Myxococcus xanthus produces two categories of low molecular weight antibacterial materials, autocides and paracides, that have diametrically opposite host ranges. Low concentrations of autocides lyse M. xanthus, the producing organism, whereas paracides exert their effects on other bacteria. Antibiotic TA (a paracide) kills all growing bacteria tested that have a peptidoglycan cell wall except M. xanthus. It is a macrocyclic polyketide with a molecular weight of 623. The two major autocides produced by M. xanthus are phosphatidylethanolamine and a mixture of fatty acids. The modes of action, host ranges and biosynthesis of antibiotic TA and the autocides are presented, and then an attempt is made to explain their role in the complex life cycle of M. xanthus. In addition, the remarkable adhesion properties of antibiotic TA and a new semisynthetic derivative of it, focusin, are presented.