Biology and Fertility of Soils

, Volume 11, Issue 3, pp 216–220

An improved and accurate method for determining the dehydrogenase activity of soils with iodonitrotetrazolium chloride

  • W. von Mersi
  • F. Schinner

DOI: 10.1007/BF00335770

Cite this article as:
von Mersi, W. & Schinner, F. Biol Fertil Soils (1991) 11: 216. doi:10.1007/BF00335770


Conditions for a rapid, precise [100 μg iodonitrotetrazolium chloride (INT)-formazan ml-1 assay mixture], and easily reproducible assay of potential soil dehydrogenase activity are described, using 2(p-iodophenyl)-3-(p-nitrophenyl)-5-phenyl tetrazolium chloride (iodonitrotetrazolium chloride, INT) as the substrate. Reduced iodonitrotetrazolium formazan (INTF) was measured by spectrophotometry (464 nm) after extraction with N,N-dimethylformamide and ethanol. With this method, the coloured complex formed is highly stable. The effects of pH, buffer concentration, temperature, substrate concentration, amount of soil weight, and reaction time on dehydrogenase activity were investigated. The rate of substrate hydrolysis was proportional to soil weight; the optimal INT reduction was achieved with 1 M TRIS buffer (pH 7.0) at 40 °C. It was possible to determine the biotic and abiotic substrate reduction by comparing assays of autoclaved and unsterile soil samples. Different investigations have confirmed that the intracellular enzyme is highly correlated with the microbial biomass, and indicate that this activity is suitable as an indirect parameter of microbial biomass, measurement.

Key words

Dehydrogenase activity Iodonitrotetrazolium chloride (INT) Microbial biomass Microbial activity 

Copyright information

© Springer-Verlag 1991

Authors and Affiliations

  • W. von Mersi
    • 1
  • F. Schinner
    • 1
  1. 1.Institute of MicrobiologyUniversity of InnsbruckInnsbruckAustria

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