Fecal Microbiota in Healthy Subjects Following Omnivore, Vegetarian and Vegan Diets: Culturable Populations and rRNA DGGE Profiling

Abstract

In this study, the fecal microbiota of 153 healthy volunteers, recruited from four different locations in Italy, has been studied by coupling viable counts, on different microbiological media, with ribosomal RNA Denaturing Gradient Gel Electrophoresis (rRNA-DGGE). The volunteers followed three different diets, namely omnivore, ovo-lacto-vegetarian and vegan. The results obtained from culture-dependent and -independent methods have underlined a high level of similarity of the viable fecal microbiota for the three investigated diets. The rRNA DGGE profiles were very complex and comprised a total number of bands that varied from 67 to 64 for the V3 and V9 regions of the 16S rRNA gene, respectively. Only a few bands were specific in/of all three diets, and the presence of common taxa associated with the dietary habits was found. As far as the viable counts are concerned, the high similarity of the fecal microbiota was once again confirmed, with only a few of the investigated groups showing significant differences. Interestingly, the samples grouped differently, according to the recruitment site, thus highlighting a higher impact of the food consumed by the volunteers in the specific geographical locations than that of the type of diet. Lastly, it should be mentioned that the fecal microbiota DGGE profiles obtained from the DNA were clearly separated from those produced using RNA, thus underlining a difference between the total and viable populations in the fecal samples.

Immune-modulating effects in mouse dendritic cells of lactobacilli and bifidobacteria isolated from individuals following omnivorous, vegetarian and vegan diets

“…Interestingly, a significant association between consumption of agrarian-based diets and increased levels of faecal SCFAs has been previously found in the individuals herein examined [11]. Furthermore, the culturable lactic acid bacteria (LAB) loads were found to be lower in the vegan and ovo-lactovegetarian groups [12]. On the contrary, no significant difference between the ovo-lacto-vegetarian and omnivorous groups was observed in relation to the culturable bifidobacteria load, although such load was significantly lower in the vegan group [12].…”

“…Healthy adult volunteers (n=155) who followed an omnivorous (n= 55), ovo-lacto-vegetarian (n= 53) or vegan (n= 47) diet for more than 1 year were recruited at 4 Italian centres (Bari, Bologna, Parma and Turin) [11][12][13] (https://clinicaltrials.gov; ClinicalTrials.gov Identifier: NCT02118857; MRMOVVD), as indicated in Table 1. The research was conducted according to the Declaration of Helsinki.…”

“…Serial dilutions were prepared in , and 100 l aliquots of each dilution were included into Rogosa Agar (Oxoid) with 21 M acetic acid or spread onto Bifidobacterium Agar (Becton Dickinson, Milan, Italy) [12][13][14]. Growth conditions were aerobic at 30°C for 48 h and anaerobic at 37°C for 48-72 h for selection of mesophilic lactobacilli and bifidobacteria, respectively.…”

“…cDNA was prepared from 1 g of total RNA by reverse transcription with M-MLV Reverse Transcriptase (Invitrogen) and Oligo-(dT) [12][13][14][15][16][17][18] Primer at 42°C for 60 min. hydrogen peroxide were dispensed into each well, and the wells were allowed to develop.…”

“…Herein, we addressed these issues by establishing whether lactobacilli and bifidobacteria species and strains arising from specific diets actually translate to the modulation of immune function. We evaluated, for the first time, a large microbiological screening of lactobacilli and bifidobacteria isolated from individuals undergoing omnivorous, vegan and ovo-lactovegetarian diets [11,12] to determine their role in modulating in vitro immune markers of mouse dendritic cell functions. Our data revealed genus-specific effects of selected bacteria on the maturation of DCs, as well as on inducible immune mediators produced by DCs in vitro, thus establishing a differential degree of modulation of the phenotype of DCs.…”