Isolation and Molecular Characterization of Heavy Metal-Resistant Alcaligenes faecalis from Sewage Wastewater and Synthesis of Silver Nanoparticles

Abstract

Environmental pollution with toxic heavy metals is increasing throughout the world alongside industrial development. Microorganisms and microbial products can be highly efficient bioaccumulators of soluble and particulate forms of metals, especially dilute external solutions. Microbe related technologies (Biotechnology) may provide an alternative or additive conventional method for metal removal or metal recovery. This study dealt with isolation, identification and characterization of heavy metal-resistant (Pb²⁺, Cd²⁺, Al³⁺, Cu²⁺, Ag²⁺ and Sn²⁺) bacteria from sewage wastewater at Taif Province, Saudi Arabia. Nine bacterial isolates were selected by using an enrichment isolation procedure based on high level of heavy metal resistance. All the isolates showed high resistance to heavy metals with Minimum Inhibitor Concentration (MIC) ranging from 800 μg/ml to 1400 μg/ml. All nine resistant isolates showed multiple tolerances to heavy metals. On the basis of morphological, biochemical and 16S rRNA characterization, the most potent isolates (Cd1-1, Ag1-1, Ag1-3 and Sn1-1) were identified as Alcaligenes faecalis. Scanning electron microscope analysis showed that the morphology of Alcaligenes faecalis Ag1-1 was unchanged after growth in medium without and with addition of Ag²⁺ indicative Ag²⁺ is not toxic to the isolate under the conditions tested. The ability of Alcaligenes faecalis Ag1-1 to synthesize sliver nanoparticles was examined. The heavy metal-resistant bacteria obtained could be useful for the bioremediation of heavy metal-contaminated environment.

Keywords:

• 16S rRNA
• Alcaligenes faecalis
• heavy metal resistance
• scanning electron microscope
• silver nanoparticles
• sewage
• transmission electron microscope

Funding

This work was supported by the research grant from Taif University, Contract No. 1/434/2466.