Figure 1.

(A) Schematic map of thiC gene of R. etli. The stippled box represents the thiC coding sequence. The lines above represent the location of the probes used in the Northern experiment. (B) Deletion constructions fused to lacZ. The fragments obtained by PCR were cloned into pMP220 vector to generate lacZ transcriptional fusions for determination of β-galactosidase activities from cultures grown in MM with or without thiamin as indicated. The letters alongside the arrows represent the names of the oligonucleotides used to obtain the different PCR fragments. The nucleotide positions are given with reference to the tss (position +1) of thiC. The black box represents the thi box sequence, and the potential stem-loop structures in the transcript that comprises the S-D sequence and the attenuator are marked by an inverted U. β-galactosidase activity is expressed as nmol of o-nitrophenol produced min⁻¹⋅mg protein⁻¹. Representative results of three experiments are shown. RR is the repression ratio, the β-galactosidase activity observed in media without thiamin divided by the activity observed in media supplemented with thiamin.