Molecular genetic identification and metal biosorption by a Geobacillus genospecies IRKM1 isolated from Deeymand hot spring, Kerman, Iran

Aims: This study deals with molecular identification, susceptibility, and metal biosorption of a Geobacillus genospecies isolated from Deeymand hot spring at the south east region of Kerman, Iran. Materials and Methods: Two samples were collected from water and sediment of the hot spring. Genomic DNA was extracted by sucrose lysis technique and polymerase chain reaction (PCR) was performed using the universal primers corresponding to Escherichia coli 16S rRNA gene. Both strands of the PCR product were sequenced by dideoxy chain termination method. The susceptibility of the isolate to Cu ²⁺ and Ni ²⁺ was determined by broth dilution method. Biosorption of dried biomass for the metal solutions was measured at different time intervals (5-300 min). Effect of temperature on biosorption of Cu ²⁺ and Ni ²⁺ was also determined. Results: Temperature of hot spring was 73°C and pH was 8. As result of sequencing of 16S rRNA gene, it was found that the organism had 99.8% similarity with member of genus Geobacillus. Phylogenetic tree and neighbor-joining phylogeny revealed that the isolate had 99.22% sequence similarity with Geobacillus uzenensis and 99.15% with Geobacillus jurassicus. The isolate exhibited minimum inhibitory concentration (MIC) of 4 mM to Cu ²⁺ and 5 mM to Ni ²⁺ . Minimum biosorption of Ni ²⁺ occurred at 5 min (0.07%/0.1 g biomass) and maximum biosorption occurred at 120 min (29.6%/0.1 g biomass), while minimum biosorption of Cu ²⁺ ion occurred within 5 min (16.6%/0.1 g biomass) and maximum occurred at 210 min (77.8%/0.1 g biomass) (P < 0.05). Biosorption of Ni ²⁺ was the highest at 27°C (89.8%) and Cu ²⁺ biosorption occurred at 65°C (77.8%). Geobacillus genospecies IRKM1 did not carry any plasmid. Conclusions: The above results showed that the isolate was a member of Geobacillus spp. and the thermophilic bacteria was moderately resistant to Cu and Ni metals even though there was not any previous contamination of that biological niche. The organism exhibited highest biosorption of Cu ²⁺ at 65°C and Ni ²⁺ at 27°C. No plasmid was detected in the Geobacillus isolate.