The grape string theory is inspired by Mortierella and Trichocladium species that promote soil aggregation more than indigenous microorganisms

•Biological and abiotic aggregates are clearly presented.•The grape cluster theory of soil agglomeration is proposed.•A single fungus has more advantages in accelerating soil aggregation.•Both lower and higher fungi promote soil aggregation.•Extracellular polymeric substance uronic acid promotes soil aggregation.