  Antibiotics such as the quinolones and fluoroquinolones kill bacterial
pathogens ultimately through DNA damage. They target the essential type IIA
topoisomerases in bacteria by stabilising the normally transient double strand
break state which is created to modify the supercoiling state of the DNA. Here
we discuss the development of these antibiotics and their method of action.
Existing methods for DNA damage visualisation, such as the comet assay and
immunofluorescence imaging can often only be analysed qualitatively and this
analysis is subjective. We describe a putative single-molecule fluorescence
technique for quantifying DNA damage via the total fluorescence intensity of a
DNA origami tile fully saturated with an intercalating dye, along with the
optical requirements for how to implement these into a light microscopy imaging
system capable of single-molecule millisecond timescale imaging. This system
promises significant improvements in reproducibility of the quantification of
DNA damage over traditional techniques.
