This chapter gives an overview of the minimum genome factory (MGF) of the fission yeast Schizosaccharomyces pombe (S. pombe). The S. pombe genome is one of the smallest found in free-living eukaryotes. We engineered a reduction in the number of S. pombe genes using a large-scale gene deletion method called the LATOUR method. This method enabled us to identify the minimum gene set required for growth under laboratory conditions. The genome-reduced strain has four deleted regions: 168.4 kb of the left arm of chromosome I
155.4 kb of the right arm of chromosome I
211.7 kb of the left arm of chromosome II
and 121.6 kb of the right arm of chromosome II. These changes represent a loss of 223 genes of an estimated 5,100. The 657.3-kb deletion strain was less efficient at taking up glucose and some amino acids from the growth media than the parental strain. This strain also showed increased gene expression of the mating pheromone M-factor precursor and NADP-specific glutamate dehydrogenase. There was also a 2.7-fold increase in the concentration of cellular ATP, whereas levels of heterologously produced proteins, such as the green fluorescent protein and the secreted human growth hormone, increased by 1.7 fold and 1.8 fold, respectively.