HDAC9 and inflammatory bowel disease: Species belonging to Firmicutes (especially Faecalibacterium prausnitzii and Roseburia species [109]) and Bacteroides genera, known to be reduced in IBD [110], have an epigenetically mediated anti-inflammatory action (HDAC inhibition) via the production of short-chain fatty acids (SCFAs) (the role of these will be discussed in more detail below) [111].