FN1 and infection: The supernatants from co-cultures between WIDR and Fn, where Fn grew, induced γ-H2AX in various colon cancer cell lines (Fig. 3c, d), a hallmark of DNA double strand breaks (DSBs) and suggesting that Fn infection may be carcinogenic to infected tissues, whereas the supernatants from co-cultures between HCEC-1CT and Fn, where Fn growth was not permissive, did not induce γ-H2AX in the exposed colon cancer cell lines (Fig. 3e).