Application of resazurin for estimating abundance of contaminant-degrading micro-organisms

AIMS: The aim of the current study was to test whether resazurin changed colour when incubated with a range of organic chemicals used as growth substrates in bioremediation studies and to determine whether resazurin was more effective in estimating microbial growth than turbidity alone (i.e. no resazurin) or use of the dye, methylene blue. METHODS AND RESULTS: Resazurin was incubated with a range of organic chemicals that were used as substrates in an MPN assay. Only 1,2-dichlorobenzene, 2,4-D, glycol sulphite and sulphinol reacted to generate false positives. Resazurin was also used to estimate micro-organisms in a series of bioremediation studies. CONCLUSION: The results showed that resazurin was more sensitive than methylene blue or turbidity alone as an indicator of microbial growth. SIGNIFICANCE AND IMPACT OF THE STUDY: The significance of the current study is that resazurin should be used in MPN assays for estimating contaminant-degrading micro-organisms instead of turbidity alone or other dyes such as methylene blue.