Density-gradient sedimentation in silica sols. Anomalous shifts in the banding densities of polystyrene ‘latex’ beads

Jj, Morgenthaler; Price, C A

doi:10.1042/bj1550465b

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“…Certain aspects of the equilibration of particles in gradients of colloidal silica appear anomalous, in particular the ' density shifts ' of particles (polystyrene latex beads) induced by inclusion of polymers (Pertoft? 1966;Morgenthaler & Price, 1976). In the present study, polyvinylpyrrolione caused a significant decrease in the mean buoyant density of bacterial cells, similar to the response of thylakoid membranes of chloroplasts (Morgenthaler, Marsden & Price, 1975).…”

Section: Discussionsupporting

confidence: 56%

Fluctuations in Buoyant Density during the Cell Cycle of Escherichia coli K12: Signiacance for the Preparation of Synchronous Cultures by Age Selection

Poole

1977

Journal of General Microbiology

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K I~ were investigated by isopycnic centrifugation in gradients of colloidal silica (Ludox) and polyvinylpyrrolidone. Bacteria from an exponential culture in a defined medium supplemented with hydrolysed casein banded at densities between 1.060 and 1.1 15 g ml-l; the mean density was 1-081 g ml-l. At the higher densities, two populations of cells were present: smaller cells were approximately twice as numerous as, and half the modal volume of, the population of larger cells. A homogeneous population of cells of intermediate volume equilibrated in the least dense region of the density band. Synchronous cultures were established by inoculating cells selected from the most or least dense regions of the band into spent growth medium. The results are consistent with a fluctuation between maximal density at cell birth and division, and minimal density near the middle of the cell cycle. In synchronous cultures prepared by continuous-flow age selection, the first division occurred after a period that was significantly shorter than the length of subsequent cell cycles. Cells selected by this procedure were of similar mean density to those in the exponential culture but were more homogeneous with respect to size. The possibility that the smallest (and densest) cells in an exponential culture are retained in the rotor, and are thus excluded from the synchronous culture, is discussed.

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Section: Discussionsupporting

confidence: 56%

Fluctuations in Buoyant Density during the Cell Cycle of Escherichia coli K12: Signiacance for the Preparation of Synchronous Cultures by Age Selection

Poole

1977

Journal of General Microbiology

View full text Add to dashboard Cite

show abstract

Density-gradient sedimentation in silica sols. Anomalous shifts in the banding densities of polystyrene ‘latex’ beads

Cited by 1 publication

References 5 publications

Fluctuations in Buoyant Density during the Cell Cycle of Escherichia coli K12: Signiacance for the Preparation of Synchronous Cultures by Age Selection

Fluctuations in Buoyant Density during the Cell Cycle of Escherichia coli K12: Signiacance for the Preparation of Synchronous Cultures by Age Selection

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