Detailed three-dimensional analysis of structural features of Myxococcus xanthus fruiting bodies using confocal laser scanning microscopy

Myxococcus xanthus is a motile soil bacterium with complex social behaviors. Upon starvation, a developmental program is initiated that results in cellular aggregation and fruiting body formation. This process requires the exopolysaccharide (EPS) component of the extracellular matrix. With prolonged starvation, a part of the cells within a fruiting body die, while the other cells differentiate into spores. Extensive genetic and biochemical information has been generated that elucidates this interesting developmental process. Little is known, however, about the detailed three-dimensional structural features of native fruiting bodies or the EPS and distribution of live/dead cells (spores) within these structures. In this study, changes in the three-dimensional architecture of fruiting bodies and the distribution of the extracellular matrix within the fruiting bodies during the developmental process were investigated using a gfp-expressing M. xanthus strain and carbohydratespecific lectins or monoclonal antibodies in combination with confocal laser scanning microscopy. The extracellular matrix was found to form a scaffold within the fruiting body structure. Furthermore, using a bacterial viability staining assay, the distribution of live/dead cells within fruiting bodies was examined at different times. The majority of live cells were found to localize at the outer layer of a mature fruiting body, with dead cells underneath.