Multiple responses of gram-positive and gram-negative bacteria to mixture of hydrocarbons

Engineering green wall botanical biofiltration to abate indoor volatile organic compounds: A review on mechanisms, phyllosphere bioaugmentation, and modeling

Indoor air pollution affects the global population, especially in developed countries where people spend around 90% of their time indoors. The recent pandemic exacerbated the exposure by relying on indoor spaces and a teleworking lifestyle. VOCs are a group of indoor air pollutants with harmful effects on human health at low concentrations. It is widespread that plants can remove indoor VOCs. To this day, research has combined principles of phytoremediation, biofiltration, and bioremediation into a holistic and sustainable technology called botanical biofiltration. Overall, it is sustained that its main advantage is the capacity to break down and biodegrade pollutants using low energy input. This differs from traditional systems that transfer VOCs to another phase. Furthermore, it offers additional benefits like decreased indoor air health costs, enhanced work productivity, and well-being. However, many disparities exist within the field regarding the role of plants, substrate, and phyllosphere bacteria. Yet their role has been theorized; its stability is poorly known for an engineering approach. Previous research has not addressed the bioaugmentation of the phyllosphere to increase the performance, which could boost the system. Moreover, most experiments have studied passive potted plant systems at a lab scale using small chambers, making it difficult to extrapolate findings into tangible parameters to engineer the technology. Active systems are believed to be more efficient yet require more maintenance and knowledge expertize; besides, the impact of the active flow on the long term is not fully understood. Besides, modeling the system has been oversimplified, limiting the understanding and optimization. This review sheds light on the field's gains and gaps, like concepts, experiments, and modeling. We believe that embracing a multidisciplinary approach encompassing experiments, multiphysics modeling, microbial community analysis, and coworking with the indoor air sector will enable the optimization of the technology and facilitate its adoption.

Medium-chain alkane biodegradation and its link to some unifying attributes of alkB genes diversity

Hydrocarbon footprints in the environment, via biosynthesis, natural seepage, anthropogenic activities and accidents, affect the ecosystem and induce a shift in the healthy biogeochemical equilibrium that drives needed ecological services. In addition, these imbalances cause human diseases and reduce animal and microorganism diversity. Microbial bioremediation, which capitalizes on functional genes, is a sustainable mitigation option for cleaning hydrocarbon-impacted environments. This review focuses on the bacterial alkB functional gene, which codes for a non-heme di‑iron monooxygenase (AlkB) with a di‑iron active site that catalyzes C₈-C₁₆ medium-chain alkane metabolism. These enzymes are ubiquitous and share common attributes such as being controlled by global transcriptional regulators, being a component of most super hydrocarbon degraders, and their distributions linked to horizontal gene transfer (HGT) events. The phylogenetic approach used in the HGT detection suggests that AlkB tree topology clusters bacteria functionally and that a preferential gradient dictates gene distribution. The alkB gene also acts as a biomarker for bioremediation, although it is found in pristine environments and absent in some hydrocarbon degraders. For instance, a quantitative molecular method has failed to link alkB copy number to contamination concentration levels. This limitation may be due to AlkB homologues, which have other functions besides n-alkane assimilation. Thus, this review, which focuses on Pseudomonas putida GPo1 alkB, shows that AlkB proteins are diverse but have some unifying trends around hydrocarbon-degrading bacteria; it is erroneous to rely on alkB detection alone as a monitoring parameter for hydrocarbon degradation, alkB gene distribution are preferentially distributed among bacteria, and the plausible explanation for AlkB affiliation to broad-spectrum metabolism of hydrocarbons in super-degraders hitherto reported. Overall, this review provides a broad perspective of the ecology of alkB-carrying bacteria and their directed biodegradation pathways.

Whole-cell bioconversion using non-Leloir transglycosylation reactions: a review

Microbial biocatalysts are evolving technological tools for glycosylation research in food, feed and pharmaceuticals. Advances in bioengineered Leloir and non-Leloir carbohydrate-active enzymes allow for whole-cell biocatalysts to curtail production costs of purified enzymes while enhancing glucan synthesis through continued enzyme expression. Unlike sugar nucleotide-dependent Leloir glycosyltransferases, non-Leloir enzymes require inexpensive sugar donors and can be designed to match the high value, yield and selectivity of the former. This review addresses the current state of bacterial cell-based production of glucans and glycoconjugates via transglycosylation, and describes how alterations made to microbial hosts to surpass purified enzymes as the preferred mode of catalysis are steadily being acquired through genetic engineering, rational design and process optimization. A comprehensive exploration of relevant literature has been summarized to describe whole-cell biocatalysis in non-Leloir glycosylation reactions with various donors and acceptors, and the characterization, application and latest developments in the optimization of their use.

New insights for tracking bacterial community structures in industrial wastewater from textile factories to surface water using phenotypic, 16S rRNA isolates identifications and high-throughput sequencing

Industrial wastewater can possibly change the microbial ecological environment. There are few studies that focus on the bacterial variety in textile wastewater effluents and after combination with domestic wastewater. Thus, this study aimed to determine dye degrading bacteria from textile wastewater and environmental water samples using cultural method followed by phenotypic using BIOLOG and genotypic identification (16S rRNA) for dye degrading isolates identifications. Moreover, the bacterial communities in three textile and four environmental samples using Illumina MiSeq high-throughput sequencing were investigated. The findings revealed that in textile water samples, the ratio of dye-degrading bacteria (DDB) to total bacterial counts (TBC) was 27%. The identified DDB genera by 16S rRNA based on the cultural approach were Citrobacter spp., Klebsiella spp., Enterobacter spp., Pseudomonas spp., and Aeromonas spp. Regarding to the metagenomics analyses, the environmental samples had 5,598 Operational Toxanomic Units (OTUs) more than textile wastewater samples (1,463 OTUs). Additionally, the most abundant phyla in the textile wastewater were Proteobacteria (24.45-94.83%), Bacteriodetes (0.5-44.84%) and Firmicutes (3.72-67.40%), while, Proteobacteria (30.8-76.3%), bacteroidetes (8.5-50%) and Acentobacteria (0.5-23.12%) were the most abundant phyla in the environmental samples. The maximum abundant bacteria at species level in environmental samples were Aquabacterium parvum (36.71%), Delftia tsuruhatensis (17.61%), Parabacteriodes chartae (15.39%) and Methylorubrum populi (7.51%) in El-Rahawy Drain water (RDW), River Nile water (RNW), wastewater (RWW) from WWTP in Zennin and El-Rahawy Drain sediment (RDS), respectively, whereas the maximum abundant bacteria at species level in textile wastewater were Alkalibacterium pelagium (34.11%), Enterobacter kobei (26.09%) and Chryseobacterium montanum (16.93%) in factory 1 (HBT) sample, SHB sample (before mixing with domestic wastewater) and SHB sample (after mixing with domestic wastewater), respectively. In conclusion, the microbial communities in textile wastewaters are similar to those in environmental samples at the phylum level but distinct at the genus and species levels because they are exposed to a wider range of environmental circumstances.

Identification of cultivable bacterial strains producing biosurfactants/bioemulsifiers isolated from an Algerian oil refinery

Algerian petrochemical industrial areas are usually running spills and leakages of hydrocarbons, which constitutes a major source of toxic compounds in soil such as aromatic hydrocarbons. In this paper, samples of crude oil-polluted soil were collected from Skikda's oil refinery and were subjected to mono and polyaromatic hydrocarbons threshold assessment. Soil physicochemical parameters were determined for each sample to examine their response to pollution. Amid 34 isolated bacteria, eleven strains were selected as best Biosurfactants (Bs)/Bioemulsifiers (Be) producers and were assigned to Firmicutes and Proteobacteria phyla based on molecular identification. Phylogenetic analysis of partial 16S rDNA gene sequences allowed the construction of evolutionary trees by means of the maximum likelihood method. Accordingly, strains were similar to Bacillus spp., Priesta spp., Pseudomonas spp., Enterobacter spp. and Kosakonia spp. with more than 95% similarity. These strains could be qualified candidates for an efficient bioremediation process of severally polluted soils.

Vertical distribution characteristics and interactions of polycyclic aromatic compounds and bacterial communities in contaminated soil in oil storage tank areas

Polycyclic aromatic compound (PAC) contamination in soil as a result of oil spills is a serious issue because of the huge global demand for fossil energy. This study assessed the vertical variation in polycyclic aromatic hydrocarbons (PAHs), derivatives of PAHs (dPAHs) and bacterial community structure in deep soil with long-term contamination by oil spillage. Our results suggest that the content of total PACs ranged from 1196.6 μg/kg to 14980.9 μg/kg and decreased with depth at all sites. PAHs were the most abundant PACs, with a mean concentration of 6640.7 μg/kg, followed by oxygenated PAHs (mean 156.3 μg/kg) and nitrated PAHs (mean 33.4 μg/kg). PAHs are mainly low molecular weight PACs such as naphthalene, fluorene and phenanthrene, while derivatives of PAHs are all low molecular weight PACs and mainly oxygenated PAHs. Low molecular weight PAHs were an important source of dPAHs under specific conditions. The bacterial community structure showed higher bacterial diversity and lower bacterial richness in shallow soil (2-6 m in depth) than in deep soil (8-10 m in depth). Spearman's analysis confirmed that dramatic bacterial community shifts are a response to contamination. At the genus level, the presence of PACs highly selected for Pseudomonas, belonging to Proteobacteria. Moreover, functional predictions based on Tax4Fun revealed that soil with long-term contamination had a strong potential for PAC degradation. In addition, statistical analysis showed that oxidation-reduction potential (Eh) was closely related to variations of bacterial community composition and function. Finally, Ramlibacter, Pseudomonas, Pseudonocardia, c_MB-A2-108, f_Amb-16S-1323, and Qipengyuania were identified by cooccurrence network analysis as keystone taxa contributing to the maintenance of bacterial ecological function. Together, our results provide evidence of tight bacterial effects of PAHs and dPAHs and a more complete understanding of the fate of PACs in deep contaminated soils.

A comparative study on chemical characterization and properties of surface active compounds from Gram-positive Bacillus and Gram-negative Ochrobactrum strains utilizing pure hydrocarbons and waste mineral lubricating oils

Mineral lubricating oils are widely used in various industrial sectors for their applications in maintenance and functioning of machineries. However, indiscriminate dumping of these used oils have resulted in polluting the natural reservoirs which subsequently destroys ecological balance. Bacteria can emulsify or lower surface tension between phases of immiscible substrates and can acquire them as their carbon and energy sources. Such a phenomenon is mediated by production of extracellular polymers which can function as eminent surface active compounds based on their surfactant or emulsifying nature. The comparison between bacterial strains (Gram-positive Bacillus stratosphericus A15 and Gram-negative Ochrobactrum pseudintermedium C1) on utilization of pure straight chain hydrocarbons, waste mineral lubricating oils as sole carbon source and chemical characterization of the synthesized surface active compounds were studied. Characterization analysis by Ultraviolet Visible spectrophotometry, Fourier transform infrared spectroscopy, Nuclear Magnetic Resonance spectroscopy, Carbon-Hydrogen-Nitrogen analysis has given detailed structural elucidation of surface active compounds. The contrasting nature of bacterial strains in utilization of different hydrocarbons of waste mineral lubricating oils was observed in Gas Chromatography-Mass Spectroscopy analysis. The variation between both strains in utilization of hydrocarbons can be manifested in chemical structural differences and properties of the produced surface active compounds. Scanning Electron Microscopy has given detailed insight into the microstructural difference of the compounds. The utilization of lubricating oils can address waste disposal problem and offer an economical feasible approach for bacterial production of surface active compounds. Our results suggest that these surface active compounds can maneuver applications in environmental bioremediation and agriculture, pharmaceuticals and food as functional biomaterials.

Designing novel MgFe2O4 coupled V2O5 nanorod for synergetic photodegradation of tetracycline with enhanced visible-light energy harvesting: Photoluminescence, kinetics, intrinsic mechanism and bactericidal effect

The present study focused on the enhancement of degradation of an important pharmaceutical pollutant, tetracycline with the help of nano photocatalyst under visible light irradiation. The study found that the synergetic effect of novel MgFe₂O₄-V₂O₅ enhanced the photocatalytic degradation of tetracycline. Here, the photocatalyst was synthesized by sonochemical technique. Scanning electron microscopy image indicates the coupling of MgFe₂O₄ nanocapsules on the surface of the V₂O₅ nanorod. The bandgap of MgFe₂O₄ (1.8 eV) and V₂O₅ (2.5 eV) was shifted to 2.32 eV in MgFe₂O₄-V₂O₅ to promote visible-light harvesting and it was depicted by the UV-visible DRS. XPS was used to identify the presence of chemical states with the existence of Mg 1s, Fe 2p, V 2p, and O 1s. The electrochemical impedance spectroscopy and photoluminescence spectra indicate the better separation of charge carriers owing to the formation of type II heterojunction formation. The tetracycline (25 mg/L) was degraded with MgFe₂O₄-V₂O₅ (150 mg/L) that exhibited 3.3 and 5 folds enhanced rates than its counterparts (MgFe₂O₄ and V₂O₅) owing to synergism. The possible intermediate formation and degradation pathway was determined based on GC/MS analysis. TOC analysis of end products indicated maximum mineralization of tetracycline. The MgFe₂O₄-V₂O₅ showed excellent recycling ability and reusability. The key photo-degradation of tetracycline was occurred by the generation of hydroxyl radicals. The MgFe₂O₄-V₂O₅ exhibited high antibacterial activity that ensures the dual functionality of the prepared nanocomposites (NCs). Therefore, the present study displays MgFe₂O₄ decorated V₂O₅ nanorod as an ideal candidate for environmental remediation.

Microbial Involvement in the Bioremediation of Total Petroleum Hydrocarbon Polluted Soils: Challenges and Perspectives

Nowadays, soil contamination by total petroleum hydrocarbons is still one of the most widespread forms of contamination. Intervention technologies are consolidated; however, full-scale interventions turn out to be not sustainable. Sustainability is essential not only in terms of costs, but also in terms of restoration of the soil resilience. Bioremediation has the possibility to fill the gap of sustainability with proper knowledge. Bioremediation should be optimized by the exploitation of the recent “omic” approaches to the study of hydrocarburoclastic microbiomes. To reach the goal, an extensive and deep knowledge in the study of bacterial and fungal degradative pathways, their interactions within microbiomes and of microbiomes with the soil matrix has to be gained. “Omic” approaches permits to study both the culturable and the unculturable soil microbial communities active in degradation processes, offering the instruments to identify the key organisms responsible for soil contaminant depletion and restoration of soil resilience. Tools for the investigation of both microbial communities, their degradation pathways and their interaction, will be discussed, describing the dedicated genomic and metagenomic approaches, as well as the interpretative tools of the deriving data, that are exploitable for both optimizing bio-based approaches for the treatment of total petroleum hydrocarbon contaminated soils and for the correct scaling up of the technologies at the industrial scale.

Microbial valorization of underutilized and nonconventional waste streams

The growing burden of waste disposal coupled with natural resource scarcity has renewed interest in the remediation, valorization, and/or repurposing of waste. Traditional approaches such as composting, anaerobic digestion, use in fertilizers or animal feed, or incineration for energy production extract very little value out of these waste streams. In contrast, waste valorization into fuels and other biochemicals via microbial fermentation is an area of growing interest. In this review, we discuss microbial valorization of nonconventional, aqueous waste streams such as food processing effluents, wastewater streams, and other industrial wastes. We categorize these waste streams as carbohydrate-rich food wastes, lipid-rich wastes, and other industrial wastes. Recent advances in microbial valorization of these nonconventional waste streams are highlighted, along with a discussion of the specific challenges and opportunities associated with impurities, nitrogen content, toxicity, and low productivity.

Innovative Culturomic Approaches and Predictive Functional Metagenomic Analysis: The Isolation of Hydrocarbonoclastic Bacteria with Plant Growth Promoting Capacity

Innovative culturomic approaches were adopted to isolate hydrocarbonoclastic bacteria capable of degrading diesel oil, bitumen and a selection of polycyclic aromatic hydrocarbons (PAH), e.g., pyrene, anthracene, and dibenzothiophene, from a soil historically contaminated by total petroleum hydrocarbons (TPH) (10,347 ± 98 mg TPH/kg). The culturomic approach focussed on the isolation of saprophytic microorganisms and specialist bacteria utilising the contaminants as sole carbon sources. Bacterial isolates belonging to Pseudomonas, Arthrobacter, Achromobacter, Bacillus, Lysinibacillus, Microbacterium sps. were isolated for their capacity to utilise diesel oil, bitumen, pyrene, anthracene, dibenzothiphene, and their mixture as sole carbon sources. Pseudomonas, Arthrobacter, Achromobacter and Microbacterium sps. showed plant growth promoting activity, producing indole-3-acetic acid and expressing 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase activity. In parallel to the culturomic approach, in the microbial community of interest, bacterial community metabarcoding and predictive functional metagenomic analysis were adopted to confirm the potentiality of the isolates in terms of their functional representativeness. The combination of isolation and molecular approaches for the characterisation of a TPH contaminated soil microbial community is proposed as an instrument for the construction of an artificial hydrocarbonoclastic microbiota for environmental restoration.

Molecular and functional analysis of naphthalene-degrading bacteria isolated from the effluents of indigenous tanneries

During present study, four naphthalene- metabolizing bacteria were isolated from tanneries effluents through enrichment on naphthalene as sole carbon source in minimal salt medium. The bacteria were analyzed to document growth pattern, naphthalene removal efficiency, biochemical and molecular characteristics, antibiotic sensitivity, and metabolic profile. The 16S ribosomal RNA gene sequences were compared through BLAST (basic local alignment search tool) similarity search tool and three isolates were found homologous to Brevibacillus agri strain NBRC 15538 and one similar to Burkholderia lata strain 383. The naphthalene removal efficiencies ranged from 1.16 ± 0.056 mg/h (IUBN1) to 1.379 ± 0.021 mg/h (IUBN26). All isolates were positive for p-nitrophenyl phosphate (PO₄ ), esculin, and inulin fermentation tests. Majority were positive for glucosaminidase (IUBN3, 17, and 26) and a few for mannitol and sorbitol fermentation (IUBN1). Identification of metabolites through gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry analysis allowed tracing pathways associated with naphthalene degradation. Intermediates such as cis-dihydrodiolnaphthalene, 2-hydroxychromene-2-carboxylate, 6-hydroxyhexanoic acid, acetyl-CoA confirmed that the present study bacteria can metabolize naphthalene through a pathway which differs from the pathways reported in earlier known bacteria. Due to fast growth rates, high naphthalene removal potentials, and multiple degradation pathways, these bacteria can be exploited for bioremediation of naphthalene.

Synthesis of high-performance conjugated microporous polymer/TiO2 photocatalytic antibacterial nanocomposites

High-performance conjugated microporous polymer (CMP)/TiO₂ photocatalytic antibacterial nanocomposites were successfully synthesized by in situ Sonogashira polymerization. TiO₂ was uniformly dispersed onto the surface and within the CMP which show the microporous nature with narrow pore size distribution. The high crystallinity and thermal stability of the CMP/TiO₂ nanocomposites are attractive for use as antibacterial materials. The composites we prepared showed excellent photocatalytic antibacterial properties for the inactivation of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) under visible light irradiation. The photocatalytic antibacterial rates of nanocomposites against E. coli and S. aureus after 120 min of visible light irradiation were 98.14% and 100%, respectively. The superoxide anion (O₂^-) was confirmed to be an important substance in the antibacterial process above. The cytocompatibility of the antibacterial agents was studied in terms of cytotoxicity against NIH 3T3 fibroblasts. More than 95% of the cells were still alive in the presence of the nanocomposites, both without and with light irradiation, indicating the good cytocompatibility of the nanocomposites. Judging from the excellent photocatalytic antibacterial properties and ultralow toxicity of nanocomposites, these materials can be used in many fields such as medical treatment, transportation and construction.

Enhanced phytoremediation of PAHs and cadmium contaminated soils by a Mycobacterium

This study investigated Fire Phoenix (Festuca L.) and Echinacea purpurea (L.) Moench inoculated with a Mycobacterium strain N12 in remediation of soils contaminated with both polycyclic aromatic hydrocarbons (PAHs) and cadmium (Cd). Plant growth and PAH and Cd removal were monitored in 60, 120, and 150 days after transplanting. Results showed that Fire Phoenix plants grown in soil containing 200 mg/kg PAHs and 15 mg/kg Cd inoculated with N12 were able to remove 76.3% PAHs compared to removal of 68.3% of PAHs by the plants without N12 inoculation. On day 150, the underground biomass of Fire Phoenix plants grown in soil inoculated with N12 increased 59.40% compared to that without N12 inoculation. The enhanced removal of PAH by Fire Phoenix and N12 was related to the improved rhizosphere microbial activities. However, inoculation of N12 to E. purpurea grown soil did not significantly improve the removal of PAHs and Cd. Our results showed that phytoremediation of PAHs and Cd can be enhanced by a Mycobacterium strain N12, especially when PLFA concentrations of bacteria and fungi exceeded 60% of the initial concentrations, but the enhancement is plant species dependent.

Response of bacterial and fungal communities to high petroleum pollution in different soils

Petroleum pollution of soils is a major environmental problem. Soil microorganisms can decompose a significant fraction of petroleum hydrocarbons in soil at low concentrations (1-5%). This characteristic can be used for soil remediation after oil pollution. Microbial community dynamics and functions are well studied in cases of moderate petroleum pollution, while cases with heavy soil pollution have received much less attention. We studied bacterial and fungal successions in three different soils with high petroleum contents (6 and 25%) in a laboratory experiment. The proportion of aliphatic and aromatic compounds decreased by 4-7% in samples with 6% pollution after 120 days of incubation but remained unchanged in samples with 25% hydrocarbons. The composition of the microbial community changed significantly in all cases. Oil pollution led to an increase in the relative abundance of bacteria such as Actinobacteria and the candidate TM7 phylum (Saccaribacteria) and to a decrease in that of Bacteroidetes. The gene abundance (number of OTUs) of oil-degrading bacteria (Rhodococcus sp., candidate class TM7-3 representative) became dominant in all soil samples, irrespective of the petroleum pollution level and soil type. The fungal communities in unpolluted soil samples differed more significantly than the bacterial communities. Nonmetric multidimensional scaling revealed that in the polluted soil, successions of fungal communities differed between soils, in contrast to bacterial communities. However, these successions showed similar trends: fungi capable of lignin and cellulose decomposition, e.g., from the genera Fusarium and Mortierella, were dominant during the incubation period.

Impact of the Biological Cotreatment of the Kalina Pond Leachate on Laboratory Sequencing Batch Reactor Operation and Activated Sludge Quality

Hauling landfill leachate to offsite urban wastewater treatment plants is a way to achieve pollutant removal. However, the implementation of biological methods for the treatment of landfill leachate can be extremely challenging. This study aims to investigate the effect of blending wastewater with 3.5% and 5.5% of the industrial leachate from the Kalina pond (KPL) on the performance of sequencing batch reactor (SBR) and capacity of activated sludge microorganisms. The results showed that the removal efficiency of the chemical oxygen demand declined in the contaminated SBR from 100% to 69% and, subsequently, to 41% after the cotreatment with 3.5% and 5.5% of the pollutant. In parallel, the activities of the dehydrogenases and nonspecific esterases declined by 58% and 39%, and 79% and 81% after 32 days of the exposure of the SBR to 3.5% and 5.5% of the leachate, respectively. Furthermore, the presence of the KPL in the sewage affected the sludge microorganisms through a reduction in their functional capacity as well as a decrease in the percentages of the marker fatty acids for different microbial groups. A multifactorial analysis of the parameters relevant for the wastewater treatment process confirmed unambiguously the negative impact of the leachate on the operation, activity, and structure of the activated sludge.

Long-term effect of water diversion and CSOs on the remediation of heavy metals and microbial community in river sediments

Untreated combined sewer overflows (CSOs) cause serious water pollution problems. In this study, the effects of CSO-induced heavy metals and the remediation practice of installation of a long-term water diversion (LTWD) on the microbial environment in river sediments were analyzed in an inland river. The Zn, Cd, Cr, and Cu contents in sediments and water were analyzed. DNA extraction and polymerase chain reaction analysis were conducted based on the Illumina MiSeq platform. The results showed that CSOs have a significant adverse impact on the diversity of microbial populations in river sediments. The LTWD is helpful in improving the richness of microorganisms and the proportion of Gram -ves, but it is challenging to reduce the accumulation of heavy metals in the sediment. The correlation analysis shows a strong relationship between some metabolic pathways and Zn and Cd accumulation in river sediments. Some detoxification compound metabolisms are also promoted at these sites. Thus, chronic exposure to environmental heavy metals from CSOs decreases the river microbial community, and further affects the ecological environment of the river. Therefore, without eliminating CSOs or reducing overflow frequency, it is difficult to alleviate the accumulation of heavy metals in river sediments and improve river ecology via water diversion alone.

Biodegradation of the aromatic fraction from petroleum diesel fuel by Oerskovia sp. followed by comprehensive GC×GC-TOF MS

Polycyclic aromatic hydrocarbons (PAHs) from petroleum and fossil fuels are one of the most dominant pollutants in the environment. Since aromatic fraction from petroleum diesel fuel is mainly composed of PAHs, it is important to discover new microorganisms that can biodegrade these compounds. This article describes the biodegradation of the aromatic fraction separated from petroleum diesel fuel using the strain Oerskovia sp. CHP-ZH25 isolated from petroleum oil-contaminated soil. The biodegradation was monitored by gravimetry and GC × GC-TOF MS. An innovative method was applied to visualize degraded compounds in the data provided by a GC × GC-TOF MS. It was shown that Oerskovia sp. CHP-ZH25 degraded 77.4% based on gravimetric analysis within 30 days. Average rate of degradation was 14.4 mg/L/day, 10.5 mg/l/day and 4.0 mg/l/day from 0 to 10 day, 10-20 and 20-30 day, respectively. The order of PAH degradation based on decrease in peak volume after 30 days of incubation was as follows: dibenzothiophene derivatives > benzo[b]thiophene derivatives > naphthalene derivatives > acenaphthene derivatives > acenaphthylene/biphenyl derivatives > fluorene derivatives > phenanthrene/anthracene derivatives. Here we demonstrated that Oerskovia sp. CHP-ZH25 could potentially be a suitable candidate for use in bioremediation of environments polluted with different PAHs.

Degradation of polycyclic aromatic hydrocarbons in a mixed contaminated soil supported by phytostabilisation, organic and inorganic soil additives

In soil, mixed contamination with potentially toxic trace elements and polycyclic aromatic hydrocarbons (PAHs) may persist for a long time due to strong adsorption to the soil matrix and to its toxicity to microorganism. We conducted an incubation batch experiment to test the effect of soil amendments (biochar, gravel sludge, iron oxides) on the immobilisation of trace elements. To monitor microbial degradation, a ¹³C-PHE (phenanthrene) label was introduced to soil for ¹³C-PLFA (phospholipid fatty acid) analysis. Soil amendments increased soil pH, reduced mobility of NH₄NO₃-extractable trace elements Cd and Zn, and increased mobile Cu. A small consortium of PHE degraders was identified mainly in the microbial groups of gram-negative bacteria and actinomycetes. The degradation process of PHE peaked 9days after incubation start. PAH concentrations remained constant in the soil within the 30-day incubation, except for the easily available ¹³C-PHE in the amended treatment. In order to test the effect of plants and soil amendments under more realistic conditions, we also conducted an outdoor pot experiment with black locust (Robinia pseudoacacia Nyirsegi). Furthermore, soil amendments increased the mobility of soil Cu and As and decreased the mobility of Cd, Pb and Sb. The uptake of trace elements to leaves was low. Σ 16 U.S. EPA PAHs were significantly reduced only in the combined treatment of black locust and soil amendments after 12months of plant growth. Soil amendment-assisted phytoremediation showed a high efficiency in PAH dissipation and may be a useful remediation technique for mixed contaminated soils.

Characterizing heavy metals in combined sewer overflows and its influence on microbial diversity

This study characterized the pollution levels and potential ecological risk of heavy metals in combined sewer overflows (CSOs) and their effects on microbial diversity in nearby riparian sediments. The chemical fractionations of Zn, Cd, Cr, and Cu in dry-weather flows, wet-weather flows (CSO discharges), sewer sediments, and surface runoffs were determined. Geo-accumulation (I_geo) and ecological risk (RI) indexes were employed for metal risk assessment. DNA extraction and polymerase chain reaction (PCR) amplification on the Illumina MiSeq platform were conducted. The results show that heavy metals contents in fine-sized fractions have higher values than those in coarse-sized fractions. Chemical fractionation analysis suggests that Zn and Cd are two of the most bioavailable metals impacted by anthropogenic activities. Cr and Cu contents in CSOs are relatively stable and could exist for extended periods. According to the RI analysis, CSOs pose a considerable risk (RI-G2) to receiving waters due to the higher bioavailability of Cd, which was consistent with the I_geo index. Furthermore, under the stress of the highly-bioavailable Cd and Cu, Gram +ves in the riparian benthic sediment gradually became dominant with metal-tolerance property. Therefore, long-term exposure to highly bioavailable metals could exhibit great impacts on microbial diversity.

Shift in microbial group during remediation by enhanced natural attenuation (RENA) of a crude oil-impacted soil: a case study of Ikarama Community, Bayelsa, Nigeria

Acute and chronic pollution of environments with crude oil does not bode well for biota living within the vicinity of polluted environments. This is due to environmental and public health concerns on the negative impact of crude oil pollution on living organisms. Enhancing microbial activities by adding nutrients and other amendments had proved effective in pollutant removal during bioremediation. This study was carried out to determine how microbial group respond during remediation by enhanced natural attenuation (RENA) during a field-scale bioremediation. Crude oil-polluted soil samples were collected (before, during, and after remediation) from a site undergoing remediation by enhanced natural attenuation (RENA) at Ikarama Community, Bayelsa State, Nigeria, and were analyzed for total petroleum hydrocarbon (TPH), polyaromatic hydrocarbon (PAH), and a shift in microbial community. The gas chromatography-flame ionization detector (GC-FID) results showed that the pollutant concentrations (TPH and PAH) reduced by 98 and 85%, respectively, after the remediation. Culturable hydrocarbon utilizing bacteria (CHUB) was highest (8.3 × 10⁴ cfu/g) for sample collected during the remediation studies, whilst sample collected after remediation had low CHUB (6.1 × 10⁴ cfu/g) compared to that collected before remediation (7.7 × 10⁴ cfu/g). Analysis of 16S rRNA of the isolated CHUB showed they belonged to eight bacterial genera namely: Achromobacter, Alcaligenes, Azospirillus, Bacillus, Lysinibacillus, Ochrobactrum, Proteus, and Pusillimonas, with Alcaligenes as the dominant genus. In this study, it was observed that the bacterial community shifted from mixed group (Gram-positive and -negative) before and during the remediation, to only the latter group after the remediation studies. The betaproteobacteria groups were the dominant isolated bacterial phylotype. This study showed that RENA is an effective method of reducing pollutant concentration in crude oil-polluted sites, and could be applied to other polluted sites in the Niger Delta region of Nigeria to mitigate the devastating effects of crude oil pollution.

Structural Degradation and Swelling of Lipid Bilayer under the Action of Benzene

Benzene and other nonpolar organic solvents can accumulate in the lipid bilayer of cellular membranes. Their effect on the membrane structure and fluidity determines their toxic properties and antibiotic action of the organic solvents on the bacteria. We performed molecular dynamics simulations of the interaction of benzene with the dimyristoylphosphatidylcholine (DMPC) bilayer. An increase in the membrane surface area and fluidity was clearly detected. Changes in the acyl chain ordering, tilt angle, and overall bilayer thickness were, however, much less marked. The dependence of all computed quantities on the benzene content showed two regimes separated by the solubility limit of benzene in water. When the amount of benzene exceeded this point, a layer of almost pure benzene started to grow between the membrane leaflets. This process corresponds to the nucleation of a new phase and provides a molecular mechanism for the mechanical rupture of the bilayer under the action of nonpolar compounds.

Biodegradation of diesel oil by a novel microbial consortium: comparison between co-inoculation with biosurfactant-producing strain and exogenously added biosurfactants

Bioremediation, involving the use of microorganisms to detoxify or remove pollutants, is the most interesting strategy for hydrocarbon remediation. In this aim, four hydrocarbon-degrading bacteria were isolated from oil-contaminated soil in Tunisia. They were identified by the 16S rDNA sequence analysis, as Lysinibacillus bronitolerans RI18 (KF964487), Bacillus thuringiensis RI16 (KM111604), Bacillus weihenstephanensis RI12 (KM094930), and Acinetobacter radioresistens RI7 (KJ829530). Moreover, a lipopeptide biosurfactant produced by Bacillus subtilis SPB1, confirmed to increase diesel solubility, was tested to increase diesel biodegradation along with co-inoculation with two biosurfactant-producing strains. Culture studies revealed the enhancement of diesel biodegradation by the selected consortium with the addition of SPB1 lipopeptide and in the cases of co-inoculation by biosurfactant-producing strain. In fact, an improvement of about 38.42 and 49.65 % of diesel degradation was registered in the presence of 0.1 % lipopeptide biosurfactant and when culturing B. subtilis SPB1 strain with the isolated consortium, respectively. Furthermore, the best improvement, evaluated to about 55.4 %, was recorded when using the consortium cultured with B. subtilis SPB1 and A. radioresistens RI7 strains. Gas chromatography analyses were correlated with the gravimetric evaluation of the residual hydrocarbons. Results suggested the potential applicability of the selected consortium along with the ex situ- and in situ-added biosurfactant for the effective bioremediation of diesel-contaminated water and soil.

Cometabolic Degradation of Naproxen by Planococcus sp. Strain S5

Naproxen is a non-steroidal anti-inflammatory drug frequently detected in the influent and effluent of sewage treatment plants. The Gram-positive strain Planococcus sp. S5 was able to remove approximately 30 % of naproxen after 35 days of incubation in monosubstrate culture. Under cometabolic conditions, with glucose or phenol as a growth substrate, the degradation efficiency of S5 increased. During 35 days of incubation, 75.14 ± 1.71 % and 86.27 ± 2.09 % of naproxen was degraded in the presence of glucose and phenol, respectively. The highest rate of naproxen degradation observed in the presence of phenol may be connected with the fact that phenol is known to induce enzymes responsible for aromatic ring cleavage. The activity of phenol monooxygenase, naphthalene monooxygenase, and hydroxyquinol 1,2-dioxygenase was indicated in Planococcus sp. S5 culture with glucose or phenol as a growth substrate. It is suggested that these enzymes may be engaged in naproxen degradation.

Joint action and lethal levels of toluene, ethylbenzene, and xylene on midge (Chironomus plumosus) larvae

Aquatic ecosystems are vulnerable to the exposure with petrochemicals such as toluene, ethylbenzene, and xylene (o-, m-, and p-xylene) (TEX) and their adverse effects. Considering the widespread use, occurrence, and high toxicity of TEX, the aim of this work was to investigate the differential toxicity of TEX against midge (Chironomus plumosus) larvae and reveal the joint action of binary and ternary mixtures of TEX using the predictive concentration addition model. More importantly, this research can afford the basic toxicity data and scientific reference for the establishment of water quality criteria or benchmark, water pollution control, and aquatic risk assessment. Single and joint toxic effects of TEX on C. plumosus larvae were investigated using a semi-static bioassay, and the type of joint effects of TEX was ascertained. In the single toxicant experiments, the toxicity of the three pollutants could be sequenced as ethylbenzene > xylene > toluene. Specifically, LC(50s) of T, E, and X after a 48-h exposure were 64.9, 37.8, and 42.0 mg/L, respectively. In the binary mixture experiments, the interaction between toluene and ethylbenzene, ethylbenzene and xylene, and toluene and xylene was largely in conformity with partial additive or additive effect as determined by isobologram representation and toxic unit models. In the ternary mixture experiments, the interaction was basically dependent on the use of additive index and mixture toxicity index methods. However, the antagonistic and synergistic actions were not significant. Thus, the tertiary mixture interaction could be regarded as additive action. The concentration addition model could successfully predict the joint action of TEX mixtures on C. plumosus larvae. Particularly, the additive action of TEX on C. plumosus larvae can be further recommended to evaluate water quality criteria of TEX.