Structure and diversity of native bacterial communities in soils contaminated with polychlorinated biphenyls

Abstract

Persistent organic pollutants (POPs) such as polychlorinated biphenyls (PCBs) are a group of high-risk synthetic substances for human and environmental health. Currently, the study of sites contaminated by the spillage of equipment PCBs containing have been considered targeted areas for the study of bacterial communities with potential for PCBs degradation. There in isolation of bacterial strains is vital for use in biodegradable processes, such as bacterial bioaugmentation, which accelerates the development of phenomena such as natural attenuation of contaminated sites. The objective of this study was to assess biodiversity of bacteria contained in anthropogenic contaminated soils (H S and H P) with PCBs compared to a control sample without contaminant and the modified forest (F) and agricultural (A) soil in the laboratory with 100 mg L −1 PCB. For the analysis of 16S rRNA genes amplified from DNA extracted from the soils evaluated, the latest generation of Illumina Miseq and Sanger sequencing for the cultivable strains were detected. The bacteria identified as the most abundant bacterial phyla for H S and H P soil was Proteobacteria (56.7%) and Firmicutes (22.9%), which decreased in F and A soils. The most abundant bacterial genera were Burkholderia, Bacillus, Acinetobacter, Comamonas and Cupriavidus. Several species identified in this study, such as Bacillus cereus, Burkholderia cepacia, Comamonas testosteroni and Acinetobacter pittii have been reported as PCBs degraders. Finally, by means of a principal component analysis (PCA), a correlation between the physical and chemical characteristics of the soils in relation to the relative abundances of the bacteria identified was obtained. The C/N ratio was directly related to the control soil (without contaminant), while SOM maintained a relationship with F and A soils and the bacterial abundances were directly related to Hs and Hp soils due to the presence of aroclor 1260. Bacteria with the ability to tolerate high concentrations of this pollutant are considered for future use in biostimulation and bioaugmentation processes in contaminated soils.

Variability of Nitrogen Mineralization from Organic Matter in Agricultural Soils in the North of Colombia

“…The C/N ratio is a parameter that indicates the functionality of soils mainly because infuence biochemical processes of decomposition of OM and mineralization that occurs in soils (Zenteno-Rojas et al, 2020). The variability of this parameter can also be attributed to nitrogen mineralization due the C/N ratio of the soil determines OM decay, therefore, it has an important impact in plant nitrogen availability.…”

Biostimulation and Bioaugmentation of Soils Contaminated with Decachlorobiphenyl (PCB-209) Using Native Bacterial Strains Individually and in Consortia

“…DCB104 (MZ544388) (Table 1), were used in this study. The strains were isolated from a historically PCB-contaminated soil (the content of PCBs in terms of Aroclor 1260 mixtures had a final concentration of 100 mg/kg) and identified via 16S rRNA gene sequencing [6]. Complete-genome sequencing of the three bacterial strains was performed in order to detect Bph genes that encode biphenyldioxygenase, which are located in chromosomal and plasmid DNA (data not shown).…”

“…To measure the removal potential of PCB-209 in the bioaugmentation processes evaluated, the concentration of PCB-209 in the experiment was measured at an initial time (day 0) and at a final time (day 21) in the treatments that contained the contaminant (T 1 , T 2 , T 3 , T 4 , and C Q ). For this, the soil samples of the evaluated treatments were dried at 80 • C (drying oven, Novatech ® HS45-ED, Tlaquepaque, México) for 24 h, and the extraction of the PCB-209 content was carried out as described by Zenteno-Rojas et al [6]. Briefly, 5.0 g of soil was taken from each treatment and mixed with 25 mL of pentane, mixing in vortex for 5 min and 40 min in ultrasound (Ultrasonic Power, Skymen ® , Guangzhou, China).…”

“…Likewise, rhizospheric and endophytic bacteria associated with the Ocimun basilicum plant had the ability to remove up to 500 mg/L of PCB-209 [16]. From another study, in agricultural and forest soils contaminated with PCBs, we isolated bacteria classified within the genera Burkholderia, Bacillus, Acinetobacter, Comamonas, and Cupriavidus, which showed high efficiency in removing and degrading PCB-209 as well as Aroclor 1260 (mixture of PCBs) [6]. We recently demonstrated that the native strain Pseudomonas extremaustralis ADA-5 has the biochemical ability to bioaccumulate and biodegrade PCB-209 at concentrations of 250 to 1000 mg/L [17].…”

“…In Mexico, the presence and accumulation of PCBs in different aquatic sediments and soils has been reported as an effect of industrial activities or due to the spillage of fluids from electrical equipment that contain this contaminant [5,6]. These sediments are now becoming biologically important areas, as substantial sources of micro-organisms with a biodegradable potential for PCBs.…”