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Review
. 2015 Mar 25:6:238.
doi: 10.3389/fmicb.2015.00238. eCollection 2015.

A ten-year search for synchronous cells: obstacles, solutions, and practical applications

Charles E Helmstetter  1
Affiliations
Review

A ten-year search for synchronous cells: obstacles, solutions, and practical applications

Charles E Helmstetter. Front Microbiol. .

Abstract

My effort to use synchronously dividing cultures to examine the Escherichia coli cell cycle involved a 10-year struggle with failure after failure punctuated by a few gratifying successes, especially at the end. In this essay, I recount my personal journey in this obsessive experimental pursuit. That narrative is followed by a description of a simplified version of the "baby machine," a technique that was developed to obtain minimally disturbed, synchronously growing E. coli cells. Subsequent studies with this methodology led to an understanding of the basic properties of the relationship between chromosome replication and cell division. Accordingly, I end this reminiscence with a simple, fool-proof graphical strategy for deducing the pattern of chromosome replication during the division cycle of cells growing at any rate.

Keywords: E. coli; cell cycle; cell division; cellular baby machine; chromosome replication; synchronous cells.

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Figures

Figure 1
Figure 1
Bacterial baby machine cartoon. Caricature of the technique sketched by Avshalom Falk while a student in the laboratory of Eliora Ron at Tel Aviv University.
Figure 2
Figure 2
Argonne National Laboratory, 1968. Ole Maaløe facilitating discussion after a presentation by Charles Helmstetter at a Division of Biological and Medical Sciences symposium.
Figure 3
Figure 3
Charles Helmstetter and Steve Cooper during a reception at a conference in 1987.
Figure 4
Figure 4
Buchner funnel version of a cellular baby machine. (A) Funnel set-up for binding cells to a membrane filter surface. (B) Orientation and appearance of the funnel during elution of newborn cells from the membrane filter surface.
Figure 5
Figure 5
Construction of a chromosomal replication pattern during the bacterial division cycle. The construction, starting at the top left, is based on the (I + C + D) rule with I = 35 min, C = 40 min, and D = 20 min.
Figure 6
Figure 6
Addition of chromosome configurations to a division cycle construction. Chromosomal DNA is represented by red lines, with small filled circles indicating replication sites. The configurations in rectangles indicate cell divisions. Only one cell is followed after the first division. Number of replication forks per cell (RF/cell) is shown during the division cycle.
Figure 7
Figure 7
Genome equivalents of DNA per cell (G) during the division cycle. Calculations of the values for G are shown in red for three select times in the division cycle: 0, 10, and 15 min.
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