Bacterial community structure in soils contaminated with electronic waste pollutants from Delhi NCR, India

Background: Microbial community analysis of electronic waste (e-waste)-polluted environments is of interest to understand the effect of toxic e-waste pollutants on the soil microbial community and to evaluate novel microorganisms resisting the toxic environment. The present study aims to investigate the bacterial community structure in soils contaminated with e-waste from various sites of Loni and Mandoli (National Capital Region (NCR), India) where e-waste dumping and recycling activities are being carried out for many years. Results: Interferences to soil metagenomic DNA extraction and PCR amplification were observed because of the presence of inhibiting components derived from circuit boards. Whole-metagenome sequencing on the Illumina MiSeq platform showed that the most abundant phyla were Proteobacteria and Firmicutes. Deltaproteobacteria and Betaproteobacteria were the most common classes under Proteobacteria. Denaturing gradient gel electrophoresis (DGGE) analysis of the bacterial 16S rRNA gene showed that e-waste contamination altered the soil bacterial composition and diversity. There was a decrease in the number of predominant bacterial groups like Proteobacteria and Firmicutes but emergence of Actinobacteria in the contaminated soil samples. Conclusions: This is the first report describing the bacterial community structure of composite soil samples of ewaste-contaminated sites of Loni and Mandoli, Delhi NCR, India. The findings indicate that novel bacteria with potential bioremediating properties may be present in the e-waste-contaminated sites and hence need to be evaluated further.

Proteobacteria, extremophiles and unassigned species dominate in a tape-like showerhead biofilm

Abstract The development of showerhead biofilms exposes the user to repeated contact with potentially pathogenic microbes, yet we know relatively little about the content of these aggregates. The aim of the present study was to examine the microbial content of tape-like films found protruding from a domestic showerhead. Culturing showed that the films were dominated by aerobic α- and β-proteobacteria. Three isolates made up almost the entire plate count. These were a Brevundimonas species, a metalophilic Cupriavidus species and a thermophile, Geobacillus species. Furthermore, it was shown that the Cupriavidus isolate alone had a high capacity for biofilm formation and thus might be the initiator of biofilm production. A clone library revealed the same general composition. However, half of the 70 clones analyzed could not be assigned to a particular bacterial phylum and of these 29 differed from one another by only 1–2 base pairs, indicating a single species. Thus both the culture dependent and culture independent characterizations suggest a simple yet novel composition. The work is important as the biofilm is fundamentally different in form (tape-like) and content from that of all previously reported ones, where variously Mycobacterium, Methylobacterium and Xanthomonas species have dominated, and extremophiles were not reported.