For a metagenomic project a want to make a blast database of viruses. I dont want to blast my reads on the entire nt database. But I dont know how to make it. Downloading the result of a query like viruses[organism] from the nucleotide database of NCBI is impossible, due to the weight of the data. Maybe there is a solution using the taxononomy files for extract sequences of the Fasta nt file available on the ncbi ftp ?
So could anyone give me a solution ?
Thank you very much !