Phototaxigraph: Recording Instrument for Determination of Rate of Response of Phototactic Microorganisms to Light of Controlled Intensity and Wavelength

Abstract

An instrument has been developed which measures the rate of phototaxis in a suspension of microorganisms by recording the increase in optical density which results when the organisms accumulate in a beam of stimulating light. Intensity and spectral quality of the actinic light, as well as of randomly scattered background illumination, can be controlled. Density changes are measured with a dual chopped beam arrangement using infrared light. Thermostatic control of the temperature of the sample is provided.