Real Time Robotic Respirometer for Microplate Formats.

Evolved CO₂ from living cells is used to assess metabolic activity, growth rate, substrate utilization efficiency, and also as a proxy for toxicity.  In individual 20ml or larger incubation vessels, head space analysis by infrared gas analysis or laser spectroscopy are favored for measuring evolved CO₂ due to their accuracy and the fact that chemical reagents are not needed. However, an increasing amount of microbial ecology work is now being performed in high throughput microplate formats, but current microplate lids prevent sampling the headspace of individual wells in real time. Agar-based colorimetric respiration lid systems are available for microplates, but the lid-securing mechanism obscures the plate, making it difficult to acquire data during the incubation period. In addition, the colorimetric response is non-linear; the sealed plate also limits the length of aerobic experiments and prevents reagent additions during its course. Therefore, I developed a real time, robotic, data logging respirometer for microplate formats. A non-invasive robotic gantry controls the X,Y and Z position of a non dispersive infrared CO₂ sensor. A custom fabricated microplate lid enables the sensor to sample the head space and exchange it with fresh air or choice of gas. The data is logged to an SD card, while a duplicate data packet is pushed to the internet. Real time graphs can be viewed online. The system can send text messages or email when preset threshold levels are reached. Researchers can monitor ongoing experiments while they are outside the lab using a smart phone. The bench top device is expected to incubate and assay up to 12 microplates at a time (6, 12, 24, 48 or 96 wells each), with a sampling rate as high as ~5 min/plate.