This protocol describes the use of the 2,3,5-triphenyl-2H-tetrazolium chloride (TTC) salt to evaluate the cell redox potential of rhizobia cells. The production of brightly colored and insoluble 1,3,5-Triphenyltetrazolium formazan arising from TTC reduction is irreversible and can be easily quantified using a spectrophotometer. This protocol allows the production of reproducible results in a relatively short time for Sinorhizobium meliloti 1021 cells grown both in exponential and stationary phases. The results here presented show that the S. meliloti cells deriving from exponential-phase cultures had increased cell redox potential as compared to the ones deriving from stationary-phase cultures. This means that under exponential growth conditions the S. meliloti cells generate higher amount of reducing equivalents needed for TTC reduction.
Keywords: 1; 2; 3; 5-Triphenyltetrazolium formazan; 5-triphenyl-2H-tetrazolium chloride (TTC); Bacterial cells; Cell redox potential; Sinorhizobium meliloti 1021.
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