Merge pull request #6509 from paulzierep/update-decontam

Add description to decontam

tools/decontam/decontam.xml

@@ -1,4 +1,5 @@
 <tool id="decontam" name="Decontam" version="@TOOL_VERSION@+galaxy@VERSION_SUFFIX@" profile="@PROFILE@">
+    <description>Identification and removal of contaminants</description>
     <macros>
         <import>macros.xml</import>
     </macros>
@@ -150,6 +151,18 @@ control samples.
    Currently, only the negative control sample method is implemented in this
    wrapper.
 
+**Method**
+
+To identify contaminants decontam requires a defined set of “negative control” samples in
+ which sequencing was performed on blanks without any biological sample added. 
+Extraction controls are preferred, and in amplicon sequencing the negative controls
+ should also be carried through the PCR step, as each step in the workflow 
+ has the potential to introduce new contaminants.
+
+Decontam then uses Fisher’s exact tests to detect weather a feature is a contaminant or not,
+by comparing true samples to ngeative controls. For more details on the detection method see 
+the publication of decontam.
+
 **Output**
 
 - If a phyloseq object is provided as input, the output will be a phyloseq