This study demonstrates that applied electrical fields significantly influence polarized growth in filamentous fungi. Researchers exposed five fungal species—Neurospora crassa, Aspergillus nidulans, Mucor mucedo, Trichoderma harzianum, and Achlya bisexualis—to electrical fields ranging from 0-40 V cm⁻¹ embedded in agarose gels. N. crassa and A. bisexualis exhibited anodotropism (growth toward the anode), while A. nidulans and M. mucedo showed cathodotropism (growth toward the cathode). T. harzianum displayed complex behavior with hyphae growing cathodotropically while branches formed anodotropically. Electric fields polarized germ tube emergence, controlled branching location and frequency, and directed hyphal extension. At higher field strengths, hyphae reoriented perpendicular to the applied field. The threshold field strength for effects was approximately 1-2 mV per cell diameter, comparable to endogenous electrical fields measured in fungal hyphae. The results support the hypothesis that electrical fields control cell polarity through mechanisms involving electrophoresis of intracellular proteins and organelles or by modulating ion currents essential for polarized growth.

Key findings

• Applied electrical fields polarize growth in multiple fungal species, with different species showing either anodotropic or cathodotropic responses
• Threshold field strength for galvanotropism (~1-2 mV per cell diameter) is comparable to endogenous fields measured in fungal hyphae
• At higher field strengths, hyphae reorient perpendicular to the applied field, potentially minimizing membrane potential perturbations
• Electric fields accelerate and synchronize germination and increase branching frequency in N. crassa
• The mixed directional responses across species despite similar endogenous electrical polarity suggests electrical fields control polarity through multiple mechanisms