Repetitive sampling and control threshold improve 16S rRNA results from produced waters associated with hydraulically fractured shales

Frontiers in Microbiology
By: , and 

Links

Abstract

Sequencing microbial DNA from deep subsurface environments is complicated by a number of issues ranging from contamination to non-reproducible results. Many samples obtained from these environments - which are of great interest due to the potential to stimulate microbial methane generation - contain low biomass. Therefore, samples from these environments are difficult to study as sequencing results can be easily impacted by contamination. In this case, the low amount of sample biomass may be effectively swamped by the contaminating DNA and generate misleading results. Additionally, performing field work in these environments can be difficult, as researchers generally have limited access to and time on site. Therefore, optimizing a sampling plan to produce the best results while collecting the greatest number of samples over a short period of time is ideal. This study aimed to recommend an adequate sampling plan for field researchers obtaining microbial biomass for 16S rRNA gene sequencing, applicable specifically to oil and gas-producing environments.
Forty-nine different samples were collected by filtering specific volumes of produced water from a hydraulically fractured well producing from the Niobrara Shale. Water was collected in two different sampling events 24 hours apart. Four to five samples were collected from 11 specific volumes. These samples along with eight different blanks were submitted for analysis. DNA was extracted from each sample, and quantitative polymerase chain reaction (qPCR) and 16S rRNA Illumina MiSeq gene sequencing were performed to determine relative concentrations of biomass and microbial community composition, respectively. The qPCR results varied across sampled volumes, while no discernible trend correlated contamination to volume of water filtered. This suggests that collecting a larger volume of sample may not result in larger biomass concentrations or better representation of a sampled environment. Researchers could prioritize collecting many low volume samples over few high-volume samples. Our results suggest that there also may be variability in the concentration of microbial communities present in produced waters over short (i.e., hours) time scales, which warrants further investigation. Submission of multiple blanks is also vital to determining how contamination or low biomass effects may influence a sample set collected from an unknown environment.

Study Area

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Repetitive sampling and control threshold improve 16S rRNA results from produced waters associated with hydraulically fractured shales
Series title Frontiers in Microbiology
DOI 10.3389/fmicb.2020.536978
Volume 11
Year Published 2020
Language English
Publisher Frontiers Media
Contributing office(s) Eastern Energy Resources Science Center
Description 536978, 14 p.
Country United States, Canada
State Montana, Wyoming, Colorado, New Mexico, Texas, Oklahoma, Kansas, Nebraska, North Dakota, South Dakota, Alberta, Saskatchewan, Manitoba
Other Geospatial Great Plains, Niobrara Formation
Google Analytic Metrics Metrics page
Additional metadata about this publication, not found in other parts of the page is in this table