Human's have 23,000 genes, vs 525 in this organism. On the assumption that complexity increases with the square of the number of genes you would need 245,000 computers today to simulate one human cell. And it could be more than that because of RNA etc.
Human cells may have tens of times more forms of proteins expressed from these 23,000 genes if you take into account alternative splicing of pre-mRNA and many other post-translational modifications. These are all processes which prokaryotic organisms like M. genitalium generally lack.
Even when we look aside from the level of DNA/RNA there are huge differences in morphological organisation of eukaryotic cells when compared to most prokaryotes: dynamic compartmentalisation of cytoplasm, different types of cytoskeleton, vesicle trafficking, complex signal transduction networks instead of usually simple two-component regulatory systems... So the simulation of whichever human cell type could be much more complicated than one could initially thought.
I don't want to sound too much pessimistic, as someone with background in both CS and molecular biology I'm truly excited about this, but I still had to cool myself down a little bit after reading the article. I can't wait to read the original paper.
