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Microbiology 154 (2008), 3686-3696; DOI  10.1099/mic.0.2008/021584-0
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Microbiology 154 (2008), 3686-3696; DOI  10.1099/mic.0.2008/021584-0
© 2008 Society for General Microbiology

Divergent roles of CprK paralogues from Desulfitobacterium hafniense in activating gene expression

Krisztina Gábor{dagger}, Kagnew Hailesellasse Sene, Hauke Smidt, Willem M. de Vos and John van der Oost

Wageningen University and Research Centre, Laboratory of Microbiology, Dreijenplein 10, Wageningen 6703-HB, The Netherlands

Correspondence
Krisztina Gábor
krisztina.gabor{at}codexis.com

Gene duplication and horizontal gene transfer play an important role in the evolution of prokaryotic genomes. We have investigated the role of three CprK paralogues from the cAMP receptor protein–fumarate and nitrate reduction regulator (CRP–FNR) family of transcriptional regulators that are encoded in the genome of Desulfitobacterium hafniense DCB-2 and possibly regulate expression of genes involved in the energy-conserving terminal reduction of organohalides (halorespiration). The results from in vivo and in vitro promoter probe assays show that two regulators (CprK1 and CprK2) have an at least partially overlapping effector specificity, with preference for ortho-chlorophenols, while meta-chlorophenols proved to be effectors for CprK4. The presence of a potential transposase-encoding gene in the vicinity of the cprK genes indicates that their redundancy is probably caused by mobile genetic elements. The CprK paralogues activated transcription from promoters containing a 14 bp inverted repeat (dehalobox) that closely resembles the FNR-box. We found a strong negative correlation between the rate of transcriptional activation and the number of nucleotide changes from the optimal dehalobox sequence (TTAAT-N4-ATTAA). Transcription was initiated by CprK4 from a promoter that is situated upstream of a gene encoding a methyl-accepting chemotaxis protein. This might be the first indication of taxis of an anaerobic bacterium to halogenated aromatic compounds.

Abbreviations: CHPA, 3-chloro-4-hydroxyphenylacetic acid; CRP, cAMP receptor protein; DCP, dichlorophenol; EMSA, electrophoretic mobility shift assay; FNR, fumarate and nitrate reduction regulator; HTH, helix–turn–helix; RNAP, RNA polymerase; TCP, trichlorophenol

{dagger}Present address: Codexis Laboratories Hungary Kft., 1045 Budapest, Berlini utca 47–49, Hungary.






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