Abiotic-biotic networks
The interplay of abiotic and biotic reactions on a molecular scale is poorly understood and we are just beginning to disentangle what is biotic and abiotic in natural systems.
Denitrification in tropical acidic soils is a "mosaic" of abiotic and biotic reactions. Iron and organic matter provide catalytic sites for nitrite reduction.
The nitrogen cycle on the Archean Earth was completely abiotic in its early stages. Slowly, life inserted enzymatic reactions to harvest energy from chemical disequilibria.