In the first review, Torsvik and Øvreås (pp 240–245) introduce the complexity of the soil microbial community. The soil contains vast diversity,and most of the microorganisms that contribute to that diversity are unculturable by standard methods. A gram of undisturbed soil may contain 10 billion microorganisms representing 6000–10 000 different genomes. The review
explores emerging approaches to dissecting and understanding the soil community that involve methods that circumvent culturing its members, including PCR analysis, fluorescent in situ hybridization, microautoradiography, oligonucleotide arrays and metagenomics. Abraham et al.
(pp 246–253) delve deeper into microbial communities, exploring both individual and cooperative abilities to degrade polychlorinated biphenyl (PCB) compounds in soils and sediments. This rapidly evolving field is driven by the industrial need to manage the impact of the annual
production of 1.5 million tons of PCBs, but the research contributes to our fundamental knowledge of bacterial biochemistry and community function as well as to bioremediation
applications. Studying PCB degradation highlights the need to study consortia of microbes rather
than individuals. Abraham et al. teach us that “mosaic pathways”, segmented into more than one species, are often responsible for transformation of PCB compounds, so that studying one taxon in pure culture will reveal only a partial image of the complex biochemistry occurring among partners in the interactive environment of the soil microbial community. It is likely that many other functions are accomplished by cooperative efforts among microorganisms, and cooperative biochemical pathways will emerge as one of the key principles of microbial ecology