Diversity and Efficiency of Cyanide Degrading Alkaliphilic Bacteria from Ethiopian Soda Lakes

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Addis Ababa University


The aim of this study was to isolate and characterize cyanide degrading alkaliphilic bacteria from Ethiopian Soda Lakes. Seventy two isolates capable of growing on a medium provided with cyanide as a sole nitrogen source has been found. Based on their morphological features, thirty isolates were screened for subsequent identification. ARDRA of the 16S ribosomal genes amplified by PCR was used to screen these isolates. Restriction analysis was done using three endonucleases namely; AluI, HaeIII and RsaI. ARDRA revealed the presence of nine polymorphic groups among the thirty. 16S rDNA amplicons of representative strains were sequenced and compared with sequences from NCBI and RDP databases. This revealed the presence seven bacterial strains from which three belonged to genus Bacillus, three to genus Halomonas, and the other one to uncultured bacterium clone, FJ152630. Based on phylogenetic analysis, the unidentified strain was more related to and clustered with the Halomonas sublineages. Strains CNS10, CNA12 and CNC1 isolated from Lake Shala, Lake Abijata and Lake Chitu respectively were found to be better candidates in that they have utilized up to 99.33% of 200mg/l cyanide and tolerated up to cyanide concentration of 600mg/l in batch mode with pH of 10.22. In addition to cyanide, these strains used other organic and inorganic nitrogen sources, yeast extract being the most utilized. Acetate was being provided as a source of carbon and energy source but most interestingly all the strains have aggressively grown utilizing cyanide when provided with cheap molasses as carbon source. In general, this study indicated the presence of diverse cyanide utilizing bacteria with visible potential for practical application.