Figure 3. Role of short chain fatty acid production in EcN mediate 5-HT overflow.

To determine if the capacity for production of short chain fatty acids (SCFA) was enhanced in EcN compared to MG1655, and relevant to EcN mediated 5-HT overflow, the levels of SCFA generated by each strain during growth in mucosal co-culture was measured. Bacterial cell suspensions in krebs buffer with ileal mucosal scrapings were incubated at 37 °C with 5% CO₂ for 1 h, before measurement of SCFA by HPLC. Propionate and butyrate were not detected in this assay but both EcN and MG1655 generate acetate as show in charts. Data show means ± S.E.M. (n = 3). **P ≤ 0.01 ***P ≤ 0.001 Vs KB. KB - Krebs buffer only; EcN – E. coli Nissle 1917; MG1655 – E. coli MG1655