Update README.md

1_taxonomic_profiling_and_vizualization/3_practical_taxonomic_profiling/README.md

@@ -90,6 +90,15 @@ We use [mOTUs2](https://github.com/motu-tool/mOTUs_v2) to create taxonomic profi
    ```
    
    With `cat test_sample.motus | grep -v "0.0000000000" | grep -v "#" | wc -l`, we can see that we have 139 detected species.
+   
+   To count the number of ref-mOTUs you can use:
+   ```
+   cat test_sample.motus | grep -v "0.0000000000" | grep -c "ref_mOTU_"
+   ```
+   and for meta-mOTUs:
+   ```
+   cat test_sample.motus | grep -v "0.0000000000" | grep -c "meta_mOTU_"
+   ```
    </p>