Fig. 3

Influence of TMAO on growth and metabolism of pure cultures of gut bacteria. a Representative growth curves for isolates grown in the presence and absence of TMAO. Red lines, TMAO-supplemented cultures; blue lines, negative controls. Data are shown as mean ± SD (n = 3). b Biplot showing production of various metabolites when isolates were grown in the presence of TMAO. Summary of data from Additional file 1: Table S2. The larger a circle, the more of the metabolite produced by an isolate. c Differences in metabolites produced when caecal and faecal isolates of Escherichia coli were grown in the presence (+) and absence (−) of 1% TMAO. Adjusted (Benjamini–Hochberg) P values indicate the caecal isolates were significantly different from the faecal isolates for a particular metabolite. d Lactate production by lactic acid bacteria was increased in the presence of TMAO. Enterobacteriaceae, n = 20; Bifidobacteriaceae, n = 17; Streptococcaceae, n = 7; Enterococcaceae, n = 5. Members of the Enterococcaceae and Streptococcaceae are homofermenters (produce only lactic acid from glucose fermentation), whereas the Bifidobacteriaceae are heterofermenters (produce ethanol, CO₂, and lactic acid from glucose fermentation), though it should be noted the bifidobacteria included in this study were grown on raffinose-containing media. Red, TMAO-containing medium; blue, negative control. *Statistically significantly different from its negative control (adjusted P value < 0.05)