Fig. 6.

Model for M. pneumoniae terminal organelle duplication and growth cycle. The yellow circle represents the initial terminal organelle, and green, red, and blue circles represent subsequent organelles, appearing in that order. The dashed arrows reflect movement of the indicated terminal organelle, and open arrows indicate cytokinesis. Solid arrows indicate steps in the cell cycle, with arrow size reflecting relative frequency. In most cases, multiple duplications of the terminal organelle occur before daughter cells emerge (a), although rarely some cells do undergo a single duplication of the terminal organelle followed by cytokinesis (b), according to the previous model for cell division in M. pneumoniae (18).