| With the development of industrialization and urbanization,the soil polluted by polycyclic aromatic hydrocarbons(PAHs)seriously destroys the ecological safety and human health.The remediation of PAHs-polluting soil becomes urgent.Bioremediation has the advantages of simple operation and environmental friendliness,with a great development prospect.Microbes as well as plants have the ability to degrade phenanthrene or naphthalene in soil,but bioremediation only using microbes has the shortages of low efficiency and strict environmental requirement,and the poor survival of microbes will affect the removal ability of PAHs as well;the phytoremediation that only use plants takes a long time and is limited by the growing season of plants.In recent years,a kind of plant-microbe bioremediation was proved to combine the advantages of both bioremediation methods.In a plant-microbial bioremediation system,the roots of plants can provide a huge specific surface area for survival of microbes and furthermore the organic acids secreted by plant roots can also provide nutrients for microbes,and on the other hand,the existence of microbes can degrade and convert a part of pollutants to reduce the harm of pollutants to plants.Therefore,establishing an efficient plant-microbial remediation system is favorable to increase the removal efficiency of PAHs in soil.In this study,several compound bacteria were acclimated from the PAHs-polluted soil and the activated sludge,and their community richness and diversity were evaluated using high-throughput Illumina Miseq.Then,several kinds of dominant pure degrading bacterium were isolated and characterized from communities.Finally,the PAHs removal efficiency from contaminated soil by a combination of corn(Zea mays)and bacteria,and a corn-microbial remediation system to remove PAHs in soil was preliminarily established.The main results are as follows:1.Four kinds of compound bacteria were obtained by acclimation,including a phenanthrene-degrading bacteria from the polluted soil(T1),a naphthalene-degrading bacteria from the polluted soil(T2),a phenanthrene-degrading bacteria from the activated sludge(W1)and a naphthalene-degrading bacteria from the activated sludge(W2).The community richness and diversity in these compound bacteria were evaluated through the high-throughput sequencing of V3-V4 region in 16S r DNA,and it was indicated that the order of species richness for different community was T1>W2>T2>W1 whereas that of species diversity was T1>W2>W1>T2.Dominant genus in phenanthrene-degrading bacteria from the polluted soil were Enterobacter(38.21%),Comamonas(32.78%)and Acinetobacter(20.49%),with Enterobacter(85.16%)and Acinetobacter(9.67%)in naphthalene-degrading bacteria from the polluted soil,Stenotrophomonas(90.58%)in phenanthrene-degrading bacteria from the activated sludge,and Acinetobacter(52.74%)and Enterobacter(40.11%)in naphthalene-degrading bacteria from the activated sludge.2.A total of 20 strains of phenanthrene-degrading bacteria were isolated from T1 and W1,and9 strains of naphthalene-degrading bacteria were from T2 and W2.Of those,EF3(Klebsiella oxytoca),Nei2(Comasonas pittii),F2-6(Arthrobacter oxydans)and N1-3(Pseudomonas putida),N2-2(Comasonas sp.)and ETN2(Acinetobacter sp.)were proved to have an ability of degrading phenanthrene or naphthalene for the first time.Cultured for 96 h in an inorganic salt medium supplemented with 100 mg·L-1 phenanthrene or naphthalene,the phenanthrene degradation ability of compound bacteria or isolated pure bacterium was W1(85.89%)>EF3(77.71%)>T1(52.63%)>F2-6(47.27%)>Nei(41.22%),and their ability to degrade naphthalene was W2(79.45%)>N1-3(64.61%)>T2(52.15%)>N2-2(48.60%)>ETN2(42.54%).3.In the pot experiments,the removal efficiency of phenanthrene or naphthalene from the polluted soil using the combination of corn and bacteria was significantly higher than that of only using bacteria or corn,and furthermore the removal efficiency using corn combined with compound bacteria was significantly higher than that of corn combined with pure bacterium as well.When experimented for 30 days in the soil with 100 mg·kg-1phenanthrene or naphthalene,the removal efficiency of phenanthrene by corn-bacteria remediation was corn-W1(75.13%)>corn-T1(69.55%)>corn-EF3(66.61%)>corn-F2-6(64.54%)>corn Nei2(58.40%)>corn(33.28%),and that of naphthalene was corn-W2(78.55%)>corn-T2(69.40%)>corn-N1-3(64.17%)>corn-N2-2(62.41%)>corn-ETN2(59.19%)>corn(34.55%).4.In the corn-bacterium remediation system,the existing of corn seedlings increased the number of degrading bacteria in the soil by 3-10 times,and on the other hand the addition of degrading bacteria reduced the toxicity of phenanthrene or naphthalene on corn seedlings and as a result significantly increased the corn biomass yield in most of corn-bacterium treatments.Bacteria also promoted the enrichment of phenanthrene and naphthalene in corn,resulting in that the phenanthrene or naphthalene concentration in aboveground parts(stem and leaf)and roots of corn was increased significantly. |
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