Biological Activity of Autochthonic Bacterial Community in Oil-Contaminated Soil

Bio-augmentation and bio-stimulation with kenaf core enhanced bacterial enzyme activities during bio-degradation of petroleum hydrocarbon in polluted soil

Indigenous micro-organisms often possess the ability to degrade petroleum hydrocarbon (PHC) in polluted soil. However, this process can be improved by supplementing with nutrients or the addition of more potent microbes. In this study, the ability of kenaf-core to stimulate the PHC degradation capability of microbial isolates from PHC polluted soil samples was evaluated. The standard experimental methods used in this study include: the digestion and analysis of the physico-chemical properties of petroleum hydrocarbon contaminated and non-contaminated soil samples; evaluation of petroleum hydrocarbon biodegradation using bio-augmentation and bio-stimulation (with kenaf-core) treatments; and, determination of soil microbial enzyme activities. Results from this study show that K, Na, total nitrogen, organic carbon, exchangeable cations, and heavy metals were found to be significantly (P < 0.05) higher in the polluted soil than in the non-polluted soil. Also, the polluted samples had pH values ranging from 5.5 to 6.0 while the non-polluted samples had a pH of 7.6. The microbial enzyme activities were comparatively lower in the polluted soils as compared to the non-polluted soil. The percentage degradation in the kenaf-core treated samples (AZ1T2-78.38; BN3T2-70.69; OL1T2-71.06; OT1T2-70.10) were significantly (P < 0.05) higher than those of the untreated (AZ1T1-13.50; BN3T1-12.50; OL1T1-10.55; OT1T1-9.50). The degradation of petroleum hydrocarbon in the bio-augmented and bio-stimulated treatments increased with increasing time of incubation, and were higher than that of the untreated sample. Comparatively, the treatment with a combination of kenaf-core and rhamnolipid exhibited a significantly (P < 0.05) higher degradation rate than that of the treatment with only kenaf core or rhamnolipid. While, the bio-stimulated and bio-augmented treatments had appreciable microbial counts that are higher than that of the untreated. In conclusion, the nutrient-supplement with kenaf-core significantly enhanced microbial growth and activities in the soil, thus improving their ability to biodegrade petroleum hydrocarbons in the polluted soils. Thus, supplementing with Kenaf core to encourage microbiological degradation of petroleum hydrocarbon is recommended.

Diminishing toxicity of pyrene on photosynthetic performance of soybean using Bacillus subtilis (NCIM 5594)

Polycyclic aromatic hydrocarbons are persistent organic pollutants causing serious environmental problems, being toxic to plants and difficult to remediate. Pyrene is one such extremely dangerous compound that is toxic for the environment. This study suggests the use of Bacillus subtilis (National Collection of Industrial Microorganisms [NCIM] 5594) to overcome inhibitory effects of pyrene on soybean photosynthesis. The toxicity of pyrene to soybean was evident from a significant decrease in seed germination parameters, photosynthetic performance and biomass during growth of soybean in pyrene contaminated soil. Efficiency of performance index, light absorption, trapping and electron transport were reduced in plants grown in pyrene contaminated soil while significant recovery in these parameters was observed in plants grown in pyrene+B. subtilis treated soil. Activity levels of dehydrogenase and lipase enzymes significantly recovered in pyrene+B. subtilis treated soil. After extraction of pyrene from soil and soybean plant, concentration of pyrene was lowered in pyrene+B. subtilis treated soil and plants. These findings suggest efficient degradation of pyrene by B. subtilis . About 70% degradation of pyrene was achieved in soil using B. subtilis ; thus it is a useful strain for crop improvement in pyrene polluted soil.

Indirect effects of COVID-19 on the environment: How plastic contamination from disposable surgical masks affect early development of plants

Personal protective equipment, used extensively during the COVID-19 pandemic, heavily burdened the environment due to improper waste management. Owing to their fibrous structure, layered non-woven polypropylene (PP) disposable masks release secondary fragments at a much higher rate than other plastic waste types, thus, posing a barely understood new form of ecological hazard. Here we show that PP mask fragments of different sizes induce morphogenic responses in plants during their early development. Using in vitro systems and soil-filled rhizotrons, we found that several PP mask treatments modified the root growth of Brassica napus (L.) regardless of the experimental system. The environment around the root and mask fragments seemed to influence the effect of PP fabric fragment contamination on early root growth. In soil, primary root length was clearly inhibited by larger PP mask fragments at 1 % concentration, while the two smallest sizes of applied mask fragments caused distinct, concentration-dependent changes in the lateral root numbers. Our results indicate that PP can act as a stressor: contamination by PP surgical masks affects plant growth and hence, warrants attention. Further investigations regarding the effects of plastic pollution on plant-soil interactions involving various soil types are urgently needed.

Degradability of commercial mixtures of polychlorobiphenyls by three Rhodococcus strains

Biodegradative characteristics were investigated for the commercially available mixtures of polychlorinated biphenyls (PCBs) Trikhlorbifenil and Sovol degraded by the Rhodococcus wratislaviensis КT112-7, Rhodococcus wratislaviensis CH628 and Rhodococcus ruber P25 strains isolated from the natural habitats. For bioutilization of the Trikhlorbifenil, all three strains were found to have a high biodegrading potential: the complete destruction was achieved in 10-14 days. For the mixture Sovol, the bioutilization parameters were found to be of lower values: the degradation of the PCBs congeners was 96-98% after 14 days. For the tested polychlorobiphenyl mixtures, the structural specificities of congeners are discussed, the genes encoding monooxygenases are revealed, and explanation is given to the differences in biodegradative characteristics of the Rhodococcus strains towards di-, tri-, tetra-, penta-, hexa- and heptachlorobiphenyls. The presented data are highly relevant for environmental remediation of objects polluted with the extremely hazardous polychlorobiphenyls.

Influence of Hydrocarbon-Oxidizing Bacteria on the Growth, Biochemical Characteristics, and Hormonal Status of Barley Plants and the Content of Petroleum Hydrocarbons in the Soil

Much attention is paid to the relationship between bacteria and plants in the process of the bioremediation of oil-contaminated soils, but the effect of petroleum degrading bacteria that synthesize phytohormones on the content and distribution of these compounds in plants is poorly studied. The goal of the present field experiment was to study the effects of hydrocarbon-oxidizing bacteria that produce auxins on the growth, biochemical characteristics, and hormonal status of barley plants in the presence of oil, as well as assessing the effect of bacteria and plants separately and in association with the content of oil hydrocarbons in the soil. The treatment of plants with strains of Enterobacter sp. UOM 3 and Pseudomonas hunanensis IB C7 led to an increase in the length and mass of roots and shoots and the leaf surface index, and an improvement in some parameters of the elements of the crop structure, which were suppressed by the pollutant. The most noticeable effect of bacteria on the plant hormonal system was a decrease in the accumulation of abscisic acid. The data obtained indicate that the introduction of microorganisms weakened the negative effects on plants under abiotic stress caused by the presence of oil. Plant-bacteria associations were more effective in reducing the content of hydrocarbons in the soil and increasing its microbiological activity than when either organism was used individually.

Combined microbial degradation of crude oil under alkaline conditions by Acinetobacter baumannii and Talaromyces sp

The purpose of this work was to study the biodegradation of crude oil under alkaline condition by defined co-culture of Acinetobacter baumannii and Talaromyces sp. The n-alkanes in crude oil could be completely degraded by bacteria and fungi with the ratio of 1:1 at pH 9 in 14 d water simulation experiment. Meanwhile, the total degradation rate of crude oil could reach 80%. Fungi had stronger ability to degrade n-alkanes, while bacteria could better degrade other components such as aromatics and branched alkanes. The two strains were both capable of producing a small amount of biosurfactant. High cell viability was the main factor for strains to exert high degradation ability in alkaline environment. It was preliminarily verified that bacteria and fungi rely on the differences of enzyme systems to achieve synergy in the degradation process. These results indicated that the defined co-culture had great potential for bioremediation in alkaline soils.

Influence of pipe material on biofilm microbial communities found in drinking water supply system

The biofilms and water samples from a model installation built of PVC-U, PE-HD and cast iron pipes were investigated using standard heterotrophic plate count and 16S rRNA Next Generation Sequencing. The results of the high throughput identification imply that the construction material strongly influences the microbiome composition. PVC-U and PE-HD pipes were dominated with Proteobacteria (54-60%) while the cast pipe was overgrown by Nitrospirae (64%). It was deduced that the plastic pipes create a more convenient environment for the potentially pathogenic taxa than the cast iron. The 7-year old biofilms were described as complex habitats with sharp oxidation-reduction gradients, where co-existence of methanogenic and methanotrophic microbiota takes place. Furthermore, it was found that the drinking water distribution systems (DWDS) are a useful tool for studying the ecology of rare bacterial phyla. New ecophysiological aspects were described for Aquihabitans, Thermogutta and Vampirovibrio. The discrepancy between identity of HPC-derived bacteria and NGS-revealed composition of biofilm and water microbiomes point to the need of introducing new diagnostical protocols to enable proper assessment of the drinking water safety, especially in DWDSs operating without disinfection.

Plant-Soil-Microbiota Combination for the Removal of Total Petroleum Hydrocarbons (TPH): An In-Field Experiment

The contamination of soil with total petroleum hydrocarbons (TPH) may result in dramatic consequences and needs great attention, as soil rehabilitation would need more effort from a sustainability perspective. However, there is still no known general method since the remediation technology is strictly site-specific. Adaptive biological system dynamics can play a key role in understanding and addressing the potential of situ-specific biological combinations for soil pollutants removal. The potential worst-case of TPH contamination reflects soil affected by heavy industrial activities, such as oil refineries. Therefore, the experimental trial was conducted on a 2,000 m2 area from a contaminated site located in northern Italy. We evaluated the remediation potential over time (270 days) assessing (i) the phytoremediation efficiency of two species of Poaceae (Festuca arundinacea Schreb. and Dactylis glomerata L.) and two species of Fabaceae (Medicago sativa L. and Lotus corniculatus L.) and (ii) the role of the indigenous bacteria flora and endo-mycorrhizae consortium addition in plant growth promotion. We also induced resistance to contamination stress in a field experiment. Thirty-three indigenous bacteria selected from the contaminated soils showed marked plant growth promotion. Moreover, functional metagenomics confirmed the metabolic capability of hydrocarbon-degrading microorganisms living in the polluted soil. Our data showed that soil enzymatic activities increased with hydrocarbon degradation rate after 60 days. Both Poaceae and Fabaceae resulted in remarkable remediation potential. Stress markers and antioxidant activity indicated that the selected plant species generally need some time to adapt to TPH stress. In conclusion, our evaluation implied both the rhizosphere effects and functional features of the plant and suggested that plants should (i) have marked tolerance to specific contaminants, (ii) be characterized by an extensive root system, and (iii) be susceptible to arbuscular mycorrhizal fungi (AMF) infection.

The Role of Dactylis Glomerata and Diesel Oil in the Formation of Microbiome and Soil Enzyme Activity

The global demand for petroleum contributes to a significant increase in soil pollution with petroleum-based products that pose a severe risk not only to humans but also to plants and the soil microbiome. The increasing pollution of the natural environment urges the search for effective remediation methods. Considering the above, the objective of this study was to determine the usability of Dactylis glomerata for the degradation of hydrocarbons contained in diesel oil (DO), as well as the effects of both the plant tested and DO on the biochemical functionality and changes in the soil microbiome. The experiment was conducted in a greenhouse with non-polluted soil as well as soil polluted with DO and phytoremediated with Dactylis glomerata. Soil pollution with DO increased the numbers of microorganisms and soil enzymes and decreased the value of the ecophysiological diversity index of microorganisms. Besides, it contributed to changes in the bacterial structure at all taxonomic levels. DO was found to increase the abundance of Proteobacteria and to decrease that of Actinobacteria, Acidobacteria, Chloroflexi, Gemmatimonadetes and Firmicutes. In the non-polluted soil, the core microbiome was represented by Kaistobacter and Rhodoplanes, whereas in the DO-polluted soil, it was represented by Parvibaculum and Rhodococcus. In soil sown with Dactylis glomerata, gasoline fraction (C₆–C₁₂) degradation was higher by 17%; mineral oil (C₁₂–C₃₅), by 9%; benzene, by 31%; anthracene, by 12%; chrysene, by 38%; benzo(a)anthracene, by 19%; benzo(a)pyrene, by 17%; benzo(b)fluoranthene, by 15%; and benzo(k)fluoranthene, by 18% than in non-sowed soil. To conclude, Dactylis glomerata proved useful in degrading DO hydrocarbons and, therefore, may be recommended for the phytoremediation of soils polluted with petroleum-based products. It has been shown that the microbiological, biochemical and chemical tests are fast and sensitive in the diagnosis of soil contamination with petroleum products, and a combination of all these tests gives a reliable assessment of the state of soils.

Catabolic Fingerprinting and Diversity of Bacteria in Mollic Gleysol Contaminated with Petroleum Substances

This study focused on the determination of both catabolic and genetic fingerprinting of bacteria inhabiting soil contaminated with car fuels. A surface layer (0–20 cm) of Mollic Gleysol was used for the experiment and was contaminated with car fuels—unleaded 95-octane petrol and diesel at a dose of 15 g per 10 g of soil. The experiment lasted 42 days and was performed at 20 °C. The metabolic potential of soil bacterial communities was evaluated using the Biolog EcoPlate system. The results demonstrated that petroleum substances influenced the structure of the microbial populations and their catabolic activity. The Arthrobacter, Paenibacillus, and Pseudomonas genera were found in diesel-contaminated soil, whilst Bacillus and Microbacterium were found in petrol-contaminated soil. Rhodococcus species were identified in both variants of impurities, suggesting the widest capability of car fuel degradation by this bacterial genus. The contamination with unleaded 95-octane petrol caused rapid inhibition of the metabolic activity of soil bacteria in contrast to the diesel treatment, where high metabolic activity of bacteria was observed until the end of the incubation period. Higher toxicity of petrol in comparison with diesel car fuel was evidenced.

Evaluation of Hydrocarbon Soil Pollution Using E-Nose

The possibility of detecting low levels of soil pollution by petroleum fuel using an electronic nose (e-nose) was studied. An attempt to distinguish between pollution caused by petrol and diesel oil, and its relation to the time elapsed since the pollution event was simultaneously performed. Ten arable soils, belonging to various soil groups from the World Reference Base (WRB), were investigated. The measurements were performed on soils that were moistened to field capacity, polluted separately with both hydrocarbons, and then allowed to dry slowly over a period of 180 days. The volatile fingerprints differed throughout the course of the experiment, and, by its end, they were similar to those of the unpolluted soils. Principal component analysis (PCA) and artificial neural network (ANN) analysis showed that the e-nose results could be used to detect soil contamination and distinguish between pollutants and contamination levels.