The meta-omic approach in the bioremediation of heavy metals

Abstract

Heavy metal contamination poses a significant threat to ecosystems. This study initially explored the toxicological effects of heavy metals (Cr, Ni, and Al) on rats. 35 male Wistar rats were treated with two doses of LD₅₀: 1/100 and 1/50 of K2Cr2O7, NiCl2, and AlCl3. During the 3-month experiment, heavy metal exposure reduced weight gain in all treated groups compared to the control group. Weight gains in the Cr100, Ni100, and Al100 groups were 0.78g, 0.89g, and 0.9g, respectively, while in the Cr50, Ni50, and Al50 groups, they were 0.61g, 0.7g, and 0.7g, respectively. The Cr50 group exhibited anaerobic bacterial levels of 5.39 log CFU/g, while the Ni100 and Ni50 groups showed aerobic/anaerobic bacterial levels of 5.14/6 and 5.36/5.36 log CFU/g, respectively. In the Al50 group, Lactobacillus spp levels were 2.27 log CFU/g. In the second part, seven bacterial strains were isolated from agricultural soils and tested for their resistance and bioremediation capacity of heavy metals. Based on morphological, cultural, biochemical, and molecular characterization, the isolates were identified as follows: strain S1B10 as Pseudomonas aeruginosa, S1B26 as Pseudomonas fluorescens, S5B16 as a Bacillus sp, S2B1 and S6B3 as Bacillus cereus, strain S4B31 as Rhodopseudomonas palustris, and strain S5B23 as a Planomicrobium sp. The results revealed the MICs of the three heavy metals studied, ranging from 900 to 1600 µg/mL. AAS analysis showed that Bacillus sp. was the most efficient at removing Cr and Al, with bioaccumulation rates of 42.57% and 59.50%, respectively. Pseudomonas fluorescens exhibited the highest bioaccumulation rate for Ni, at 62.37%. When comparing the two consortia, bioremediation of Ni in soil was more efficient in C1, with a rate of 38.02%, while C2 demonstrated a higher bioremediation rate for Al, at 36.42%.