It is difficult to describe the properties of a microorganism without first cultivating it. There has been a great deal of effort and considerable success in predicting microbial metabolic activities from genome sequences, (i.e., functional genes), assembling genomes from metagenomic data, testing the activities of cells in situ, and from studying complex microbial assemblages in the laboratory. But, the fact remains that the most efficient way to gather information about a microorganism is to study it in culture and relate that knowledge to field observations. Genomes are easily determined from pure cultures, and cultures often offer the best possibilities to test hypotheses that emerge from genome sequences or ecological studies. Figure 1 illustrates some of these relationships.