Fig. 1

Demonstration of max_target_seqs error and correction (BLAST 2.8.0 or earlier) on the test cases presented by Shah et al. in 2018 [3]. Command 1 demonstrates the usage of BLASTN to produce only 1 top e-value hit per query sequence, using ‘-max_target_seqs 1’. Command 2 demonstrates the usage of BLAST-QC to parse the top e-value hit from the standard BLAST output, using ‘-or e -n 1’ to order by e-value and return only 1 top hit per query. These commands are executed for 3 separate query sequences (represented in the respective commands by infile.fasta), sequences 1, 2 and 3. As the e-values in figure show (column 5), BLAST-QC is able to extract the top e-value hit from these test case examples, while max_target_seqs is not. This error has been corrected in BLAST 2.8.1, but we show this example for compatibility with those who might be running older versions of BLAST or have older BLAST results datasets