Sequence analysis and activity determination of narU and narZ promoter genes of Salmonella Typhimurium

TORRES LAMBERTI, MF; BALLESTEROS, MARÍA F.; DELGADO MA; PESCARETTI MM,

Congreso; XIII Congreso Argentino de Microbiología General; 2018

SAMIGE

Salmonella Typhimurium and Escherichia coli cells have three nitrate reductases (Nap, NR-A and NR-Z) involved in adaptation to growth on anaerobic and/or on oxidized carbon environment. Previously, we demonstrated that RcsB and RstA regulators control the narZ gene expression, involved in the synthesis of NR-Z, in a carbon source-dependent pathway. Since the regulatory region that controls the narZ expression is not well defined and the data is controversial, here we investigate which is the promoter whose activity allows the transcription of narZ. In Salmonella, some reports postulated that narU gene is upstream of narZ and it is the first gene of the operon, while others argue that they are independently transcribed. We localized the transcription start site, the -10 and -35 boxes in both promoters, by bioinformatics analysis. Then, these regulatory region were cloned into the plasmid pFU62, harboring the β-galactosidase encoding gene as reporter of the activity of each promoter. The effect of the RcsB overproduction was also analyzed and compared with data obtained from chromosomal narZ::lacZ transcriptional fusion to define it narZ promoter sequence and to determine the impact of this regulator in the gene expression.