Idealized assembly graphs of the 5.2 megabase-pairB. anthracisAmes Ancestor main chromosome using (a) 100 bp, (b) 1,000 bp and (c) 5,000 bp reads. The graphs encode the compressed de Bruijn graph derived from infinite coverage error-free reads, effectively representing the repeats in the genome and the upper bound of what could be achieved in a real assembly. Increasing the read length decreases the number of contigs because the longer reads will span more of the repeats. Note the assembly with 5,000 bp reads has a self-edge because the chromosome is circular.