITE element were identified by BLASTN. γ‐ray irradiation of D. radiodurans led to an increase of up to 10‐fold in the frequency of Tmp R mutants. Analysis of the induced mutations in cells exposed to 10 kGy indicated that γ‐irradiation induced transposition of IS Dra2 approximately 100‐fold. A 50‐fold induction of IS Dra2 transposition was also observed in cells exposed to 600 J m −2 UV‐irradiation. Point mutations to rifampicin resistance (Rif R ) were also induced by γ‐irradiation to reach a plateau at 2 kGy. The plateau value represented a 16‐fold increase in the mutant frequency over the background. Although error‐free repair strategies predominate in D. radiodurans , an upregulation of transposition, as well as induction of point mutations in cells recovering from DNA damage, provide a genetic variability that may have long‐term evolutionary consequences on the fitness of this organism in its habitat.