Heavy metals have adverse effects on soil ecology. Given the toxicity of heavy metals, there is an urgent need to select an appropriate indicator that will aid in monitoring their biological effects on soil ecosystems. By combining different monitoring techniques for various aspects of microbiology, the effects of heavy metals on soil microorganisms near a smelter were studied. Our goal was to determine whether proteins could be a proper indicator for soil pollution. This study demonstrated that the activities of acid phosphatase and dehydrogenase, as well as the levels of microbial biomass carbon and proteins, were negatively affected by heavy metals. In addition, significantly negative correlations were observed between these microbial indicators and heavy metals. Denaturing gradient gel electrophoresis analysis was used in this study to demonstrate that heavy metals also have a significantly negative effect on soil microbial diversity and community structure. The soil protein expression was similar across different soils, but a large quantity of presumably low molecular weight protein was observed only in contaminated soil. Based on this research, we determined that the soil protein concentration was more sensitive to heavy metals than acid phosphatase, dehydrogenase, or microbial biomass carbon because it was more dramatically decreased in the contaminated soils. Therefore, we concluded that the soil protein level has great potential to be a sensitive indicator of soil contamination. Further research is essential, particularly to identify the low molecular weight protein that only appears in contaminated soil, so that further insight can be gained into the responses of microbes to heavy metals. 1. Introduction Heavy metals (e.g., Cd, Cr, Cu, Pb, and Zn) can be introduced into soils from several sources, such as waste from mines and smelters, atmospheric deposition, animal manures, sewage sludge, and, in some circumstances, inorganic fertilizer. Once these elements enter the soil, they can remain for extremely long periods and are difficult to remove [1]. Heavy metals are known to be toxic to most organisms when present in excessive concentrations [2]. Given the toxicity of these elements, there is an urgent need to monitor their biological effects on soil ecosystems. Soil microbes play vital roles in the recycling of plant nutrients, the maintenance of soil structure, and the detoxification of poisonous chemicals [3]. Therefore, the diversity of microbial communities and the activity of microorganisms are important indicators of soil quality.
References
[1]
P. C. Brookes, “The use of microbial parameters in monitoring soil pollution by heavy metals,” Biology and Fertility of Soils, vol. 19, no. 4, pp. 269–279, 1995.
[2]
K. E. Giller, E. Witter, and S. P. Mcgrath, “Toxicity of heavy metals to microorganisms and microbial processes in agricultural soils: a review,” Soil Biology and Biochemistry, vol. 30, no. 10-11, pp. 1389–1414, 1998.
[3]
Y. Wang, J. Shi, H. Wang, Q. Lin, X. Chen, and Y. Chen, “The influence of soil heavy metals pollution on soil microbial biomass, enzyme activity, and community composition near a copper smelter,” Ecotoxicology and Environmental Safety, vol. 67, no. 1, pp. 75–81, 2007.
[4]
G. Renella, M. Mench, L. Landi, and P. Nannipieri, “Microbial activity and hydrolase synthesis in long-term Cd-contaminated soils,” Soil Biology and Biochemistry, vol. 37, no. 1, pp. 133–139, 2005.
[5]
A. K. Müller, K. Westergaard, S. Christensen, and S. J. S？rensen, “The effect of long-term mercury pollution on the soil microbial community,” FEMS Microbiology Ecology, vol. 36, no. 1, pp. 11–19, 2001.
[6]
C. Trasar-Cepeda, M. C. Leirós, S. Seoane, and F. Gil-Sotres, “Limitations of soil enzymes as indicators of soil pollution,” Soil Biology and Biochemistry, vol. 32, no. 13, pp. 1867–1875, 2000.
[7]
F. Bastida, J. L. Moreno, C. Nicolás, T. Hernández, and C. García, “Soil metaproteomics: a review of an emerging environmental science. Significance, methodology and perspectives,” European Journal of Soil Science, vol. 60, no. 6, pp. 845–859, 2009.
[8]
I. Singleton, G. Merrington, S. Colvan, and J. S. Delahunty, “The potential of soil protein-based methods to indicate metal contamination,” Applied Soil Ecology, vol. 23, no. 1, pp. 25–32, 2003.
[9]
P.-A. Maron, L. Ranjard, C. Mougel, and P. Lemanceau, “Metaproteomics: a new approach for studying functional microbial ecology,” Microbial Ecology, vol. 53, no. 3, pp. 486–493, 2007.
[10]
P. Wilmes and P. L. Bond, “The application of two-dimensional polyacrylamide gel electrophoresis and downstream analyses to a mixed community of prokaryotic microorganisms,” Environmental Microbiology, vol. 6, no. 9, pp. 911–920, 2004.
[11]
P. Wilmes and P. L. Bond, “Metaproteomics: studying functional gene expression in microbial ecosystems,” Trends in Microbiology, vol. 14, no. 2, pp. 92–97, 2006.
[12]
S. Criquet, A. M. Farnet, and E. Ferre, “Protein measurement in forest litter,” Biology and Fertility of Soils, vol. 35, no. 5, pp. 307–313, 2002.
[13]
W. X. Schulze, G. Gleixner, K. Kaiser, G. Guggenberger, M. Mann, and E.-D. Schulze, “A proteomic fingerprint of dissolved organic carbon and of soil particles,” Oecologia, vol. 142, no. 3, pp. 335–343, 2005.
[14]
E. B. Taylor and M. A. Williams, “Microbial protein in soil: influence of extraction method and C amendment on extraction and recovery,” Microbial Ecology, vol. 59, no. 2, pp. 390–399, 2010.
[15]
S. Chen, M. C. Rillig, and W. Wang, “Improving soil protein extraction for metaproteome analysis and glomalin-related soil protein detection,” Proteomics, vol. 9, no. 21, pp. 4970–4973, 2009.
[16]
H.-B. Wang, Z.-X. Zhang, H. Li et al., “Characterization of metaproteomics in crop rhizospheric soil,” Journal of Proteome Research, vol. 10, no. 3, pp. 932–940, 2011.
[17]
D. Benndorf, G. U. Balcke, H. Harms, and M. Von Bergen, “Functional metaproteome analysis of protein extracts from contaminated soil and groundwater,” ISME Journal, vol. 1, no. 3, pp. 224–234, 2007.
[18]
L. A. Brun, J. Maillet, P. Hinsinger, and M. Pépin, “Evaluation of copper availability to plants in copper-contaminated vineyard soils,” Environmental Pollution, vol. 111, no. 2, pp. 293–302, 2001.
[19]
E. Meers, R. Samson, F. M. G. Tack et al., “Phytoavailability assessment of heavy metals in soils by single extractions and accumulation by Phaseolus vulgaris,” Environmental and Experimental Botany, vol. 60, no. 3, pp. 385–396, 2007.
[20]
G. Muyzer, E. C. de Waal, and A. G. Uitterlinden, “Profiling of complex microbial populations by denaturing gradient gel electrophoresis analysis of polymerase chain reaction-amplified genes coding for 16S rRNA,” Applied and Environmental Microbiology, vol. 59, no. 3, pp. 695–700, 1993.
[21]
E. Baath, A. Frostegaard, T. Pennanen, and H. Fritze, “Microbial community structure and pH response in relation to soil organic matter quality in wood-ash fertilized, clear-cut or burned coniferous forest soils,” Soil Biology and Biochemistry, vol. 27, no. 2, pp. 229–240, 1995.
[22]
X. Tang, C. Shen, D. Shi et al., “Heavy metal and persistent organic compound contamination in soil from Wenling: an emerging e-waste recycling city in Taizhou area, China,” Journal of Hazardous Materials, vol. 173, no. 1–3, pp. 653–660, 2010.
[23]
E. Lakanen and R. Ervio, “A comparison of eight extractants for determination of plant available micronutrients in soil,” Acta Agraria Fennica, vol. 123, pp. 223–232, 1971.
[24]
W. L. Lindsay and W. A. Norvell, “Development of a DTPA soil test for zinc, iron, manganese, and copper,” Soil Science Society of America Journal, vol. 42, pp. 421–428, 1978.
[25]
P. Quevauviller, “Operationally defined extraction procedures for soil and sediment analysis I. Standardization,” Trends in Analytical Chemistry, vol. 17, no. 5, pp. 289–298, 1998.
[26]
C. Garcia, T. Hernandez, F. Costa, and B. Ceccanti, “Biochemical parameters in soils regenerated by the addition of organic wastes,” Waste Management and Research, vol. 12, no. 6, pp. 457–466, 1994.
[27]
S. Y. Guan, Soil Enzyme and Its Research Methods, Agricultural Press, Beijing, China, 1986.
[28]
X. Lin, Principles and Methods of Soil Microbiology Research, Higher Education Press, Beijing, China, 2010.
[29]
E. D. Vance, P. C. Brookes, and D. S. Jenkinson, “An extraction method for measuring soil microbial biomass C,” Soil Biology and Biochemistry, vol. 19, no. 6, pp. 703–707, 1987.
[30]
M. M. Bradford, “A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein dye binding,” Analytical Biochemistry, vol. 72, no. 1-2, pp. 248–254, 1976.
[31]
J. X. Yan, R. Wait, T. Berkelman et al., “A modified silver staining protocol for visualization of proteins compatible with matrix-assisted laser desorption/ionization and electrospray ionization- mass spectrometry,” Electrophoresis, vol. 21, pp. 3666–3672, 2000.
[32]
J. Sch？fer, U. J？ckel, and P. K？mpfer, “Development of a new PCR primer system for selective amplification of Actinobacteria,” FEMS Microbiology Letters, vol. 311, pp. 103–112, 2010.
[33]
G. W. Yeates, H. J. Percival, and A. Parshotam, “Soil nematode responses to year-to-year variation of low levels of heavy metals,” Australian Journal of Soil Research, vol. 41, no. 3, pp. 613–625, 2003.
[34]
C. D. Clegg, R. D. L. Lovell, and P. J. Hobbs, “The impact of grassland management regime on the community structure of selected bacterial groups in soils,” FEMS Microbiology Ecology, vol. 43, no. 2, pp. 263–270, 2003.
[35]
C. R. M. Rao, A. Sahuquillo, and J. F. Lopez Sanchez, “A review of the different methods applied in environmental geochemistry for single and sequential extraction of trace elements in soils and related materials,” Water, Air, and Soil Pollution, vol. 189, no. 1–4, pp. 291–333, 2008.
[36]
A. Manceau, M.-C. Boisset, G. Sarret et al., “Direct determination of lead speciation in contaminated soils by EXAFS spectroscopy,” Environmental Science and Technology, vol. 30, no. 5, pp. 1540–1552, 1996.
[37]
D. G. Strawn and L. L. Baker, “Molecular characterization of copper in soils using X-ray absorption spectroscopy,” Environmental Pollution, vol. 157, no. 10, pp. 2813–2821, 2009.
[38]
J. Zhou, X. Sun, J. Jiao, M. Liu, F. Hu, and H. Li, “Dynamic changes of bacterial community under the influence of bacterial-feeding nematodes grazing in prometryne contaminated soil,” Applied Soil Ecology, vol. 64, pp. 70–76, 2013.
[39]
J. C. García-Gil, C. Plaza, P. Soler-Rovira, and A. Polo, “Long-term effects of municipal solid waste compost application on soil enzyme activities and microbial biomass,” Soil Biology and Biochemistry, vol. 32, no. 13, pp. 1907–1913, 2000.
[40]
P. Brookes, S. McGrath, D. Klein, and E. Elliott, “Effects of heavy metals on microbial activity and biomass in field soils treated with sewage sludge,” in Environmental Contamination, pp. 574–583, CEP Consultants, Edinburgh, Scotland, 1984.
[41]
K. Chander and P. C. Brookes, “Is the dehydrogenase assay invalid as a method to estimate microbial activity in copper-contaminated soils?” Soil Biology and Biochemistry, vol. 23, no. 10, pp. 909–915, 1991.
[42]
M. Cea, M. Jorquera, O. Rubilar, H. Langer, G. Tortella, and M. C. Diez, “Bioremediation of soil contaminated with pentachlorophenol by Anthracophyllum discolor and its effect on soil microbial community,” Journal of Hazardous Materials, vol. 181, no. 1–3, pp. 315–323, 2010.
[43]
K. Arnebrant, E. B？？th, and A. Nordgren, “Copper tolerance of microfungi isolated from polluted and unpolluted forest soil,” Mycologia, vol. 79, no. 6, pp. 890–895, 1987.
[44]
E. Baath, “Effects of heavy metals in soil on microbial processes and populations (a review),” Water, Air, and Soil Pollution, vol. 47, no. 3-4, pp. 335–379, 1989.
[45]
P. Roberts and D. L. Jones, “Critical evaluation of methods for determining total protein in soil solution,” Soil Biology and Biochemistry, vol. 40, no. 6, pp. 1485–1495, 2008.
[46]
M. Hodson, “Effects of heavy metals and metalloids on soil organisms,” in Heavy Metals in Soils, B. J. Alloway, Ed., pp. 141–160, Springer, Amsterdam, The Netherlands, 2013.
[47]
C. A. Blindauer, “Bacterial metallothioneins: past, present, and questions for the future,” Journal of Biological Inorganic Chemistry, vol. 16, no. 7, pp. 1011–1024, 2011.
[48]
M. Mejáre and L. Bülow, “Metal-binding proteins and peptides in bioremediation and phytoremediation of heavy metals,” Trends in Biotechnology, vol. 19, no. 2, pp. 67–73, 2001.
