Self-cleaning of very heavily oil-polluted sites proceeds even under heavy-metal stress while involved bacteria exhibit bizarre pleomorphism

Simultaneous removal of crude oil and heavy metals by highly adapted bacterial strain Cutibacterium sp. NL2 isolated from Algerian oilfield

Investigating the ability of bacteria to simultaneously enhance hydrocarbon removal and reduce heavy metals' toxicity is necessary to design more effective bioremediation strategies. A bacterium (NL2 strain) isolated from an Algerian oilfield was cultivated on crude oil as sole carbon and energy sources. Molecular analyses of the 16S rRNA gene sequence placed the strain within the Cutibacterium genera. This isolate was able to tolerate up to 60% of crude oil as sole carbon source. Chemical analyses (GC-MS) evidenced that strain NL2 was able to degrade 92.22% of crude oil (at optimal growing conditions: pH 10, 44 °C, 50 g L-1 NaCl, and 20% of crude oil (v/v) as sole carbon source) in only 7 days. NL2 isolate was also able to produce biosurfactants with reduction of surface tension of growing media (29.4 mN m-1). On the other hand, NL2 strain was able to tolerate high lead (Pb) and copper (Cu) concentrations (up to 60 mM). In fact, NL2 cultivated in the presence of 20% of crude oil, and 0.48 mM of Pb was able to reduce Pb concentration by a 41.36%. In turn, when cultivated on high Pb concentration (15 mM), the strain was able to remove 35.19% of it and 86.25% of crude oil, both in a time frame of 7 days. Our findings suggest that Cutibacterium strain NL2 is able to efficiently use and remove a wide range of crude oil substrates in presence of high Pb concentration. Accordingly, NL2 strain is of extreme interest from a biotechnological standpoint.

Indigenous oil-degrading bacteria more efficient in soil bioremediation than microbial consortium and active even in super oil-saturated soils

A microbial consortium of the hydrocarbonoclastic bacterial species, comprising Actinotalea ferrariae, Arthrobacter ginsengisoli, Dietzia cinnamea, Dietzia papillomatosis, and Pseudomonas songnenensis, isolated from oil-saturated desert soil did not consume more oil in batch cultures than the individual species with the maximum oil consumption. In oil-polluted desert soil microcosms, the rate of oil removal in the soil samples bioaugmented with the microbial consortium was similar to the rate of oil removal in the unbioaugmented ones through a 6-month bioremediation experiment. Although the composition of hydrocarbonoclastic bacterial communities in the unbioaugmented and bioaugmented soil samples was different, the predominant bacterial species during most of the months were the same. Toward the end of the bioremediation experiment, Ar. ginsengisoli prevailed in both soil samples, suggesting its important role in oil removal. Self-cleaning proceeded in desert soil samples artificially polluted with 1, 10, 20, and 30% of crude oil and incubated at 30 °C for 6 months. Oil was removed effectively at rates reaching 73.6 and 69.3% in the soils polluted with 1 and 10% oil concentrations, respectively, and reached 50% in desert soils polluted with 20 and 30% oil concentrations. The bacterial numbers increased in all soil samples from hundreds of thousands per gram of soil samples at time zero to millions and tens of millions per gram of soil samples after 6 months. It was concluded that bioaugmenting oil-polluted soil samples with microbial consortium of hydrocarbonoclastic bacterial species with high oil removal potential did not drastically enhance oil bioremediation and that even in super oil-saturated soils, indigenous oil-degrading bacteria will prevail and effectively contribute to oil removal from the surrounding environment.

Crude oil exploration in Africa: socio-economic implications, environmental impacts, and mitigation strategies

Crude oil exploration is a source of significant revenue in Africa via trade and investment since its discovery in the mid-19th Century. Crude oil has bolstered the continent's economy and improved the wellbeing of the citizenry. Historically, Africa has suffered from conflicts due to uneven redistribution of crude oil revenue and severe environmental pollution. Advancements in geophysical survey techniques, such as magnetic and gravity methods, to seismic methods, have made the commercial exploration of crude oil possible for some other countries in Africa apart from Nigeria, Angola, Algeria, Libya, and Egypt. The occurrence of organic-rich, oil-prone Type I, II, and mixed II/III kerogens in sedimentary basins and entrapment within reservoir rocks with intrinsic petrophysical properties are majorly responsible for the large deposits of hydrocarbon in Africa. The unethical practices by some multinational oil corporations have resulted in social movements against them by host communities and human rights groups. The unscrupulous diversion of public funds, award of oil blocks, and production rights to certain individuals have impaired economic growth in Africa. The over-dependence on crude oil revenues has caused the economic recession in oil-producing countries due to plummeting oil prices and global pandemic. Most host communities of crude oil deposits suffer from a lack of infrastructure, arable soils, clean water, and their functioning capabilities are violated by crude oil exploratory activities, without adequate compensations and remedial actions taken by oil companies and the government. Thus, this review examines crude oil exploration in Africa and provides insight into the environmental and socio-economic implications of crude oil exploration in Africa. Furthermore, this report highlights some recommendations that may ensure ethical and sustainable practices toward minimizing negative impacts and improving the quality of life in affected communities.