Figure 1.

The plot shows an original registration of the oxygen concentration during a titration experiment at low oxygen. The method used to calculate the oxygen flux (JO2) in terms of the decay of oxygen concentration over time corresponds to the standard in respirometry. However, it was modified for the actual experiment to account for the need to maintain the oxygen concentrations within narrow ranges. Therefore, the titration pump (TIP-2K^®, see arrows in the botton) was used to automatically inject small volumes (50 – 100 nl) of peroxide to the catalase supplemented respiration medium, in order to restore the oxygen concentration once it felled due to the cell’s respiration below the lower limit set for the control algorithm of the pump (lower horizontal line). In that way, oxygen concentration re-increased up to the upper limit of the control algorithm (upper horizontal line), and was then allowed to fall again. This linear fall of the oxygen concentration, which is the result of the cell’s respiration, is used to calculate the JO2 (dotted line). In summary, the basic principle of calculating the JO2 is that normally used in respirometry, but slightly modified to account for the necessity to keep the oxygen within very small concentration ranges.