Bioaccumulation, tolerance, and removal of U(VI) and Th(IV) by a novel thermophilic Bacillus cereus ST14 isolated from hot spring mud samples in Afyonkarahisar, Turkey

Abstract

In this study, a novel thermophilic Bacillus cereus ST14 with heavy metal tolerance was isolated from a hot spring mud sample in Afyonkarahisar (Omer). 16S rRNA analysis revealed that strain ST14 was mostly related to Bacillus cereus strain 151,007-R3_K09_40_27F (98.18%) and Bacillus cereus strain 2 k (98.10%). We hypothesized that U(VI) and Th(IV) affected B. cereus at the cell level and that this bacterium can be used as a bioindicator. Therefore, U(VI) and Th(IV) tolerance, removal, bioaccumulation, and impacts on antioxidant enzymes of thermophilic B. cereus have been examined in detail. Changes in the surface macrostructure and functionality of B. cereus following interaction with U(VI) and Th(IV) were studied using a scanning electron microscope and fourier transform infrared spectroscopy. B. cereus was found to be highly resistant to 10 and 12.5 mg/L of U(VI) and Th(IV) after 24-h incubation. Superoxide dismutase (SOD) and catalase (CAT) activities were observed to be increased by different U(VI) and Th(IV) concentrations. The highest bioaccumulation capacity quantities were detected as 100.79 and 87.96 mg metal/g dried bacteria at 24th h at 12.5 mg/L concentration for U(VI) and Th(IV), respectively. The highest U(VI) and Th(IV) cell membrane bioaccumulation capabilities of B. cereus have been measured as 318.94 and 263.89 mg metal/g wet membrane, respectively, at 24 h and 12.5 mg/L. This study's findings suggested that B. cereus could be employed as a bioindicator organism for detecting metal contamination in natural or industrial water samples. However, further research should focus on other thermophilic microorganisms.