A turbidostat is a continuous

microbiological culture A microbiological culture, or microbial culture, is a method of multiplying microbial organisms by letting them reproduce in predetermined culture medium under controlled laboratory conditions. Microbial cultures are foundational and basic diagn ...

device, similar to a

chemostat A chemostat (from ''chem''ical environment is ''stat''ic) is a bioreactor to which fresh medium is continuously added, while culture liquid containing left over nutrients, metabolic end products and microorganisms is continuously removed at the sa ...

or an

auxostat An auxostat is a continuous culture device which, while in operation, uses feedback from a measurement taken on the growth chamber to control the media flow rate, maintaining the measurement at a constant. Auxo was the Greek goddess of spring gr ...

, which has feedback between the

turbidity Turbidity is the cloudiness or haziness of a fluid caused by large numbers of individual particles that are generally invisible to the naked eye, similar to smoke in air. The measurement of turbidity is a key test of water quality. Fluids ...

of the culture vessel and the dilution rate. The theoretical relationship between growth in a

and growth in a turbidostat is somewhat complex, in part because they are similar. A

has a fixed volume and flow rate, and thus a fixed dilution rate. A turbidostat dynamically adjusts the flow rate (and therefore the dilution rate) to make the turbidity constant. At steady state, operation of both the chemostat and turbidostat are identical. It is only when classical chemostat assumptions are violated (for instance, out of equilibrium; or the cells are mutating) that a turbidostat is functionally different. One case may be while cells are growing at their maximum growth rate, in which case it is difficult to set a chemostat to the appropriate constant dilution rate. While most turbidostats use a spectrophotometer/turbidimeter to measure the optical density for control purposes, there exist other methods, such as dielectric permittivity. The morbidostat is a similar device built to study the evolution of antimicrobial resistance. The aim is also to maintain constant turbidity levels, but this is controlled using the addition of antimicrobials.

References

{{Laboratory equipment Bioreactors