Open AccessConstruction of a double hha hns mutant of Escherichia coli : effect on DNA supercoiling and α‐haemolysin production
Author(s) -
Nieto J.M.,
Mouriño M.,
Balsalobre C.,
Madrid C.,
Prenafeta A.,
Muñoa F.J.,
Juárez A.
Publication year - 1997
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.1997.tb12683.x
Subject(s) - mutant , plasmid , escherichia coli , microbiology and biotechnology , biology , operon , dna supercoil , hemolysin , dna , gene , genetics , dna replication , virulence
A double hha hns Escherichia coli mutant was constructed. The effect of the single hns mutation and of the double hha hns mutation on the expression of the α‐haemolysin determinant of plasmid pANN202‐312 was assessed. Whereas the hns mutant moderately increased expression of the toxin, the double hha hns mutant strongly enhanced transcription of the hly operon and hence expression of the toxin. This suggests that both Hha and H‐NS proteins participate in the modulation of the expression of the toxin. The enhancement of haemolysin expression in the double mutant could not be correlated to a global alteration of DNA topology: DNA preparations of a reporter plasmid isolated from this mutant gave a topoisomer distribution similar to that of the parental strain.