Variation in pickleweed root-associated microbial communities at different locations of a saline solid waste management unit contaminated with petroleum hydrocarbons

Authors: KHAN, A - University Of California; REICHMANN, L - University Of California; IBAL, J - Kyungpook National University; SHIN, J - Kyungpook National University; LIU, Y - University Of California; Collins, Harold; LEPAGE, B - Pacific Gas And Electric Company; TERRY, N - University Of California

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/11/2019
Publication Date: 10/3/2019
Citation: Khan, A.R., Reichmann, L.G., Ibal, J.C., Shin, J.H., Liu, Y., Collins, H.P., LePage, B., Terry, N. 2019. Variation in pickleweed root-associated microbial communities at different locations of a saline solid waste management unit contaminated with petroleum hydrocarbons. PLoS One. 14(10):e0222901. https://doi.org/10.1371/journal.pone.0222901.
DOI: https://doi.org/10.1371/journal.pone.0222901

Interpretive Summary: As a result of industrial runoff, effluent releases and accidental spills, many places around the world are contaminated by total petroleum hydrocarbons (TPHs). The magnitude of worldwide contamination by petroleum-derived products is such that TPHs are considered the most widespread class of organic contaminants. TPHs accumulate in soil and can remain over long periods. Because of their toxicity, mutagenicity, and carcinogenicity, TPHs may have significant effects on the microbiota and other ecosystem components and pose serious health risks to humans and animals. This study evaluated the potential effects of pickleweed vegetation on the abundance, diversity and metabolic activities of microbial communities in four petroleum-contaminated solid waste management unit (SWMU) located in Contra Costa County, northern California. This study showed that rhizosphere microbial communities spatially differ in a contaminated soil and this can have important consequences for phytoremediation of contaminated zones. This spatial variability can lead to different hydrocarbon degradation rates. Similarly, soil salinity in petroleum contaminated sites is one of the major constraints to the biodegradation processes as it adversely affects soil physiochemical properties, crop productivity and microbiological activities to a significant extent.

Technical Abstract: Industrial runoff, effluent releases and accidental spills in many places around the world are contaminated by petroleum hydrocarbons. Four areas within the SWMU were sampled including two central areas, one of which is central vegetated (CV) and one unvegetated (UV), and two peripheral vegetated areas, one of which is located to the west side of the SWMU (V-West) and one located to the east side (V-East). Measurements were made of total petroleum hydrocarbons (TPH), polyaromatic hydrocarbons (PAH), soil physicochemical properties, and various aspects of microbial communities including metabolic activities, microbial abundances (PLFAs), diversity and composition based on amplicon sequencing. Microbial activities (in terms of soil respiration and the activities of three soil enzymes, i.e., urease, lipase, and phosphatase) were greatest in the vegetated sites compared to unvegetated sites. The prokaryotic community was not diverse as revealed by the Shannon index with no significant variation among the four groups of samples. However, the fungal community of the peripheral sites, V-East and V-West had significantly higher OTU richness and Shannon index. Structure of prokaryotic communities inhabiting the rhizosphere of pickleweed plants at the three sites differed significantly and were also different from those found in the UV region of the central site according to pairwise, global PERMANOVA and ANOSIM analyses. The results suggest that saline TPH-contaminated areas that are vegetated with pickleweed are likely to have increased abundances, diversity and metabolic activities in the rhizosphere compared to unvegetated areas, even in the presence of high salinity.