Envelope-associated nucleoid from Caulobacter crescentus stalked and swarmer cells

Envelope-associated nucleoids have been isolated from Caulobacter crescentus by using a modification of the procedure of T. Kornberg et al. (Proc. Natl. Acad. Sci. U.S.A. 71:3189-3193, 1974). The development of a Ludox density gradient procedure has permitted preparation of large quantities of synchronous cells. The sedimentation coefficients of the envelope-associated nucleoids of stalked and swarmer cells, prepared under conditions of equivalent cell lysis, were 3,000S and greater than 6,000S respectively. Small differences in the relative amounts of deoxyribonucleic acid, ribonucleic acid, and protein in stalked and swarmer cell envelope-associated nucleoids could not account for the large differences in sedimentation behavior. These characteristic sedimentation coefficients were retained in mixing experiments.