biostudies-literatureUnknown6(11)Pedro LThe nucleoid-associated proteins Hha and YdgT repress the expression of the toxin α-hemolysin. An Escherichia coli mutant lacking these proteins overexpresses the toxin α-hemolysin encoded in the multicopy recombinant plasmid pANN202-312R. Unexpectedly, we could observe that this mutant generated clones that no further produced hemolysin (Hly(-)). Generation of Hly(-) clones was dependent upon the presence in the culture medium of the antibiotic kanamycin (km), a marker of the hha allele (hha::Tn5). Detailed analysis of different Hly(-) clones evidenced that recombination between partial IS91 sequences that flank the hly operon had occurred. A fluctuation test evidenced that the presence of km in the culture medium was underlying the generation of these clones. A decrease of the km concentPloS onee27606https://www.ebi.ac.uk/biostudies/studies/S-EPMC3214074biostudies-literatureAntibiotics shaping bacterial genome: deletion of an IS91 flanked virulence determinant upon exposure to subinhibitory antibiotic concentrations.PMC3214074Madrid CAznar SPedro LBanos RCJuarez ABalsalobre CfalseAntibiotics shaping bacterial genome: deletion of an IS91 flanked virulence determinant upon exposure to subinhibitory antibiotic concentrations.The nucleoid-associated proteins Hha and YdgT repress the expression of the toxin α-hemolysin. An Escherichia coli mutant lacking these proteins overexpresses the toxin α-hemolysin encoded in the multicopy recombinant plasmid pANN202-312R. Unexpectedly, we could observe that this mutant generated clones that no further produced hemolysin (Hly(-)). Generation of Hly(-) clones was dependent upon the presence in the culture medium of the antibiotic kanamycin (km), a marker of the hha allele (hha::Tn5). Detailed analysis of different Hly(-) clones evidenced that recombination between partial IS91 sequences that flank the hly operon had occurred. A fluctuation test evidenced that the presence of km in the culture medium was underlying the generation of these clones. A decrease of the km concent2011-01-01T00:00:00Z20112026-04-08T00:53:28.471Z2025-07-09T03:05:11.382ZS-EPMC32140742209660310.1371/journal.pone.0027606