The chemical reactions and pathways involving the epipolythiodioxopiperazine gliotoxin, a poisonous substance produced by some species of fungi. [ http://www.ebi.ac.uk/chebi/searchId.do?chebiId=CHEBI:299453 http://www.ncbi.nlm.nih.gov/pubmed/16333108 http://www.ncbi.nlm.nih.gov/pubmed/17574915 http://www.ncbi.nlm.nih.gov/pubmed/18272357 http://www.ebi.ac.uk/chebi/searchId.do?chebiId=CHEBI:5385 ]