Found at high concentrations and a known biomarker of CF, TNF is the most studied GM in CF [9, 34], associated with an increased risk of osteoporosis, increased liver disease and cirrhosis development, increased gastrointestinal complications and also an increase in pulmonary disease severity with increased airway colonisation and levels of neutrophil elastase [9]. The gene discussed is TNF; the disease is cystic fibrosis.