Investigation of the effects of heavy metal resistant bacteria on heavy metal biodegradation and plant development

In this thesis, the removal of lead, zinc, copper, cadmium, arsenic, and mercury, as well as plant growth in soils contaminated by these metals, were investigated using seven different bacterial strains isolated from Burdur Lake that exhibited resistance to heavy metals. To this end, bacteria were cultured in laboratory-prepared media containing heavy metals, and heavy metal concentrations were measured at various time points using ICP-OES. The analysis revealed the highest reduction rates for zinc at 35.9% (Pseudomonas sp. As30), cadmium at 72.5% (Delftia tsuruhatensis As23), arsenic at 85.1% (Delftia sp. As37), copper at 31.1% (Delftia sp. As37), lead at 89.4% (Delftia tsuruhatensis As23), and mercury at 96.1% (Delftia sp. As37). To observe the effects of bacteria on plant growth, barley (Hordeum vulgare) was cultivated in peat enriched with heavy metals, and active cultures of the seven strains were added. At the end of the plant trials, measurements were conducted using morphological, chromatographic, and molecular techniques. The results indicated that the addition of bacterial cultures led to a significant increase in plant growth and a reduction in heavy metal contamination in the peat samples. The highest metal reduction rates observed in the peat samples were 60% for zinc (Pseudomonas sp. As30), 93% for cadmium (MIX), 83% for arsenic (MIX), 38% for copper (MIX), 68% for lead (MIX), and 43% for mercury (Ochrabactrum anthropi As7). When evaluating the metal removal and plant growth parameters together, it was determined that Delftia tsuruhatensis As23 and Delftia sp. As37 strains showed a statistically significant difference compared to other strains. These strains hold potential for use in heavy metal remediation and the restoration of agricultural lands degraded by soil contamination, thereby enhancing productivity. The bacterial strains identified in this study for their biotechnological potential offer a significant solution to the global and national challenges of heavy metal pollution and the associated agricultural productivity problems.