Name: the use of chemostats in microbial systems biology
Uploaded: 2013-10-14T20:45:00
Description: Watch this Scientific Journal Video about The Use of Chemostats in Microbial Systems Biology at JoVE.com

This work was supported by start up funds form New York University. We thank Maitreya Dunham and Matt Brauer who initially developed the use of Sixfors bioreactors as chemostats.

The principle of continuous culturing using a chemostat can be realized in a variety of implementations. In all chemostats it is essential to have 1) methods for maintaining sterility of all components, 2) a well-mixed culture, 3) appropriate aeration of the culture vessel and 4) a reliable means of media addition and culture removal. Here, we describe the use of a Sixfors bioreactor (Infors Inc) as a chemostat using methods that can be readily adapted to alternative setups.
1. Assembling the Ch...

<ol>
	<li>Ingraham, J. L., Maaloe, O., Neidhardt, F. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Growth of the Bacterial Cell. , (1983).</li><li>Hall, M. N., Raff, M. C., Thomas, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Cell Growth: Control of Cell Size. , (2004).</li><li>Monod, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=La+technique+de+culture+continue,+theorie+et+applications.">La technique de culture continue, theorie et applications.</a> Ann. Inst. Pasteur. 79, 390-410 (1950).</li><li>Novick, A., Szilard, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Description+of+the+chemostat.">Description of the chemostat.</a> Science. 112, 715-716 (1950).</li><li>Kjeldgaard, N. O., Maaloe, O., Schaechter, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+transition+between+different+physiological+states+during+balanced+growth+of+Salmonella+typhimurium.">The transition between different physiological states during balanced growth of Salmonella typhimurium.</a> J. Gen. Microbiol. 19, 607-616 (1958).</li><li>Maaloe, O., Kjeldgaard, N. O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Control+of+macromolecular+synthesis.">Control of macromolecular synthesis.</a> , (1966).</li><li>Saldanha, A. J., Brauer, M. J., Botstein, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nutritional+Homeostasis+in+Batch+and+Steady-State.">Nutritional Homeostasis in Batch and Steady-State.</a> Culture of Yeast. Mol. Biol. Cell. 15, 4089-4104 (2004).</li><li>Boer, V. M., Crutchfield, C. A., Bradley, P. H., Botstein, D., Rabinowitz, J. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Growth-limiting+intracellular+metabolites+in+yeast+growing+under+diverse+nutrient+limitations.">Growth-limiting intracellular metabolites in yeast growing under diverse nutrient limitations.</a> Mol. Biol. Cell. 21, 198-211 (2010).</li><li>Boer, V. M., de Winde, J. H., Pronk, J. T., Piper, M. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+genome-wide+transcriptional+responses+of+Saccharomyces+cerevisiae+grown+on+glucose+in+aerobic+chemostat+cultures+limited+for+carbon,+nitrogen,+phosphorus,+or+sulfur.">The genome-wide transcriptional responses of Saccharomyces cerevisiae grown on glucose in aerobic chemostat cultures limited for carbon, nitrogen, phosphorus, or sulfur.</a> J. Biol. Chem. 278, 3265-3274 (2003).</li><li>Brauer, M. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Coordination+of+growth+rate,+cell+cycle,+stress+response,+and+metabolic+activity+in+yeast.">Coordination of growth rate, cell cycle, stress response, and metabolic activity in yeast.</a> Mol. Biol. Cell. 19, 352-367 (2008).</li><li>Gresham, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Adaptation+to+diverse+nitrogen-limited+environments+by+deletion+or+extrachromosomal+element+formation+of+the+GAP1+locus.">Adaptation to diverse nitrogen-limited environments by deletion or extrachromosomal element formation of the GAP1 locus.</a> Proc. Natl. Acad. Sci. U.S.A. 107, 18551-18556 (2010).</li><li>Regenberg, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Growth-rate+regulated+genes+have+profound+impact+on+interpretation+of+transcriptome+profiling+in+Saccharomyces+cerevisiae.">Growth-rate regulated genes have profound impact on interpretation of transcriptome profiling in Saccharomyces cerevisiae.</a> Genome Biol. 7, R107 (2006).</li><li>Castrillo, J. I., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Growth+control+of+the+eukaryote+cell:+a+systems+biology+study+in+yeast.">Growth control of the eukaryote cell: a systems biology study in yeast.</a> J. Biol. 6, 4 (2007).</li><li>Cipollina, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Revisiting+the+role+of+yeast+Sfp1+in+ribosome+biogenesis+and+cell+size+control:+a+chemostat+study.">Revisiting the role of yeast Sfp1 in ribosome biogenesis and cell size control: a chemostat study.</a> Microbiology. 154, 337-346 (2008).</li><li>Gresham, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=System-level+analysis+of+genes+and+functions+affecting+survival+during+nutrient+starvation+in+Saccharomyces+cerevisiae.">System-level analysis of genes and functions affecting survival during nutrient starvation in Saccharomyces cerevisiae.</a> Genetics. 187, 299-317 (2011).</li><li>Levy, S. F., Ziv, N., Siegal, M. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bet+hedging+in+yeast+by+heterogeneous,+age-correlated+expression+of+a+stress+protectant.">Bet hedging in yeast by heterogeneous, age-correlated expression of a stress protectant.</a> PLoS Biol. 10, e1001325 (2012).</li><li>Kao, K. C., Sherlock, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Molecular+characterization+of+clonal+interference+during+adaptive+evolution+in+asexual+populations+of+Saccharomyces+cerevisiae.">Molecular characterization of clonal interference during adaptive evolution in asexual populations of Saccharomyces cerevisiae.</a> Nat. Genet. 40, 1499-1504 (2008).</li><li>Gresham, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+repertoire+and+dynamics+of+evolutionary+adaptations+to+controlled+nutrient-limited+environments+in+yeast.">The repertoire and dynamics of evolutionary adaptations to controlled nutrient-limited environments in yeast.</a> PLoS Genet. 4, e1000303 (2008).</li><li>Wenger, J. W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hunger+Artists:+Yeast+Adapted+to+Carbon+Limitation+Show+Trade-Offs+under+Carbon+Sufficiency.">Hunger Artists: Yeast Adapted to Carbon Limitation Show Trade-Offs under Carbon Sufficiency.</a> PLoS Genet. 7, e1002202 (2011).</li><li>Dunham, M. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characteristic+genome+rearrangements+in+experimental+evolution+of+Saccharomyces+cerevisiae.">Characteristic genome rearrangements in experimental evolution of Saccharomyces cerevisiae.</a> Proc. Natl. Acad. Sci. U.S.A. 99, 16144-16149 (2002).</li><li>Ronen, M., Botstein, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transcriptional+response+of+steady-state+yeast+cultures+to+transient+perturbations+in+carbon+source.">Transcriptional response of steady-state yeast cultures to transient perturbations in carbon source.</a> Proc. Natl. Acad. Sci. U.S.A. 103, 389-394 (2006).</li><li>Kresnowati, M. T. A. P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=When+transcriptome+meets+metabolome:+fast+cellular+responses+of+yeast+to+sudden+relief+of+glucose+limitation.">When transcriptome meets metabolome: fast cellular responses of yeast to sudden relief of glucose limitation.</a> Mol. Sys. Biol. 2, 49 (2006).</li><li>Tu, B. P., Kudlicki, A., Rowicka, M., McKnight, S. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Logic+of+the+yeast+metabolic+cycle:+temporal+compartmentalization+of+cellular+processes.">Logic of the yeast metabolic cycle: temporal compartmentalization of cellular processes.</a> Science. 310, 1152-1158 (2005).</li><li>Tzur, A., Kafri, R., LeBleu, V. S., Lahav, G., Kirschner, M. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cell+Growth+and+Size+Homeostasis+in+Proliferating+Animal+Cells.">Cell Growth and Size Homeostasis in Proliferating Animal Cells.</a> Science. 325, 167-171 (2009).</li><li>Conlon, I., Raff, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Size+control+in+animal+development.">Size control in animal development.</a> Cell. 96, 235-244 (1999).</li><li>Conlon, I. J., Dunn, G. A., Mudge, A. W., Raff, M. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Extracellular+control+of+cell+size.">Extracellular control of cell size.</a> Nat. Cell Biol. 3, 918-921 (2001).</li><li>Fussmann, G. F., Ellner, S. P., Shertzer, K. W., Hairston, N. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Crossing+the+hopf+bifurcation+in+a+live+predator-prey+system.">Crossing the hopf bifurcation in a live predator-prey system.</a> Science. 290, 1358-1360 (2000).</li><li>Cohen, E. P., Eagle, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+simplified+chemostat+for+the+growth+of+mammalian+cells:+characteristics+of+cell+growth+in+continuous+culture.">A simplified chemostat for the growth of mammalian cells: characteristics of cell growth in continuous culture.</a> J. Exp. Med. 113, 467-474 (1961).</li></ol>

Chemostats enable the cultivation of microbes in growth-controlled steady-state conditions. The cells grow continuously at a constant rate resulting in an invariant external environment. This is in contrast to batch culture methods in which the external environment is continuously changing and the rate of cell growth is determined by the complex interaction of environment and genotype. Thus, a major advantage of culturing microbes in chemostats over batch cultures is the ability to experimentally control the growth rate ...

The growth of cells is regulated by complex networks of interacting genetic and environmental factors1,2. The multifactorial regulation of cell growth necessitates a system-level approach to its study. However, the rigorous study of regulated cell growth is challenged by the difficulty of experimentally controlling the rate at which cells grow. Moreover, in even the simplest experiments extracellular conditions are frequently dynamic and complex as cells continuously alter their environment as they proliferate. A solution to these problems is provided by the chemostat: a method of culturing cells that enables experimental control of cell growth rates in defined, invariant and controlled environments.
The method of continuous culturing using a chemostat was independently described by Monod3 and Novick &amp; Szilard4 in 1950. As originally conceived, cells are grown in a fixed volume of media that is continually diluted by addition of new media and simultaneous removal of old media and cells (Figure 1). Coupled ordinary differential equations (Figure 2) describe the rate of change in cell density (x) and the concentration of a growth-limiting nutrient (s) in the chemostat vessel. Importantly, this system of equations predicts a single (nonzero) stable steady-state (Figure 3) with the remarkable implication that at steady-state, the specific growth rate of the cells (i.e. the exponential growth rate constant) is equal to the rate at which the culture is diluted (D). By varying the dilution rate it is possible to establish steady-state populations of cells at different growth rates and under different conditions of nutrient limitation.
The experimental control of growth rate using chemostats was critical to the development of an understanding of how cell physiology changes with rates of growth5,6. However, this former mainstay of microbiological methods became increasingly obscure during the explosion in molecular biology research during the late twentieth century. Today, renewed interest in growth control in both microbes and multicellular organisms and the advent of genome-scale methods for systems-level analysis has renewed motivation for the use of chemostats. Here, we describe three applications that capitalize on the precise control of cell growth rates and the external environment that are uniquely possible using chemostats. First, we describe the use of chemostats to investigate how the abundance of thousands of biomolecules - such as transcripts and metabolites - are coordinately regulated with growth rate. Second, we describe how chemostats can be used to obtain precise estimates of growth-rate differences between different genotypes in nutrient-limited environments using competition experiments. Third, we describe how chemostats can be used to study adaptive evolution of cells growing in constant nutrient-poor environments. These examples exemplify the ways in which chemostats are enabling systems-level investigations of cell growth regulation, gene by environment interactions and adaptive evolution.

<table border="1">
	<tbody>
		<tr>
			<td>Name of the reagent</td>
			<td>Company</td>
			<td>Catalogue number</td>
			<td>Comments (optional)</td>
		</tr>
		<tr>
			<td>Infors-HT Sixfors Chemostat</td>
			<td>Appropriate Technical Resources, Inc.</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Glass Bottle 9.5 L</td>
			<td>Fisher Scientific</td>
			<td>02-887-1</td>
			<td>For Media Vessel and Hosing</td>
		</tr>
		<tr>
			<td>Pinchcock</td>
			<td>Fisher Scientific</td>
			<td>05-867</td>
			<td>For Media Vessel and Hosing</td>
		</tr>
		<tr>
			<td>Stopper, Size 12, Green Neoprene</td>
			<td>Cole-Palmer</td>
			<td>EW-62991-42</td>
			<td>For Media Vessel and Hosing</td>
		</tr>
		<tr>
			<td>Straight Connector</td>
			<td>Cole-Palmer</td>
			<td>EW-30703-02</td>
			<td>For Media Vessel and Hosing</td>
		</tr>
		<tr>
			<td>General purpose ties 4 in</td>
			<td>Fisher Scientific</td>
			<td>NC9557052</td>
			<td>For Media Vessel and Hosing</td>
		</tr>
		<tr>
			<td>Tubing, Silicone Rubber</td>
			<td>Small Parts</td>
			<td>B000FMWTDE</td>
			<td>For Media Vessel and Hosing</td>
		</tr>
		<tr>
			<td>Tubing, Silicone, 3/8 in OD</td>
			<td>Fisher Scientific</td>
			<td>02-587-1Q</td>
			<td>For Media Vessel and Hosing</td>
		</tr>
		<tr>
			<td>Tubing, Silicone, 7/32 in OD</td>
			<td>Fisher Scientific</td>
			<td>02-587-1E</td>
			<td>For Media Vessel and Hosing</td>
		</tr>
		<tr>
			<td>Tubing, Stainless Steel, 3/16 in OD</td>
			<td>McMaster-Carr</td>
			<td>6100K164</td>
			<td>For Media Vessel and Hosing</td>
		</tr>
		<tr>
			<td>Tubing, Stainless Steel, 3/8 in OD</td>
			<td>McMaster-Carr</td>
			<td>6100K161</td>
			<td>For Media Vessel and Hosing</td>
		</tr>
		<tr>
			<td>Hook Connectors</td>
			<td>Fisher Scientific</td>
			<td>14-66-18Q</td>
			<td>For Media Vessel and Hosing</td>
		</tr>
		<tr>
			<td>Ratchet Clamp</td>
			<td>Cole-Palmer</td>
			<td>EW-06403-11</td>
			<td>For Media Vessel and Hosing</td>
		</tr>
		<tr>
			<td>Luer, Female</td>
			<td>Cole-Palmer</td>
			<td>EW-45512-34</td>
			<td>For Media Vessel and Hosing</td>
		</tr>
		<tr>
			<td>Luer, Male</td>
			<td>Cole-Palmer</td>
			<td>EW-45513-04</td>
			<td>For Media Vessel and Hosing</td>
		</tr>
		<tr>
			<td>Millipore Aervent MTGR05010 62 mm Filter, 0.2 &mu;m</td>
			<td>Fisher Scientific</td>
			<td>MTGR05010</td>
			<td>For Media Vessel and Hosing</td>
		</tr>
		<tr>
			<td>PTFE Acrodisc CR 13 mm filters, 0.2 &mu;m</td>
			<td>Fisher Scientific</td>
			<td>NC9131037</td>
			<td>For Media Vessel and Hosing</td>
		</tr>
		<tr>
			<td>Direct-Reading Flowtube for Air</td>
			<td>Cole-Palmer</td>
			<td>EW-32047-77</td>
			<td>For Nitrogen Gas Setup</td>
		</tr>
		<tr>
			<td>Direct-Reading Flowtube for Nitrogen</td>
			<td>Cole-Palmer</td>
			<td>EW-32048-63</td>
			<td>For Nitrogen Gas Setup</td>
		</tr>
		<tr>
			<td>Gas Proportioner Multitube Frames</td>
			<td>Cole-Palmer</td>
			<td>EW-03218-50</td>
			<td>For Nitrogen Gas Setup</td>
		</tr>
		<tr>
			<td>Regulator, Two-Stage Analytical</td>
			<td>Airgas</td>
			<td>Y12-N145D580</td>
			<td>For Nitrogen Gas Setup</td>
		</tr>
		<tr>
			<td>Hose Adaptor, Stainless Steel</td>
			<td>Airgas</td>
			<td>Y99-26450</td>
			<td>For Nitrogen Gas Setup</td>
		</tr>
		<tr>
			<td>Hose Male Adaptor</td>
			<td>Airgas</td>
			<td>WES544</td>
			<td>For Nitrogen Gas Setup</td>
		</tr>
		<tr>
			<td>Norprene Tubing</td>
			<td>US Plastics</td>
			<td>57280</td>
			<td>For Nitrogen Gas Setup</td>
		</tr>
		<tr>
			<td>Tripod Base</td>
			<td>Cole-Palmer</td>
			<td>EW-03218-58</td>
			<td>For Nitrogen Gas Setup</td>
		</tr>
		<tr>
			<td>Valve Cartridges</td>
			<td>Cole-Palmer</td>
			<td>EW-03217-92</td>
			<td>For Nitrogen Gas Setup</td>
		</tr>
		<tr>
			<td>Carboy 10 L</td>
			<td>Fisher Scientific</td>
			<td>02-963-2A</td>
			<td>For Media Preperation</td>
		</tr>
		<tr>
			<td>Steritop Sterile Vacuum Bottle-Top Filters, 1,000 ml, PES membrane; for 45 mm neck size</td>
			<td>Fisher Scientific</td>
			<td>SCGP-T10-RE</td>
			<td>For Media Preperation</td>
		</tr>
		<tr>
			<td>Media Bottle 100 ml, 45 mm neck size</td>
			<td>Fisher Scientific</td>
			<td>FB-800-100</td>
			<td>For Media Preperation</td>
		</tr>
		<tr>
			<td>calcium chloride&middot;2H2O</td>
			<td>Fisher Scientific</td>
			<td>C79-500</td>
			<td>Media Reagents</td>
		</tr>
		<tr>
			<td>sodium chloride</td>
			<td>Fisher Scientific</td>
			<td>BP358-1</td>
			<td>Media Reagents</td>
		</tr>
		<tr>
			<td>magnesium sulfate&middot;7H2O</td>
			<td>Sigma Aldrich</td>
			<td>230391</td>
			<td>Media Reagents</td>
		</tr>
		<tr>
			<td>potassium phosphate monobasic</td>
			<td>Fisher Scientific</td>
			<td>AC424205000</td>
			<td>Media Reagents</td>
		</tr>
		<tr>
			<td>ammonium sulfate</td>
			<td>Fisher Scientific</td>
			<td>AC423400010</td>
			<td>Media Reagents</td>
		</tr>
		<tr>
			<td>potassium chloride</td>
			<td>Sigma Aldrich</td>
			<td>P9541</td>
			<td>Media Reagents</td>
		</tr>
		<tr>
			<td>boric acid</td>
			<td>Sigma Aldrich</td>
			<td>B6768</td>
			<td>Media Reagents</td>
		</tr>
		<tr>
			<td>copper sulfate&middot;5H2O</td>
			<td>Sigma Aldrich</td>
			<td>209198</td>
			<td>Media Reagents</td>
		</tr>
		<tr>
			<td>potassium iodide</td>
			<td>Sigma Aldrich</td>
			<td>60400</td>
			<td>Media Reagents</td>
		</tr>
		<tr>
			<td>ferric chloride&middot;6H2O</td>
			<td>Fisher Scientific</td>
			<td>I88-100</td>
			<td>Media Reagents</td>
		</tr>
		<tr>
			<td>manganese sulfate&middot;H2O</td>
			<td>Sigma Aldrich</td>
			<td>230391</td>
			<td>Media Reagents</td>
		</tr>
		<tr>
			<td>sodium molybdate&middot;2H2O</td>
			<td>Sigma Aldrich</td>
			<td>M7634</td>
			<td>Media Reagents</td>
		</tr>
		<tr>
			<td>zinc sulfate&middot;7H2O</td>
			<td>Fisher Scientific</td>
			<td>Z68-500</td>
			<td>Media Reagents</td>
		</tr>
		<tr>
			<td>biotin</td>
			<td>Fisher Scientific</td>
			<td>BP232-1</td>
			<td>Media Reagents</td>
		</tr>
		<tr>
			<td>calcium pantothenate</td>
			<td>Fisher Scientific</td>
			<td>AC24330-1000</td>
			<td>Media Reagents</td>
		</tr>
		<tr>
			<td>folic acid</td>
			<td>Sigma Aldrich</td>
			<td>F7876</td>
			<td>Media Reagents</td>
		</tr>
		<tr>
			<td>inositol (aka myo-inositol)</td>
			<td>Fisher Scientific</td>
			<td>AC12226-1000</td>
			<td>Media Reagents</td>
		</tr>
		<tr>
			<td>niacin (aka nicotinic acid)</td>
			<td>Sigma Aldrich</td>
			<td>N4126</td>
			<td>Media Reagents</td>
		</tr>
		<tr>
			<td>p-aminobenzoic acid</td>
			<td>Fisher Scientific</td>
			<td>AC14621-2500</td>
			<td>Media Reagents</td>
		</tr>
		<tr>
			<td>pyridoxine HCl</td>
			<td>Sigma Aldrich</td>
			<td>P9755</td>
			<td>Media Reagents</td>
		</tr>
		<tr>
			<td>riboflavin</td>
			<td>Sigma Aldrich</td>
			<td>R4500-25G</td>
			<td>Media Reagents</td>
		</tr>
		<tr>
			<td>thiamine HCl</td>
			<td>Fisher Scientific</td>
			<td>BP892-100</td>
			<td>Media Reagents</td>
		</tr>
		<tr>
			<td>Leucine</td>
			<td>Sigma Aldrich</td>
			<td>L8000-100G</td>
			<td>Media Reagents</td>
		</tr>
		<tr>
			<td>Uracil</td>
			<td>Sigma Aldrich</td>
			<td>U0750</td>
			<td>Media Reagents</td>
		</tr>
		<tr>
			<td>Dextrose</td>
			<td>Fisher Scientific</td>
			<td>DF0155-08-5</td>
			<td>Media Reagents</td>
		</tr>
	</tbody>
</table>

the use of chemostats in microbial systems biology

Cells regulate their rate of growth in response to signals from the external world. As the cell grows, diverse cellular processes must be coordinated including macromolecular synthesis, metabolism and ultimately, commitment to the cell division cycle. The chemostat, a method of experimentally controlling cell growth rate, provides a powerful means of systematically studying how growth rate impacts cellular processes - including gene expression and metabolism - and the regulatory networks that control the rate of cell growth. When maintained for hundreds of generations chemostats can be used to study adaptive evolution of microbes in environmental conditions that limit cell growth. We describe the principle of chemostat cultures, demonstrate their operation and provide examples of their various applications. Following a period of disuse after their introduction in the middle of the twentieth century, the convergence of genome-scale methodologies with a renewed interest in the regulation of cell growth and the molecular basis of adaptive evolution is stimulating a renaissance in the use of chemostats in biological research.

A major advantage of chemostats is the ability to control the growth rate of cells experimentally by varying the dilution rate. In the budding yeast, Saccharomyces cerevisiae, the morphology of a cell is informative of its phase in the cell division cycle. Populations with higher growth rates contain a higher proportion of actively dividing cells as determined by measuring the fraction of unbudded cells (Figure 5A). Analyses of global mRNA expression in chemostat cultures has shown that the expression of...

Watch this Scientific Journal Video about The Use of Chemostats in Microbial Systems Biology at JoVE.com

The Use of Chemostats in Microbial Systems Biology

Cell growth rate is a regulated process and a primary determinant of cell physiology. Continuous culturing using chemostats enables extrinsic control of cell growth rate by nutrient limitation facilitating the study of molecular networks that control cell growth and how those networks evolve to optimize cell growth.

Cells regulate their rate of growth in response to signals from the external world. As the cell grows, diverse cellular processes must be coordinated ...

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