Looking at that supplementary Excel spreadsheet, only 42 of those essential genes are annotated as "hypothetical protein/unknown function/unclear functional cat

Looking at that supplementary Excel spreadsheet, only 42 of those essential genes are annotated as "hypothetical protein/unknown function/unclear functional category". For example, locus MMSYN1_0421 has unknown function, but belongs to the alkaline shock protein family, so we can't say we have no idea what it does. They seem to be the only loci where we're truly in the dark. There are many more with "putative" or "probable" roles and known homologs. In total the headline seems to be misleading. We're only truly lost on about 9% of these essential genes.