Molecular Responses of Lactobacilli to Plant Phenolic Compounds: A Comparative Review of the Mechanisms Involved

Physiological and genomic characterization of Lactiplantibacillus plantarum isolated from Indri indri in Madagascar

AIMS

Indri indri is a lemur of Madagascar which is critically endangered. The analysis of the microbial ecology of the intestine offers tools to improve conservation efforts. This study aimed to achieve a functional genomic analysis of three Lactiplantibacillus plantarum isolates from indris.

METHODS AND RESULTS

Samples were obtained from 18 indri; 3 isolates of Lp. plantarum were obtained from two individuals. The three isolates were closely related to each other, with <10 single nucleotide polymorphisms, suggesting that the two individuals shared diet-associated microbes. The genomes of the three isolates were compared to 96 reference strains of Lp. plantarum. The three isolates of Lp. plantarum were not phenotypically resistant to antibiotics but shared all 17 genes related to antimicrobial resistance that are part of the core genome of Lp. plantarum. The genomes of the three indri isolates of Lp. plantarum also encoded for the 6 core genome genes coding for enzymes related to metabolism of hydroxybenzoic and hydroxycinnamic acids. The phenotype for metabolism of hydroxycinnamic acids by indri isolates of Lp. plantarum matched the genotype.

CONCLUSIONS

Multiple antimicrobial resistance genes and gene coding for metabolism of phenolic compounds were identified in the genomes of the indri isolates, suggesting that Lp. plantarum maintains antimicrobial resistance in defense of antimicrobial plant secondary pathogens and that their metabolism by intestinal bacteria aids digestion of plant material by primate hosts.

Revised Aspects into the Molecular Bases of Hydroxycinnamic Acid Metabolism in Lactobacilli

Hydroxycinnamic acids (HCAs) are phenolic compounds produced by the secondary metabolism of edible plants and are the most abundant phenolic acids in our diet. The antimicrobial capacity of HCAs is an important function attributed to these phenolic acids in the defense of plants against microbiological threats, and bacteria have developed diverse mechanisms to counter the antimicrobial stress imposed by these compounds, including their metabolism into different microbial derivatives. The metabolism of HCAs has been intensively studied in Lactobacillus spp., as the metabolic transformation of HCAs by these bacteria contributes to the biological activity of these acids in plant and human habitats or to improve the nutritional quality of fermented foods. The main mechanisms known to date used by Lactobacillus spp. to metabolize HCAs are enzymatic decarboxylation and/or reduction. Here, recent advances in the knowledge regarding the enzymes that contribute to these two enzymatic conversions, the genes involved, their regulation and the physiological significance to lactobacilli are reviewed and critically discussed.

Comprehensive analysis of the metabolic and genomic features of tannin transforming Lactiplantibacillus plantarum strains

Extracellular tannase Lactiplantibacillus plantarum-producing strains (TanA+) release bioactive metabolites from dietary tannins. However, there is a paucity of knowledge of TanA+ strains and their hydrolyzing capacities. This study aimed to shed light on the metabolic and genomic features of TanA+ L. plantarum strains and to develop a screening technique. The established spectrophotometric was validated by UPLC-UV-QToF. Eight of 115 screened strains harbored the tanA gene, and six presented TanA activity (PROBI S126, PROBI S204, RKG 1-473, RKG 1-500, RKG 2-219, and RKG 2-690). When cultured with tannic acid (a gallotannin), TanA+ strains released 3.2-11 times more gallic acid than a lacking strain (WCFS1) (p < 0.05). TanA+ strains with gallate decarboxylase (n = 5) transformed this latter metabolite, producing 2.2-4.8 times more pyrogallol than the TanA lacking strain (p < 0.05). However, TanA+ strains could not transform punicalagin (an ellagitannin). Genomic analysis revealed high similarity between TanA+ strains, as only two variable regions of phage and polysaccharide synthesis were distinguished. A phylogenetic analysis of 149 additional genome sequences showed that tanA harboring strains form a cluster and present two bacteriocin coding sequences profile. In conclusion, TanA+ L. plantarum strains are closely related and possess the ability to resist and transform gallotannins. TanA can be screened by the method proposed herein.

Polyphenols as Drivers of a Homeostatic Gut Microecology and Immuno-Metabolic Traits of Akkermansia muciniphila: From Mouse to Man

Akkermansia muciniphila is a mucosal symbiont considered a gut microbial marker in healthy individuals, as its relative abundance is significantly reduced in subjects with gut inflammation and metabolic disturbances. Dietary polyphenols can distinctly stimulate the relative abundance of A. muciniphila, contributing to the attenuation of several diseases, including obesity, type 2 diabetes, inflammatory bowel diseases, and liver damage. However, mechanistic insight into how polyphenols stimulate A. muciniphila or its activity is limited. This review focuses on dietary interventions in rodents and humans and in vitro studies using different phenolic classes. We provide critical insights with respect to potential mechanisms explaining the effects of polyphenols affecting A. muciniphila. Anthocyanins, flavan-3-ols, flavonols, flavanones, stilbenes, and phenolic acids are shown to increase relative A. muciniphila levels in vivo, whereas lignans exert the opposite effect. Clinical trials show consistent findings, and high intervariability relying on the gut microbiota composition at the baseline and the presence of multiple polyphenol degraders appear to be cardinal determinants in inducing A. muciniphila and associated benefits by polyphenol intake. Polyphenols signal to the AhR receptor and impact the relative abundance of A. muciniphila in a direct and indirect fashion, resulting in the restoration of intestinal epithelial integrity and homeostatic crosstalk with the gut microbiota by affecting IL-22 production. Moreover, recent evidence suggests that A. muciniphila participates in the initial hydrolysis of some polyphenols but does not participate in their complete metabolism. In conclusion, the consumption of polyphenol-rich foods targeting A. muciniphila as a pivotal intermediary represents a promising precision nutritional therapy to prevent and attenuate metabolic and inflammatory diseases.

Date Seeds Flour Used as Value-Added Ingredient for Wheat Sourdough Bread: An Example of Sustainable Bio-Recycling

Our study proposed date seeds flour (DSF) as an innovative ingredient for sourdough bread production through sustainable bio-recycling. We isolated autochthonous lactic acid bacteria and yeasts from DSF and DSF-derived doughs to build up a reservoir of strains from which to select starters ensuring rapid adaptation and high ecological fitness. The screening based on pro-technological criteria led to the formulation of a mixed starter consisting of Leuconostoc mesenteroides, Lactiplantibacillus plantarum, and Saccharomyces cerevisiae strains, which allowed obtaining a mature type I sourdough after consecutive refreshments, in which an aliquot of the durum wheat flour (DWF) was replaced by DSF. The resulting DSF sourdough and bread underwent an integrated characterization. Sourdough biotechnology was confirmed as a suitable procedure to improve some functional and sensory properties of DWF/DSF mixture formulation. The radical scavenging activity increased due to the consistent release of free phenolics. Perceived bitterness and astringency were considerably diminished, likely because of tannin degradation.