<span>This would be an estimated average requirement, or EAR. This amount is considered what would be "average" for the predominant body type and person regarding the intake of a nutrient. This may be more or less than what will be later calculated as the recommended daily allowance for that nutrient.</span>
Because they are prokaryotic cells.
Those organisms don't have chloroplasts in their cells which is required for photosynthesis to occur.