This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
Continuous cell culture of bacteria 
Select and explain. 
A. U tube, B. Craige tube, C. Chemostat device, D. Agar dilution method
C: Chemostat device
Answer: C: Chemostat device 
Explanation: Ans. is 'c' i.e., Chemostat device Bacterial cultures can be maintained in a state of exponentional growth over long periods of time using a system of continuous culture. Continuous culture, in a device called chemostat, can be used to maintain a bacterial population at a constant density, a situation that is, in many ways, more similar to bacterial growth in natural environments. In a chemostat microbial cells are grown at a steady state where cell biomass production, substrates and products concentrations remains constant, and growth occurs at a constant rate. These features make a chemostat unique and powerful tool for biological and physiological research.