built as described here: https://github.com/nasa/GeneLab_Data_Processing/blob/master/Metagenomics/Estimate_host_reads_in_raw_data/Workflow_Documentation/SW_MGEstHostReads/reference-database-info.md
Test fastq files hold 4 read pairs: 1 phage, 1 e. coli, 1 human, 1 mouse