A high-efficiency phenanthrene-degrading Diaphorobacter sp. isolated from PAH-contaminated river sediment

Biodegradation of high molecular weight polycyclic aromatic hydrocarbons by Sarocladium terricola strain PYR-233 isolated from petrochemical contaminated sediment

Polycyclic aromatic hydrocarbons (PAHs) were frequently found in sediment and were primarily treated through microbial degradation. Thus, efficient management of PAH pollution requires exploring the molecular degradation mechanisms of PAHs and expanding the pool of available microbial resources. A fungus (identified as Sarocladium terricola strain RCEF778) with the remarkable ability to degrade pyrene was screened from sediment near a petrochemical plant, and its growth and pyrene degradation characteristics were comprehensively investigated. The results showed that the fungus exhibited great effectiveness in pyrene degradation, with a degradation ratio of 88.97% at 21 days at the conditions: 35 °C, pH 7, 10 mg L-1 initially pyrene concentration, 3% supplementary salt, and glucose supplementation. The generation and concentration variation of the intermediate products were identified, and the results revealed that the fungus degraded pyrene through two pathways: by salicylic acid and by phthalic acid. Three sediments (M1, M2, M3), each exhibiting different levels of PAH pollution, were employed to examine the effectiveness of fungal degradation of PAHs in practical sediment samples. These data showed that with the fungus, the degradation ratios ranged from 13.64% to 23.50% for 2-3 rings PAHs, 40.93%-49.41% for 4 rings PAHs, and 39.59%-48.07% for 5-6 rings PAHs, which were significantly higher than those for the sediment without the fungus and confirmed the excellent performance of the fungal. Moreover, the Gompertz model was employed to analyze the degradation kinetics of 4-rings and 5-6 rings PAHs in these sediments, and the results demonstrated that the addition of the fungus could significantly increase the maximum degradation ratio, degradation start-up rate and maximum degradation rate of 4-rings and 5-6 rings PAHs and shorten the time required to reach the maximum degradation rate. This study not only supplied fungal materials but also established crucial theoretical foundations for the development of bioremediation technologies aimed at high molecular weight PAH-contaminated sediments.

Enhanced degradation of phthalate esters (PAEs) by biochar-sodium alginate immobilised Rhodococcus sp. KLW-1

In this study, a new strain of bacteria, named Rhodococcus sp. KLW-1, was isolated from farmland soil contaminated by plastic mulch for more than 30 years. To improve the application performance of free bacteria and find more ways to use waste biochar, KLW-1 was immobilised on waste biochar by sodium alginate embedding method to prepare immobilised pellet. Response Surface Method (RSM) predicted that under optimal conditions (3% sodium alginate, 2% biochar and 4% CaCl2), di (2-ethylhexyl) phthalate (DEHP) degradation efficiency of 90.48% can be achieved. Under the adverse environmental conditions of pH 5 and 9, immobilisation increased the degradation efficiency of 100 mg/L DEHP by 16.42% and 11.48% respectively, and under the high-stress condition of 500 mg/L DEHP concentration, immobilisation increased the degradation efficiency from 71.52% to 91.56%, making the immobilised pellets have strong stability and impact load resistance to environmental stress. In addition, immobilisation also enhanced the degradation efficiency of several phthalate esters (PAEs) widely existing in the environment. After four cycles of utilisation, the immobilised particles maintained stable degradation efficiency for different PAEs. Therefore, immobilised pellets have great application potential for the remediation of the actual environment.

Degradation of pyrene by Xanthobacteraceae bacterium strain S3 isolated from the rhizosphere sediment of Vallisneria natans: active conditions, metabolite identification, and proposed pathways

Polycyclic aromatic hydrocarbons (PAHs) were typical environmental contaminants that accumulated continuously in sediment. Microbial degradation is the main way of PAH degradation in the natural environment. Therefore, expanding the available pool of microbial resources and investigating the molecular degrading mechanisms of PAHs are critical to the efficient control of PAH-polluted sites. Here, a strain (identified as Xanthobacteraceae bacterium) with the ability to degrade pyrene was screened from the rhizosphere sediment of Vallisneria natans. Response surface analysis showed that the strain could degrade pyrene at pH 5-7, NaCl addition 0-1.5%, and temperature 25-40 °C, and the maximum pyrene degradation (~ 95.4%) was obtained under the optimum conditions (pH 7.0, temperature 28.5 °C, and NaCl-free addition) after 72 h. Also, it was observed that the effect of temperature on the degradation ratio was the most significant. Furthermore, eighteen metabolites were identified by mass spectrometry, among which (2Z)-2-hydroxy-3-(4-oxo-4H-phenalen-3-yl) prop-2-enoic acid, 7-(carboxymethyl)-8-formyl-1-naphthyl acetic acid, phthalic acid, naphthalene-1,2-diol, and phenol were the main metabolites. And the degradation pathway of pyrene was proposed, suggesting that pyrene undergoes initial ortho-cleavage under the catalysis of metapyrocatechase to form (2Z)-2-hydroxy-3-(4-oxo-4H-phenalen-3-yl) prop-2-enoic acid. Subsequently, this intermediate was progressively oxidized and degraded to phthalic acid or phenol, which could enter the tricarboxylic acid cycle. Furthermore, the pyrene biodegradation by the strain followed the first-order kinetic model and the degradation rate changed from fast to slow, with the rate remaining mostly slow in the later stages. The slow biodegradation rate was probably caused by a significant amount of phenol accumulation in the initial stage of degradation, which resulted in a decrease in bacterial activity or death.

Isolation of Diaphorobacter sp. LW2 capable of degrading Phenanthrene and its migration mediated by Pythium ultimum

Phenanthrene, one of the polycyclic aromatic hydrocarbons, is stubborn and persistent and exists widely in petroleum-contaminated soil. Filamentous fungi are good assistants to bacterial transport, by hyphae passing through soil pores and reaching further positions. An isolated bacterial strain, from the contaminated soil of the coking plant, was identified as Diaphorobacter and named LW2, which could use phenanthrene as the only carbon source and energy for its growth. LW2 could degrade phenanthrene in a wide range of pH, temperature and initial concentration. When pH was 6 and 10, the removal rate of phenanthrene was 38.59% and 76.44%, respectively, and the removal rate of phenanthrene was 68.25% at 15 ℃. And LW2 could degrade 86.64% phenanthrene when the initial concentration was 100 mg L-1. The detection of DI-N-octyl phthalate, phthalic acid and p-hydroxybenzoic acid revealed that the strain LW2 metabolised phenanthrene through the phthalic acid pathway. Meanwhile, swimming and swarming test results suggested that LW2 was motile. The auxiliary effect of Pythium ultimum on LW2 migration was assessed. In the presence of Pythium ultimum, LW2 could migrate within the range of centimters by its mycelium, which was also observed by fluorescence microscopy. Meanwhile, the degradation ability of LW2 after the migration was also explored. The results proved that the migration process had no significant effect on its degradation ability, and LW2 still showed good phenanthrene metabolism ability. This study provides more possibilities for the bioremediation of phenanthrene-contaminated soil by screening the degradation bacteria and testing the effect of fungi on its migration.

Flexible catabolism of monoaromatic hydrocarbons by anaerobic microbiota adapting to oxygen exposure

Microbe-mediated anaerobic degradation is a practical method for remediation of the hazardous monoaromatic hydrocarbons (BTEX, including benzene, toluene, ethylbenzene and xylenes) under electron-deficient contaminated sites. However, how do the anaerobic functional microbes adapt to oxygen exposure and flexibly catabolize BTEX remain poorly understood. We investigated the switches of substrate spectrum and bacterial community upon oxygen perturbation in a nitrate-amended anaerobic toluene-degrading microbiota which was dominated by Aromatoleum species. DNA-stable isotope probing demonstrated that Aromatoleum species was involved in anaerobic mineralization of toluene. Metagenome-assembled genome of Aromatoleum species harbored both the nirBD-type genes for nitrate reduction to ammonium coupled with toluene oxidation and the additional meta-cleavage pathway for aerobic benzene catabolism. Once the anaerobic microbiota was fully exposed to oxygen and benzene, 1.05 ± 0.06% of Diaphorobacter species rapidly replaced Aromatoleum species and flourished to 96.72 ± 0.01%. Diaphorobacter sp. ZM was isolated, which was not only able to utilize benzene as the sole carbon source for aerobic growth and but also innovatively reduce nitrate to ammonium with citrate/lactate/glucose as the carbon source under anaerobic conditions. This study expands our understanding of the adaptive mechanism of microbiota for environmental redox disturbance and provides theoretical guidance for the bioremediation of BTEX-contaminated sites.

Cometabolic degradation of pyrene with phenanthrene as substrate: assisted by halophilic Pseudomonas stutzeri DJP1

At present, cometabolic degradation is an extensive method for the biological removal of high molecular weight polycyclic aromatic hydrocarbons (HMW-PAHs) in the marine environment. However, due to the refractory to degradation and high toxicity, there are few studies on pyrene (PYR) cometabolic degradation with phenanthrene (PHE) as substrate. In this study, a Pseudomonas stutzeri DJP1 strain isolated from sediments was used in the cometabolic system of PHE and PYR. The biomass and the activity of key enzymes such as dehydrogenase and catechol 12 dioxygenase of strain were improved, but the enhancement of biotoxicity resulted in the inhibition of cometabolism simultaneously. Seven metabolites were identified respectively in PYR, PHE degradation cultures. It was speculated that the cometabolism of PHE and PYR had a common phthalic acid pathway, and the degradation pathway of PHE was included in the downstream pathway of PYR. The functional genes such as PhdF, NidD and CatA involved in DJP1 degradation were revealed by Genome analysis. This study provides a reference for the biodegradation of PYR and PHE in real marine environment.

Effect of different size microplastic particles on the construction of algal-bacterial biofilms and microbial communities

Algal-bacterial symbiotic system is a biological purification system that combines sewage treatment with resource utilization and has the dual effects of carbon sequestration and pollution reduction. In this study, an immobilized algal-bacterial biofilm system was constructed for the treatment of natural sewage. Effects of exposure to microplastics (MPs) with different particle diameters (0.065 μm, 0.5 μm and 5 μm) were determined in terms of algal biomass recovery efficiency, the composition of extracellular polymeric substances (EPS) and morphologic characteristics. The impacts of MPs on the bacterial diversity and community structure of biofilms were also examined. The metagenomic analysis of key microorganisms and related metabolism pathways involved in system was further investigated. Results showed that following exposure to 5 μm MP, a maximum algal recovery efficiency of 80% was achieved, with a minimum PSII primary light energy conversion efficiency (Fv/Fm ratio) of 0.513. Furthermore, 5 μm MP caused the highest level of damage to the algal-bacterial biofilm, enhancing the secretion of protein-rich EPS. The biofilm morphology became rough and loose following exposure to 0.5 μm and 5 μm MP. Community diversity and richness were significantly high in biofilms exposed to 5 μm MP. Proteobacteria (15.3-24.1%), Firmicutes (5.0-7.8%) and Actinobacteria (4.2-4.9%) were dominant in all groups, with exposure to 5 μm MP resulting in the highest relative abundance for these species. The addition of MPs promoted the related metabolic functions while inhibited the degradation of harmful substances by algal-bacterial biofilms. The findings have environmental significance for the practical application of algal-bacterial biofilms for sewage treatment, providing novel insights into the potential effects of MPs on immobilized algal-bacterial biofilm systems.

Microbial Consortium HJ-SH with Very High Degradation Efficiency of Phenanthrene

Phenanthrene (PHE) is one of the model compounds of polycyclic aromatic hydrocarbons (PAHs). In this study, a natural PHE-degrading microbial consortium, named HJ-SH, with very high degradation efficiency was isolated from soil exposed to long-term PHE contamination. The results of GC analysis showed that the consortium HJ-SH degraded 98% of 100 mg/L PHE in 3 days and 93% of 1000 mg/L PHE in 5 days, an efficiency higher than that of any other natural consortia, and even most of the engineered strains and consortia reported so far. Seven dominating strains were isolated from the microbial consortium HJ-SH, named SH-1 to SH-7, which were identified according to morphological observation and 16S rDNA sequencing as Pseudomonas sp., Stenotrophomonas sp., Delftia sp., Pseudomonas sp., Brevundimonas sp., Curtobacterium sp., and Microbacterium sp., respectively. Among all the seven single strains, SH-4 showed the strongest PHE degradation ability, and had the biggest degradation contribution. However, it is very interesting that the microbial consortium can hold its high degradation ability only with the co-existence of all these seven single strains. Moreover, HJ-SH exhibited a very high tolerance for PHE, up to 4.5 g/L, and it can degrade some other typical organic pollutants such as biphenyl, anthracene, and n-hexadecane with the degradation ratios of 93%, 92% and 70%, respectively, under 100 mg/L initial concentration in 5 days. Then, we constructed an artificial consortium HJ-7 consisting of the seven single strains, SH-1 to SH-7. After comparing the degradation ratios, cell growth, and relative degradation rates, it was concluded that the artificial consortium HJ-7 with easier reproducibility, better application stability, and larger room for modification can largely replace the natural consortium HJ-SH. In conclusion, this research provided novel tools and new insights for the bioremediation of PHE and other typical organic pollutants using microbial consortia.

Microbial metabolism regulation on the efficient degradation of aromatic compounds for biochemical treatment process of coal chemical wastewater in pilot scale

At present, the common problems of biochemical treatment systems of coal chemical wastewater were the poor system stability and the difficulty in reaching COD discharge standards. Aromatic compounds were the main contributors to COD value. The effective removal of aromatic compounds was an urgent problem in the biochemical treatment systems of coal chemical wastewater. In this study, the dominant microbial strains that could degrade phenol, quinoline, and phenanthrene were isolated respectively and inoculated into the pilot scale biochemical tank of coal chemical wastewater. The regulation effect and mechanism of microbial metabolism on the efficient degradation of aromatic compounds were studied. The results indicated that the various aromatic compounds were significantly removed under the regulation of microbial metabolism, the removal efficiencies of COD, TOC, phenols, benzenes, N-CHs, and PAHs were increased by about 25%, 20%, 33%, 25%, 42%, and 45%, respectively, and their biotoxicity was also drastically reduced. Moreover, the abundance and diversity of microbial community, and the microbial activity were obviously improved, as well as the various functional strains were selectively enriched, suggesting that the regulation system could resist environmental stresses with high substrate concentration and toxicity, which could lead to more enhanced performance for aromatic compounds removal. In addition, the microbial EPS content was significantly increased, implying the formation of microbial hydrophobic cell surfaces, which could improve the bioavailability of aromatic compounds. Furthermore, the enzymatic activity analysis revealed that the relative abundance and activity of key enzymes were all obviously improved. In conclusion, multiple lines of evidence were provided to clarify the regulation mechanism of microbial metabolism on the efficient degradation of aromatic compounds for biochemical treatment process of coal chemical wastewater in pilot scale. The results laid a good foundation for realizing the harmless treatment of coal chemical wastewater.

Evaluation of aerobic biodegradation of phenanthrene using Pseudomonas turukhanskensis: an optimized study

The ability of Pseudomonas turukhanskensis GEEL-01 to degrade the phenanthrene (PHE) was optimized by response surface methodology (RSM). Three factors as independent variables (including temperature, pH, and inoculum) were studied at 600 mg/L PHE where the highest growth of P. turukhanskensis GEEL-01 was observed. The optimum operating conditions were evaluated through the fit summary analysis, model summary statistics, fit statistics, ANOVA analysis, and model graphs. The degradation of PHE was monitored by high-performance liquid chromatography (HPLC) and the metabolites were identified by gas chromatography-mass spectrometry (GC-MS). The results showed that the correlation among independent variables with experimental and predicted responses was significant (p < 0.0001). The optimal temperature, pH, and inoculum were 30 ℃, 8, and 6 mL respectively. The HPLC peaks exhibited a reduction in PHE concentration from 600 mg/L to 4.97 mg/L with 99% degradation efficiency. The GC-MS peaks indicated that the major end products of PHE degradation were 1-Hydroxy-2-naphthoic acid, salicylic acid, phthalic acid, and catechol. This study demonstrated that the optimized parameters by RSM for P. turukhanskensis GEEL-01 could degrade PHE by phthalic and salicylic acid pathways.

Denitrification for acidic wastewater treatment: Long-term performance, microbial communities, and nitrous oxide emissions

Acidic nitrogenous wastewater often requires alkali pretreatment before biological treatment, which results in increased system complexity and operating costs. The demonstration of denitrification under acidic conditions would provide a theoretical basis for the direct treatment of such wastewater. In this study, the denitrification performance, microbial community, and nitrous oxide (N₂O) emissions under acidic conditions were investigated using a sequencing batch reactor. When the influent pH decreased from 5.5 to 4.5, the sequencing batch reactor removed 99.8 ± 0.2% of the nitrate and 92.5 ± 1.6% (n = 171) of the chemical oxygen demand, and the production efficiency of N₂O increased significantly to 11.45%. This was 2.6-fold higher than that observed at pH 5.5. The long-term denitrification treatment of acidic wastewater (pH 4.5) led to the formation of granular sludge, and Thauera, Allorhizobium-Neorhizobium-Parararhizobium-Rhizobium, and Diaphorobacter became the dominant microbes with a collective abundance of 81.3%. More importantly, only 0.25% of the nitrate was denitrified as N₂O, and the batch test revealed that the emissions of N₂O decreased with the increase in sludge size. These results indicate that denitrifying granular sludge formed under acidic conditions and denitrifying bacteria capable of N₂O reduction proliferated, which both resulted in a significant reduction in the release of N₂O.

A novel Diaphorobacter sp. strain isolated from saponification wastewater shows highly efficient phenanthrene degradation

Polycyclic aromatic hydrocarbons (PAHs), such as phenanthrene, are a type of organic pollutants that exist widely in the environment. Of the currently known degradation methods, bioremediation is a desirable and feasible option. A novel Diaphorobacter sp. Strain MNS-0 was isolated from saponification wastewater and showed the ability to degrade phenanthrene, fluorene, acenaphthene, anthracene, benzo[a]anthracene, or chrysene using phenanthrene as the sole carbon source. Gas chromatography mass spectroscopy analysis of catabolic intermediates indicates that phenanthrene degradation occurs through the phthalic acid pathway in strain MNS-0. Genome sequencing shows that strain MNS-0 has two plasmids and one chromosome containing a presumptive phenanthrene degradation gene cluster. Strain MNS-0 was able to completely degrade 100 mg/L phenanthrene within 40 h and tolerate up to 10 g/L NaCl at pH 9.0, while maintaining phenanthrene degradation activity. We thus propose that strain MNS-0 is an effective degrader for bioremediation of PAHs pollution, even in relatively harsh alkali environments such as saponification wastewater.

Metagenomic Analysis of Microbial Alliances for Efficient Degradation of PHE: Microbial Community Structure and Reconstruction of Metabolic Network

Polycyclic aromatic hydrocarbons are a widespread organic pollutant worldwide. In this study, a highly efficient phenanthrene (PHE)-degrading microbial community was enriched from oil extraction soil, which could degrade 500 mg/L PHE within 4 days. Using 16S rRNA sequencing, the dominant bacteria in this community at the phylum level were found to be Proteobacteria, Actinobacteria, and Firmicutes. Metagenomic annotation of genes revealed the metabolic pathways and the contribution of different bacteria to the degradation process. Pseudomonadaceae contributed multiple functional genes in the degradation process. This study revealed the functional genes, metabolic pathways, and microbial interactions of the microbial community, which are expected to provide guidance for practical management.

Tolerance of phyllospheric Wickerhamomyces anomalus to BDE-3 and heavy metals

Few research have focused on the potential microorganism and gene resources for plant resistance to polybrominated diphenyl ether (PBDE) and heavy metal (HM) co-contamination. The purpose of this study was to investigate the impact of phyllospheric Wickerhamomyces anomalus bioremediation ability on PBDE and HM co-contamination. The results showed that the toleration capability of W. anomalus to cadmium (Cd²⁺) was higher than that to chromium (Cr) or 4-bromodiphenyl ether (BDE-3) contamination. The threshold levels of W. anomalus tolerance to BDE-3, Cd²⁺, and Cr were 30 mg/L, 500 mg/L, 30 mg/L, respectively. The use of the higher concentration of BDE-3 (30 mg/L) as a carbon source may improve tolerance to Cd²⁺ and Cr (10 mg/L Cd²⁺ and 10 mg/L Cr). Overexpression of Wapdr15 gene of ABCG subfamily from W. anomalus improved the tolerance to BDE-3 (10 mg/mL) and Cd²⁺ (0.5 mg/mL) significantly in transgenic tobacco lines. The synergism effect of BDE-3 and Cd²⁺ stress existed similarly in W. anomalus and transgenic lines. The findings suggest that W. anomalus should be taken into account for providing an efficient method in improving crops' tolerance during PBDE and HM co-contamination in soil.

Efficient biodegradation of phenanthrene using Pseudomonas stutzeri LSH-PAH1 with the addition of sophorolipids: Alleviation of biotoxicity and cometabolism studies

Phenanthrene (PHE) is widely distributed, and it can cause genotoxicity in humans by interacting with enzymes in the body. A current challenge for PHE bioremediation is the inhibitory effect of biotoxic intermediates on bacterial growth. Notably, the aerobic biotransformation processes for PHE in the presence of sophorolipids have been poorly studied. Here, a PHE-degrading strain was isolated from sediments and identified as Pseudomonas stutzeri and named LSH-PAH1. It was observed that 1-naphthol (a biotoxic substance that can inhibit strain growth) was produced during the PHE metabolism process of LSH-PAH1. The biodegradation ratio increased from 21.4% to 91.7% within 48 h after the addition of sophorolipids. Unexpectedly, this addition accelerated the metabolic process for 1-naphthol rather than causing its accumulation. The cometabolism of 1-naphthol and sophorolipids alleviated the biotoxic effects for the strain, which was verified by gene expression analysis. We identified a new PHE-degrading strain and provided a mechanism for PHE biodegradation using LSH-PAH1 with the addition of sophorolipids, which provides a reference for practical applications of the bioremediation of PHE and study of the cometabolism of biotoxic intermediates.

Temporal changes of microbial community structure and nitrogen cycling processes during the aerobic degradation of phenanthrene

Phenanthrene (PHE) is frequently detected in worldwide soils. But it is still not clear that how the microbial community succession happens and the nitrogen-cycling processes alter during PHE degradation. In this study, the temporal changes of soil microbial community composition and nitrogen-cycling processes during the biodegradation of PHE (12 μg g^-1) were explored. The results showed that the biodegradation of PHE followed the second-order kinetics with a half-life of 7 days. QPCR results demonstrated that the bacteria numbers increased by 67.1%-194.7% with PHE degradation, whereas, no significant change was observed in fungi numbers. Thus, high-throughput sequencing based on 16 S rRNA was conducted and showed that the abundances of Methylotenera, Comamonadaceae, and Nocardioides involved in PHE degradation and denitrification were significantly increased, while those of nitrogen-metabolism-related genera such as Nitrososphaeraceae, Nitrospira, Gemmatimonadacea were decreased in PHE-treated soil. Co-occurrence network analysis suggested that more complex interrelations were constructed, and Proteobacteria instead of Acidobacteriota formed intimate associations with other microbes in responding to PHE exposure. Additionally, the abundances of nifH and narG were significantly up-regulated in PHE-treated soil, while that of amoA especially AOAamoA was down-regulated. Finally, correlation analysis found several potential microbes (Methylotenera, Comamonadaceae, and Agromyces) that could couple PHE degradation and nitrogen transformation. This study confirmed that PHE could alter microbial community structure, change the native bacterial network, and disturb nitrogen-cycling processes.

Reducing Phenanthrene Contamination in Trifolium repens L. With Root-Associated Phenanthrene-Degrading Bacterium Diaphorobacter sp. Phe15

Some root-associated bacteria could degrade polycyclic aromatic hydrocarbons (PAHs) in contaminated soil; however, their dynamic distribution and performance on root surface and in inner plant tissues are still unclear. In this study, greenhouse container experiments were conducted by inoculating the phenanthrene-degrading bacterium Diaphorobacter sp. Phe15, which was isolated from root surfaces of healthy plants contaminated with PAHs, with the white clover (Trifolium repens L.) via root irrigation or seed soaking. The dynamic colonization, distribution, and performance of Phe15 in white clover were investigated. Strain Phe15 could efficiently degrade phenanthrene in shaking flasks and produce IAA and siderophore. After cultivation for 30, 40, and 50 days, it could colonize the root surface of white clover by forming aggregates and enter its inner tissues via root irrigation or seed soaking. The number of strain Phe15 colonized on the white clover root surfaces was the highest, reaching 6.03 Log CFU⋅g^–1 FW, followed by that in the roots and the least in the shoots. Colonization of Phe15 significantly reduced the contents of phenanthrene in white clover; the contents of phenanthrene in Phe15-inoculated plants roots and shoots were reduced by 29.92–43.16 and 41.36–51.29%, respectively, compared with the Phe15-free treatment. The Phe15 colonization also significantly enhanced the phenanthrene removal from rhizosphere soil. The colonization and performance of strain Phe15 in white clove inoculated via root inoculation were better than seed soaking. This study provides the technical support and the resource of strains for reducing the plant PAH pollution in PAH-contaminated areas.

Microbial degradation of multiple PAHs by a microbial consortium and its application on contaminated wastewater

Polycyclic aromatic hydrocarbons (PAHs) are widely distributed in the environment and pose a serious threat to human health. Due to their unfavorable biological effects and persistent properties, it is extremely urgent to effectively degrade PAHs that are present in the environment, especially in wastewater. In this study, we obtained an efficient bacterial consortium (PDMC), consisting of the genera Sphingobium (58.57-72.40%) and Pseudomonas (25.93-39.75%), which is able to efficiently utilize phenanthrene or dibenzothiophene as the sole carbon source. The phenanthrene-cultivated consortium could also degrade naphthalene, acenaphthene, fluorene, anthracene, fluoranthene, benzo[a]anthracene, dibenzofuran, carbazole and indole, respectively. Furthermore, we identified the multiple key intermediates of aforementioned 11 substrates and discussed proposed pathways involved. Notably, a novel intermediate 1,2-dihydroxy-4a,9a-dihydroanthracene-9,10-dione of anthracene degradation was detected, which is extremely rare compared to previous reports. The PDMC consortium removed 100% of PAHs within 5 days in the small-scale wastewater bioremediation added with PAHs mixture, with a sludge settling velocity of 5% after 10 days of incubation. Experiments on the stability reveal the PDMC consortium always has excellent degrading ability for totaling 24 days. Combined with the microbial diversity analysis, the results suggest the PDMC consortium is a promising candidate to facilitate the bioremediation of PAHs-contaminated environments.

Identification and Metabolism of Naturally Prevailing Microorganisms in Zinc and Copper Mineral Processing

It has only recently been discovered that naturally prevailing microorganisms have a notable role in flotation in addition to chemical process parameters and overall water quality. This study’s aim was to assess the prevailing microbial communities in relation to process chemistry in a zinc and copper mineral flotation plant. Due to the limitations of cultivation-based microbial methods that detect only a fraction of the total microbial diversity, DNA-based methods were utilised. However, it was discovered that the DNA extraction methods need to be improved for these environments with high mineral particle content. Microbial communities and metabolism were studied with quantitative PCR and amplicon sequencing of bacterial, archaeal and fungal marker genes and shotgun sequencing. Bacteria dominated the microbial communities, but in addition, both archaea and fungi were present. The predominant bacterial metabolism included versatile sulfur compound oxidation. Putative Thiovirga sp. dominated in the zinc plant and the water circuit samples, whereas Thiobacillus spp. dominated the copper plant. Halothiobacillus spp. were also an apparent part of the community in all samples. Nitrogen metabolism was more related to assimilatory than dissimilatory nitrate and nitrite oxidation/reduction reactions. Abundance of heavy metal resistance genes emphasized the adaptation and competitive edge of the core microbiome in these extreme conditions compared to microorganisms freshly entering the process.