Bacterial Community Dynamics in Dichloromethane-Contaminated Groundwater Undergoing Natural Attenuation

Abstract

The uncontrolled release of the industrial solvent methylene chloride, also known as dichloromethane (DCM), has resulted in widespread groundwater contamination in the United States. Here we investigate the role of groundwater bacterial communities in the natural attenuation of DCM at an undisclosed manufacturing site in New Jersey. This study investigates the bacterial community structure of groundwater samples differentially contaminated with DCM to better understand the biodegradation potential of these autochthonous bacterial communities. Bacterial community analysis was completed using high-throughput sequencing of the 16S rRNA gene of groundwater samples (n = 26) with DCM contamination ranging from 0.89 to 9,800,000 μg/L. Significant DCM concentration-driven shifts in overall bacterial community structure were identified between samples, including an increase in the abundance of Firmicutes within the most contaminated samples. Across all samples, a total of 6,134 unique operational taxonomic units (OTUs) were identified, with 16 taxa having strong correlations with increased DCM concentration. Putative DCM degraders such as Pseudomonas, Dehalobacterium and Desulfovibrio were present within groundwater across all levels of DCM contamination. Interestingly, each of these taxa dominated specific DCM contamination ranges respectively. Potential DCM degrading lineages yet to be cited specifically as a DCM degrading organisms, such as the Desulfosporosinus, thrived within the most heavily contaminated groundwater samples. Co-occurrence network analysis revealed aerobic and anaerobic bacterial taxa with DCM-degrading potential were present at the study site. Our 16S rRNA gene survey serves as the first in situ bacterial community assessment of contaminated groundwater harboring DCM concentrations ranging over seven orders of magnitude. Diversity analyses revealed known as well as potentially novel DCM degrading taxa within defined DCM concentration ranges, indicating niche-specific responses of these autochthonous populations. Altogether, our findings suggest that monitored natural attenuation is an appropriate remediation strategy for DCM contamination, and that high-throughput sequencing technologies are a robust method for assessing the potential role of biodegrading bacterial assemblages in the apparent reduction of DCM concentrations in environmental scenarios.

Arsenic disturbs the gut microbiome of individuals in a disadvantaged community in Nepal

“…We observed two distinctly defined taxonomic compositions between the two communities, shaped by geographic separation and differences in arsenic concentration. Our finding supports a previous study that identified similar spatial and concentration related differences in bacterial community response to a toxin [48]. Our study is the first of its kind to analyze changes to the gut microbiota of individuals in South East Asia, and lays the groundwork for future, more in-depth studies on the influence of arsenic on the health of the gut microbiome and overall human health.…”

“…Both communities shared selection for some arsenic volatilizing taxa like Desulfovibrionaceae, but each was possessive of its own unique assemblage of pathogenic bacteria and both showed higher selection for certain arsenic volatilizing bacteria that the other did not. As noted earlier, the observation of site specific compositional differences in response to a contaminant is not unique to this study [48].…”

Do composition and diversity of bacterial communities and abiotic conditions of spring water reflect characteristics of groundwater ecosystems exposed to different agricultural activities?

“…Despite this potential drawback, similarly to the diversity estimates, relative BCC also showed only few differences at the phylum level. All samples are dominated by the phylum Proteobacteria, a result that corresponds to observations reported from other studies (Braun, Schröder, Knecht, & Szewzyk, ; Wright et al., ). Due to the fact that geochemical characteristics are the main drivers of BCC (Constancias et al., ), and since geochemical characteristics differ only slightly across sampling sites, we suggest that this results in a similar taxonomic community composition at the phylum level.…”

Analysis of viral and bacterial communities in groundwater associated with contaminated land

“…Among the most abundant bacterial members at the site (Figure 3), a number have been linked to hydrocarbon biodegradation processes and/or hydrocarboncontaminated environments. These include the Actinobacterial order iii1-15 (Morais et al, 2016), Anaerolineaceae (Kümmel et al, 2015;Liang et al, 2015;Rosenkranz et al, 2013), the Chloroflexi class GIF9 (Alfreider et al, 2002), the Elusimicrobiales order (Wright et al, 2017), Thermoanaerobacteraceae (Marozava et al, 2018), -Von Abercron et al, 2017;Morais et al, 2016;Yang et al, 2014Yang et al, , 2016, Rhodospirillaceae (Cui et al, 2008;Viñas et al, 2005),…”