Fungi vs Bacteria: Their Different Roles in Decomposition of Organic Matter

Even though a high proportion of both fungi and bacteria are decomposers in the soil, they degrade plant residues differently and have different roles in the recycling of nutrients. This is partly due to their different choice of habitats within the soil and the different types of organic matter they consume.

Fungi are generally much more efficient at assimilating and storing nutrients than bacteria. One reason for this higher carbon (C) storage by fungi lies in the chemical composition of their cell walls. They are composed of polymers of chitin and melanin, making them very resistant to degradation. Bacterial membranes, in comparison, are phospholipids, which are energy-rich. They degrade easily and quickly and function as a food source for a wide range of microorganisms.

The different proportions of C and N (i.e. different C:N ratios) of bacteria and fungi might also play a role in the mineralisation and immobilisation processes of nutrients in the soil. Due to their structure and C:N ratio between 7:1 and 25:1, fungi need a greater amount of carbon to grow and reproduce and will therefore 'collect' the required amount of carbon available for this from the soil organic matter. Bacteria, however, have a lower C:N ratio (between 5:1 and 7:1) and a higher nitrogen requirement and take more nitrogen from the soil for their own requirements.

Refer to ‘Soils are Alive’ newsletter Volume 3 Number 3 “The fungal-bacterial ratio: Tipping the balance for soil health” by Florian Wichern.