Structural diversity of microorganisms in chemically perturbed soil assessed by molecular and cytochemical approaches

Until recently, our understanding of microbial community development in soi l ecosystems exposed to different inorganic and organic pollutants has been limited to culturable microorganisms because of the techniques available. The discovery that most soil microorganisms are non-culturable but potentia lly viable and metabolically active accelerated the application of differen t culture-independent methods for structural diversity assessments of the m icrobial community. This review examines the results of recent studies on t he impact of heavy metals and organic pollutants on the diversity of the mi croflora obtained with methods based on analyses of signature biomarkers su ch as nucleic acids and fatty acids. The application of these techniques al lowed researchers to pinpoint reduction of microbial diversity in contamina ted soil, and significant shifts in the community structure, lending to the dominance of only a few populations (species) and the disappearance of oth ers, some of which were never isolated by conventional methods (e.g. an inc rease in Acidobacterium or a decrease in terrestrial non-thermophilic Crena rchaeota). Although the new techniques are not free from limitations, they allow the monitoring of the virtual impact of stressors on soil microorgani sms and the direction of resuscitation of the microbial community during na tural or induced bioremediation, especially when using combined approaches. (C) 2001 Elsevier Science B.V. All rights reserved.