Effect of Condensed Tannins on Bacterial Diversity and Metabolic Activity in the Rat Gastrointestinal Tract

Abstract

The effect of dietary condensed tannins (proanthocyanidins) on rat fecal bacterial populations was ascertained in order to determine whether the proportion on tannin-resistant bacteria increased and if there was a change in the predominant bacterial populations. After 3 weeks of tannin diets the proportion of tanninresistant bacteria increased significantly (P < 0.05) from 0.3% ؎ 5.5% to 25.3% ؎ 8.3% with a 0.7% tannin diet and to 47.2% ؎ 5.1% with a 2% tannin diet. The proportion of tannin-resistant bacteria returned to preexposure levels in the absence of dietary tannins. A shift in bacterial populations was confirmed by molecular fingerprinting of fecal bacterial populations by denaturing gradient gel electrophoresis (DGGE). Posttreatment samples were generally still distinguishable from controls after 3.5 weeks. Sequence analysis of DGGE bands and characterization of tannin-resistant isolates indicated that tannins selected for Enterobacteriaceae and Bacteroides species. Dot blot quantification confirmed that these gram-negative bacterial groups predominated in the presence of dietary tannins and that there was a corresponding decrease in the gram-positive Clostridium leptum group and other groups. Metabolic fingerprint patterns revealed that functional activities of culturable fecal bacteria were affected by the presence of tannins. Condensed tannins of Acacia angustissima altered fecal bacterial populations in the rat gastrointestinal tract, resulting in a shift in the predominant bacteria towards tannin-resistant gram-negative Enterobacteriaceae and Bacteroides species.

The BaeSR Two-Component Regulatory System Mediates Resistance to Condensed Tannins in Escherichia coli

“…However, the mechanisms behind this resistance are still unknown (22). Gram-negative bacteria may be less sensitive to the inhibitory effects of tannins, as gastrointestinal bacterial populations shifted toward gram-negative Enterobacteriaceae and Bacteroides species in rats fed diets containing 0.7 to 2.0% condensed tannins (20). There was a corresponding decrease in the gram-positive Clostridium leptum group.…”

“…High concentrations of tannins in fodder plants inhibit gastrointestinal bacteria (6,9,10,20) and reduce animal performance (9,18,21,23). Numerous mechanisms of how tannins may inhibit bacteria have been proposed, including tannin-polymer complexation, tannin-induced membrane disruption, and metal ion chelation (22).…”

Dose-Response Relationship between Dietary Polyphenols from Acorns and Parotid Gland Hypertrophy in Pigs

“…From a nutritional point of view, high tannins diets consumption leads to different episodes in humans and animals. Scientific references report evident correlation between dietary polyphenols rich diets and health enhancing properties: antioxidant properties [11][12][13], antibacterial activity on different bacterial strains in vitro and in vivo [7,[14][15][16][17][18][19][20], antiparasitic [21], antiulcerogenic [22][23][24] antidiarrhoic [25], antimutagenic [26][27][28][29][30][31][32][33], antitumor [34][35][36][37][38], and some neoplastic cell line apoptosis [39,40]. On the other hand, high tannins diets might also result in detrimental effects like hepatotoxicity [41,42], toxic nephrosis [43], oesphageal cancer [44], depression of feed intake and growth rate in many animal species [45][46][47][48][49][50][51].…”

Microbial Community Structure at Different Fermentation Stages of Kutajarista, a Herbal Formulation

“…[22], Bacillus sp. [28], and some species of Enterobacteriaceae family [31] were also found to be tolerant to higher concentration of tannins. A report on microbial diversity analysis for tannin bioremediation processes also revealed the presence of Pseudomonas sp.…”

“…Specific modifications or transformation of these biodegradation mechanisms depend on the syntrophic association between different group of microbial species involved [4]. c-Proteobacteria have also been shown to be predominantly associated with efficient tannin or cellulose degradation into non toxic chemicals [3,10,31]. We have also isolated Saccharomyces cerevisiae strains, involved in alcoholic fermentation from these sources (unpublished data).…”