Effects of biochar immobilization of Serratia sp. F4 OR414381 on bioremediation of petroleum contamination and bacterial community composition in loess soil.

Petroleum hydrocarbons pose a significant threat to human health and the environment. Biochar has increasingly been utilized for soil remediation. This study investigated the potential of biochar immobilization using Serratia sp. F4 OR414381 for the remediation of petroleum-contaminated soil through a pot experiment conducted over 90 days. The treatments in this study, denoted as IMs (maize straw biochar-immobilized Serratia sp. F4), degraded 82.5% of the total petroleum hydrocarbons (TPH), 59.23% of the aromatic, and 90.1% of the saturated hydrocarbon fractions in the loess soils. During remediation, the soil pH values decreased from 8.76 to 7.33, and the oxidation-reduction potential (ORP) increased from 156 to 229 mV. The treatment-maintained soil nutrients of the IMs were 138.94 mg/kg of NO3- -N and 92.47 mg/kg of available phosphorus (AP), as well as 11.29% of moisture content. The activities of soil dehydrogenase (SDHA) and catalase (CAT) respectively increased by 14% and 15 times compared to the CK treatment. Three key petroleum hydrocarbon degradation genes, including CYP450, AJ025, and xylX were upregulated following IMs treatment. Microbial community analysis revealed that a substantial microbial population of 1.01E+ 09 cells/g soil and oil-degrading bacteria such as Salinimicrobium, Saccharibacteria_genera_incertae_sedis, and Brevundimonas were the dominant genera in IMs treatment. This suggests that the biochar immobilized on Serratia sp. F4 OR414381 improves soil physicochemical properties and enhances interactions among microbial populations, presenting a promising and environmentally friendly approach for the stable and efficient remediation of petroleum-contaminated loess soil.

Unraveling the Positive Effect of Soil Moisture on the Bioaugmentation of Petroleum-Contaminated Soil Using Bioinformatics.

Petroleum contamination is a severe threat to the soil environment. Previous studies have demonstrated that petroleum degradation efficiency is promoted by enhancing soil moisture content (MC). However, the effects of MC on soil microbial ecological functions during bioremediation remain unclear. Here, we investigated the impacts of 5% and 15% of moisture contents on petroleum degradation, soil microbial structures and functions, and the related genes using high-throughput sequencing and gene function prediction. Results indicated that petroleum biodegradation efficiency was increased by 8.06% in the soils with 15% MC when compared to that with 5% of MC. The complexity and stability of soil microbial community structures with 15% MC were higher than those in the soils with 5% MC when hydrocarbon-degrading bacterial flora (HDBF) were inoculated into the soils. Fifteen percent of moisture content strengthened the interaction of the bacterial community network and reduced the loss of some key bacteria species including Mycobacterium, Sphingomonas, and Gemmatimonas. Some downregulated gene pathways relating to bioaugmentation were enhanced in the soils with 15% MC. The results suggested that the dynamic balances of microbial communities and the metabolic interactions by 15% MC treatment are the driving forces for the enhancement of bioremediation in petroleum-contaminated soil.

New insight into the effect of nitrogen on hydrocarbon degradation in petroleum-contaminated soil revealed through 15N tracing and flow cytometry.

Nitrogen (N) has been widely used to dissipate total petroleum hydrocarbons (TPH) in the oil-contaminated soil, but the relationships of hydrocarbon transformation, N cycling and utilization, and microbial characteristics during TPH biodegradation still remain unclear. In this study, 15N tracers (K15NO3 and 15NH4Cl) were used as stimulants for TPH degradation to compare the bioremediation potential of TPH in the historically (5 a) and freshly (7 d) petroleum-contaminated soils. During bioremediation process, TPH removal and carbon balance, N transformation and utilization, as well as microbial morphologies were investigated using 15N tracing and flow cytometry. Results showed that TPH removal rates were higher in the freshly polluted soils (61.59 % for K15NO3 amendment and 48.55 % for 15NH4Cl amendment) than in the historically polluted soils (35.84 % for K15NO3 amendment and 32.30 % for 15NH4Cl amendment), and TPH removal rate through K15NO3 amendment was higher than that of 15NH4Cl in the freshly polluted soils. This result was attributed to the higher N gross transformation rates in the freshly contaminated soils (0.0034-0.432 mmol N kg-1 d-1) when compared with that in the historically contaminated soils (0.009-0.04 mmol N kg-1 d-1), which led to more TPH transformation to residual carbon (51.84 %-53.74 %) in the freshly polluted soils than that in the historically polluted soils (24.67 %-33.47 %). Based on the fluorescence intensity displayed by the combination of stains and cellular components to indicate microbial morphology and activity, flow cytometry analysis showed that nitrogen addition was beneficial for the membrane integrity of TPH-degrading bacteria, and nitrogen also enhanced DNA synthesis and activity of TPH-degrading fungi in freshly polluted soil. Correlation and structural equation modeling analysis identified that K15NO3 was beneficial to synthesize DNA of the TPH-degrading fungi but not the bacteria, which contributed to enhance TPH bio-mineralization in the soils with K15NO3 amendment.

Assessment of bioremediation potential of petroleum-contaminated soils from the shanbei oilfield of China revealed by qPCR and high throughput sequencing.

With the crude oil exploration activities in the Shanbei oilfield of China, the risk of soil contamination with crude oil spills has become a major concern. This study aimed at assessing the bioremediation potential of the petroleum polluted soils by investigating the expression of key functional genes decoding alkane and aromatic component degradation using an array of primers and real-time quantitative PCR (qPCR), and the functional microbiomes were determined using a combination of substrate-induced metabolic responses and high throughput sequencing. The results showed that the species that were more inclined to degrade aliphatic fraction of crude oil included Acinetobacter, Stenotrophomonas, Neorhizobium and Olivebacter. And Pseudomonas genus was a highly specific keystone species with the potential to degrade PAH fraction. Both aliphatic and PAH-degrading genes were upregulated when the soil petroleum contents were less than 10,000 mg/kg but downregulated when the oil contents were over 10,000 mg/kg. Bioremediation potential could be feasible for medium pollution with petroleum contents of less than 10,000 mg/kg. Optimization of the niche of Acinetobacter, Stenotrophomonas, Pseudomonas, Neorhizobium and Olivebacter species was beneficial to the biodegradation of refractory hydrocarbon components in the Shanbei plateau oilfield.

Isotope fractionation (δ13C, δ15N) and microbial community response in degradation of petroleum hydrocarbons by biostimulation in contaminated soil.

This study investigated the isotope effects of δ13C and δ15N and microbial response during biodegradation of hydrocarbons by biostimulation with nitrate or compost in the petroleum-contaminated soil. Compost and KNO3 amendments promoted the total petroleum hydrocarbon (TPH) removal accompanied by a significant increase of Actinobacteria and Firmicutes phyla. Soil alpha diversity decreased after 90 days of biostimulation. An inverse significant carbon isotope effect (εc = 16.6 ± 0.8‰) and strong significant nitrogen isotope effect (εN = -24.20 ± 9.54‰) were shown by the KNO3 supplementation. For compost amendment, significant carbon and nitrogen isotope effect were εc = 38.8 ± 1.1‰ and εN = -79.49 ± 16.41‰, respectively. A clear difference of the carbon and nitrogen stable isotope fractionation was evident by KNO3 or compost amendment, which indicated that the mechanisms of petroleum degradation by adding compost or KNO3 may be different.

Effect of petroleum hydrocarbon pollution levels on the soil microecosystem and ecological function.

Petroleum hydrocarbon pollution is a global problem. However, the effects of different petroleum pollution levels on soil microbial communities and ecological functions are still not clear. In this study, we analyzed the changes in microbial community structures and carbon and nitrogen transformation functions in oil-contaminated soils at different concentrations by chemical analysis, high-throughput sequencing techniques, cooccurrence networks, and KEGG database comparison functional gene annotation. The results showed that heavy petroleum concentrations (petroleum concentrations greater than 20,000 mg kg-1) significantly decreased soil microbial diversity (p = 0.01), soil microbiome network complexity, species coexistence patterns, and prokaryotic carbon and nitrogen fixation genes. In medium petroleum contamination (petroleum concentrations of between 4000 mg kg-1 and 20,000 mg kg-1), microbial diversity (p > 0.05) and carbon and nitrogen transformation genes showed no evident change but promoted species coexistence patterns. Heavy petroleum contamination increased the Proteobacteria phylum abundance by 3.91%-57.01%, while medium petroleum contamination increased the Actinobacteria phylum abundance by 1.69%-0.26%. The results suggested that petroleum concentrations played a significant role in shifting soil microbial community structures, ecological functions, and species diversities.

Hydrocarbon transformation pathways and soil organic carbon stability in the biostimulation of oil-contaminated soil: Implications of 13C natural abundance.

Mineralization, assimilation, and humification are key processes to detoxify oil-contaminated soil by biostimulation remediation strategies, and these processes are affected by stimulants. In this study, we investigated the effects of either inorganic salts or organic stimulants (organic compost and sawdust) on hydrocarbon transformation. Total petroleum hydrocarbons (TPH) and hydrocarbon components were determined by gravimetry and gas chromatography, and the 13C of CO2, microbial biomass carbon (MBC), and humus were measured by stable isotope mass spectrometry. The results showed that organic compost was the most beneficial for the dissipation of hydrocarbons. After 60 days of remediation, the removal rates of TPH, saturates, aromatics, C7-C30 n-alkanes, and 16 PAHs were 35.7%, 39.6%, 15.9%, 80.5%, and 8.8%, respectively. A total of 84.7%-88.5% of the removed hydrocarbons were mineralized in all the treatments. The hydrocarbon degradation pathway in the control soil (without stimulant addition) was "assimilation → humification → mineralization". The hydrocarbon transformation pathways in the biostimulation treatments were "assimilation → mineralization → humification". The soil organic carbon (SOC) stability decreased during remediation, which was attributed to the enhanced microbial activity and the removal of recalcitrant hydrocarbons.

Acupuncture for the Treatment of Alzheimer's Disease: An Overview of Systematic Reviews.

Background: Acupuncture may be an effective complementary treatment for Alzheimer's disease (AD). The aim of this study was to summarize the evidence provided by systematic reviews (SRs)/meta-analyses (MAs) on the effect of acupuncture on AD. Methods: Eight electronic databases were searched from their inception until October 19, 2020. The methodological quality, reporting quality, and risk of bias of the included SRs were assessed by the Assessing the Methodological Quality of Systematic Reviews 2 (AMSTAR-2), the Risk of Bias in Systematic Reviews (ROBIS) tool, and the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). Moreover, the evidence quality of the outcome measures was assessed by the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE). Results: Eleven SRs/MAs met all inclusion criteria. According to the results of the AMSTAR-2, all included reviews were rated critically as being of low quality. With PRISMA, the reporting checklist was relatively complete, but some reporting weaknesses remained in the topics of the protocol and registration, search strategy, risk of bias, additional analyses, and funding. Based on the ROBIS tool, only two SRs/MAs had a low risk of bias. With the GRADE system, no high-quality evidence was found, and only seven outcomes provided moderate-quality evidence. Among the downgraded factors, the risk of bias within the original trials was ranked first, followed by inconsistency, imprecision, and publication bias. Conclusions: Acupuncture is a promising complementary treatment for AD. However, due to the low quality of the SRs/MAs supporting these results, high-quality studies with rigorous study designs and larger samples are needed before widespread recommendations can be made.

Clinical Effects and Safety of Electroacupuncture for the Treatment of Poststroke Dysphagia: A Comprehensive Systematic Review and Meta-Analysis.

OBJECTIVES: Electroacupuncture (EA), an extension of acupuncture, which is based on traditional acupuncture combined with modern electrotherapy, is commonly used for poststroke dysphagia (PSD) in clinical treatment and research. However, there is still a lack of sufficient evidence to recommend the routine use of EA for PSD. The aim of this study was to assess the efficacy and safety of EA in the treatment of PSD. METHODS: Randomized controlled trials (RCTs) evaluating the effects of EA on PSD were identified through a comprehensive literature search of the PubMed, Embase, Cochrane Library, Web of Science, Chinese National Knowledge Infrastructure, Chinese Biomedical Database, and VIP databases from their inception to July 2020. The quality assessment of the included trials was performed based on the guidance of the Cochrane Reviewers' Handbook, and meta-analysis (MA) was performed by using the RevMan 5.3 software. RESULTS: Sixteen trials were identified, and these included 1,216 patients with PSD. The results demonstrated that EA in combination with swallowing rehabilitation training (SRT) was significantly superior to SRT alone with regard to effective rate (OR 5.40, 95% CI [3.78, 7.72], P < 0.00001, water swallow test (WST) (MD -0.78, 95% CI [-1.07, -0.50], P < 0.00001), the video fluoroscopic swallowing study (VFSS) (MD 1.47, 95% CI [1.11, 1.84], P < 0.00001), the Ichiro Fujishima Rating Scale (IFRS) (MD 1.94, 95% CI [1.67, 2.22], P < 0.00001), and the incidence of aspiration pneumonia (IAP) (OR 0.20, 95% CI [0.06, 0.61], P=0.005). CONCLUSIONS: The results showed that EA was better than the control treatment in terms of the effective rate, WST, VFSS, IFRS, and IAP of dysphagia after stroke. Strict evaluation standards and high-quality RCT designs are necessary for further exploration.

A Critical Overview of Systematic Reviews and Meta-Analyses on Acupuncture for Poststroke Insomnia.

OBJECTIVES: Acupuncture has increasingly been used for insomnia relief after stroke. We aimed to evaluate the methodological quality and summarize the evidence regarding the effectiveness of acupuncture for poststroke insomnia (PSI) from systematic reviews/meta-analyses (SRs/MAs). METHODS: Eight databases were searched from inception through August 23, 2020. SRs/MAs on acupuncture treatment for PSI were included. Methodological quality assessment was performed using Assessing the Methodological Quality of Systematic Reviews 2 (AMSTAR-2), and evidence quality assessment was performed using the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE). RESULTS: Six SRs/MAs on acupuncture treatment for PSI were included. The AMSTAR-2 showed that the methodological quality of all included SRs/MAs was rated as critically low. According to the evaluation results of GRADE, 38.9% (7/18) of outcomes were rated as very low-quality evidence, 22.2% (4/18) were low-quality evidence, and 8.9% (7/18) were moderate-quality evidence. Descriptive analysis results showed that acupuncture was an effective treatment modality for PSI. CONCLUSIONS: All included reviews indicated that acupuncture was more effective than the control group for the treatment of PSI, but the credibility of the results is limited owing to the generally low methodological and evidence quality of the included SRs/MAs. More high-quality evidence is needed to determine whether acupuncture is more effective than other treatments.

Effect of compost amendment and bioaugmentation on PAH degradation and microbial community shifting in petroleum-contaminated soil.

Efficient degradation of polycyclic aromatic hydrocarbons (PAHs) in a petroleum-contaminated soil was challenging which requires ample PAH-degrading flora and nutrients. In this study, we investigated the effects of 'natural attenuation', 'bioaugmentation', 'compost only (raw materials of compost included pig manure and rice husk mixed at a 1:2 proportion, supplemented with 2.5% charcoal)', and 'compost with bioaugmentation' treatments on degradation of polycyclic aromatic hydrocarbons (PAHs) and microbial community shifts during the remediation of petroleum-contaminated soil. After sixteen weeks of incubation, the removal efficiencies of PAHs were 0.52 ± 0.04%, 6.92 ± 0. 32%, 9.53 ± 0.29%, and 18.2 ± 0.64% in the four treatments, respectively. 'Compost with bioaugmentation' was the most effective for PAH removal among all the treatments. Illumina sequencing analysis suggested that both the 'compost only' and 'compost with bioaugmentation' treatments changed soil microbial community structures and enhanced microbial biodiversity. Some of the microorganisms affiliated with the compost including Azomonas, Luteimonas, Pseudosphingobacterium, and Parapedobacter were able to survive and become dominant in the contaminated soil. The 'bioaugmentation and 'natural attenuation' treatments had no significant effects on soil microbial community structure. Inoculation of the PAH degraders including Bacillus, Pseudomonas, and Acinetobacter directly into the contaminated soil led to lower biodiversity under natural conditions. This result suggested that compost addition increased the α-diversity of both the bacterial and fungal communities in petroleum-contaminated soil, leading to higher PAH degradation efficiency in petroleum-contaminated soil.

Nutrient drip irrigation for refractory hydrocarbon removal and microbial community shift in a historically petroleum-contaminated soil.

An adequate amount of nutrients is required to enable biodegradation of refractory hydrocarbons in petroleum-contaminated soil. In this study, a microcosm experiment was conducted using a drip fertigation method for petroleum-contaminated soil remediation. Nitrogen and phosphorus were homogeneously and periodically sprayed into a historically contaminated soil using a modified horticultural drip irrigation device. Various petroleum hydrocarbon fraction contents were then determined by gravimetry and gas chromatography (GC), and changes in the soil microbial community were analyzed by high throughput sequencing. After 90 days of remediation, the removal efficiencies of total petroleum hydrocarbon (TPH), saturates, aromatics, C7-C30 n-alkanes, and 16 PAHs were respectively enhanced by 21.5%, 25.5%, 12.4%, 10.4%, and 19.6% compared with the use of a single nutrient amendment application. The high throughput sequencing result showed that obvious changes had occurred in the soil microbial community compositions during drip fertigation; however, fungi were more sensitive to drip fertigation than bacteria. The resulting predominant bacterial and fungal genera were Dietzia, Nocardioides, Mycobacterium, Sphaerobacter, Leifsonia, and Aspergillus, Scolecobasidium, and Fusarium, respectively. Remediating polluted soils by regular fertigation ensures the automatic addition of even amounts of nutrients, which achieves high refractory hydrocarbon removal efficiencies. It is expected that this method can be applied in the in-situ remediation of petroleum-contaminated soil on a large scale.

Effect of bioaugmentation and biostimulation on hydrocarbon degradation and microbial community composition in petroleum-contaminated loessal soil.

This study assessed the benefits of biostimulation with nitrogen and phosphorous (BS) versus bioaugmentation with native petroleum degrading flora (BA) in terms of petroleum hydrocarbon removal and microbial community structure shift in petroleum-polluted loessal soil. After 12 weeks of remediation, the TPH degradation efficiencies were 28.3% and 13.9% in BS and BA treated soils, respectively. Biostimulation was more effective than bioaugmentation for petroleum hydrocarbon degradation. Soil microbial community composition changed while microbial diversity decreased greatly by bioaugmentation treatment. The inoculum could survive, grow up quickly and become the predominant microorganisms after one week of inoculation. In the biostimulation treatment, microbial community composition is more evenness and richness than in the bioaugmented remediation. The strong positive correlations of the nitrogen and phosphorus with the petroleum hydrocarbon suggest the importance of nutrients for petroleum biodegradation in the contaminated loessal soil. The results indicate that the stabilization and variety of the microbial community structure are essential for the petroleum biodegradation performance. Further engineering is suggested to improve the evenness and richness of the soil microbial community since an abundance of nitrogen and phosphorus nutrients ensures the degraders' activity in the petroleum polluted soil.

Botanicals as modulators of depression and mechanisms involved.

Depression is the most disastrous mood disorder affecting the health of individuals. Conventional treatments with chemical compounds for depression have limitations, while herbal medicine has unique therapeutic effects. This paper introduces the pharmacological basis and biological mechanisms underlying the botanical antidepressants over the past 5 years. Based upon the specific therapeutic targets or mechanisms, we analyzed the pathological roles of monoamine neurotransmitters, the hypothalamic-pituitary-adrenal axis, inflammation, oxidative stress, synaptic plasticity performed in antidepressant of the botanicals. In addition, gut flora and neurogenesis were also preferentially discussed as treatment approaches. Based on the complex pathogenesis of depression, we suggested that mixed use of botanicals, namely prescription would be more suitable for treatment of depression. In addition, neural circuit affected by botanicals or active components should also attract attention as the botanicals have potential to be developed into fast-acting antidepressants. Finally, gut flora might be a new systemic target for the treatment of depression by botanicals. This review would strength botanical medicine as the antidepressant and also provides an overview of the potential mechanisms involved.

[Microbial Community Structure Shift During Bioremediation of Petroleum Contaminated Soil Using High Throughput Sequencing].

The shift in microbial community structure during the bioremediation of oil-polluted soil was analyzed by high-throughput sequencing. The results demonstrated obvious changes in the soil microbial community structure and diversity during bioremediation. The species richness and evenness of the microbial community decreased substantially due to the bioaugmentation treatment. Proteobacteria became the predominant phylum, with a relative increase in abundance from 37.44% to 87.44%. Pseudomonas was the most dominant genus, which increased in abundance from 2.99% to 76.37%. In the biostimulation treated soil, the relative abundance of Proteobacteria decreased from 37.44% to 10.90%, while the phylum Firmicutes increased from 9.16% to 35.32%. At the genus level, the relative abundances of Exiguobacterium and Promicromonospora decreased from 8.49% and 18.96% to 2.19% and 14.97%, respectively. Nocardioides and Bacillus became the dominant genera and increased from 5.56% and 0.29% to 28.95% and 22.70%, respectively. The results indicated that bioaugmentation substantially influenced the soil microbial diversity and community structure. Additionally, the biostimulation treatment maintained the balance in the soil microbial community structure. The stabilization of bacteria community structure is beneficial to petroleum biodegradation in the soil.

Bacterial community shift and hydrocarbon transformation during bioremediation of short-term petroleum-contaminated soil.

A laboratory study was conducted to evaluate the impact of bioaugmentation plus biostimulation (BR, added both nutrients and bacterial consortia), and natural attenuation (NA) on hydrocarbon degradation efficiency and microflora characterization during remediation of a freshly contaminated soil. After 112 days of remediation, the initial level of total petroleum hydrocarbon (TPH) (61,000 mg/kg soil) was reduced by 4.5% and 5.0% in the NA and BR treatments, respectively. Bioremediation did not significantly enhance TPH biodegradation compared to natural attenuation. The degradation of the aliphatic fraction was the most active with the degradation rate of 30.3 and 28.7 mg/kg/day by the NA and BR treatments, respectively. Soil microbial activities and counts in soil were generally greater for bioremediation than for natural attenuation. MiSeq sequencing indicated that the diversity and structure of microbial communities were affected greatly by bioremediation. In response to bioremediation treatment, Promicromonospora, Pseudomonas, Microcella, Mycobacterium, Alkanibacter, and Altererythrobacter became dominant genera in the soil. The result indicated that combining bioaugmentation with biostimulation did not improve TPH degradation, but soil microbial activities and structure of microbial communities are sensitive to bioremediation in short-term and heavily oil-contaminated soil.

[Impacts of Bioremediation on Microbial Communities and Different Forms of Nitrogen in Petroleum Contaminated Soil].

A laboratory study was conducted to investigate the impacts of bioremediation on microbial communities and various nitrogen shifts in petroleum contaminated soil by using GC-MS and Illumia MiSeq technique. Results showed the concentrations of alkane reduced from 25987.8 mg·kg-1 to 12788.6 mg·kg-1, and the concentrations of polycyclic aromatic hydrocarbons (PAHs) decreased from 5322.9 mg·kg-1 to 2917.2 mg·kg-1. Illumia MiSeq results showed that soil microbial communities shifted significantly after remediation, and the relative abundance of some phylum of hydrocarbon degraders (Firmicutes, Bacterodetes), and some genus of degraders (Dietzia, Acinetobacter) increased. Besides, the contents of total nitrogen and ammonia nitrogen increased firstly and then decreased during remediation. However, the contents of nitrate nitrogen decreased at the early stage, and then kept stable in the later stage of remediation. It can be concluded that bioremediation effectively promoted petroleum hydrocarbon degradation, and the different fractional hydrocarbon degradation was related to the relative abundance of hydrocarbon degraders and available nitrogen contents.

[Remediation of Petroleum-Contaminated Soil Using a Bioaugmented Compost Technique].

Bioaugmented compost was created by inoculating petroleum-degrading bacteria into mature compost. The petroleum hydrocarbon degradation efficiencies were investigated by applying this enhanced compost to petroleum-contaminated soil under low temperatures. The results showed that the degrading bacteria can be enriched in the mature compost. After 30 d of remediation, the removal efficiency of TPH, alkanes, and PAHs in the soil was 27.0%, 19.6%, and 10.0%, compared to natural attenuation (CK), which was 4.5%, 9.5%, and 2.3%, respectively. In response to remediation, the relative abundance of Proteobacteria and Actinobacteria phyla decreased from 53.4% and 25.9% to 48.9% and 14.1%, respectively, and Bacteroidetes phylum increased from 5.0% to 24.5%. At the genus level, the relative abundance of Acinetobacter and Pseudomonas increased from 0.02% and 3.4% to 15.2% and 4.6%, respectively. The results indicated that the bioaugmented compost may efficiently facilitate and speed up the bioremediation of petroleum-contaminated soil under low-temperature conditions. Soil microbial diversity and structure of microbial communities are sensitive to the remediation.

Bioremediation of hydrocarbon degradation in a petroleum-contaminated soil and microbial population and activity determination.

Bioremediation of hydrocarbon degradation in petroleum-polluted soil is carried out by various microorganisms. However, little information is available for the relationships between hydrocarbon degradation rates in petroleum-contaminated soil and microbial population and activity in laboratory assay. In a microcosm study, degradation rate and efficiency of total petroleum hydrocarbons (TPH), alkanes, and polycyclic aromatic hydrocarbons (PAH) in a petroleum-contaminated soil were determined using an infrared photometer oil content analyzer and a gas chromatography mass spectrometry (GC-MS). Also, the populations of TPH, alkane, and PAH degraders were enumerated by a modified most probable number (MPN) procedure, and the hydrocarbon degrading activities of these degraders were determined by the Biolog (MT2) MicroPlates assay. Results showed linear correlations between the TPH and alkane degradation rates and the population and activity increases of TPH and alkane degraders, but no correlation was observed between the PAH degradation rates and the PAH population and activity increases. Petroleum hydrocarbon degrading microbial population measured by MPN was significantly correlated with metabolic activity in the Biolog assay. The results suggest that the MPN procedure and the Biolog assay are efficient methods for assessing the rates of TPH and alkane, but not PAH, bioremediation in oil-contaminated soil in laboratory.

[Effects and Biological Response on Bioremediation of Petroleum Contaminated Soil].

Bioaugmentation and biostimulation were used to remediate petroleum-contaminated soil which were collected from Zichang city in North of Shaanxi. The optimal bioremediation method was obtained by determining the total petroleum hydrocarbon(TPH) using the infrared spectroscopy. During the bioremediation, number of degrading strains, TPH catabolic genes, and soil microbial community diversity were determined by Most Probable Number (MPN), polymerase chain reaction (PCR) combined agarose electrophoresis, and PCR-denaturing gradient electrophoresis (DGGE). The results in different treatments showed different biodegradation effects towards total petroleum hydrocarbon (TPH). Biostimulation by adding N and P to soils achieved the best degradation effects towards TPH, and the bioaugmentation was achieved by inoculating strain SZ-1 to soils. Further analysis indicated the positive correlation between catabolic genes and TPH removal efficiency. During the bioremediation, the number of TPH and alkanes degrading strains was higher than the number of aromatic degrading strains. The results of PCR-DGGE showed microbial inoculums could enhance microbial community functional diversity. These results contribute to understand the ecologically microbial effects during the bioremediation of petroleum-polluted soil.