However more recent evidence indicates that competence for transformation is, indeed, specifically induced by DNA damaging conditions. For instance, Claverys "et al". in 2006 showed that the DNA damaging agents mitomycin C (a DNA cross-linking agent) and fluoroquinolone (a topoisomerase inhibitor that causes double-strand breaks) induce transformation in "Streptococcus pneumoniae". In addition, Engelmoer and Rozen in 2011 demonstrated that in "S. pneumoniae" transformation protects against the bactericidal effect of mitomycin C. Induction of competence further protected against the antibiotics kanomycin and streptomycin. Although these aminoglycoside antibiotics were previously regarded as non-DNA damaging, recent studies in 2012 of Foti "et al". showed that a substantial portion of their bactericidal activity results from release of the hydroxyl radical and induction of DNA damages, including double-strand breaks.