Cytogenetic Study on Mitotic Cell Division in Allium cepa by Lead (Pb) and Chromium (Cr) Containing Bacterial Strain Isolated from Tannery Effl uents of Bangladesh

In the present study, a bacterial strain capable of Pb and Cr detoxifi cation was isolated from
tannery effluents which was identified as Myroides sp. through 16S rRNA gene sequencing. In the
cytogenetic experiment, 100 and 600 μg/ml of lead and chromium were used as treatment for the root
tips of Allium cepa and caused many chromosomal abnormalities such as abnormal chromosome
position, damaged nucleus, breaks of chromosome bridges and fragments also occurred. Notably,
sticky metaphase was found where sticky chromosomes indicated highly toxic, usually irreversible
consequences leading to cell death. However, Myroides sp. treated supernatant, collected after day
7, used to treat Allium cepa tips showed less mitotic aberrations, nuclear degeneration and observed
normal anaphase and telophase stage indicating possible metal detoxifying ability of the isolated
strain. Furthermore, LC50 value was 64.63 μl/ml for Myroides sp