The effect of iron concentration on the growth rate of Chlamydomonas reinhardtii

Abstract

This study addresses how the growth rate of Chlamydomonas reinhardtii is affected by the concentration of iron present in the growth medium. To investigate this effect, we grew cells of Chlamydomonas reinhardtii under zero, half, standard and double iron concentrations defined relative to the standard concentration of iron used in their standard growth medium (46.2 µM). Exponential growth was observed under all conditions throughout the 23 day measurement period apart from under zero iron conditions, where the growth was observed to plateau at approximately day 10 resulting in significantly lower cell abundance on day 23 compared to the three iron treatments. No significant differences were observed between cells grown under the half and standard iron concentrations, suggesting half (23.1 µM) of the standard concentration of iron is sufficient to support growth over this time scale. Increased iron concentration was shown to be stimulatory to growth, with the cells grown under the double iron concentrations (92.4 µM) showing significantly higher cell abundance compared to the cells grown under half iron concentrations by day 16, and significantly higher cell abundance than the cells grown under standard iron concentrations by the end of the measurement period on day 23. This result supports our alternate hypothesis that the growth rate of Chlamydomonas reinhardtii will increase with respect to increasing iron concentration present in growth medium.