The ATCC Bacteriology Collection is the most diversified assemblage of prokaryotes in the world, containing more than 18,000 strains in more than 750 genera. Every important prokaryotic physiological group is represented. The Collection holds more than 3,600 type cultures of validly described species, forming the basis for systematic bacteriology, and nearly 500 bacteriophages. The bacteria are useful in a variety of research and industrial applications. We have methicillin-resistant/sensitive research materials; quality control organisms for commercial identification systems, a wide selection of extremophile strains from a variety of environmental sources and genomic DNA from well-characterized microbial strains suitable for amplification by PCR.