Fungal and bacterial growth measurements in soil

Background/Question/Methods

Bacterial and fungal growth rate measurements are sensitive variables to detect changes in environmental conditions. However, while methods to assess the species composition and biomass of fungi and bacteria have made prodigious progress, information about growth rates remains surprisingly rudimentary. Successful approached to assess the growing microbial community have included leucine/thymidine incorporation to estimate bacterial growth and acetate incorporation into ergosterol to estimate fungal growth. I will briefly describe underlying assumptions for these methods, compare estimates of turnover times for fungi and bacteria based on them, and discuss issues, including e.g. elusive conversion factors.

Results/Conclusions

I will review what the application of fungal and bacterial growth rate methods has revealed regarding the influence of the environmental factors temperature, moisture (including drying/rewetting), pH, as well as the influence of substrate additions. I will also highlight experiments exploring competitive and facilitative interaction between bacteria and fungi enabled using growth rate methods. Additionally, the use of growth-based methods has enabled the application of tolerance assays to accurately resolve and distinguish between the effects of various environmental factors, including toxins and pH, on the microbial community. Finally, I will show that growth methods will be an important complement to molecular approaches to elucidate fungal and bacterial ecology.