APC Microbiome Ireland, University College Cork, Ireland; Department of Anatomy and Neuroscience, University College Cork, Ireland. Electronic address: https://twitter.com/AnnaRatsika. APC Microbiome Ireland, University College Cork, Ireland; Department of Anatomy and Neuroscience, University College Cork, Ireland. Electronic address: https://twitter.com/jscruzpereira. APC Microbiome Ireland, University College Cork, Ireland; Department of Anatomy and Neuroscience, University College Cork, Ireland. Electronic address: https://twitter.com/CaoimheMKLynch. Department of Psychiatry and Neurobehavioural Science, University College Cork. Electronic address: https://twitter.com/UCCpsychiatry. APC Microbiome Ireland, University College Cork, Ireland; Department of Anatomy and Neuroscience, University College Cork, Ireland. Electronic address: j.cryan@ucc.ie.