The Role of Some Transcription Factors in Expression of GyrA and GyrB Following Exposure to Ciprofloxacin

GyrA and gyrB genes encode DNA gyrase subunits. This enzyme regulates DNA supercoiling. Inhibitors of this enzyme, such as ciprofloxacin, may change the level of supercoiling and the expression level of genes, including gyrA and gyrB.

The aims of this research were first to select some transcription factors, which regulate the expression of gyrA and gyrB. Secondly, the effect of these transcription factors was investigated on the expression of these genes in Escherichia coli mutants with different levels of resistance to ciprofloxacin in the presence and absence of these transcription factors.

For this purpose, the online software called Promoter Analyzer in Virtual Footprint version 3 was used to find and select some transcription factors. The relative expression of genes was determined by quantitative real-time polymerase chain reaction (qRT-PCR).

Theoretical results showed that CspA, FhlA, and SoxS transcription factors (with a score of match higher than 6), could be selected for further analysis. The expression of gyrA and gyrB genes remained unchanged in the presence and absence of CspA and FhlA transcription factors following exposure to the low amount of ciprofloxacin. However, SoxS transcription activator might have indirect effects on the expression of these genes, as soxS gene was overexpressed following treatment with a higher amount of ciprofloxacin.

It is concluded that overexpression of gyrA and gyrB genes is not dependent on CspA and FhlA transcription factors, but may be dependent indirectly on regulatory proteins involved in oxidative stress following exposure to ciprofloxacin.