Potential Enhancement of the In-Situ Bioremediation of Contaminated Sites through the Isolation and Screening of Bacterial Strains in Natural Hydrocarbon Springs

Abstract

Petroleum hydrocarbon contamination (PHC) is an issue of major concern worldwide. These compounds represent the most common environmental pollutants and their cleaning up is mandatory. The main goal of this research was to analyze microbial communities in a site in southern Italy characterized by the presence of hydrocarbons of natural origin by using a multidisciplinary approach based on microbiological, geological and hydrological investigations. Bacterial communities of two springs, the surrounding soils, and groundwater were studied through a combination of molecular and culture-dependent methodologies to explore the biodiversity at the study site, to isolate microorganisms with degradative abilities, and to assess their potential to develop effective strategies to restore the environmental quality. Next-generation sequencing revealed the dominance of species of the Proteobacteria phylum but also the presence of other autochthonous hydrocarbon-oxidizing microorganisms affiliated to other phyla (e.g., species of the genera Flavobacterium and Gordonia). The traditional cultivation-based approach led to the isolation and identification of 11 aerobic hydrocarbon-oxidizing proteobacteria, some of which were able to grow with phenanthrene as the sole carbon source. Seven out of the 11 isolated bacterial strains produced emulsion with diesel fuel (most of them showing emulsifying capacity values greater than 50%) with a high stability after 24 h and, in some cases, after 48 h. These results pave the way for further investigations finalized at (1) exploiting both the degradation ability of the bacterial isolates and/or microbial consortia to remediate hydrocarbon-contaminated sites and (2) the capability to produce molecules with a promoting effect for oil polluted matrices restoration.

Natural Surface Hydrocarbons and Soil Faunal Biodiversity: A Bioremediation Perspective

“…Other studies, on the other hand, highlight the fact that nematodes are petroleum fuel tolerant and are able to co-operate with bacteria to promote the biodegradation rate of petroleum hydrocarbons [51,53,54]. In fact, in a recent study on bacterial communities carried out in the same study area, several bacterial strains capable of degrading hydrocarbons were isolated and screened, such as those belonging to genera Achromobacter and Pseudomonas [55].…”

Phyto-Beneficial Traits of Rhizosphere Bacteria: In Vitro Exploration of Plant Growth Promoting and Phytopathogen Biocontrol Ability of Selected Strains Isolated from Harsh Environments

“…Identified at the genera and species level by 16S rDNA sequencing, and only partially characterized for their putative PGPR properties, bacteria strains elected for this work belonged to differently demanding environments: Pvr_5 and Pvr_9 were isolated from the rhizosphere of the As-hyperaccumulating fern Pteris vittata [27], PHA_1 from a soil rich in hydrocarbons [28], NCr-1 was found to be an endophyte of the Ni-hyperaccumulator Noccaea caerulescens [25], and Bioch_2 and Bioch_7 were isolated from a third-year biocharamended soil [26]. In this work, for this purpose, a deeper characterization of the selected bacterial strains was performed.…”

“…The capacities to solubilize phosphate and bacterial protease activity were also tested with qualitative test assays (Figure S1); PHA_1 [28] represents the only strain able to solubilize phosphate while Pvr_5, NCr-1, Bioch_2 and Bioch_7 showed protease activity. Microbial peptidases play a central role in the nitrogen cycle in the soils as they make nitrogen available for plants [29].…”

“…Six bacterial strains isolated from different sources were selected for this work from a collection of PGPR present in our laboratory: Bioch_2 (homologous to Arthrobacter defluvii) and Bioch_7 (homologous to Arthrobacter nicotinovorans) strains were previously isolated by a maize-derived biochar utilized as amendment in a three year poplar short rotation coppice plantation [26]; Ncr-1 (homologous to Arthrobacter sp.) is an endophyte strain isolated from the roots of the Ni-hyperaccumulator Noccaea caerulescens [27]; PHA_1 (homologous to Pseudomonas protegens) was isolated from a soil contaminated with hydrocarbons [28]; Pvr_5 (homologous to Paenarthrobacter ureafaciens); and Pvr_9 (homologous to Beijerinckia fluminensis) were isolated from the rhizosphere of the As-hyperaccumulator Pteris vittata fern [25]. PGPR characteristics were reported in Table 1.…”

Investigating the Potential Impact on Shallow Groundwater Quality of Oily Wastewater Injection in Deep Petroleum Reservoirs: A Multidisciplinary Evaluation at the Val d’Agri Oilfield (Southern Italy)

“…The presence of petroleum in Val d'Agri is well known. Some explorations have been carried out in the area of Tramutola's municipality, in which there are still natural hydrocarbon springs, recently studied in terms of bioremediation and migration of fluids [14][15][16], but the main Val d'Agri oilfield is hosted in a reservoir made of fractured, low-porosity carbonates belonging to the buried inner Apulian Platform belt [17][18][19]. Light-to-medium crude oil and gas are stored in limestone and dolomite (Miocene to Cretaceous ages) [20].…”