Morphological Adaptations of Paenibacillus dendritiformis VSR 204 under Extreme Metal Stress

Abstract

Morphological changes under extreme metal stress environment are one of the metal resistance mechanisms seen in bacteria. Considering this, a study was conducted on a metal tolerance bacterium i.e.  Paenibacillus dendritiformis VSR 204 isolated from metal contaminated soils and also ascertain on the functional group involvement in metal absorption or metal chelation.  Particularly, Paenibacillus dendritiformis VSR 204 exhibited an impressive tolerance to Copper (Cu), Lead (Pb), and Zinc (Zn), enduring concentrations of up to 3300 ppm, 2700 ppm, and 8000 ppm, respectively. The discernible transformations in biofilm within bacterial cells subjected to extreme metal stress were elucidated through Scanning Electron Microscopy (SEM) analyses, effectively contrasting against untreated control. Additionally, Energy-Dispersive X-ray Spectroscopy (EDX) investigation unveiled the uptake and localization patterns of heavy metals within the bacterial matrix. The functional group involved in metal chelation was revealed by FT-IR. Biofilm formation changed only after the exposure of bacterial cells to sub inhibitory concentrations of heavy metals Cu and Pb. In contrast, no changes were observed in biofilm formation even at sub inhibitory concentrations of Zn remaining similar to that of control. Hence this study clearly confirmed that Paenibacillus dendritiformis VSR 204 could be helpful in the cleanup of heavy metals like Cu, Zn and Pb from the environment.