Evaluation of the Escherichia coli HK82 and BS87 strains as tools for AlkB studies

Abstract

Within a decade the family of AlkB dioxygenases has been extensively studied as a one-protein DNA/RNArepair system in Escherichia coli but also as a group of proteins of much wider functions in eukaryotes.Two strains, HK82 and BS87, are the most commonly used E. coli strains for the alkB gene mutations. Theaim of this study was to assess the usefulness of these alkB mutants in different aspects of research onAlkB dioxygenases that function not only in alkylated DNA repair but also in other metabolic processes incells. Using of HK82 and BS87 strains, we found the following differences among these alkB−derivatives:(i) HK82 has shown more than 10-fold higher MMS-induced mutagenesis in comparison to BS87; (ii)different specificity of Arg+revertants; (iii) increased induction of SOS and Ada responses in HK82; (iv)the genome of HK82, in comparison to AB1157 and BS87, contains additional mutations: nalA, sbcC, andnuoC. We hypothesize that in HK82 these mutations, together with the non-functional AlkB protein, mayresult in much higher contents of ssDNA, thus higher in comparison to BS87 MMS-induced mutagenesis.In the light of our findings, we strongly recommend using BS87 strain in AlkB research as HK82, bearingseveral additional mutations in its genome, is not an exact derivative of the AB1157 strain, and showsadditional features that may disturb proper interpretation of obtained results.