Holographic optical manipulation of hyphal growth in filamentous fungi

The filamentous fungi are an extremely important group of organisms, e.g. in causing human and crop diseases, food spoilage, nutrient recycling in the biosphere, promoting the growth of plants with which they have symbiotic associations, food production, brewing, and as a source of pharmaceutical drugs. We present the use of holographically created light fields to produce atypical growth patterns in filamentous fungi. Extended fields of tightly focused light are shown to redirect and constrict hyphal tip growth, and induce hyphal branching in a highly reproducible manner. We compare the use of discrete and continuous light fields produced using a spatial light modulator, and the use of three dimensional ´pseudowalls´ of light to improve the consistency of growth alteration is reported. We also demonstrate that hyphal tip growth is dependent on the wavelength of light used, finding that less power is needed at shorter wavelengths to affect a similar change in the growth dynamics of fungal hyphae. It has been established that both 532 nm and 830 nm optical traps can be used to manipulate hyphal growth and branching [Wright, et al., 2007].Here we examined the effects of 532 and 1064 nm light, and included further experiments with 785 nm light for comparison. The minimum power need to cause a change in the pattern of hyphal growth varied largely with wavelength.