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1.
As one of the most widely distributed bacterial predators in the soil, the role of bacterivorous nematodes on the enhanced bioremediation of polycyclic aromatic hydrocarbon-contaminated soils is crucial, but remains to be investigated.A microcosm-level study was conducted to examine the effects of bacterial-feeding nematode grazing and tea saponin(TS) addition on bioremediation of a pyrene-contaminated soil enhanced by the polycyclic aromatic hydrocarbon(PAH)-degrading bacterial strain Sphingobium sp.PHE9.After 180 d of incubation, the highest pyrene dissipation(71.3%) was achieved through a combination of Sphingobium sp.PHE9 inoculation with nematode and TS addition.Meanwhile, high counts of culturable PAH-degrading bacteria, soil enzyme activity, and biodiversity indices were observed under the combined treatment, implying that the microbiological function of the contaminated soil was significantly restored.Additionally, the results of Tenax~ extraction with the first-order three-compartment model indicated that rate-limiting factors varied among treatments.The lack of degrading microorganisms was the main rate-limiting factor for the treatments involving TS/nematode addition, and inadequate bioaccessible pyrene was the vital rate-limiting factor in the treatments involving Sphingobium sp.PHE9 inoculation.The proposed combined clean-up strategy proved to be a promising bioremediation technology for aged pyrene-contaminated soils.  相似文献   

2.
Di-（2-ethylhexyl） phthalate（DEHP） is a high-molecular-weight phthalate ester（PAE） that has been widely used in the manufacture of polyvinylchloride and contributes to environmental pollution.The objectives of the present study were to isolate a DEHP degrader that can utilize DEHP as a carbon source and to investigate its capacity to biodegrade DEHP in both liquid culture and soil.A bacterial strain WJ4 was isolated from an intensively managed vegetable soil,which was contaminated with PAEs.The strain WJ4 was affiliated to the genus Rhodococcus and was able to remove DEHP from soil effectively.A period of only 7 d was required to degrade about 96.4%of DEHP(200 mg L-1) in the liquid culture,and more than 55%of DEHP(1.0 g kg-1) in the artificially contaminated soil was removed within 21 d.Furthermore,Rhodococcus sp.strain WJ4 had a strong ability to degrade DEHP without additional nutrients in liquid minimal medium culture and DEHP-contaminated soil and to degrade the homologue of DEHP in both liquid culture and soil.Strain WJ4 represents a novel tool for removing PAEs from contaminated soils and it may have great potential for application in the remediation of environmental pollution by PAEs.  相似文献   

3.
Bioaugmentation is an efficient and eco-friendly strategy for the bioremediation of polycyclic aromatic hydrocarbons (PAHs). Since the degrading abilities of soils can greatly alter the abilities of PAH-degrading bacteria, illustrating the potential and mechanism of highly efficient degrading bacteria in different soil environments is of great importance for bioremediation. A PAH-degrading bacterium, Paracoccus aminovorans HPD-2, and two soil types, red and paddy soils, with distinct PAH-degrading abilities, were selected for this study. A soil microcosm experiment was performed by adding pyrene (PYR) and benzo[a]pyrene (B[a]P). Illumina sequencing was used to examine bacterial community structure. The results showed that inoculation with HPD-2 significantly elevated PYR and B[a]P degradation rates by 44.7% and 30.7%, respectively, in the red soil, while it only improved the degradation rates by 1.9% and 11%, respectively, in the paddy soil. To investigate the underlying mechanism, the fate of strain HPD-2 and the response of the indigenous bacterial communities were determined. Strain HPD-2 occupied certain niches in both soils, and the addition of the bacterium changed the native community structure more noticeably in the red soil than in the paddy soil. The addition of PAHs and strain HPD-2 significantly changed the abundances of 7 phyla among the 15 detected phyla in the red soil. In the paddy soil, 5 of the 12 dominant phyla were significantly affected by PAHs and the inoculation of HPD-2, while 6 new phyla were detected in the low-abundance phyla (< 0.1%). The abundances of Massilia, Burkholderia, and Rhodococcus genera with PAH degradation efficiency were significantly increased by the inoculation of HPD-2 in the red soil during 42 d of incubation. Meanwhile, in the paddy soil, the most dominant effective genus, Massilia, was reduced by HPD-2 inoculation. This research revealed the remediation ability and inherent mechanism of the highly effective PAH-degrading strain HPD-2 in two different soil types, which would provide a theoretical basis for the application of degrading bacteria in different soils.  相似文献   

4.
石油烃类污染物降解动力学和微生物群落多样性分析   总被引：3，自引：0，他引：3  
为了探讨不同初始浓度石油污染土壤堆腐化修复机制,以石油降解菌剂和腐熟鸡粪为调理剂,研究了初始浓度分别为5 000(T1)、10 000(T2)和50 000 mg/kg(T3)的石油污染土壤堆腐化修复过程石油烃类污染物降解动力学特征和微生物群落多样性。结果表明:堆腐化修复过程石油烃类污染物降解符合一级反应动力学,反应常数分别为0.012、0.094和0.050 d-1,半衰期分别为6.79、7.37和13.86 d。整个堆腐过程石油烃类污染物平均降解速率分别为112.08、230.05和887.93 mg/(kg·d)。3个处理的孔平均颜色变化率(average well color development)和碳源利用率(除芳香烃类化合物外)随堆腐进程的推进逐渐升高,在堆腐中、后期达到最大,T3处理显著高于T1、T2处理。多聚物类和糖类代谢群是堆腐体系中的优势菌群。主成分分析表明3个处理的微生物群落差异显著(除第9天外),起分异作用的碳源主要是糖类和羧酸类。微生物群落的丰富度指数和均一度指数随堆腐进程的推进逐渐升高并在堆腐后期达到最大,与T1处理相比,T3处理分别高了0.21%和17.64%,差异达到显著水平(P0.05)。微生物群落优势度指数在中期达到最大,T1处理分别比T2、T3处理高2.12%和9.44%,3个处理间差异不显著(P0.05)。堆肥结束时3个处理的种子发芽指数(seed germination index,SGI)分别比堆腐初期提高了18.26%、20.42%和36.41%。该研究结果为黄土高原不同程度石油污染土壤堆腐化修复的应用提供参考依据和理论基础。  相似文献   

5.
A set of 21 Antarctic marine bacteria isolated from the Ross Sea and able to utilise diesel fuel as the sole carbon and energy source was characterised. Isolates were analysed by amplified 16S rDNA restriction analysis using the enzyme AluI, resulting in two different groups corresponding to different bacterial species. These species were assigned to the genera Rhodococcus and Alcaligenes, on the basis of 16S rDNA sequencing. This low degree of inter-specific biodiversity was parallel to a low intra-specific biodiversity, as shown by Random Amplified Polymorphic DNA analysis. Then, a 550-bp DNA fragment coding for the inner region of alkane mono-oxygenase was PCR-amplified from the genome of each strain. The phylogenetic analysis of the sequence of the putative AlkB protein coded for by the amplified DNA fragment revealed that these alkB genes were very likely inherited by horizontal gene transfer. Lastly, the analysis of the biodegradation ability of four strains revealed two different strategies of hydrocarbon uptake, mediated either by bio-surfactants and peculiar of Rhodococcus isolates, or by membrane modifications and shown by Alcaligenes isolates. In order to understand the interrelationships between hydrocarbon-degrading isolates, the dynamics of two strains, belonging to Rhodococcus and Alcaligenes, grown together in a co-culture was also followed over a seventeen days period.  相似文献   

6.
Purpose

Bioremediation using microorganisms is a promising strategy to remediate soil with petroleum hydrocarbons. Streptomyces sp. Hlh1, an endophytic strain, has previously demonstrated the ability to degrade crude petroleum in liquid culture. To apply this strain at field scale, it is necessary to test its ability to colonize the soil, compete with native microbiota, and remove the petroleum hydrocarbons under unfavorable conditions. Herein, a study was conducted to evaluate the performance of Streptomyces sp. Hlh1 to remove crude petroleum from contaminated sterilized and non-sterilized soils.

Materials and methods

Soils samples, contaminated with 2%, 5%, and 10% of petroleum, were inoculated with Streptomyces sp. Hlh1, and incubated at 30 °C for 4 weeks. At the end of bioremediation assays, the pollutant concentrations were determined by Gas chromatography flame ionization detector and the degradation rates were also calculated. The survival of the strain in the soil was estimated and the toxicity of metabolites was evaluated on Lactuca sativa.

Results and discussion

Streptomyces sp. Hlh1 was able to grow and remove total petroleum hydrocarbons (TPH), n-alkanes, and aromatic hydrocarbons found in soil samples. In sterilized soil samples, Streptomyces sp. Hlh1 removed up to 40% of TPH at an initial concentration of 10%. Whereas, the maximum TPH removal reached was 55% in non-sterilized soil at an initial concentration of 2%. In addition, it was observed that the degradation of aromatic hydrocarbons was more active than n-alkanes. The strain grew well and produced high biomass in contaminated soil. Lettuce seedling was found to be the adequate bioindicator to assess the toxicity of petroleum end products. Streptomyces sp. Hlh1 performed a successful bioremediation, which was confirmed through the phytotoxicity test.

Conclusions

The study shows the first insight of the contribution of free endophytic actinobacterial strain in the bioremediation of petroleum-contaminated soil; therefore, it suggests that Streptomyces sp. Hl1 can be usefully exploited at field scale.

  相似文献   

7.
A chlorothalonil(CTN)-degrading bacterial strain H4 was isolated in this study from a contaminated soil by continuous enrichment culture to identify its characteristics and to investigate its potential for remediation of CTN in contaminated soil. Based on the morphological, physiological and biochemical tests and 16 S r DNA sequence analysis, the strain was identified as Stenotrophomonas sp. After liquid culture for 7 d, 82.2% of CTN was removed by strain H4. The isolate could degrade CTN over a broad range of temperatures and p H values, and the optimum conditions for H4 degradation were p H 7.0 and 30℃. Reintroduction of the bacteria into artificially contaminated soil resulted in substantial removal of CTN( 50%) after incubation for 14 d. Soil samples treated by H4 showed significant increases(P 0.05) in soil dehydrogenase activity, soil polyphenol oxidase activity, average well-color development obtained by the Biolog Eco plate TM assay and Shannon-Weaver index, compared with the control. Strain H4 might be a promising candidate for application in the bioremediation of CTN-contaminated soils.  相似文献   

8.
Background  River sediments are natural habitats of complex bacterial and fungal communities and therefore play a decisive role in the mineralization process of organic matter in freshwater systems. By means of comparative temporal and spatial analyses of microbial communities, the in situ impact of anthropogenically generated pollutants on these biofilm associations can be assessed and discriminated from seasonal variations. Aim  The aim was the adaptation of hybridization with fluorescently labelled rRNA-targeted oligonucleotides (FISH) for the in situ characterization of the structural and functional diversity of native microbial communities in complex lotic sediments. The impact of qualitatively and quantitatively different water pollutants on the microbial diversity, metabolic potential, and relative abundance of characteristic bacterial groups was assessed by oligonucleotide probes on different phylogenetic levels. In particular, sulfate reducing bacteria (SRB) were investigated to evaluate their potential applicability as microbial biomonitors in sediments. Methods  Sediment samples from the German lowland rivers Elbe and Oder were investigated over 12 months with regard to physico-chemical parameters and the composition of the attached microbial communities. Mechanical treatment including ultrasonification and sagitation under aerobic conditions combined with the use of pyrophosphate ensured the equal dispersion of fixed microbial cells within the sediment samples. The optimized whole-sediment FISH-technique was combined with an improved cell extraction procedure and applied, due to the specific grain size fraction distribution, at the different sampling sites. Resultsand discussion  Up to 85.6% of the total bacterial cell counts as determined by DAPI (4’, 6-diamidino-2-phenylindole) staining could be successfully monitored by the eubacterial oligonucleotide probe set EUB338, EUB338-II and EUB338-III, simultaneously indicating a high proportion of Eubacteria and the high metabolic potential of the bacterial community. Desulfobacteriaceae could be detected by the specific probe SRB385Db in various relative percentages ranging from 2.4 to 16.0% of the total bacterial cell counts. The total number of bacteria and the metabolic potential of sediment related bacteria were barely affected by the different pollution pattern of the sampling sites. Conclusions  The pre-treatment step as conducted by cell extraction as well as the FISH hybridization procedure was successfully optimized to the specific conditions present within freshwater sediments. Beside seasonal variations, particularly occurring at hydrologically influenced sites, sampling sites with different pol lution levels could be successfully distinguished by the relative abundance of Desulfobacteriaceae used as microbial indicator organisms. Outlook  The integration of ongoing insights into pollution induced changes of natural bacterial consortia should result in a system of ecotoxicological classes representing the different ecological status of riverine systems. Physiological directed methods like Community Level Physiological Profiling (CLPP) or Pollution Induced Community Tolerance (PICT), and structural techniques as FISH or microarrays should be used to investigate the influence of harmful substances on the biodiversity in natural microbial sediment communities.  相似文献   

9.
During an initial screening in samples of bilge water, four bacterial strains capable to oil degrade have been isolated. Two strains, named isolates BW-1 and BW-2, were clustered with Acinetobacter genus (a similarity of 100% and 99%, respectively) and two strains, named isolates BW-3 and BW-4 were related to Rhodococcus genus (a similarity of 99% and 98%, respectively). During growth (8?days) in M9 medium with Arabian Light Crude Oil (1%, w/v), measures of microbial abundance, surface tension, emulsification index (E 24) and oil degradation, were carried out. During cultivation, isolates BW-1 and BW-2 are good biosurfactant producers and about 80% of crude oil is degraded. Also, isolates BW-3 and BW-4 show, during cultivation, production of biosurfactant but only 40% of total oil is degraded. Data obtained give important results in order to utilise these isolate native bilge waste microorganisms in the studies/process of bioremediation.  相似文献   

10.
微生物降解石油源多环芳香烃的研究进展   总被引：1，自引：0，他引：1  
申国兰  李利  陈莎 《土壤》2018,50(1):16-27
石油源多环芳香烃是存在于石油中的一类致畸、致癌污染物,具有以低环(2~3环)为主且取代基比例明显高于其他来源PAHs的组分特征。石油泄露引发的PAHs污染,其降解主要依赖于微生物的活动。本文对能够降解PAHs的微生物种类、降解机理、代谢途径及编码基因进行了概述。从PAHs作为碳源的角度将微生物降解机理划分为能以PAHs为唯一碳源进行生长的降解机理和共代谢机理。对与PAHs有关的好氧和厌氧微生物降解途径及对应的编码基因簇进行了总结。自然界中细菌、放线菌、真菌及藻类都能够降解PAHs,由加氧酶催化的苯环羟基化和还原酶介导的苯环脱芳烃化是好氧和厌氧降解途径的关键步骤,与降解有关的pca,cat,paa,nah,nah-like和bcr基因簇则分别调控好氧和厌氧降解过程。这些进展有助于系统了解石油源PAHs的降解过程、微生物作用机理和分子遗传机制,为进一步利用微生物促进环境生物修复提供理论依据。  相似文献   

11.
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12.
稠油降解菌的筛选及其对胶质和沥青质生物降解   总被引：7，自引：1，他引：7  
以稠油为唯一碳源,从辽河油田石油污染土壤、渣油中,经富集培养,分离筛选出细菌菌株11株、真菌23株和放线菌10株。将在含油培养基上长势良好的菌株进行室内摇瓶实验,发现真菌的降解效果好于细菌,F2006的降解效果最好,14d去除率达到39.8%。在胶质和沥青质污染土壤中,观察真菌F4、F2008、F9902、F2006、F2017、F6和F9904在14d、28d和42d对胶质和沥青质的去除率,测试结果表明,菌株F2006和F2008降解效果较好,在42d时去除率分别达到55.73%和57.62%。两次实验说明,菌株F2006为降解胶质和沥青质的优势菌株,在生物修复中具有较好的应用前景。  相似文献   

13.
A novel yeast named HQ-C-01 was isolated from activated sludge and identified as Pichia anomala based on the morphology and 18S rDNA sequence analysis. The HQ-C-01 strain degraded 95.2% of carbofuran when the insecticide was used as the only C source and added at 50 mg/L in a mineral salts medium within 48 h. The optimal concentration, temperature, and pH of medium for degradation of carbofuran were 50 mg/L, 30°C, and pH 7.5, respectively. Strain HQ-C-01 could also effectively degrade other carbamate insecticides including carbaryl, indoxacarb, and fenobucarb, and the degradation rates were 99%, 85%, and 67%, respectively. Gas chromatography–mass spectrometry analysis showed that the strain metabolized carbofuran to produce benzofuranol as the intermediate metabolite, which was further degraded. Degradation of carbofuran added at 50 mg/kg of soil was higher in yeast-inoculated soil than in the control. These results indicated that strain HQ-C-01 may potentially be used in bioremediation of carbofuran-contaminated soil.  相似文献   

14.
Polycyclic aromatic hydrocarbons (PAH) are ubiquitous pollutants that are toxic and recalcitrant to degradation by bacteria. This research evaluated the toxicity of different concentrations [10, 20, 40, 60, 80 and 100 μg mL−1] of phenanthrene (PHE) or benzo[a]pyrene (BaP) on the growth of Rhizobium tropici CIAT899 under in vitro conditions as well as the potential degradation of PHE and BaP by this bacterium. At 24 h, a 40% decrease in Rhizobium growth was observed when exposed to 40 μg mL−1 of either PHE or BaP. Furthermore, bacterial growth was completely inhibited by PHE or BaP applied in 80 and 100 μg mL−1. After 96 h, the growth of R. tropici at 40 μg PHE mL−1 or 60 μg BaP mL−1 was similar to those treatments without PAH. To evaluate R. tropici degrading capabilities, supernatants of cultures with 40 μg PHE mL−1 or 60 μg BaP mL−1 were analyzed by gas chromatography coupled to mass spectrophotometer (GC–MS). R. tropici was able to degrade either PHE or BaP diminishing its concentration in 20% and 25% during the first 24 h, degradation obtained at 120 h was 50% and 45% for PHE or BaP, respectively. This research shows for the first time that R. tropici CIAT 899 grows in liquid culture medium contaminated with PAH, and moreover is able to growth and to degrade either PHE or BaP.  相似文献   

15.
The effect of inoculation with Pseudomonas brassicacearum Am3, Pseudomonas marginalis Dp1 and Rhodococcus sp. Fp2 containing 1-aminocyclopropane-1-carboxylate deaminase (ACCD) on growth and uptake of N, P, K, Ca, S, Fe and Cd in shoots of pea (Pisum sativum) genotypes VIR188, VIR1658, VIR3429 and VIR4488 was studied in pot experiment with non-polluted and Cd-supplemented (10 mg Cd kg−1) sod-podzolic soil. The growth-promoting effect of bacteria depended on plant genotype and bacterial strain. Only Rhodococcus sp. Fp2 had no ACCD activity in vitro in the presence of Cd and did not stimulate pea growth in Cd-supplemented soil. Inoculation with bacteria counteracted the Cd-induced inhibition of nutrient uptake by plants probably through stimulation of root growth and enhancement of nutrient uptake processes. Nutritional effects of the bacteria were specific with respect to the nutrient.  相似文献   

16.
Previously isolated bacterial strains for chlorpyrifos and fenamiphos degradation were used to examine their potential as bioremedial agents in soils and water containing pesticide residues. Both, chlorpyrifos-degrading Enterobacter sp and fenamiphos-degrading consortium rapidly degraded pesticides when inoculated into natural and sterile water and soils. Degradation rate was slower in lower pH soils in comparison with natural and alkaline soils. Soil organic matter had no impact on pesticide degrading ability of isolates. Soil moisture <40% of maximum water-holding capacity slowed down degradation rate. The bacterial isolates were able to rapidly degrade fenamiphos and chlorpyrifos between 15 and 35 °C but their degradation ability was sharply reduced at 5 and 50 °C. Both groups of bacterial systems were also able to remove a range of pesticide degradation. An inoculum density of 104 cells g−1 of soil was required for initiating rapid growth and degradation. Ageing of pesticide in soils prior to inoculation produced contrasting results. Ageing of fenamiphos had no impact on subsequent degradation by the inoculated consortium. However, degradation of chlorpyrifos by Enterobacter sp after aging resulted in persistence of ∼10% of pesticide in soil matrix. Higher Koc value of chlorpyrifos may have resulted in a lack of bioavailability of a smaller percentage of chlorpyrifos to degrading bacteria. Overall, this paper confirms bioremedial potential of a fenamiphos degrading consortium and a chlorpyrifos degrading bacterium under different soil and water characteristics.  相似文献   

17.
The aim of the study is to analyze the biodegradation capacity of a biosurfactant exopolysaccharide (EPS2003) by heterotrophic marine bacterial strains. During the initial screening performed in two sites located at the harbor of Messina for analyzing the response of marine bacterial population with the presence of biosurfactant EPS2003, ten bacterial strains capable to degrade this substance were isolated. Between the bacterial strains isolated, two representative bacterial strains, isoDES-01, clustered with Pseudoalteromonas sp. A28 (100%), and isoDES-07, closely related to Vibrio proteolyticus (98.9%), were chosen for mineralization and respirometry test, performed to evaluate biodegradability potential of EPS2003. Assays of bacterial growth and measure of concentration of total RNA were also performed. More than 90% of EPS2003 was mineralized by the isoDE01 strain for biomass formation and respiration, while EPS2003 mineralization by the isoDE-07 strain was less effective, reaching 60%. This approach combines the study of the microbial community with its functional aspects (i.e., mineralization and respirometry test) allowing a more precise assessment of biosurfactant degradation. These results enhance our knowledge of microbial ecology of EPS-degrading bacteria and the mechanisms by which this biodegradation occurs. This will prove helpful for predicting the environmental fate of these compounds and for developing practical EPS2003 bioremediation strategies from future marine hydrocarbon pollution.  相似文献   

18.
Goal, Scope and Background  Temperature and soil moisture content are important environmental variables in bioremediation technologies. Optimizing these variables in-situ would enhance and maintain remediation of hazardous wastes during cold winter seasons or in cold regions and may lead to reduced maintenance and/or cost. The effect of elevated temperature and soil moisture on bioremediation efficiency was investigated using a laboratory mesocosm approach. Selected polycyclic aromatic hydrocarbons (PAHs) and phenols degradation in contaminated flooded soils, commonly found in Superfund sites situated in coastal plains sediments/soils, were evaluated in the mesocosms. Material and Methods  Four laboratory mesocosm treatments in triplicate simulating in-situ bioremediation of contaminated site soils using an immobilized microbe bioreactor system, i.e., bioplug, were established to evaluate temperature effects. Elevated temperature treatments of site soils with and without contaminant-specific microorganisms were established at a temperature of 42±2°C. Similarly, treatment of site soils with and without contaminant-specific microorganisms were established at an ambient temperature of 21±1°C. Composite samples were analyzed for selected PAHs and chlorinated phenols to determine rates of mineralization and overall remediation efficiency for different temperature regimes. Results  Mesocosm studies indicated that the high temperature inoculated treatment demonstrated a significant reduction in mean total PAHs and total phenols with a kinetic rate (KR) of 76±13 ng g−1 d−1 in 49 days (approximately 84% reduction; p<0.01) The KR for low temperature inoculated treatment was 54±1 ng g−1 d−1 in 49 days (approximately 66% reduction; p<0.01). High temperature non-inoculated mesocosms exhibited significant mineralization of all constituents with KR of 15±6 ng g−1 d−1 (approximately 65% reduction; p<0.01) in 49d compared to 54% reduction for low temperature non-inoculated treatment with KR of 12±3 ng g−1 d−1 (p=0.1794). Phenol compounds in inoculated treatments were also significantly reduced (65%, p<0.01) at elevated temperatures compared to ambient (52%, p<0.01). Discussion  Increased bioavailability and desorption were noted for elevated temperature and moisture in the soil laboratory mesocosms simulating a field in situ remediation protocol. This protocol employing the application of immobilized microflora indicated that in situ systems provide an economical advantage if optimal elevated temperature and moisture are controlled properly. Results also suggested that temperature and moisture optimization needs to be combined with efficient nutrients delivery systems for impacted soils/sediments. Conclusions  The study demonstrated that temperature and soil moisture contents are important factors in the success of in-situ bioremediation techniques at hazardous waste sites situated in a coastal zone. Kinetic rates were significantly enhanced to remediate known recalcitrant compounds (PAHs and phenols) in aged soil. Recommendations and Perspectives  The placement of a preferred microbial consortia such as an immobilized microbial population in an entrained bioreactor, i.e., bioplug, can significantly reduce constituents of concern in a timely manner for contaminated soils/sediments. However, frequent monitoring of the soil temperature, moisture content, nutrient level, and dissolved oxygen is necessary to achieve predictable kinetic rates of mineralization. ESS-Submission Editor: Dr. Teresa Cutright (tcutright@uakron.edu)  相似文献   

19.
The biodegradation of polycyclic aromatic hydrocarbons (PAHs) via free-living and attached micro-organisms in soil/water systems was observed in order to examine the variability in the community dynamics and physiological profiles of the micro-organisms. As determined by fluorescence in situ hybridization (FISH), the Domain Bacteria, consisting of three phyla α-, β- and γ-Proteobacteria, reached 41.27–56.05% of all organisms in the soil/water system for PAH biodegradation. Among the free-living species, Proteobacteria, including Brevundimonas (Pseudomonas) diminuta, Caulobacter spp., Mycoplana bullata, Acidovorax spp. and Pseudomonas aeruginosa were found to be dominant—making up 93.51–99.80% of the population—and therefore seem to be associated with PAH biodegradation. Total plate count numbers and the count of Pseudomonas sp. present in the free-living population increased to between 103 and 106 CFU ml−1 when clay with very low organic matter content was used as the matrix for PAH degradation. However, total plate count microbial numbers increased to only 101–102 CFU ml−1 using natural soil from Taichung containing 1.883% organic matter. The soil organic content (SOM) seemed to affect the mass transfer of PAH in soil, leading to the difference in PAH biodegradation. Two different approaches, which included community-level physiological profiling (CLPP) and ectoenzymatic activities, were used to explain the functional diversity between free-living and attached bacteria. The free-living and attached bacterial communities from the clay system showed proportionately greater differences using CLPP. Relatively high levels of esterases, aminopeptidases and some specific glycolysis-gluconeogenesis enzymes gave an identifiable correlation with PAH biodegradation. The differences in bacterial composition, numbers and physiological characteristics show that free-living and attached micro-organisms may play different biochemical roles in PAH degradation in soil.  相似文献   

20.
Horizontal transfer of catabolic genes for pollutant degradation among rhizobacteria plays an important role in environmental bioremediation, but lacks support from field trial data. To address this problem, Pseudomonas fluorescens strain TP13 was inoculated into the soils of a phenol‐contaminated farmland on which tomato seedlings were growing in April 2009, 2010, 2011 and 2012. Results consistently showed that introduction of TP13 strain significantly reduced phenol content and increased plant biomass after 20 days, compared with controls. Strain TP13 was able to colonize the plant rhizosphere and the number of rhizosphere bacteria which were grown on phenol and contained the plasmids containing the gene encoding for catechol 2, 3‐dioxygenase (C23O) increased gradually in the later stages of the experiment. The increase in magnitude of the plasmid‐containing rhizosphere bacteria correlated well with plant biomass, while the number of plasmid‐containing rhizosphere bacteria and phenol content was strongly negatively correlated. Furthermore, six strains (T1‐T6) of rhizosphere bacteria were isolated and found to possess large plasmids containing identical C23O genes and similar HindIII restriction patterns. Sequence alignment showed that the C23O genes from strains T1‐T6 contained almost identical sequences and the sequence of the C23O of strain T1 was the same as that of strain TP13. These data indicated that the plasmids were transferred from strain TP13 to these rhizosphere bacteria and that horizontal gene transfer stimulated phenol degradation and plant growth in the contaminated farmland. This is an important finding for in situ remediation of contaminated farmland.  相似文献   

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