Attempted biostimulation of division in Saccharomyces cerevisiae using red coherent light

Replicate cultures of the yeast Saccharomyces cerevisiae were irradiated with 632.8 nm coherent light from He-Ne lasers at irradiances of 6.5 x 10(15) and 1.0 x 10(16) photons s-1 cm-2. Irradiation periods ranged from 0 to 652 min, and cultures were grown until well into the exponential phase. Unirradiated control cultures were grown alongside the irradiated cultures under otherwise identical conditions. The extents of growth in the control and irradiated cultures were compared spectrophotometrically at the end of each experiment. Contrary to the expectations of Karu et al. (e.g. Karu, 1988, Lasers Life Sci. 2, 53-74) no growth enhancement was found in the irradiated cultures, but a mild inhibitory effect was observed.