The role of DNA base excision repair in filamentation in Escherichia coli K-12 adhered to epithelial HEp-2 cells

Base excision repair (BER) is dedicated to the repair of oxidative DNA damage caused by reactive oxygen species generated by chemical and physical agents or by metabolism which can react with DNA and cause a variety of mutations. Epithelial cells are typically the first type of host cell to come into contact with potential microbial invaders. In this work, we have evaluated whether the adherence to human epithelial cells causes DNA damage and associated filamentation. Experiments concerning adherence to HEp-2 cells were carried out with mutants deficient in BER that were derived from Escherichia coli K-12. Since the removal of mannose during bacterial interaction with HEp-2 cells allows adhesion through mannose-sensitive adhesins, the experiments were also performed in the presence and the absence of mannose. Our results showed enhanced filamentation for the single xth (BW9091) and triple xth nfo nth (BW535) mutants in adherence assays with HEp-2 cells performed without d-mannose. The increased filamentation growth was inhibited by complementation of BER mutants with a wild type xth gene. Moreover, we measured SOS induction of bacteria adhered to HEp-2 cells in the presence and absence of d-mannose through of SOS-chromotest assay and we observed a higher β-galactosidase expression in the absence of mannose. In this context, data showed evidence that bacterial attachment to HEp-2 epithelial surfaces can generate DNA lesions and SOS induction.