Applying molecular biological methods to investigate soils has necessitated considerable method developments. These studies generally support previous work based on culturing organism from soils but, importantly they indicate the active presence of novel consortia yet to be cultured. Bacterial populations and guilds are now beginning to be described from similar soil niches from around the world using 16S rDNA technologies (9, 17-19, 36,46). The challenge for the soil microbial ecologist, as ever, is to identify the populations and guilds of microorganisms which have key functional roles in specific soil processes. As a result of such studies it is now widely acknowledged that the diversity of microorganisms in soils is large (3, 6, 9, 30, 32, 34, 39). The first applications of nucleic acid techniques applied to molecular microbial ecology were primarily concerned with phylogenetic relationships between microorganisms determined by sequence analysis of 16S rDNA. The use of small sub-unit rRNAs in microbial ecology has been recently reviewed (22) and the reader is referred to this paper for a detailed review of the first 10 years of molecular microbial ecology. This has been due to a better awareness that biological communities have a role in maintaining a sustainable biosphere and secondly to rapid advances in molecular biology. With this in mind, when examining the impact of 16S rDNA analyses on soil bacterial ecology, one might ask to what extent our knowledge of microorganisms and their roles in natural environments has been enhanced by the introduction of molecular methods? Over the past 10 years we have seen increased interest in soil microbiology and ecology. 'a new golden age of microbiology is upon us! An age in which an entire bacterial genome can be sequenced in a matter of months.'Īs molecular technologies facilitate explorations of gene expression I support the view that the primary task of microbial ecology is to provide an understanding of the place of microorganisms in society (5). In the preface to their book ∛rock Biology of Microoganisms (37) Madigan et al. Key words: soil, bacteria, ecology, 16S rDNA It mentions their limits and suggests how they may be applied in the future. This review examines 16S ribosomal DNA (rDNA) methods and their application to soil. As we enter the third millenium, it is appropriate to review the application of 16S rDNA methods to soil microbiology. Over the next few years, the knowledge gained from molecular studies will, we hope, lead to improvements in sustainable land management and sustainable exploitation of soil genetic resources. These studies have added much to our knowledge of microbial diversity in soils, and are beginning to advance our understanding of the relationship between this diversity and its function in soil processes. New and exciting molecular methods, many using the 16S small sub-unit ribosomal nucleic acid molecule, are opening the microbial 'black box' in soil.

16sr dna sequence analysis