If radiolabeled acetate is offered in solution to fungi, the fungi will use it for membrane (ergosterol) synthesis. The instantaneous rate of fungal growth can be measured as rate of incorporation of radioacetate into ergosterol. After the hot incubation, ergosterol is extracted and determined via HPLC. The ergosterol peak is captured as it exits the chromatograph detector, and its radioactivity determined in a scintillation counter. The extent to which ergosterol has become radioactive is proportional to the fungal growth rate. The image below shows the linearity over a 4-h period of the rate of acetate incorporation into ascomycete ergosterol in naturally decaying blades of smooth cordgrass (Spartina alterniflora). See Gessner & Newell, 2002, pp 390-408 in C Hurst et al. (eds) Manual of Environmental Microbiology, 2nd Edition, ASM Press, Washington, DC; Newell SY, 2001, pp 357-372 in JH Paul (ed.), Methods in Microbiology. Volume 30. Marine Microbiology. Academic Press, London.