Macromolecular Analysis of Biopolymeric 16S rRNA for Bacterial Diversity Assessment in Heavy Metal‐Contaminated Soil

Soil contamination by heavy metals represents a significant environmental challenge, primarily due to the persistent and toxic nature of these inorganic species and their detrimental effects on the resident soil microbial communities. This study investigates the impact of heavy metal exposure on bacterial growth and diversity in contaminated soil from two distinct sites in Tikrit city: an agricultural field (S1) and an industrial‐adjacent area (S2). The core of the analysis utilizes the macromolecular biopolymer, 16S ribosomal RNA (rRNA), as a molecular marker for bacterial identification and diversity assessment. Soil samples were challenged with varying concentrations of lead (Pb) and cadmium (Cd) (0.5, 1, and 2 mg/L), and cobalt (Co) and molybdenum (Mo) (0.1, 0.2, and 0.5 mg/L) to evaluate their concentration‐dependent effects on bacterial proliferation. The 16S rRNA gene was extracted from the microbial consortia and amplified via polymerase chain reaction, followed by sequencing and comparative analysis against the NCBI rRNA database. Results demonstrated a clear inhibitory effect of heavy metals on bacterial growth, which intensified with increasing metal concentration. Specifically, lead (Pb) exhibited a stimulatory effect at the lowest concentration (0.5 mg/L) before becoming inhibitory, while cadmium (Cd) showed a strong, dose‐dependent inhibition, leading to a complete absence of growth at 2 mg/L. Cobalt (Co) and molybdenum (Mo) presented varied effects, with Mo notably supporting growth in the S2 sample at its highest tested concentration (0.5 mg/L).