The preparations were examined with an Olympus BX60 fluorescence
microscope using the proper filter set (U-MWG and FITC
31001 from Olympus). Images for each filter were captured with
an Andor camera DL-658M and merged using Gimp. The number of
signals and their localization in both the comet head and tail were
recorded for each nucleoid. DNA damage on each comet picture
was analysed using the Komet Version 5.1 image analyses system
(Kinetic Imaging, Liverpool, UK). The percentage of tail DNA (TD)
was the comet parameter selected to quantify global DNA damage.