Microbes Count! is a collection of computer-based investigations for the undergraduate microbiology laboratory. The simulations, case-studies, and computational models in Microbes Count! can be used to supplement standard textbooks throughout the undergraduate curriculum. Microbes Count! engages students in flexible problem-solving strategies using data-rich situations based on real-world problems such as the environmental impact of microbial metabolism, the analysis of phylogenetic relationships with bioinformatics tools, the challenge of Pfeisteria, and the development of antibiotic resistance in M. tuberculosis. From virtual laboratories for distance learners to quantitative extensions of wet and field laboratories, the Microbes Count! investigations enhance traditional laboratory and classroom activities with opportunities for in-depth problem solving. The investigations in the book utilize a variety of software and web-based resources, many of which are drawn from the peer-reviewed BioQUEST Library of computer-based curricular materials. The accompanying CD includes all of the software and other resources used in the book, as well as additional data sets, bibliographies, supplemental activities, and software manuals.