Low Energy Effects of Light on Growth and Pigment Content in a Yellow-in-the-Dark Mutant of Chlamydomonas reinhardi

Abstract

Summary. The y-2 mutant of Chlamydomitonas reinhardi differs from the wild type in being uinable to synthesize chlorophyll in the dark and in a reqtlirement for catalytic amounts of light for organotrophic growth. Light-grown y-2 cells given acetate are capable of the eqtuivalent of 9 to 10 divisions when placed in darkness. Cultulres adapt gradually to di,m white or monochromatic light and after 8 to 10 generations assume a steady state with respect to growth and pigment content.Two energeti,cally distinct light reactions promote the growth of y-2 on acetate. by iising Bausch and Lomb 2" X 2" neuitral density filters. To achieve the desired intensities 1 or more of these were tapetl to the bottoms oQf flasks that ha(l been otherwise thoroughly wrapped in electrician's tape. Aluminuim foil caps prevented stray light from entering through the cotton stoppers. The cuilttures inside thus received light only from helow through the filters.A second series of exiperiments called for very low energy irradiations with monochromatic light. The technique emploved was similar to that uised in PHYSIOLOGY the white light experiments except that the flasks were placed in a light-tight wooden box that contained 8 isolated compartments. Set into the bottom of each compartment was a sqtuare 2" X 2" hole that exactly held an interference filter. The filters were stipplied by Baird-Atomic, Inc. (series B-2 and B-3) and had steep-sided transmission bands with one-half band widths of 15 to 30 nm. The transmission characteristics of the filters were determined spectrophotometrically and none were found to pass additional bands in the visible or at wavelengths shorter thani 1.0 IL in the near IR. Since very small quantities of light were needed, the filters were covered with electrician's tape so that light was allowed to pass only through a small rectangular opening, uisually less than 0.5 cm2 in area. The light energies that reached flask bottom level after passing through the various filters and filter combinations were measuired with an Eppley thermopile.In the action spectruim experiments the amoulnit of energy reaching the cuilttures was regulated by varying the area of the tape-bordered openinigs OI the filters through which light was allowed to pass.MIost of the experiments were carried throulgh a number of serial transfers of the cultures. The quantity of cell suispension that wvas inoctulated into fresh meditum on each occasioin depended on the expected cell density and growth rate of the ctultuire heing transferred. IIn this manner cell densities in all the cuilttures of a series were kept withiln the same range of 104 to 3 X 106 cells/ml. At the endl of a runl, normally after 2 to 4 days of growth, each cultuire was apportioned in the following mannier.Ani appropriate amouint, usually 2 to 10 ml, was iised for inoculuim to continuie the experiment. Another-2 ml was set aside for hemacytometer cou1nts of cell density. The remainder wvas then drawn throuigh a glass fiber filter (Gelman) in order to harvest the cells. The fil...

Phytotoxicity Evaluation of Type B Trichothecenes Using a Chlamydomonas reinhardtii Model System

“…The red LED condition was able to obtain the most characteristic differences because it was the best growth condition in this study. This growth trend corresponds with another study that found maximal chlorophyll content and cell volume in the red spectrum [ 30 ]. The result of this study suggests that red spectrum lighting is the most efficient evaluation condition because it gives rapid growth and characteristic growth rates.…”

“…[ 29 ] applied 18–36 μmol m −2 s −1 of blue LED in a photo-bioreactor to produce astaxanthin using a Haematococcus pluvialis system suggesting that blue LED is a useful testing condition. However, the most efficient growth of C. reinhardtii had been observed around the red spectra in a study that employed a chlorophyll synthesis mutant [ 30 ]. The red spectrum mainly consists of 660 nm and is also an important wavelength for photosynthesis.…”

CRYPTIC DIVERSITY IN PHYTOPLANKTON CULTURES IS REVEALED USING A SIMPLE PLATING TECHNIQUE1

“…The studies presented above, documenting diversity at progressively smaller scales, could naturally be extended to assess the genetic variation that occurs within laboratory cultures of algae. Indeed, recognition that diversity can exist in cultures has come from identification and isolation of mutant individuals (Terborgh et al. 1967, Wollman 1979, Gieskes and Buma 1997).…”