Currently, actinomycetes and myxobacteria are the only bacteria believed to form sporangia. Here, we describe a sporangium-forming process identified in Dictyobacter aurantiacus strain S27T belonging t o t he cl as s Kt edonobact er i a i n t he phyl um Chloroflexi. Microscopic observations showed that strain S27T forms a substrate mycelium and subsequently produces globose or subglobose terminal sporangia arising from the vegetative mycelia through short stalk cells. This morphogenetic differentiation is similar to that seen in members of Actinoplanes belonging to the class Actinobacteria. However, unlike in Actinoplanes, motile spores could not be observed. This is the first report of t he exi s t ence of a bact eri um, ot her t han actinomycetes and myxobacteira, with a complex morphogenetic differentiation that forms sporangia and is an important microbiological discovery.