The distributions of endophytic bacteria in Alopecurus aequalis Sobol and Oxalis corniculata L. grown in soils contaminated with different levels of polycyclic aromatic hydrocarbons (PAHs) were investigated with polymerase chain reaction followed by denaturing gradient gel electrophoresis technology (PCR-DGGE) and cultivation methods. Twelve types of PAHs, at concentrations varying from 0.16 to 180 mg·kg？1, were observed in the roots and shoots of the two plants. The total PAH concentrations in Alopecurus aequalis Sobol obtained from three different PAH-contaminated stations were 184, 197, and 304 mg·kg？1, and the total PAH concentrations in Oxalis corniculata L. were 251, 346, and 600 mg·kg？1, respectively. The PCR-DGGE results showed that the endophytic bacterial communities in the roots and shoots of the two plants were quite different, although most bacteria belonged to Firmicutes, Proteobacteria, Actinobacteria and Bacteroidetes. A total of 68 endophytic bacterial strains were isolated from different tissues of the two plants and classified into three phyla: Firmicutes, Proteobacteria and Bacteroidetes. In both plants, Bacillus spp. and Pseudomonas spp. were the dominant cultivable populations. With an increase in the PAH pollution level, the diversity and distribution of endophytic bacteria in the two plants changed correspondingly, and the number of cultivable endophytic bacterial strains decreased rapidly. Testing of the isolated endophytic bacteria for tolerance to each type of PAH showed that most isolates could grow well on Luria-Bertani media in the presence of different PAHs, and some isolates were able to grow rapidly on a mineral salt medium with a single PAH as the sole carbon and energy source, indicating that these strains may have the potential to degrade PAHs in plants. This research provides the first insight into the characteristics of endophytic bacterial populations under different PAH pollution levels and provides a species resource for the isolation of PAH-degrading endophytic bacteria.
References
[1]
Tao S, Cui YH, Xu FL, Li BG, Cao J, et al. (2004) Polycyclic aromatic hydrocarbons (PAHs) in agricultural soil and vegetables from Tianjin. Sci Total Environ 320(1): 11–24.
[2]
Franzaring J, Eerden LJM (2000) Accumulation of airborne persistent organic pollutants (POPs) in plants. Basic Appl Ecol 1(1): 25–30.
[3]
Mckone TE, Maddalena RL (2007) Plant uptake of organic pollutants from soil: Bioconcentration estimates based on models and experiments. Environ Toxicol Chem 26(12): 2494–2504.
[4]
Mortelmans K, Hawarth S, Lawlor T, Speck W, Tainer B, et al. (1986) Salmonella mutagenicity tests: II. Results from the testing of 270 chemicals. Environ Mutagen 8: 7–119.
[5]
Pahlman R, Pelkonen O (1987) Mutagenicity studies of different polycyclic aromatic hydrocarbons: the significance of enzymatic factors and molecular structures. Carcinogenesis 8(6): 773–778.
[6]
Collins C, Fryer M, Grosso A (2006) Plant uptake of non-ionic organic chemicals. Environ Sci Technol 40(1): 45–52.
[7]
Gao YZ, Cao XZ, Kang FX, Cheng ZX (2011) PAHs pass through the cell wall and partition into organelles of arbuscular mycorrhizal roots of ryegrass. J Environ Qual 40(2): 653–656.
[8]
Wang YX, Yamazoe A, Suzuki S, Liu CT, Aono T, et al. (2004) Isolation and characterization of dibenzofuran-degrading Comamonas sp. strains isolated from white clover roots. Curr Microbiol 49(4): 288–294.
[9]
Gao YZ, Shen Q, Ling WT, Ren LL (2008) Uptake of polycyclic aromatic hydrocarbons by Trifolium pretense L. from water in the presence of a nonionic surfactant. Chemosphere 72(4): 636–643.
[10]
Gao Y, Li H, Gong S (2012) Ascorbic acid enhances the accumulation of polycyclic aromatic hydrocarbons (PAHs) in roots of tall fescue (Festuca arundinacea Schreb.). PLoS One 7(11): e50467.
[11]
Pulford ID, Watson C (2003) Phytoremediation of heavy metal-contaminated land by trees-a review. Environ Int 29(4): 529–540.
[12]
Vi？as M, Sabaté J, José M, Solanas AM (2005) Bacterial community dynamics and polycyclic aromatic hydrocarbon degradation during bioremediation of heavily creosote-contaminated soil. Appl Environ Microbiol 71(11): 7008–7018.
[13]
Dai CC, Tian LS, Zhao YT, Chen Y, Xie H (2010) Degradation of phenanthrene by the endophytic fungus Ceratobasidum stevensii found in Bischofia polycarpa. Biodegradation 21(2): 245–255.
[14]
Sheng XF, Chen XB, He LY (2008) Characteristics of an endophytic pyrene- degrading bacterium of Enterobacter sp. 12J1 from Allium macrostemon Bunge. Int Biodeterior Biodegrad 62(2): 88–95.
[15]
Harish S, Kavino M, Kumar N, Saravanakumara D, Soorianathasundaramb K, et al. (2008) Biohardening with plant growth promoting rhizosphere and endophytic bacteria induces systemic resistance against banana bunchy top virus. Appl Soil Ecol 39 (2): 187–200.
[16]
Lodewyckx C, Vangronsveld J, Porteous F, Moorea Edward RB, Taghavi S, et al. (2002) Endophytic bacteria and their potential applications. Crit Rev in Plant Sci 21(6): 583–606.
[17]
Shin DS, Park MS, Jung S, Lee KH, Bae KS, et al. (2007) Plant growth-promoting potential of endophytic bacteria isolated from roots of coastal sand dune plants. J Microbiol Biotechnol 17 (8): 1361–1368.
Brooksd DS, Gonzalez CF, Appel DN, Filer TH (1994) Evaluation of endophytic bacteria as potential biological control agents for oak wilt. Biol Control 4(4): 373–381.
[20]
Rajkumar M, Ae N, Freitas H (2009) Endophytic bacteria and their potential to enhance heavy metal phytoextraction. Chemosphere 77(2): 153–160.
[21]
Khan Z, Doty S (2011) Endophyte-assisted phytoremediation. Curr Top Plant Biol 12: 97–105.
[22]
Germaine KJ, Liu XM, Cabellos GG, Hogan JP, Ryan D, et al. (2006) Bacterial endophyte-enhanced phytoremediation of the organochlorine herbicide 2,4- dichlorophenoxyacetic acid. FEMS Microbiol Ecol 57(2): 302–310.
[23]
Moore FP, Barac T, Borremans B, Oeyen L, Vangronsveld J, et al. (2006) Endophytic bacterial diversity in poplar trees growing on a BTEX-contaminated site: The characterisation of isolates with potential to enhance phytoremediation. Syst Appl Microbiol 29(7): 539–556.
[24]
Tang J, Wang R, Niu X, Zhou Q (2010) Enhancement of soil petroleum remediation by using a combination of ryegrass (Lolium perenne) and different microorganisms. Soil Till Res 110: 87–93.
[25]
Kaplan CW, Kitts CL (2004) Bacterial succession in a petroleum land treatment unit. Appl Environ Microbiol 70 (3): 1777–1786.
[26]
Nogales B, Moore ERB, Llobet-Brossa E, Rossello-Mora R, Amann R, et al. (2001) Combined use of 16S ribosomal DNA and 16S rRNA to study the bacterial community of polychlorinated biphenyl-polluted soil. Appl Environ Microbiol 67(4): 1874–1884.
[27]
Ho YN, Shih CH, Hsiao SC, Huang CC (2009) A novel endophytic bacterium, Achromobacter xylosoxidans, helps plants against pollutant stress and improves phytoremediation. J Biosci Bioeng 108: S75–S95.
[28]
Sobral JK, Arau？jo WL, Mendes R, Kleiner AAP, Jo？o LA (2005) Isolation and characterization of endophytic bacteria from soybean (Glycine max) grown in soil treated with glyphosate herbicide. Plant Soil 273(1–2): 91–99.
[29]
Ling WT, Gao YZ (2004) Promoted dissipation of phenanthrene and pyrene in soils by amaranth (Amaranthus tricolor L.). Environ Geol 46(5): 553–560.
[30]
Hung PQ, Annapurna K (2004) Isolation and characterization of endophytic bacteria in soybean (Glycine sp.). Omonrice 12: 92–101.
[31]
Byers HK, Stackebrandt E, Hayward C, Blackall LL (1998) Molecular investigation of a microbial mat associated with the great artesian basin. FEMS Microbiol Ecol 25(4): 391–403.
[32]
Altschul SF, Madden TL, Schaffer AA, Zhang J, Zhang Z, et al. (1997) Gapped BLAST and PSI-BLAST: A new generation of protein database search programs. Nucleic Acids Res 25(17): 3389–3402.
[33]
Yao ZL, Shi RJ, Zhang Y, Zhang ZZ, Xu H, et al.. (2008) Improved solid double-layer flat plate method for quick high-flux sifting motion of polycyclic aromatic hydrocarbon degradation bacterium. CN 101245366.
[34]
Gao YZ, Zhu LZ (2004) Plant uptake, accumulation and translocation of phenanthrene and pyrene in soils. Chemosphere 55(9): 1169–1178.
[35]
Briggs GG, Bromilow RH, Evans AA, Williams M (1983) Relationship between lipophilicity and the distribution of non-ionised chemicals in barley shoots following uptake by the roots. Pestic Sci 14(5): 492–500.
[36]
Editorial Committee of Flora of China (1987) Flora of China. Beijing: Science Press. 9 (3): 261p.
[37]
Editorial Committee of Flora of China (1999) Flora of China. Beijing: Science Press. 43(1): 11 p.
[38]
Chiou CT, Sheng GY, Manes M (2001) A partition-limited model for the plant uptake of organic contaminants from soil and water. Environ Sci Technol 35 (7): 1437–1444.
[39]
Zhu LZ, Gao YZ (2004) Prediction of phenanthrene uptake by plants with a partition-limited model. Environ Pollut 131(3): 505–508.
[40]
Juhasz AL, Naidu R (2000) Bioremediation of high molecular weight polycyclic aromatic hydrocarbons: a review of the microbial degradation of benzo[a]pyrene. Int Biodeter Biodegr 42(1–2): 57–88.
[41]
Hoang HL, Dominik DS, Baldwin IT (2008) Native bacterial endophytes promote host growth in a species-specific manner; phytohormone manipulations do not result in common growth responses. PLoS ONE 3(7): e2702 doi:10.1371.
[42]
Brecht V, Daan V, Hester S, Braam VW, Benny L, et al. (2011) Endophytic Bacteria in Toxic South African Plants: Identification, Phylogeny and Possible Involvement in Gousiekte. PLoS ONE 6: e19265 doi:10.1371/journal. Pone. 0019265.
[43]
Mendes R, Kleiner AAP, Araujo WL, Raaijmakers JM (2007) Diversity of cultivated endophytic bacteria from sugarcane: genetic and biochemical characterization of Burkholderia cepacia complex isolates. Appl Environ Microbiol 73(22): 7259–7267.
[44]
Vendan RT, Young JY, Sun HL, Young HR (2010) Diversity of endophytic bacteria in ginseng and their potential for plant growth promotion. J Microbiol 48(5): 559–565.
[45]
Chen WM, Tang YQ, Mori K, Wu XL (2012) Distribution of culturable endophytic bacteria in aquatic plants and their potential for bioremediation in polluted waters. Aquat Biol 15: 99–110.
[46]
West ER, Cother EJ, Steel CC, Ash GJ (2010) The characterization and diversity of bacterial endophytes of grapevine. Can J Microbiol. 56 (3): 209–16 doi:10.1139/w10-004.
[47]
Miliūt？ I, Buzait？ O (2011) IAA production and other plant growth promoting traits of endophytic bacteria from apple tree. Biologija 57(2): 98–102.
[48]
Garbeva P, Overbeek VL, Vuurde VJ, Elsas VJ (2001) Analysis of endophytic bacterial communities of potato by plating and denaturing gradient gel electrophoresis (DGGE) of 16S rDNA based PCR fragments. Microbial Eco 41: 369–383.
[49]
Araújo WL, Marcon J, Maccheroni W, Elsas JD, Vuurde JW, et al. (2002) Diversity of endophytic bacterial populations and their interaction with Xylella fastidiosa in citrus plants. Appl Environ Microbiol 68: 4906–4914.
[50]
Compant S, Clement C, Sessitsch A (2010) Plant growth-promoting bacteria in the rhizo-and endosphere of plants: Their role, colonization, mechanisms involved and prospects for utilization. Soil Biol Biochem 42(5): 669–678.
[51]
McCully ME (2001) Niches for bacterial endophytes in crop plants: a plant biologist's view Aust. Aust J Plant Physiol 28(9): 983–990.
[52]
Kapley A, Siddiqui S, Misra K, Ahmad SM, Purohit HJ (2007) Preliminary analysis of bacterial diversity associated with the Porites coral from the Arabian sea. World J Microb Biot 23: 923–930.
[53]
Qing W, Zhao X, Zhao SY (2006) Application of PCR-DGGE in research of bacterial diversity in drinking water. Biomed Environ Sci 19(5): 371–374.
[54]
Robson Andreazza SP, Bortolon L, Okeke BC, Bento FM, Camargo FAO (2010) 19th World Congress of Soil Science, Soil Solutions for a Changing World 1–6 August 2010, Brisbane, Australia. Published on DVD.
[55]
Chelius M, Triplett E (2001) The Diversity of Archaea and Bacteria in Association with the Roots of Zea mays L. Microbial Eco 41: 252–263.
[56]
Sun L, Qiu F, Zhang X, Dai X, Dong X, et al. (2008) Endophytic bacterial diversity in rice (Oryza sativa L.) roots estimated by 16S rDNA sequence analysis. Microbial Eco 55: 415–424.
[57]
Zak DR, Holmes WE, White DC, Peacock AD, Tilman D (2003) Plant diversity, soil microbial communities, and ecosystem function: are there any links? Ecology 84: 2042–2050.
[58]
Sessitsch A, Reiter B, Pfeifer U, Wilhelm E (2002) Cultivation-independent population analysis of bacterial endophytes in three potato varieties based on eubacterial and Actinomycetes-specific PCR of 16S rRNA genes. FEMS Microbiol Ecol 39(1): 23–32.
[59]
Phillips LA, Germida JJ, Farrell RE (2008) Hydrocarbon degradation potential and activity of endophytic bacteria associated with prairie plants. Soil Biol Biochem 40(12): 3054–3064.
[60]
Siciliano SD, Fortin N, Mihoc A, Wisse G, Labelle S, et al. (2001) Selection of specific endophytic bacterial genotypes by plants in response to soil contamination. Appl Environ Microbiol 67(6): 2469–2475.
[61]
Compant S, Duffy B, Nowak J, Clément C, Barka EA (2005) Use of plant growth-promoting bacteria for biocontrol of plant diseases: principles, mechanisms of action, and future prospects. Appl Environ Microbiol 71(9): 4951–4959.
[62]
Taghavi S, Barac T, Greenberg B, Borremans B, Vangronsveld J, et al. (2005) Horizontal gene transfer to endogenous endophytic bacteria from poplar improves phytoremediation of toluene. Appl Environ Microbiol 71 (12): 8500–8505.
[63]
Newman LA, Reynolds CM (2005) Bacteria and phytoremediation: new uses for endophytic bacteria in plants. Trends Biotechnol 23(1): 6–8.
