Pattern Formation in an Interacting Cell System: Rippling in Myxobacterial Aggregates

Abstract

It is usual to divide organisms into two basic categories: unicellular and multicellular. However, looking at unicellular organisms such as bacteria and amoebae one can see their clear tendency to form multicellular structures, colonies and fruiting bodies [1–7]. Here we focus on pattern formation of Myxobacteria [8,9]. Myxobacteria are rod-shaped cells that glide (the precise mechanism is unknown) along their long axis. They exhibit a complex developmental cycle with individual and social phases. As long as there is sufficient food supply, vegetative cells prey, grow and divide as individuals or in small swarms. Under starvation conditions, bacteria start to act cooperatively, aggregate and finally build a multicellular structure, the fruiting body. Fruiting body formation is often preceded by a periodic pattern originally classified asoscillatory waves[10] and later namedrippling [11,12].