Protective effect of sodium selenite on ofloxacin-induced loss of chloroplast DNA inEuglena gracilis

Some xenobiotics induce permanent loss of chloroplasts inEuglena gracilis which results in the growth of white mutant colonies (bleaching effect). The effect of ofloxacin and sodium selenite on the organization of chloroplast DNA ofE. gracilis was studied by fluorescent microscopy. In the presence of ofloxacin DNA-specific staining with DAPI revealed a decrease in chloroplast DNA content and in the number of nucleoids per chloroplast. This was accompanied with a decrease of chloroplast number per cell and with the loss of stigma. Spectrophotometry of chlorophyll extract revealed changes in th ratio of chla: chlb. The presence of sodium selenite protected chloroplast DNA against the inhibitory effect of ofloxacin.