Detection of chrB and czcD Genes in Heavy Metal Resistant Soil Bacteria

Abstract

Heavy metal contamination can impose strong selective pressure on soil microorganisms and favour the persistence of bacteria with metal-tolerance mechanisms. This study investigated heavy metal-resistant bacteria from soil collected at Beehive Industries and examined the occurrence of the chrB and czcD resistance genes. Soil was enriched in Tryptone Soy Broth containing equal proportions of magnesium sulphate heptahydrate, manganese(II) sulphate monohydrate, ferrous sulphate heptahydrate and cupric sulphate. Resistant and sensitive isolates were recovered on metal-amended and metal-free media, respectively, purified by quadrant streaking, and evaluated against 60, 80 and 100 mg of the metal cocktail per 50 mL of medium. The resistant isolate was further assessed on King’s B medium, and PCR products were examined by agarose gel electrophoresis. MR1 showed the highest recorded tolerance, with an MIC of 80 mg per 50 mL, whereas MR2 and MS1 had recorded MIC values of 60 mg per 50 mL. MS4 showed no growth at the lowest test level. Green fluorescence on King’s B medium was consistent with pyoverdine production by Pseudomonas. PCR screening was undertaken for chrB and czcD; the presented electrophoretic result showed a distinct czcD amplicon in the resistant isolate and no corresponding band in the sensitive control. These findings provide preliminary phenotypic and molecular evidence of metal resistance in an industrial-soil bacterium. Further species confirmation, gene sequencing, expression analysis and metal-removal assays are required to establish the functional significance and bioremediation potential of the isolate.