Figure 1

The life cycles of B. subtilis and Epulopiscium sp. type B. A) In a favorable environment, B. subtilis undergoes growth and division. B) When nutrient limitations become critical, the cell may develop an endospore. Shown here are the morphological stages described for sporulation. The temporal and spatial activation of Spo0A and the four sporulation-specific sigma factors are shown. The grey circle around the forespore indicates the cortex. The thick black circle around the forespore at stage V and beyond represents the spore coat. C) Earliest stages of offspring development in Epulopiscium sp. type B are based on the similar morphological transitions described for sporulation in B. subtilis. See text for a detailed explanation of the process. Offspring frequently initiate the next round of reproduction prior to exiting the mother cell. Those stages that are seen in offspring still within their mother cell are highlighted with grey boxes. For all diagrams, DNA is shown in blue.