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Chemostat



 

A chemostat (from Chemical environment is static) is a continuous culture [1] device used in microbiology for growing and harvesting microbes.[2] It consists of two primary parts: a nutrient reservoir and a growth chamber. It can keep a bacterial culture growing at a reduced growth rate over an indefinite time period. Growth of the culture is controlled by the concentration of the limiting nutrient.[2] The limiting nutrient is a essential growth factor necessary for bacterial growth but present in the media at a concentration such that balanced growth consumes it to r* (a la G. David Tilman) prior to exhausting any other of the essential nutrients in the media. Chemostats allow the the growth rate and yield to be controlled independently. The most important feature of a chemostat is that all fermentation parameters; growth chamber volume, dissolved oxygen, nutrient concentrations, pH, cell density, etc., remain constant throughout the experiment.

Some sources of concern are:

  1. Foaming results in overflow with the volume of liquid not exactly constant
  2. Some very fragile cells are ruptured during agitation and aeration.
  3. Cells may grow on the walls or adhere to other surfaces
  4. Mixing may not truly be uniform
  5. Dripping the media into the chamber actually results in small pulses of nutrients and thus oscillations in concentrations
  6. Bacteria travel upstream quite easily. They will reach the reservoir of sterile medium quickly unless the liquid path is interrupted by an air break in which the medium falls in drops through air.

Additional recommended knowledge

Contents

Chemostat History

Chemostats were initially developed by Novick and Szilard. They were later refined at Cold Spring Harbor Laboratories and entered the canon of microbiological methods. They diversified rapidly as various control mechanisms led to the auxostat and turbidostat.

Chemostats in Research

Chemostats in research are used for investigations in cell biology, as a source for large volumes of uniform cells or protein. The chemostat is often used to gather steady state data about an organism in order to generate a mathematical model relating to its metabolic processes. Chemostats are also used as microcosms in ecology[3][4] and evolutionary biology[5][6][7][8]. In the one case, mutation/selection is a nuisance, in the other case, it is the desired process under study.

Topics in ecology and evolution that have been studied in chemostats include competition for single and multiple resources, the evolution of resource acquisition and utilization pathways, cross-feeding/symbiosis, antagonism, predation, and competition among predators.

Chemostats in Industry

Chemostats are frequently used in the industrial manufacture of ethanol. In this case, several chemostats are used in series, each maintained at decreasing sugar concentrations.

See also

References

  1. ^ James TW (1961). "Continuous Culture of Microorganisms". Annual Review of Microbiology 15: 27-46.
  2. ^ a b Novick A, Szilard L (1950). "Description of the Chemostat". Science 112 (2920): 715-6. PMID 14787503.
  3. ^ Becks L, Hilker FM, Malchow H, Jürgens K, Arndt H (2005). "Experimental demonstration of chaos in a microbial food web". Nature 435 (7046): 1226–9. doi:10.1038/nature03627. PMID 15988524.
  4. ^ Pavlou S, Kevrekidis IG (1992). "Microbial predation in a periodically operated chemostat: a global study of the interaction between natural and externally imposed frequencies". Math Biosci 108 (1): 1–55. PMID 1550993.
  5. ^ Wichman HA, Millstein J, Bull JJ (2005). "Adaptive molecular evolution for 13,000 phage generations: a possible arms race". Genetics 170 (1): 19–31. doi:10.1534/genetics.104.034488. PMID 15687276.
  6. ^ Dykhuizen DE, Dean AM (2004). "Evolution of specialists in an experimental microcosm". Genetics 167 (4): 2015–26. doi:10.1534/genetics.103.025205. PMID 15342537.
  7. ^ Wick LM, Weilenmann H, Egli T (2002). "The apparent clock-like evolution of Escherichia coli in glucose-limited chemostats is reproducible at large but not at small population sizes and can be explained with Monod kinetics". Microbiology (Reading, Engl.) 148 (Pt 9): 2889–902. PMID 12213934.
  8. ^ Jones LE, Ellner SP (2007). "Effects of rapid prey evolution on predator-prey cycles". J Math Biol 55 (4): 541–73. doi:10.1007/s00285-007-0094-6. PMID 17483952.
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Chemostat". A list of authors is available in Wikipedia.
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