Caulobacter crescentus nucleoid: analysis of sedimentation behavior and protein composition during the cell cycle.

The envelope-associated nucleoid (EAN) of Caulobacter crescentus has been isolated during major developmental stages in the cell cycle. The sedimentation coefficient of the Caulobacter EAN changes as a function of development and is closely correlated with the periodicity of DNA synthesis in this bacterium. The contribution of proteins to the structure of the Caulobacter nucleoid has been analyzed by using polyacrylamide gel electrophoresis of proteins labeled both for short intervals and continuously throughout the cell cycle. The EAN proteins are derived primarily from membranes and are sequentially associated with the EAN during the cell cycle. Several distinct proteins are isolated with the EAN at specific stages of differentiation. A 26,000 Mr protein, which appears uniquely associated with the swarmer cell EANs, was identified and shown to segregate preferentially with the swarmer cell EAN at cell division.