Heavy metal (As, Cd, Cr, Hg, Pb) analysis and identification of heavy metal resistant bacteria in sediments from Manado Bay

Environmental pollution from heavy metals is becoming a growing concern due to the adverse effects it is causing throughout the world. This study aims to analyze heavy metal concentrations and identify heavy metal resistant bacteria in the bay of Manado. Sediment samples were collected from five bays in Manado. The concentrations of heavy metals As, Cd, Cr, Hg and Pb were analyzed using ICP-OES, and Hg using CV-AFS. Bacteria from the sediment were grown in nutrient broth media containing heavy metals As, Cd, Cr, Hg and Pb respectively. Microbiology and 16SrRNA gene analysis were used to identify the bacteria that grown on media containing varying concentrations of heavy metals. The results showed that the sediments from the five bays in Manado contained heavy metals with an average concentration of As <1mg/kg, Cd 1.8mg/kg), Cr 6.2mg/kg, Hg <0.07mg/kg). and Pb 11.2mg/kg. The results of microbiological and molecular analysis showed that 5 species of heavy metal resistant bacteria were Pseudomonas aeruginosa, Bacillus cereus, Staphylococcus arlettae, Acinobacter sp., and Brevibacterium sp. The five bacteria found to be resistant to heavy metals can be used to detoxify As, Cd, Cr, Hg, and Pb.

Composition and Niche-Specific Characteristics of Microbial Consortia Colonizing Marsberg Copper Mine in the Rhenish Massif

The Kilianstollen Marsberg (Rhenish Massif, Germany) has been extensively mined for copper ores, dating from Early Medieval Period till 1945. The exposed organic-rich alum shale rocks influenced by the diverse mine drainages at an ambient temperature of 10 °C could naturally enrich biogeochemically distinct heavy metal resistant microbiota. This metagenomic study evaluates the microbially colonized subterranean rocks of the abandoned copper mine Kilianstollen to characterize the colonization patterns and biogeochemical pathways of individual microbial groups. Under the selective pressure of the heavy metal contaminated environment at illuminated sites, Chloroflexi (Ktedonobacteria) and Cyanobacteria (Oxyphotobacteria) build up whitish-greenish biofilms. In contrast, Proteobacteria, Firmicutes and Actinobacteria dominate rocks around the uncontaminated spring water streams. The metagenomic analysis revealed that the heavy metal resistant microbiome was evidently involved in redox cycling of transition metals (Cu, Zn, Co, Ni, Mn, Fe, Cd, Hg). No deposition of metals or minerals, though, was observed by transmission electron microscopy in Ktedonobacteria biofilms which may be indicative for the presence of different detoxification pathways. The underlying heavy metal resistance mechanisms, as revealed by analysis of metagenome-assembled genomes, were mainly attributed to transition metal efflux pumps, redox enzymes, volatilization of Hg0, methylated intermediates of As(III) and reactive oxygen species detoxification pathways.