Upstream-directed Growth of Filamentous Fungi in a Flowing Medium.

In a flowing medium, more than 80% of the hyphae of filamentous fungi tended to grow against the flow. We call this phenomenon upstream-directed growth. Five strains of Aspergillus spp. showed this upstream-directed growth, but Rhizopus stolonifer and two strains of Penicillium spp. did not. In the flow rate range of 1-11ml/h (200-2200μm/s), no appreciable difference was observed in the manner of growth. In response to an alteration in the direction of flow, the growth direction of the hyphae altered accordingly, which suggested that fungi were sensing the flow direction all the time. It was also suggested that such a phenomenon was controlled by physical rather than by a chemical factors.