Prevotella enterotype associates with diets supporting acidic faecal pH and production of propionic acid by microbiota

Abstract

Metabolism of dietary fibres by colon microbiota plays an important role for human health. Personal data from a nutrition study (57 subjects) were analysed to elucidate quantitative associations between the diet, faecal microbiome, organic acid concentrations and pH. Ratios of the predominant acids acetate, butyrate and propionate ranged from 1:0.67:0.27 to 1:0.17:0.36. Pectin-rich diets resulted in higher faecal acetate concentrations. Negative correlation between faecal pH and BSS was observed. Higher faecal pH and lower acid concentrations were related to the higher abundance of amino acid degrading Clostridium, Odoribacter and Eubacterium coprostanoligenes, which are weak carbohydrate fermenting taxa. Propionic acid correlated especially to high abundance of Prevotella and low abundance of proteobacteria. The acetate to propionate ratio of the Prevotella enterotype was about half of that of the Bacteroides enterotype. Based on the results we suggest the measurement of faecal pH and organic acid composition for research and diagnostic purposes.

Keywords: Enterotypes; Faecal pH; Food diary; Gut microbiota; Short chain fatty acids (SCFA).

Graphical abstract

Fig. 1

Distribution of faecal pH and concentrations (mmol/kg) of acetate, lactate, butyrate, propionate and succinate of all participants. Samples S1, S2 were taken in April–May, S3, S4 in June–July and S5, S6 in August–September.

Fig. 2

Heatmap of the food consumption patterns indicating seasonal variation. The numbers indicate the percentage of the participants consuming the food in the given category at a certain sampling period (April–May, June–July, August–Sept). Only the amounts of foods providing at least 1 g of dietary fibre per day are presented.

Fig. 3

Pearson correlation between acetate and butyrate concentrations with pectin-rich fruits (A) and white wheat product consumption (B), respectively. The colour of points (individual samples) and regression lines indicate the participant ID. Pectin-rich fruits indicate the sum of apples, plums and black and red currants.

Fig. 4

Bacterial taxa (A–H) significantly different in faecal samples of high and low pH (A–D), as well as high and low concentrations of butyrate (E–F) and propionate (G–H). Samples of each participant were grouped based on the sampling period (Apr–May, June–July, Aug–Sept) and then grouped by pH or acid concentrations. Grouping details are given in materials and methods.

Fig. 5

Comparison of the abundances of bacterial genera (A–D) and acid profiles (E–H) significantly different in Bacteroides/Prevotella ratio.

Fig. 6

Correlation between faecal microbiota and faecal pH (A–B), total acid concentrations (C–D) or propionic acid (E–F).

Fig. 7

Pearson correlation between faecal pH and Bristol stool score (BSS). The colour of points (individual samples) and regression lines indicate the participant ID.