LAUSR

Symbiosis Filamentous fungi such as Aspergillus nidulans grow by hyphal branching and extension in a multicellular network. These networks make “highways” through the soil for motile bacteria such as Bacillus subtilis , but whether this relationship is exploitative or mutualist is not well understood. Abeysinghe et al. found that when B. subtilis grows together with A. nidulans , the bacteria's thiamine biosynthesis operon is induced. However, the fungal equivalent is repressed, and the authors presume that this is to save metabolic costs. If the fungal operon is experimentally ablated, the resulting growth defect of the fungus can be rescued by intact B. subtilis . It appears that bacteria using the fungal highway to reach new foraging grounds pay for the ride by delivering thiamine to the hyphal tips. Life Sci. Alliance 3 , e202000878 (2020).