Algal Lipid Body Quantification

The number of algal cells with and without lipid bodies was counted along with the total number of lipid bodies present per ten fields of view [75 (link), 76 (link)]. An average lipid body per cell was determined for every 1024 × 1024 8-bit frame. The average size of lipid bodies per frame was also measured by Nikon confocal software per field of view to compare the treated algal cells with the control [73 (link), 77 (link)]. The Nikon NIS-Elements confocal software counted and summed all the pixels in the chosen fields that were above the selected threshold of brightness, thereby computing the total area of the above-threshold entities [72 (link)]. The threshold was adjusted by highlighting lipid bodies; if they varied in brightness, the least bright lipid body in the selected field served as the threshold baseline [72 (link)]. The output of each calculation yielded the average lipid body area per frame. It should be noted that measurement of lipid body area underestimates the spherical volume and hence will also underestimate the yield. It will be a comparison of lipid body areas that allows for accurate assessment of the relative yields from different samples [72 (link)].