Exposure of Pseudomonas aeruginosa to green tea polyphenols enhances the tolerance to various environmental stresses

Effects of Cross-Resistance of Salmonella Enterica Serovar Enteritidis Induced by Sodium Hypochlorite to Environmental Stress

To investigate the effects of repeated sodium hypochlorite stress on the resistance of Salmonella enterica Serovar Enteritidis (S. Enteritidis) LWCC1051. LWCC1051 was exposed to Trypticase Soy Broth (TSB) containing sodium hypochlorite concentrations of 9 mmol/L, 10 mmol/L, and 11 mmol/L. After 13 repeated transfers and incubations, three sodium hypochlorite resisted LWCC1051 strains were obtained. The D-values and colony morphologies of these strains were assessed. Their survival rates at 60 °C, 65 °C, 70 °C, 75 °C, and - 20 °C were determined and lethality curves at these temperatures were fitted using the Weibull model. Additionally, the Minimal Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) for these strains in various chemicals, including malic acid, citric acid, ascorbic acid, acetic acid, lactic acid, hydrochloric acid, sodium hydroxide, potassium hydroxide, calcium chloride, sodium chloride, and potassium chloride were ascertained. Sodium hypochlorite concentrations of 9 mmol/L, 10 mmol/L, and 11 mmol/L in TSB induced sodium hypochlorite resistance in S. Enteritidis. D-value increased with the frequency of stress exposure. Higher concentrations of sodium hypochlorite resulted in greater D-values and noticeable differences in colony morphologies. The Weibull model accurately represented the temperature resistance curves of LWCC1051 at the specified temperatures. With increasing sodium hypochlorite stress, both high and low-temperature resistances of LWCC1051 improved. Furthermore, under acetic acid stress, the MIC and MBC values of LWCC1051 strains, post exposure to 9 mmol/L, 10 mmol/L, and 11 mmol/L sodium hypochlorite, doubled. Sodium hypochlorite stress enhances the cross-resistance of LWCC1051 to high temperature, low temperature, and acetic acid treatments.

The potential of EGCG in modulating the oral-gut axis microbiota for treating inflammatory bowel disease

Inflammatory bowel disease (IBD) is a recurrent chronic intestinal disorder that includes ulcerative colitis (UC) and Crohn's disease (CD). Its pathogenesis involves intricate interactions between pathogenic microorganisms, native intestinal microorganisms, and the intestinal immune system via the oral-gut axis. The strong correlation observed between oral diseases and IBD indicates the potential involvement of oral pathogenic microorganisms in IBD development. Consequently, therapeutic strategies targeting the proliferation, translocation, intestinal colonization and exacerbated intestinal inflammation of oral microorganisms within the oral-gut axis may partially alleviate IBD. Tea consumption has been identified as a contributing factor in reducing IBD, with epigallocatechin gallate (EGCG) being the primary bioactive compound used for IBD treatment. However, the precise mechanism by which EGCG mediates microbial crosstalk within the oral-gut axis remains unclear. In this review, we provide a comprehensive overview of the diverse oral microorganisms implicated in the pathogenesis of IBD and elucidate their colonization pathways and mechanisms. Subsequently, we investigated the antibacterial properties of EGCG and its potential to attenuate microbial translocation and colonization in the gut, emphasizing its role in attenuating exacerbations of IBD. We also elucidated the toxic and side effects of EGCG. Finally, we discuss current strategies for enhancing EGCG bioavailability and propose novel multi-targeted nano-delivery systems for the more efficacious management of IBD. This review elucidates the role and feasibility of EGCG-mediated modulation of the oral-gut axis microbiota in the management of IBD, contributing to a better understanding of the mechanism of action of EGCG in the treatment of IBD and the development of prospective treatment strategies.

RNA-Seq Transcriptomic Analysis of Green Tea Polyphenols Modulation of Differently Expressed Genes in Enterococcus faecalis Under Bile Salt Stress

Enterococcus faecalis (E. faecalis) belongs to lactic acid bacteria which can be used as a probiotic additive and feed, bringing practical value to the health of humans and animals. The prebiotic function of tea polyphenols lays a foundation for green tea polyphenols (GTP) to repair the adverse changes of E. faecalis under stress conditions. In this study, RNA-sequence analysis was used to explore the protective effect of GTP on E. faecalis under bile salt stress. A total of 50 genes were found to respond to GTP under bile salts stress, containing 18 up-regulated and 32 down-regulated genes. The results showed that multiple genes associated with cell wall and membrane, transmembrane transport, nucleotide transport and metabolism were significantly differentially expressed (P < 0.05), while GTP intervention can partly alleviate the detrimental effects of bile salt on amino acid metabolism and transport. The present study provides the whole genome transcriptomics of E. faecalis under bile salt stress and GTP intervention which help us understand the growth and mechanism of continuous adaptation of E. faecalis under stress conditions.

RNA-seq analysis of green tea polyphenols modulation of differently expressed genes in Enterococcus faecalis under low pH

Enterococcus faecalis (E. faecalis) is a resident bacterium in the host. The increase of internal stress like low pH may affect the biological effects of E. faecalis. The prebiotic-like function of tea polyphenols can enhance the beneficial effects of its tolerance to environmental stress. In this study, RNA-sequence analysis was used to explore the protective effect of green tea polyphenols (GTP) on E. faecalis under low pH stress. A total of 28 genes were found to be responsive to GTP under low pH stress, including 16 up-regulated and 12 down-regulated. GTP intervention can partly relieve some undesired negative influences, such as the down-regulation of the base excision repair gene and amino acid transport and metabolism gene. The significantly changes were associated with selenocompound metabolism and aminoacyl-tRNA biosynthesis after the intervention of GTP. The present study provided new insights into the growth and continuous adaptation of E. faecalis under stress.

Analysis of Cyclocarya paliurus flavonoids modulation on the physiology and gene expression in Enterococcus faecalis under bile salt stress

Enterococcus faecalis (E. faecalis) is one of the probiotic groups in the intestinal tract which has varieties of functional effects in the host, such as a protective barrier, nutritional efficacy and antibacterial effects. Stress conditions such as low pH, bile salts, and hypertonicity are inevitable negative factors for the normal survival of E. faecalis in the gastrointestinal tract. Under the stress and inhibition of bile salt, E. faecalis needs specific adaptation and coping style if it wants to successfully colonize the intestine stably. The appropriate concentration of flavonoids can assist probiotics to serve a beneficial role and help them resist the stress of external irresistible environmental factors. In the present research, RNA-sequence (RNA-seq) technology was employed to investigate the influence of Cyclocarya paliurus flavonoids (CPF) on Enterococcus faecalis 131-2 (E. faecalis 131-2) exposed to bile salt stress. Analysis results revealed that under bile salt stress, many genes related to cellular process, catalytic activity, and transport activity were significantly differentially expressed (P < 0.05), and some not expected variations of which could be partly alleviated by supplementation of CPF, indicating its capacity to improve the bile salt tolerances of E. faecalis 131-2. Additionally, CPF alleviated the obvious inhibitory effects of bile salt stress on the exponential growth of E. faecalis 131-2. An overall view of the physiological and transcriptomic changes of E. faecalis 131-2 under bile salt stresses with or without CPF will further deepen our understanding of the mechanism by which CPF assists E. faecalis 131-2 to perform beneficial functions in the gastrointestinal environment.

Effects of environmental conditions (temperature, pH, and glucose) on biofilm formation of Salmonella enterica serotype Kentucky and virulence gene expression

Salmonella is a foodborne pathogen and an emerging zoonotic bacterial threat in the food industry. The aim of this study was to evaluate the biofilm formation by a cocktail culture of 3 wild isolates of Salmonella enterica serotype Kentucky on plastic (PLA), silicon rubber (SR), and chicken skin surfaces under various temperatures (4, 10, 25, 37, and 42°C) and pH values (4.0, 5.0, 6.0, 7.0, and 8.0). Then, at the optimum temperature and pH, the effects of supplementation with glucose (0, 0.025, 0.05, and 0.4% w/v) on biofilm formation were assessed on each of the surfaces. The results indicated that higher temperatures (25 to 42°C) and pH values (7.0 and 8.0) led to more robust biofilm formation than lower temperatures (4 and 10°C) and lower pH levels (4.0 to 6.0). Moreover, biofilm formation was induced by 0.025% glucose during incubation at the optimum temperature (37°C) and pH (7.0) but inhibited by 0.4% glucose. Consistent with this finding, virulence related gene (rpoS, rpoH, hilA, and avrA) expression was increased at 0.025% glucose and significantly reduced at 0.4% glucose. This results also confirmed by field emission scanning electron microscope, confocal laser scanning microscopy, and autoinducer-2 determination. This study concluded that optimum environmental conditions (temperature 37°C, pH 7.0, and 0.25% glucose) exhibited strong biofilm formation on food and food contract surfaces as well as increased the virulence gene expression levels, indicating that these environmental conditions might be threating conditions for food safety.

Antibacterial green tea catechins from a molecular perspective: mechanisms of action and structure-activity relationships

This review summarizes the mechanisms of antibacterial action of green tea catechins, discussing the structure-activity relationship (SAR) studies for each mechanism. The antibacterial activity of green tea catechins results from a variety of mechanisms that can be broadly classified into the following groups: (1) inhibition of virulence factors (toxins and extracellular matrix); (2) cell wall and cell membrane disruption; (3) inhibition of intracellular enzymes; (4) oxidative stress; (5) DNA damage; and (6) iron chelation. These mechanisms operate simultaneously with relative importance differing among bacterial strains. In all SAR studies, the highest antibacterial activity is observed for galloylated compounds (EGCG, ECG, and theaflavin digallate). This observation, combined with numerous experimental and theoretical evidence, suggests that catechins share a common binding mode, characterized by the formation of hydrogen bonds and hydrophobic interactions with their target.

Unveiling the activating mechanism of tea residue for boosting the biological decolorization performance of refractory dye

Conventional microbial treatments are challenged by new synthetic refractory dyes. In this work, tea residue was found serving as an effective activator to boost the decolorization performance of anthraquinone dye (reactive blue 19, RB19) by a new bacterial flora DDMY2. The unfermented West Lake Longjing tea residue showed the best enhancement performance. Seventeen main kinds of components in tea residue had been selected to take separate and orthogonal experiments on decolorization of RB19 by DDMY2. Results suggested epigallocatechin gallate (EGCG) in tea residue played important roles in boosting the treatment performance. Illumina MiSeq sequencing results confirmed that EGCG and tea residue pose similar impact on the change of DDMY2 community structure. Some functional bacterial genera unclassified_o_Pseudomonadales, Stenotrophomonas and Bordetella were enriched during the treatment of RB19 by EGCG and tea residue. These evidences suggested EGCG might be the key active component in tea residue that responsible for the enhancement effect on decolorization performance. These results revealed the activating mechanism of tea residue from the perspective of composition.

Combined Transcriptome and Proteome Analysis of RpoS Regulon Reveals Its Role in Spoilage Potential of Pseudomonas fluorescens

Microbial contamination is considered the main cause of food spoilage. Pseudomonas fluorescens is a typical spoilage bacterium contributing to a large extent to the spoilage process of proteinaceous foods. RpoS is known as an alternative sigma factor controlling stress resistance and virulence in many pathogens. Our previous work revealed that RpoS contributes to the spoilage activities of P. fluorescens by regulating resistance to different stress conditions, extracellular acylated homoserine lactone (AHL) levels, extracellular protease and total volatile basic nitrogen (TVB-N) production. However, RpoS-dependent genes in P. fluorescens remained undefined. RNA-seq transcriptomics analysis combined with quantitative proteomics analysis based on multiplexed isobaric tandem mass tag (TMT) labeling was performed in the P. fluorescens wild-type strain UK4 and its derivative carrying an rpoS mutation. A total of 375 differentially expressed coding sequences (DECs) and 212 differentially expressed proteins (DEPs) were identified. The DECs were further verified by qRT-PCR. The combined transcriptome and proteome analyses revealed the involvement of this regulator in several cellular processes, mainly including polysaccharide metabolism, intracellular secretion, extracellular structures, cell wall biogenesis, stress responses, and amino acid and biogenic amine metabolism, which may contribute to the biofilm formation, stress resistance, and spoilage activities of P. fluorescens. Moreover, we indeed observed that RpoS contributed to the production of the macrocolony biofilm's matrix. Our results provide insights into the regulatory network of RpoS and expand the knowledge about the role of RpoS in the functioning of P. fluorescens in food spoilage.

Transcriptomic analysis of the response of Pseudomonas fluorescens to epigallocatechin gallate by RNA-seq

Epigallocatechin gallate (EGCG) is a main constituent of green tea polyphenols that are widely used as food preservatives and are considered to be safe for consumption. However, the underlying antimicrobial mechanism of EGCG and the bacterial response to EGCG are not clearly understood. In the present study, a genome-wide transcriptional analysis of a typical spoilage bacterium, Pseudomonas fluorescens that responded to EGCG was performed using RNA-seq technology. A total of 26,365,414 and 23,287,092 clean reads were generated from P. fluorescens treated with or without 1 mM EGCG and the clean reads were aligned to the reference genome. Differential expression analysis revealed 291 upregulated genes and 134 downregulated genes and the differentially expressed genes (DEGs) were verified using RT-qPCR. Most of the DGEs involved in iron uptake, antioxidation, DNA repair, efflux system, cell envelope and cell-surface component synthesis were significantly upregulated by EGCG treatment, while most genes associated with energy production were downregulated. These transcriptomic changes are likely to be adaptive responses of P. fluorescens to iron limitation and oxidative stress, as well as DNA and envelope damage caused by EGCG. The expression of specific genes encoding the extra-cytoplasmic function sigma factor (PvdS, RpoE and AlgU) and the two-component sensor histidine kinase (BaeS and RpfG) were markedly changed by EGCG treatment, which may play important roles in regulating the stress responses of P. fluorescens to EGCG. The present data provides important insights into the molecular action of EGCG and the possible cross-resistance mediated by EGCG on P. fluorescens, which may ultimately contribute to the optimal application of green tea polyphenols in food preservation.

Targeting oxidative stress response by green tea polyphenols: clinical implications

Green tea polyphenols, the most interesting constituent of green tea leaves, have been shown to have both pro-oxidant and antioxidant properties. Both pro-oxidant and antioxidant properties are expected to contribute to modulation of oxidative stress response under ideal optimal dosage regimens. Exposure to a low concentration of a pro-oxidant prior to exposure to oxidative stress induces the expression of genes that code for proteins that induce adaptation in a subsequent oxidative stress. On the other hand, exposure to an antioxidant concurrently with exposure to the oxidative stress affords protection through free radical scavenging or through other indirect antioxidant mechanisms. In any case, the optimal conditions that afford protection from oxidative stress should be defined for any substance with redox properties. Green tea polyphenols, being naturally occurring substances, seem to be an ideal option for the modulation of oxidative stress response. This paper reviews available data on the pro-oxidant and antioxidant properties of green tea polyphenols focusing on their potential on the modulation of oxidative stress response.