morbidostat

A morbidostat is a type of bioreactor designed to maintain a population of microorganisms at a constant, sub-lethal level of a toxic agent. This is achieved by continuously measuring the population density and adjusting the concentration of the toxic agent to keep it just below the threshold that would cause a significant population decline. The name is derived from the words "morbid" (referencing the presence of a toxin) and "stat" (fromostat, referring to a continuous culture system that maintains constant conditions).

The primary application of a morbidostat is in the study of microbial evolution, particularly in the development of resistance to antibiotics or other toxic compounds. By exposing a microbial population to a low but persistent level of a toxin, researchers can observe the selection and adaptation processes that lead to the emergence of resistant strains. Over time, the population will evolve to tolerate higher concentrations of the toxin, allowing researchers to track the genetic and phenotypic changes associated with this adaptation.

Morbidostats typically involve automated feedback loops. Sensors monitor cell density, and this data is used to control a pump that adds fresh media containing the toxic agent. If the cell density drops, indicating the toxin is too potent, the concentration of the toxin in the incoming media is reduced. Conversely, if the cell density rises significantly, the toxin concentration can be increased. This continuous adaptation allows for the generation of populations with incrementally increased resistance.