Antibiotics are chemicals that are selectively toxic for bacteria, and have been used for decades to treat infectious disease. This use, and concomitant abuse, have driven the evolution of antibiotic resistance among populations of bacterial pathogens, and common antibiotics are becoming ineffective. One strategy to deal with this problem is the discovery of new antibacterial compounds. Our lab is seeking such compounds from natural sources, soil microorganisms which secrete such chemicals to further their success in competition with other soil organisms. We have identified a large number of "candidate" bacteria which inhibit the growth, not just of soil organisms, but also human associated bacteria related to known pathogens. Competition tests in vitro indicate that some candidates produce broad spectrum agents, able to inhibit the growth of many different test species. Other candidates target a narrower spectrum of test strains. There is great need for novel antibiotics in both categories. Several candidates have been chosen for further study, based on criteria such as spectrum of action. Efforts are underway to characterize the active antibacterial compounds and, in particular, to purify those chemicals in order to determine their molecular composition and structure. Any that represent novel compounds will be further studied for their potential as antibiotics.