Abstract
Lactobacilli are well-studied bacteria that can undergo oxidative selective pressures by plant phenolic compounds (PPCs) in plants, during some food fermentations or in the gastrointestinal tract of animals via dietary inputs. Lactobacilli are known to be more tolerant to PPCs than other bacterial groups and, therefore, must have mechanisms to cope with the effects of these metabolites. In this review, we intend to present what is currently known about the basics beyond the responses of Lactobacillus spp. to individual PPCs. We review the molecular mechanisms that are engaged in the PPC-modulated responses studied to date in these bacteria that have been mainly characterized by system-based strategies, and we discuss their differences and similarities. A wide variety of mechanisms are induced to increase the oxidative stress response highlighting the antimicrobial nature of PPCs. However other uncovered mechanisms that are involved in the response to these compounds are reviewed, including the capacity of PPCs to modulate the expression of molecular functions used by lactobacilli to adapt to host environments. This shows that these phytochemicals can act as more than just antimicrobial agents in the dual interaction with lactobacilli.
Highlights
Plant phenolic compounds (PPCs) are a class of phytochemicals with high diverse structural complexity
Genes related to GTP biosynthetic and GTP-consuming pathways were differentially regulated by p-coumaric acid (p-CA) [25], OLE [28], and HXT [29], indicating that GTP regulation is involved in the response to these PPCs, and that maintaining GTP levels within a range is essential for viability under different environmental conditions
The different biochemical properties and production levels of cell wall teichoic acids (WTA) and lipoteichoic acids (LTA) are directly related to the inmunodulatory capacity of Lactobacillus spp. [104] and severely impact its capacity to communicate with their hosts [68]
Summary
Plant phenolic compounds (PPCs) are a class of phytochemicals with high diverse structural complexity. Owing to their antimicrobial properties PPCs may exert broad effects on microorganisms that can result in rapid shifts and long-term modification in plant and animal microbiomes In this regard, several studies have shown that supplementation with food substrates rich in PPCs variates the structure of the gut microbiota, commonly resulting in alteration of the Firmicutes to Bacteroidetes ratio and leading to Lactobacillus spp. as one of the predominant bacterial populations [4,5,6,7,8]. Comparative transcriptomic analysis of the specific responses to these individual PPCs revealed functional gene categories that highlighted the importance of adaptation of Lactobacillus cell surface properties, carbon and nitrogen metabolism, stress responsive pathways, and transport functions. WCFS1 genes genes differentially differentially expressed in response to various plant phenolic compounds: p-coumaric acid (p-CA), resveratrol expressed in response to various plant phenolic compounds: p-coumaric acid (p-CA), resveratrol (RSV), hydroxytyrosol (HXT), and oleuropein (OLE)
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