Dyes Biodegradation in the Presence of Hexavalent Chromium by Streptomyces sp. KY75: a Novel Heavy Metal Resistant Strain Isolated in Algeria

A novel heavy metal resistant actinobacterial strain was isolated from an old lead and zinc mine in north-eastern Algeria. This strain was shown to resist high concentrations of heavy metals, including up to 500 ppm arsenic, 700 ppm cadmium, 1750 ppm chromium, 1250 ppm cobalt, 1000 ppm copper, 2750 ppm iron, 2750 ppm lead, 800 ppm mercury, 1750 ppm nickel, and 2750 ppm zinc. In addition, it was able to degrade dyes of the most used families, i.e., triphenylmethane (Malachite Green), azo (Ponceau S), and anthraquinone (Remazol Brilliant Blue R) dyes at 97.79%, 62.93%, and 39.41%, respectively. This bacterium was identified by sequencing the 16S rRNA encoding gene and affiliated to the genus Streptomyces by the RDP Naive Bayesian rDNA Classifier Version 2.11. The genome of Streptomyces sp. KY75 was sequenced using Illumina MiSeq and Oxford Nanopore. It was annotated by the MicroScope platform, and gene codings for resistance to heavy metals and dye biodecolorization were identified. It has a single linear chromosome with 7,837,660 bp and a GC content of 71.58%, 7509 of coding sequences (CDS), 66 tRNA genes, 18 rRNA genes, and 11 pseudogenes. The effect of hexavalent chromium on the dye biodegradation in liquid medium was also tested. Surprisingly, the dye biodegradation was not affected by the addition of hexavalent chromium. These observations make the actinobacterial strain Streptomyces sp. KY75 a good candidate for the bioremediation of textile dyeing industry effluents.