title: blast database index error
body: <p>I got the following err msg when I ran tblastn</p>
  
  <p>tblastn -query ~/seq.fa -out ~/seq.out -db ~/blast/ncbi-blast-2.2.29+/db/nr -num_alignments 20000
  BLAST Database error: No alias or index file found for nucleotide database [~/blast/ncbi-blast-2.2.29+/db/nr] in search path [~/blast/ncbi-blast-2.2.29+/bin::/directory/path/to/blast/databases:]</p>
  
  <p>in the /db, there are nr file with phd, phi, phr, pin, pnd, pni, pgo, ppd, ppi, psd, psi and psq extensions for all nr files ranging from 00 to 16 namely, nr.00.phr etc.</p>
  
  <p>If the index files are one of these files that are in db folder, why does blast not find them?</p>
  
  <p>does nr contain representative genome because this is what I want to use?</p>
  
  <p>how about microbial database?</p>
  
  <p>Many thanks</p>