We have performed an extensive phylogenetic survey of a typical mid-western agricultural soil based on partial 16S rRNA sequence analysis. A unique aspect of this project is that the complex mixture of DNA from the total soil community was first fractionated based on %G+C content to reduce the complexity of the DNA in each fraction and facilitate more complete detection and coverage of less abundant soil microbial populations. To date, this analysis is showing very extensive diversity in soil bacterial populations with 3,067 out of 3,722 sequences analyzed being unique when 100% similarity is required to group sequences. We are now performing meta-analysis of this data using computational approaches to determine if there are any signatures or trends in the data that correlate with biological parameters such as the hierarchical organization into groups or phyla, or likely physiological/metabolic types. This will underpin and punctuate our rapidly developing mass library of sequences, primers and probes for monitoring soil bacterial populations at various levels of resolution. We are also interested in assessing whether different bacterial groups (taxa) exhibit different levels of apparent diversity and developing an understanding of the relationship between molecular diversity and ecological function of important groups of soil microbes.