Two cell-density domains within the Myxococcus xanthus fruiting body.

Myxococcus xanthus, one of the simplest of multicellular organisms, develops into an organized, multicellular aggregate, called a fruiting body. Examination of the internal structure of the nascent fruiting body showed it to consist of a hemispherical outer domain of densely packed and ordered cells. Inside this dense shell is an inner domain of less ordered cells at 3-fold lower cell density. Single cells move in a bidirectional stream in the outer domain, orbiting the fruiting body throughout development, whereas in the inner domain, cell movement ceases as the fruiting body matures. The fruiting body thus consists of two domains, distinguished from each other by differential cell density, cell arrangements, and cell movements.