PFN2 and necrotizing enterocolitis: We noted that pyruvate formate lyase (PFL) (KEGG: KO0656; EC 2.3.1.54), the rate limiting enzyme in mixed acid fermentation of pyruvate (Figure 7), was 2–3 times more abundant (counts per million, NEC vs. control) in NEC patients than control and was significantly associated with Klebsiella pneumoniae (P = 0.02; FDR) and Enterobacter cloacae (P = 3.48 × 10−7; FDR), the leading species associated with NEC.