∞ generated and posted on 2016.12.15 ∞

Means of culturing microorganisms under constant physiological conditions over long time frames that involves a constant rate of input of fresh media.

A Chemostat is a microorganism culturing devise in which a constant amount of media is supplied to a growth chamber in which cells grow in number to the point that they utilize media as fast as it enters, with the volume entering the growth chamber exactly balanced by the volume leaving, which carryies wastes as well as organisms out of the growth chamber.

Chemostats are a means of achieving what more generally can be described as continuous cultures and chemostats specifically are also known as continuously stirred tank reactors. At its simplest, a chemostat involves a constant-rate inflow of fresh media, stirring within a growth vessel, and a constant-rate outflow (equal to the rate of inflow) of the resulting culture.

Figure legend: Schematic of a chemostat. Fresh media flows from the media reservoir (containing sterile growth media) into the growth chamber where it is consumed. Spent media flows out of the growth chamber as into the waste chamber, and this occurs at the same rate as>inflow. Chemostats can be completely gravity fed though more typically peristaltic pumps are enlisted to move media at some constant rate into the growth chamber. Note that resources are 'born' into chemostats via inflow while all constituents within growth chambers 'die' due to washout, as occurs during outflow from the growth chamber. Note also that more complicated chemostats can be assembled. In a so-called two-stage chemostat, for example, mediaflows into a first-stage growth chamber in which cells can replicate while those cells then flow, as 'die' due to washout/die due to outflow, into a second-stage growth chamber in which organisms that prey on those cells, such as viruses, display their replication. In another variation on continuous culture, called a turbidostat, the rate of media inflow is not entirely continuous but instead is controlled by the culture's turbidity such that culture turbidity is maintained at a more or less constant level. In many instances chemostats too display a constant turbidity.

A chemostat resembles a simple as well as well-mixed pond.