This question is being addressed by eliminating "unnecessary" gene from simple bacteria. Cells placed in a rich nutrient broth with essential lipids, vitamins, and amino acids would need fewer genes than those placed in a more nutrient-poor medium. Bacteria cells like Mycoplasma genetalium, that live within "nutrient rich" eukaryotic cell, have been genetically manipulated to delete unnecessary genes. Based on knockout studies, it may be possible for the cell to survive with only 300-350 genes. Bacillus subtilis has approximately 4100 genes. Estimates have been made that it could survive with as few as 271 genes.
more to be added