The proportions of unique, not unique and not hit reads for 454 simulation datasets from NeSSM.

Unique: the read is mapped back only to its original genome; Not unique: the read is mapped back to more than one reference genomes; Not hit: the read can’t be mapped back to any reference genome. LC-100 is the simulated data from the low complexity metagenome (Dataset A) with read length 100 bps and other datasets are named similarly for simulated data derived from Dataset B and C.*most reads of not hit are because of the repeats in the reads so that they can’t be mapped back uniquely by Blast.