morbidostaten

The morbidostat, sometimes referred to as morbidostaten in some languages, is a laboratory device used for experimental evolution of bacteria under antibiotic pressure. It automates culture growth and drug dosing to study how organisms acquire resistance.

Design and operation: The morbidostat uses measurements of bacterial growth, typically via optical density, and employs a feedback control system to adjust antibiotic concentrations in the culture medium. The aim is to keep growth at a submaximal but ongoing rate, creating a persistent selection pressure that favors resistance while preventing culture washout. By continuously cycling drug exposure with growth, it enables real-time observation of evolutionary trajectories.

Background and usage: Morbidostats are specialized variants of continuous culture systems, alongside chemostats and turbidostats, tailored for antibiotic evolution experiments. They were described in the scientific literature in the early 2010s as a means to accelerate the study of how resistance emerges under controlled drug pressure. Although commonly demonstrated with Escherichia coli, the approach has been applied to other bacterial species and a range of antimicrobial compounds to explore the dynamics of mutation and adaptation.

Applications and limitations: The morbidostat supports investigation of resistance mechanisms, mutation order, and cross-resistance patterns under dynamic drug regimens. It can reveal how selective pressure shapes evolutionary pathways in real time. Limitations include technical complexity, the need for precise calibration and maintenance of equipment, potential biases from culture conditions, and challenges in translating laboratory results to clinical contexts.

See also: Chemostat, Turbidostat, Experimental evolution.