Paenibacillus is a genus of facultative anaerobic, endospore-forming bacteria, originally included within the genus Bacillus and then reclassified as a separate genus in 1993.Bacteria belonging to this genus have been detected in a variety of environments, such as: soil, water, rhizosphere, vegetable matter, forage and insect larvae, as well as clinical samples. The name reflects: Latin paene means almost, so the paenibacilli are literally “almost bacilli”.

Several Paenibacillus species can form complex patterns on semisolid surfaces. Development of such complex colonies require self-organization and cooperative behavior of individual cells while employing sophisticated chemical communication. Pattern formation and self-organization in microbial systems is an intriguing phenomenon and reflects social behaviors of bacteria that might provide insights into the evolutionary development of the collective action of cells in higher organisms.