Kibret M
The early phases of soil microbiology were often dominated by attempts to characterize soil populations using culture techniques through laboratory growth on selective (favors a particular group of microbes over others) or non-selective media. While these attempts produced valuable information, little more could be said other than that there was some number of colony-forming-units per gram (CFU g–1) of soil. We are becoming increasingly aware that our knowledge of the soil microbial community is far from complete. We have learned that many microbes in the soil exist in a “viable (alive) but nonculturable” state. It has long been observed that as many as 99% of microorganisms in a given soil sample, as quantified using microscopy or another direct technique, are not detected using traditional culture-based methods. This has led many to surmise that the vast majority (90%–99%) of soil microorganisms are not cultural. While it is true that lab culture remains elusive for many soil organisms, creative modifications in isolation methods, media, and incubation conditions have demonstrated that isolation and culture of many of these previously uncultured organisms may be possible if the appropriate conditions are provided. In fact, research using new culture-based methods has experienced somewhat of a renaissance in recent years due to the realization above and the need for cultured type-strains to characterize phenotypes that can be connected with the wealth of sequence data currently being produced through DNAbased approaches.