Synchronous Culture
We deal with properties of very large numbers of cells
as if they were continuous functions. Actually, there is a broad
spectrum of cell ages, and cell growth occurs as small increments
that meld into smooth curves for anything that is measured. In
other words, a single event for a cell is a tiny invisible blip for
the many, many cells present. Using differential equations.
There are some natural situations in
which cells become synchronized. Cells can all be stopped if
darkness halts photosynthesis, and reillumination may start growth
simultaneously. In the laboratory, restricted light or low
temperature or some other factor can impair a step in division. The
cells can be triggered to proceed together from that point with
overall numbers that are stepwise with time. This is termed a
synchronous culture when all the cells divide simultaneously.
The steps are seldom distinct for more than a few generations unless
the triggering event continues to be applied periodically.
Synchronous culture is an important case where differential
equations are not appropriate.
Research with synchronous cultures has been very enlightening in terms
of understanding what goes on in cells. One cell is far too tiny
to be analyzed extensively, although there are techniques such as
flow cytometry that provide some information as an individual
cell passes through a laser beam. With synchronous culture, all the
cells are the same age, and large samples analyzed by any technique,
complicated or simple, can be translated to information about a
single cell just by dividing by the number of cells in the sample.
Concentrations of biochemicals during the life
cycle of a cell have been studied in this manner.
Concept of the limiting nutrient
Fedbatch culture
Relating product to growth
Backseeding
Teaching games
References
Back to index page for fundamentals