IF USAIN BOLT WERE STRUCK BY LIGHTNING – THE WORLD’S FASTEST GROWING PLANT CELL MANAGES EXTREME ENERGY INPUTS

When photoautotrophic organisms grow in full sunlight, they are provided with an energy source far exceeding their needs even for rapid growth. In these situations, not only is energy not the limiting factor for growth, but the excess may even be detrimental (e.g. due to oxygen radical formation). For this reason, most photoautotrophs exposed to strong irradiance actively limit their photic energy input to a level necessary for growth. Not so with the fastest-growing member of this group. Chlorella ohadii (a green microalga) outstrips all known plant cells in its growth and yet does not exhibit the mechanism commonly associated with energy input reduction – photoinhibition. Thus, this organism grows with a generation time as short as 1.5 hours under 3500 μE light without changing its affective antenna cross-section. The result is a physiologically well-functioning cell with a massive energy input, far beyond requirement for even as high a growth rate as indicated. This situation indicates an energy management strategy unique to this organism, which may be a major factor in enabling the unprecedented growth rate. Using a combination of physiological methods, we explore and quantify the energy fluxes in C. ohadii and analyze the overall strategy implied thereby. We hypothesize on the role of said strategies in the natural environment and implications for the broader study of growth rate in primary producers.