Microbial Monitoring of the Recovery of Soil Quality During Heavy Metal Phytoremediation María T. Gómez-Sagasti & Itziar Alkorta & José M. Becerril & Lur Epelde & Mikel Anza & Carlos Garbisu Received: 19 October 2011 / Accepted: 31 January 2012 / Published online: 16 February 2012 # Springer Science+Business Media B.V. 2012 Abstract Soil pollution with heavy metals is a world- wide environmental problem. Phytoremediation through phytoextraction and phytostabilization appears to be a promising technology for the remediation of polluted soils. It is important to strongly emphasize that the ultimate goal of a heavy metal remediation process must be not only to remove the heavy metals from the soil (or instead to reduce their bioavailability and mobility) but also to restore soil quality. Soil qual- ity is defined as the capacity of a given soil to perform its functions. Soil microbial properties are increasingly being used as biological indicators of soil quality due to their quick response, high sensitivity, and, above all, capacity to provide information that integrates many environmental factors. Indeed, micro- bial properties are among the most ecologically relevant indicators of soil quality. Consequently, microbial mon- itoring of the recovery of soil quality is often carried out during heavy metal phytoremediation processes. How- ever, soil microbial properties are highly context depen- dent and difficult to interpret. For a better interpretation of microbial properties as indicators of soil quality, they may be grouped within categories of higher ecological relevance, such as soil functions, ecosystem health attributes, and ecosystem services. Keywords Bioindicators . Phytoextraction . Phytostabilization . Soil contamination . Soil health 1 Soil Metal Pollution Is a Worldwide Environmental Problem As a result of anthropogenic activities, soil pollution with toxic heavy metals is currently an environmental problem of great magnitude and with global repercus- sions (Ruttens et al. 2006). Mining, agriculture, met- allurgy, tanning, combustion of fossil fuels, waste disposal, and other human activities are responsible for the enormous amounts of heavy metals and metal- loids presently found in our soils (He et al. 2005). Among these, cadmium (Cd), lead (Pb), cobalt (Co), copper (Cu), mercury (Hg), nickel (Ni), selenium (Se), and zinc (Zn) are some of the most frequently found in polluted soils (Kavamura and Espósito 2010). Both organic and inorganic pollutants can interfere with the functionality of the soil ecosystem, but heavy Water Air Soil Pollut (2012) 223:3249–3262 DOI 10.1007/s11270-012-1106-8 M. T. Gómez-Sagasti : L. Epelde : M. Anza : C. Garbisu (*) Soil Microbial Ecology Group, NEIKER-Tecnalia, c/Berreaga 1, 48160 Derio, Spain e-mail: cgarbisu@neiker.net I. Alkorta Department of Biochemistry and Molecular Biology, University of the Basque Country, UPV/EHU, P.O. Box 644, 48080 Bilbao, Spain J. M. Becerril Department of Plant Biology and Ecology, University of the Basque Country, UPV/EHU, P.O. Box 644, 48080 Bilbao, Spain