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Front. Microbiol. | doi: 10.3389/fmicb.2017.02300

Bacterial Community Dynamics in Dichloromethane-contaminated Groundwater Undergoing Natural Attenuation

 Justin R. Wright1, 2,  Veronica Kirchner2, William Bernard Rubio2, Nikea Ulrich2,  Chris McLimans1, 2,  Maria F. Campa3,  Terry C. Hazen3, Tamzen Macbeth4,  David Marabello4, Jacob McDermott4, Rachel Mackelprang5, Kimberly Roth2 and  Regina Lamendella1, 2*
  • 1Wright Labs, LLC, United States
  • 2Department of Biology, Juniata College, United States
  • 3Department of Biology, University of Tennessee, Knoxville, United States
  • 4CDM Smith (United States), United States
  • 5Department of Biology, California State University, Northridge, United States

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.

Keywords: Dichloromethane, DCM, 16S rRNA, Biodegradation, Xenobiotic, Groundwater, bacterial community, monitored natural attenuation

Received: 15 Jun 2017; Accepted: 07 Nov 2017.

Edited by:

Hongyue Dang, Xiamen University, China

Reviewed by:

Muhammad Saleem, University of Kentucky, United States
Dongdong Zhang, Zhejiang University, China  

Copyright: © 2017 Wright, Kirchner, Bernard Rubio, Ulrich, McLimans, Campa, Hazen, Macbeth, Marabello, McDermott, Mackelprang, Roth and Lamendella. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Regina Lamendella, Wright Labs, LLC, Huntingdon, Pennsylvania, United States,