Cell synchrony and periodic behaviour in yeast populations

Abstract

The underlying basis for the behaviour of a population of cells is the cell growth and division cycles of the individual cells. Under certain special circumstances, oscillations in cell cultures can be observed that are a reflection of metabolic oscillations, such as in glycolysis, or cell cycle oscillations from a partially synchronized population. These oscillations can sometimes occur spontaneously, as in the chemostat culture of Saccharomyes cerevisiae at low dilution rates, or can be induced using chemical blockers or entrainment by a periodic nutrient environment. Continuous methods for inducing a synchronized culture include the pulsed chemostat, continuous phasing and self-cycling fermentation. Results obtained by studying both spontaneously oscillating cultures and synchronized cultures have provided insight into the mechanisms responsible for the progress and control of the cell cycle as well as the intimate relationship that exists between the cellular dynamics and the dynamics of the environment.Le fondement expliquant le comportement d'une population de cellules reside dans la croissance des cellules et les cycles de division de chaque cellule. Dans certaines circonstances particulieres, des oscillations peuvent ttre observees dans les cultures de cellules, qui sont un reflet des oscillations metaboliques, comme dans la glycolyse, ou des oscillations dans les cycles des cellules d'une population partiellement synchronisee. Ces oscillations peuvent parfois survenir spontanement, c o m e dans la culture par chemostat de Saccharomyes cerevisiae a de faibles vitesses de dilution, ou peuvent ttre provoquees a I'aide de bloqueurs chimiques ou par entrainement par un milieu nutritif periodique. Les methodes continues pour provoquer une culture synchronisee englobent le chemostat pulse, la mise en phase continue et la fermentation auto-cyclique. Les resultats obtenus par I'etude a la fois des cultures spontanement oscillatoires et des cultures synchronisees nous donnent des indications sur les mecanismes responsables de la progression et du contrde du cycle des cellules ainsi que sur la relation etroite qui existe entre la dynamique cellulaire et la dynamique de I'environnement.Keywords: cell cycle, yeast, oscillations, synchrony.ew people would deny that periodic behaviour is a F fundamental characteristic of living systems, whether it be multi-year cycles in animal populations, seasonal variations in plant species or diurnal variations in human activity. The examples are endless, yet those who practice the science and technology of microbial cell culturing often ignore the underlying basis of their process -the cell growth and division cycle. Rather than base an understanding and subsequent process design on periodic cell cycle events, the process is typically characterized and controlled based on a presumably homogeneous population (usually referred to as simply "biomass") that will hopefully not demonstrate any curious periodic behaviour. Indeed, for many, engineers included, the so-called "batch growth ...

Observation of a chaotic multioscillatory metabolic attractor by real‐time monitoring of a yeast continuous culture

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