Exopolysaccharides of Lactobacillus rhamnosus GG form a protective shield against innate immune factors in the intestine

Exploring the anti-inflammatory effects of microencapsulated probiotic bacteria: in vivo and in vitro evaluation in healthy mouse models

BACKGROUND

Encapsulation technology has been extensively employed in recent years to enhance the efficacy and efficiency of probiotics. Nevertheless, existing studies have primarily concentrated on product efficacy, with inadequate scrutiny concerning potential effects on living organisms. This study aimed to evaluate the effects of various encapsulated probiotic strains on inflammatory responses in healthy mice, alongside their in vitro viability. Nissle (EcN) and Lactobacillus rhamnosus GG (LGG) were microencapsulated for the study.

RESULTS

The differences in serum levels of Total Oxidant Status, Total Antioxidant Status, and C-reactive protein among the groups were statistically significant (LGG, P = 0.039, P = 0.024, and P < 0.001; EcN, P = 0.019, P = 0.012, and P = 0.037, respectively). The highest levels were found in the control group, while the lowest levels were observed in the microencapsulated group. There were no significant differences in tissue tumor necrosis factor or interleukin-6 levels for either LGG or EcN.

CONCLUSION

Probiotics reduced inflammation-related parameters in serum of healthy mice. Microencapsulation preserved viability in vitro, but in vivo no significant differences were observed in anti-inflammatory parameters or body weight between microencapsulated and free probiotics. © 2025 The Author(s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Functional diversity of AI-2/LuxS system in lactic acid bacteria: Impacts on biofilm formation and environmental resilience

A key component of microbial communication, autoinducer-2 (AI-2) signaling, affects several physiological processes, including environmental adaptation and biofilm formation in lactic acid bacteria (LAB). The multifarious contribution of AI-2, synthesized by LuxS, in improving biofilms and tolerance to hostile conditions in LAB has been investigated in this review. The evolutionary conservation and diversity of AI-2 are shown by a phylogenetic analysis of luxS gene among several LAB species. Furthermore, AI-2 signaling in LAB improves resistance to unfavorable environmental factors, including pH fluctuations, temperature extremes, and antimicrobial agents. Lactic acid bacteria could set off defenses against harmful impacts from environmental stresses.

Molecular Mechanisms of Lacticaseibacillus rhamnosus, LGG® Probiotic Function

To advance probiotic research, a comprehensive understanding of bacterial interactions with human physiology at the molecular and cellular levels is fundamental. Lacticaseibacillus rhamnosus LGG® is a bacterial strain that has long been recognized for its beneficial effects on human health. Probiotic effector molecules derived from LGG®, including secreted proteins, surface-anchored proteins, polysaccharides, and lipoteichoic acids, which interact with host physiological processes have been identified. In vitro and animal studies have revealed that specific LGG® effector molecules stimulate epithelial cell survival, preserve intestinal barrier integrity, reduce oxidative stress, mitigate excessive mucosal inflammation, enhance IgA secretion, and provide long-term protection through epigenetic imprinting. Pili on the cell surface of LGG® promote adhesion to the intestinal mucosa and ensure close contact to host cells. Extracellular vesicles produced by LGG® recapitulate many of these effects through their cargo of effector molecules. Collectively, the effector molecules of LGG® exert a significant influence on both the gut mucosa and immune system, which promotes intestinal homeostasis and immune tolerance.

Study on the effect and mechanism of Lacticaseibacillus rhamnosus AFY06 on inflammation-associated colorectal cancer induced by AOM/DSS in mice

Introduction

Lacticaseibacillus rhamnosus AFY06 (LR-AFY06) is a microorganism isolated from naturally fermented yogurt in Xinjiang, China.

Methods

In this study, we investigated the effects and mechanisms of LR-AFY06 in a mouse model of inflammation-associated colon cancer. The mouse model was established by azoxymethane/dextran sulfate sodium (AOM/DSS) induction. The tumor number in intestinal tissues was counted, and the histopathological analysis was performed on colon tissues. Enzyme-linked immunosorbent assay and real-time quantitative polymerase chain reaction were performed to measure relevant protein levels in colon tissues.

Results

LR-AFY06 treatment alleviated weight loss, increased organ index, reduced intestinal tumor incidence, improved histopathological damage, decreased the levels of inflammatory cytokines such as interleukin-6 (IL-6), interleukin-1 beta (IL-1β), tumor necrosis factor alpha (TNF-α), nuclear factor κB (NF-κB), and inducible nitric oxide synthase (iNOS) in the serum and colon tissue, downregulated the mRNA expression of inhibitor of NF-κB beta (IκBβ), p65, p50, p52, B-cell lymphoma-2 (Bcl-2), and B-cell lymphoma-extra large (Bcl-xL) in colon tissues, and increased the mRNA expression of Bid and caspase-8. The high concentration of LR-AFY06 exerted a better effect than the low concentration; however, the effect was slightly inferior to that of aspirin. Moreover, LR-AFY06 mitigated the intestinal inflammatory process and inhibited intestinal tumor development by regulating the NF-κB and apoptosis pathways.

Discussion

The present study indicates the regulatory potential of LR-AFY06 in inflammation-associated colorectal cancer in mice, providing a valuable basis for further research.

Beyond probiotics: Exploring the potential of postbiotics and parabiotics in veterinary medicine

Postbiotics and parabiotics (PP) are emerging fields of study in animal nutrition, preventive veterinary medicine, and animal production. Postbiotics are bioactive compounds produced by beneficial microorganisms during the fermentation of a substrate, while parabiotics are inactivated beneficial microbial cells, either intact or broken. Unlike probiotics, which are live microorganisms, PP are produced from a fermentation process without live cells and show significant advantages in promoting animal health owing to their distinctive stability, safety, and functional diversity. PP have numerous beneficial effects on animal health, such as enhancing growth performance, improving the immune system and microbiota of the gastrointestinal tract, aiding ulcer healing, and preventing pathogenic microorganisms from colonizing in the skin. Moreover, PP have been identified as a potential alternative to traditional antibiotics in veterinary medicine due to their ability to improve animal health without the risk of antimicrobial resistance. This review comprehensively explores the current research and applications of PP in veterinary medicine. We aimed to thoroughly examine the mechanisms of action, benefits, and potential applications of PP in various species, emphasizing their use specifically in livestock and poultry. Additionally, we discuss the various routes of administration to animals, including feed, drinking water, and topical use. This review also presents in-depth information on the methodology behind the preparation of PP, outlining the criteria employed to select appropriate microorganisms, and highlighting the challenges commonly associated with PP utilization in veterinary medicine.

Milk phospholipids protect Bifidobacterium longum subsp. infantis during in vitro digestion and enhance polysaccharide production

Bifidobacterium longum subsp. infantis is associated with the gut microbiota of breast-fed infants. Bifidobacterium infantis promotes intestinal barrier and immune function through several proposed mechanisms, including interactions between their surface polysaccharides, the host, and other gut microorganisms. Dairy foods and ingredients are some of the most conspicuous food-based niches for this species and may provide benefits for their delivery and efficacy in the gut. Milk phospholipid (MPL)-rich ingredients have been increasingly recognized for their versatile benefits to health, including interactions with the gut microbiota and intestinal cells. Therefore, our objective was to investigate the capacity for MPL to promote survival of B. infantis during simulated digestion and to modulate bacterial polysaccharide production. To achieve these aims, B. infantis was incubated with or without 0.5% MPL in de Man, Rogosa, and Sharpe (MRS) media at 37°C under anaerobiosis. Survival across the oral, gastric, and intestinal phases using in vitro digestion was measured using plate count, along with adhesion to goblet-like intestinal cells. MPL increased B. infantis survival at the end of the intestinal phase by at least 7% and decreased adhesion to intestinal cells. The bacterial surface characteristics, which may contribute to these effects, were assessed by ζ-potential, changes in surface proteins using comparative proteomics, and production of bound polysaccharides. MPL decreased the surface charge of the bifidobacteria from -17 to -24 mV and increased a 50 kDa protein (3-fold) that appears to be involved in protection from stress. The production of bound polysaccharides was measured using FTIR, HPLC, and TEM imaging. These techniques all suggest an increase in bound polysaccharide production at least 1.7-fold in the presence of MPL. Our results show that MPL treatment increases B. infantis survival during simulated digestion, induces a stress resistance surface protein, and yields greater bound polysaccharide production, suggesting its use as a functional ingredient to enhance probiotic and postbiotic effects.

Enhanced probiotic potential of Lactobacillus kefiranofaciens OSU-BDGOA1 through co-culture with Kluyveromyces marxianus bdgo-ym6

Introduction

Due to the increasing consumer demand for the development and improvement of functional foods containing probiotics, new probiotic candidates need to be explored as well as novel means to enhance their beneficial effects. Lactobacillus kefiranofaciens OSU-BDGOA1 is a strain isolated from kefir grains that has demonstrated probiotic traits. This species is the main inhabitant of kefir grains and is responsible for the production of an exopolysaccharide (EPS) whit vast technological applications and potential bioactivities. Research has shown that interkingdom interactions of yeast and lactic acid bacteria can enhance metabolic activities and promote resistance to environmental stressors.

Methods

Comparative genomic analyses were performed to distinguish OSU-BDGOA1 from other strains of the same species, and the genome was mined to provide molecular evidence for relevant probiotic properties. We further assessed the cumulative effect on the probiotic properties of OSU-BDGOA1 and Kluyveromyces marxianus bdgo-ym6 yeast co-culture compared to monocultures.

Results

Survival during simulated digestion assessed by the INFOGEST digestion model showed higher survival of OSU-BDGOA1 and bdgo-ym6 in co-culture. The adhesion to intestinal cells assessed with the Caco-2 intestinal cell model revealed enhanced adhesion of OSU-BDGOA1 in co-culture. The observed increase in survival during digestion could be associated with the increased production of EPS during the late exponential and early stationary phases of co-culture that, by enhancing co-aggregation between the yeast and the bacterium, protects the microorganisms from severe gastrointestinal conditions as observed by SEM images. Immune modulation and barrier function for recovery and prevention of flagellin-mediated inflammation by Salmonella Typhimurium heat-killed cells (HKSC) in Caco-2 cells were also measured. OSU-BDGOA1 in mono- and co-culture regulated inflammation through downregulation of pro-inflammatory cytokine expression and increased membrane barrier integrity assessed by TEER, FD4 permeability, and expression of tight junctions.

Discussion

The results of the study warrant further research into the application of co-cultures of yeast and LAB in functional probiotic products and the potential to increase EPS production by co-culture strategies.

Unveiling the Antibiotic Susceptibility and Antimicrobial Potential of Bacteria from Human Breast Milk of Pakistani Women: An Exploratory Study

BACKGROUND

Human life quality and expectancy have increased dramatically over the past 5 decades because of improvements in nutrition and antibiotic's usage fighting against infectious diseases. Yet, it was soon revealed that the microbes adapted to develop resistance to any of the drugs that were used. Recently, there is great concern that commensal bacteria from food and the gastrointestinal tract of humans and animals could act as a reservoir for antibiotic resistance genes. Methodology. This study was intended for evaluating the phenotypic antibiotic resistance/sensitivity profiles of probiotic bacteria from human breast milk and evaluating the inhibitory effect of the probiotic bacteria against both Gram-negative and Gram-positive bacteria.

RESULTS

The results point out that some of the isolated bacteria were resistant to diverse antibiotics including gentamycin, imipenem, trimethoprim sulfamethoxazole, and nalidixic acid. Susceptibility profile to certain antibiotics like vancomycin, tetracycline, ofloxacin, chloramphenicol, streptomycin, rifampicin, and bacitracin was also observed. The antimicrobial qualities of cell-free supernatants of some probiotic bacteria inhibited the growth of indicator bacteria. Also, antimicrobial properties of the probiotic bacteria from the present study attributed to the production of organic acid, bacterial adhesion to hydrocarbons (BATH), salt aggregation, coaggregation with pathogens, and bacteriocin production. Some isolated bacteria from human milk displayed higher hydrophobicity in addition to intrinsic probiotic properties like Gram-positive classification, catalase-negative activity, resistance to gastric juice (pH 2), and bile salt (0.3%) concentration.

CONCLUSION

This study has added to the data of the antibiotic and antimicrobial activity of some probiotic bacteria from some samples of Pakistani women breast milk. Probiotic bacteria are usually considered to decrease gastrointestinal tract diseases by adhering to the gut epithelial and reducing population of pathogens and in the case of Streptococcus lactarius MB622 and Streptococcus salivarius MB620 in terms of hydrophobicity and exclusion of indicator pathogenic strains.

Lactic acid bacteria-derived exopolysaccharide: Formation, immunomodulatory ability, health effects, and structure-function relationship

Exopolysaccharides (EPSs) synthesized by lactic acid bacteria (LAB) have implications for host health and act as food ingredients. Due to the variability of LAB-EPS (lactic acid bacteria-derived exopolysaccharide) gene clusters, especially the glycosyltransferase genes that determine monosaccharide composition, the structure of EPS is very rich. EPSs are synthesized by LAB through the extracellular synthesis pathway and the Wzx/Wzy-dependent pathway. LAB-EPS has a strong immunomodulatory ability. The EPSs produced by different genera of LAB, especially Lactobacillus, Leuconostoc, and Streptococcus, have different immunomodulatory abilities because of their specific structures. LAB-EPS possesses other health effects, including antitumor, antioxidant, intestinal barrier repair, antimicrobial, antiviral, and cholesterol-lowering activities. The bioactivities of LAB-EPS are tightly related to their structures such us monosaccharide composition, glycosidic bonds, and molecular weight (MW). For the excellent physicochemical property, LAB-EPS acts as product improvers in dairy, bakery food, and meat in terms of stability, emulsification, thickening, and gelling. We systematically summarize the detailed process of EPS from synthesis to application, with emphasis on physiological mechanisms of EPS, and specific structure-function relationship, which provides theoretical support for the potential commercial value in the pharmaceutical, chemical, food, and cosmetic industries.

Over-production of exopolysaccharide by Lacticaseibacillus rhamnosus CNCM I-3690 strain cutbacks its beneficial effect on the host

Most lactobacilli produce extracellular polysaccharides that are considered to contribute to the probiotic effect of many strains. Lacticaseibacillus rhamnosus CNCM I-3690 is an anti-inflammatory strain able to counterbalance gut barrier dysfunction. In this study ten spontaneous variants of CNCM I-3690 with different EPS-production were generated and characterized by their ropy phenotype, the quantification of the secreted EPS and genetic analysis. Amongst them, two were further analysed in vitro and in vivo: an EPS over-producer (7292) and a low-producer derivative of 7292 (7358, with similar EPS levels than the wild type (WT) strain). Our results showed that 7292 does not have anti-inflammatory profile in vitro, and lost the capacity to adhere to the colonic epithelial cells as well as the protective effect on the permeability. Finally, 7292 lost the protective effects of the WT strain in a murine model of gut dysfunction. Notably, strain 7292 was unable to stimulate goblet cell mucus production and colonic IL-10 production, all key features for the beneficial effect of the WT strain. Furthermore, transcriptome analysis of colonic samples from 7292-treated mice showed a down-regulation of anti-inflammatory genes. Altogether, our results point out that the increase of EPS production in CNCM I-3690 impairs its protective effects and highlight the importance of the correct EPS synthesis for the beneficial effects of this strain.

Antimicrobial and immunoregulatory effects of Lactobacillus delbrueckii 45E against genitourinary pathogens

BACKGROUND

Lactobacilli are essential microbiota that maintain a healthy, balanced vaginal environment. Vaginitis is a common infection in women during their reproductive years. Many factors are associated with vaginitis; one of them is the imbalance of microbiota in the vaginal environment. This study aimed to evaluate the antimicrobial properties of Lactobacillus delbrueckii 45E (Ld45E) against several species of bacteria, namely, Group B Streptococcus (GBS), Escherichia coli, Klebsiella spp., and Candida parapsilosis, as well as to determine the concentration of interleukin-17 (IL-17) in the presence of Ld45E.

METHODS

The probiotic characteristics of Ld45E were evaluated by examining its morphology, pH tolerance, adhesive ability onto HeLa cells, hemolytic activity, antibiotic susceptibility, and autoaggregation ability. Then, the antimicrobial activity of Ld45E was determined using Ld45E culture, cell-free supernatant, and crude bacteriocin solution. Co-aggregation and competition ability assays against various pathogens were conducted. The immunoregulatory effects of Ld45E were analyzed by measuring the proinflammatory cytokine IL-17. A p-value less than 0.05 was considered statistical significance.

RESULTS

Ld45E is 3-5 mm in diameter and round with a flat-shaped colony. pH 4 and 4.5 were the most favorable range for Ld45E growth within 12 h of incubation. Ld45E showed a strong adhesion ability onto HeLa cells (86%) and negative hemolytic activities. Ld45E was also sensitive to ceftriaxone, cefuroxime, ciprofloxacin, and doxycycline. We found that it had a good autoaggregation ability of 80%. Regarding antagonistic properties, Ld45E culture showed strong antimicrobial activity against GBS, E. coli, and Klebsiella spp. but only a moderate effect on C. parapsilosis. Cell-free supernatant of Ld45E exerted the most potent inhibitory effects at 40 °C against all genital pathogens, whereas bacteriocin showed a robust inhibition at 37 °C and 40 °C. The highest co-aggregation affinity was observed with GBS (81%) and E. coli (40%). Competition ability against the adhesion of GBS (80%), E. coli (76%), Klebsiella (72%), and C. parapsilosis (58%) was found. Ld45E was able to reduce the induction of the proinflammatory protein IL-17.

CONCLUSIONS

Ld45E possessed antimicrobial and immunoregulatory properties, with better cell-on-cell activity than supernatant activity. Thus, Ld45E is a potential probiotic candidate for adjunct therapy to address vaginal infections.

Beneficial insights into postbiotics against colorectal cancer

Colorectal cancer (CRC) is one of the most prevalent and life-threatening cancer types with limited therapeutic options worldwide. Gut microbiota has been recognized as the pivotal determinant in maintaining gastrointestinal (GI) tract homeostasis, while dysbiosis of gut microbiota contributes to CRC development. Recently, the beneficial role of postbiotics, a new concept in describing microorganism derived substances, in CRC has been uncovered by various studies. However, a comprehensive characterization of the molecular identity, mechanism of action, or routes of administration of postbiotics, particularly their role in CRC, is still lacking. In this review, we outline the current state of research toward the beneficial effects of gut microbiota derived postbiotics against CRC, which will represent the key elements of future precision-medicine approaches in the development of novel therapeutic strategies targeting gut microbiota to improve treatment outcomes in CRC.

Postbiotic Lipoteichoic acid of probiotic Lactobacillus origin ameliorates inflammation in HT-29 cells and colitis mice

Lipoteichoic acid (LTA) is a key surface component of probiotic lactobacilli that is involved in important cellular functions including cross talk with the host immune cells. In this study, the anti-inflammatory and ameliorative properties of LTA from probiotic lactobacilli strains were assessed in in vitro HT-29 cells and in vivo colitis mice. The LTA was extracted with n-butanol and its safety was confirmed based on its endotoxin content and cytotoxicity in HT-29 cells. In the Lipopolysaccharide stimulated HT-29 cells, the LTA from the test probiotics evoked a visible but non-significant increase in IL-10 and decrease in TNF-α levels. During the colitis mice study, probiotic LTA treated mice showed substantial improvement in external colitis symptoms, disease activity score and weight gain. The treated mice also showed improvements in key inflammatory markers such as the gut permeability, myeloperoxidase activity and histopathological damages in colon, although non-significant improvements were recorded for the inflammatory cytokines. Furthermore, structural studies by NMR and FTIR revealed increased level of D-alanine substitution in the LTA of LGG strain over MTCC5690. The present study demonstrates the ameliorative effect of LTA as a postbiotic component from probiotics which can be helpful in building effective strategies for combating gut inflammatory disorders.

A systematic review on selection characterization and implementation of probiotics in human health

Probiotics are live bacteria found in food that assist the body's defence mechanisms against pathogens by reconciling the gut microbiota. Probiotics are believed to aid with gut health, the immune system, and brain function, among other factors. They've furthermore been shown to help with constipation, high blood pressure, and skin issues. The global probiotics market has been incrementally growing in recent years, as consumers' demand for healthy diets and wellness has continued to increase. This has prompted the food industry to develop new probiotic-containing food products, as well as researchers to explore their specific characteristics and impacts on human health. Although most probiotics are fastidious microorganisms that are nutritionally demanding and sensitive to environmental conditions, they become less viable as they are processed and stored. In this review we studied the current literature on the fundamental idea of probiotic bacteria, their medical benefits, and their selection, characterization, and implementations.

Graphical Abstract

Independent and Combined Effects of Probiotics and Prebiotics as Supplements or Food-Rich Diets on a Propionic-Acid-Induced Rodent Model of Autism Spectrum Disorder

The link between nutrition and autism spectrum disorder (ASD) as a neurodevelopmental condition, which is clinically presented as significant delays or deviations in interaction and communication, has provided a fresh point of view and signals that nutrition may play a role in the etiology of ASD, as well as playing an effective role in treatment by improving symptoms. In this study, 36 male albino rat pups were used. They were randomly divided into five groups. The control group was fed only a standard diet and water for the 30 days of the experiment. The second group, which served as a propionic acid (PPA)-induced rodent model of ASD, received orally administered PPA (250 mg/kg body weight (BW)) for 3 days, followed by feeding with a standard diet until the end of the experiment. The three other groups were given PPA (250 mg/kg body weight (BW)) for 3 days and then fed a standard diet and orally administered yogurt (3 mL/kg BW/day), artichokes (400 mL/kg BW/day), and a combination of Lacticaseibacillus rhamnosus GG at 0.2 mL daily (1 × 10⁹ CFU; as the probiotic of yogurt) and luteolin (50 mg/kg BW/day; as the major antioxidant and anti-inflammatory ingredient of artichokes) for 27 days. Biochemical markers, including gamma-aminobutyric acid (GABA), reduced glutathione (GSH), glutathione peroxidase (GPx1), tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and interleukin-10 (IL-10), were measured in brain homogenates in all groups. The data showed that while PPA demonstrated oxidative stress and neuroinflammation in the treated rats, yogurt, Lacticaseibacillus rhamnosus GG as a probiotic, and luteolin as a prebiotic ingredient in artichokes were effective in alleviating the biochemical features of ASD. In conclusion, nutritional supplementation seems to be a promising intervention strategy for ASD. A combined dietary approach using pro- and prebiotics resulted in significant amelioration of most of the measured variables, suggesting that multiple interventions might be more relevant for the improvement of biochemical autistic features, as well as psychological traits. Prospective controlled trials are needed before recommendations can be made regarding the ideal ASD diet.

A systematic, complexity-reduction approach to dissect the kombucha tea microbiome

One defining goal of microbiome research is to uncover mechanistic causation that dictates the emergence of structural and functional traits of microbiomes. However, the extraordinary degree of ecosystem complexity has hampered the realization of the goal. Here, we developed a systematic, complexity-reducing strategy to mechanistically elucidate the compositional and metabolic characteristics of microbiome by using the kombucha tea microbiome as an example. The strategy centered around a two-species core that was abstracted from but recapitulated the native counterpart. The core was convergent in its composition, coordinated on temporal metabolic patterns, and capable for pellicle formation. Controlled fermentations uncovered the drivers of these characteristics, which were also demonstrated translatable to provide insights into the properties of communities with increased complexity and altered conditions. This work unravels the pattern and process underlying the kombucha tea microbiome, providing a potential conceptual framework for mechanistic investigation of microbiome behaviors.

AI-2/LuxS Quorum Sensing System Promotes Biofilm Formation of Lactobacillus rhamnosus GG and Enhances the Resistance to Enterotoxigenic Escherichia coli in Germ-Free Zebrafish

The LuxS enzyme plays a key role in both quorum sensing (QS) and the regulation of bacterial growth. It catalyzes the production of autoinducer-2 (AI-2) signaling molecule, which is a component of the methyl cycle and methionine metabolism. This study aimed at investigating the differences between the Lactobacillus rhamnosus GG (LGG) wild-type strain (WT) and its luxS mutant (ΔluxS) during biofilm formation and when resisting to inflammation caused by Enterotoxigenic Escherichia coli (ETEC) in germ-free zebrafish. Our results suggest that in the absence of luxS when LGG was knocked out, biofilm formation, extracellular polysaccharide secretion and adhesion were all compromised. Addition of synthetic AI-2 indeed rescued, at least partially, the deficiencies observed in the mutant strain. The colonizing and immunomodulatory function in WT versus ΔluxS mutants were further studied in a germ-free zebrafish model. The concentration of AI-2 signaling molecules decreased sharply in zebrafish infected with the ΔluxS. At the same time, compared with the ΔluxS, the wild-type strain could colonize the germ-free zebrafish more effectively. Our transcriptome results suggest that genes involved in immunity, signal transduction, and cell adhesion were downregulated in zebrafish infected with ΔluxS and WT. In the WT, the immune system of germ-free zebrafish was activated more effectively through the MAPK and NF-κB pathway, and its ability to fight the infection against ETEC was increased. Together, our results demonstrate that the AI-2/LuxS system plays an important role in biofilm formation to improve LGG and alleviate inflammation caused by ETEC in germ-free zebrafish.

IMPORTANCELactobacillus rhamnosus GG is a widely used probiotic to improve host intestinal health, promote growth, reduce diarrhea, and modulate immunity. In recent years, the bacterial quorum sensing system has attracted much attention; however, there has not been much research on the effect of the LuxS/AI-2 quorum sensing system of Lactobacillus on bacteriostasis, microbial ecology balance, and immune regulation in intestine. In this study, we used germ-free zebrafish as an animal model to compare the differences between wild-type and luxS mutant strains. We showed how AI-2/LuxS QS affects the release of AI-2 and how QS regulates the colonization, EPS synthesis and biofilm formation of LGG. This study provides an idea for the targeted regulation of animal intestinal health with probiotics by controlling bacteria quorum sensing system.

Synbiotics: a New Route of Self-production and Applications to Human and Animal Health

Synbiotics are preparations in which prebiotics are added to probiotics to achieve superior performance and benefits on the host. A new route of their formation is to induce the prebiotic biosynthesis within the probiotic for synbiotic self-production or autologous synbiotics. The aim of this review paper is first to overview the basic concept and (updated) definitions of synergistic synbiotics, and then to focus particularly on the prebiotic properties of probiotic wall components while describing the environmental factors/stresses that stimulate autologous synbiotics, that is, the biosynthesis of prebiotic-forming microcapsule by probiotic bacteria, and finally to present some of their applications to human and animal health.

Targeting Nrf2 with Probiotics and Postbiotics in the Treatment of Periodontitis

Periodontitis is a destructive disease of the tooth-surrounding tissues. Infection is the etiological cause of the disease, but its extent and severity depend on the immune–inflammatory response of the host. Immune cells use reactive oxygen species to suppress infections, and there is homeostasis between oxidative and antioxidant mechanisms during periodontal health. During periodontitis, however, increased oxidative stress triggers tissue damage, either directly by activating apoptosis and DNA damage or indirectly by activating proteolytic cascades. Periodontal treatment aims to maintain an infection and inflammation-free zone and, in some cases, regenerate lost tissues. Although mechanical disruption of the oral biofilm is an indispensable part of periodontal treatment, adjunctive measures, such as antibiotics or anti-inflammatory medications, are also frequently used, especially in patients with suppressed immune responses. Recent studies have shown that probiotics activate antioxidant mechanisms and can suppress extensive oxidative stress via their ability to activate nuclear factor erythroid 2-related factor 2 (Nrf2). The aim of this narrative review is to describe the essential role of Nrf2 in the maintenance of periodontal health and to propose possible mechanisms to restore the impaired Nrf2 response in periodontitis, with the aid of probiotic and postbiotics.

Biological Functions of Exopolysaccharides from Lactic Acid Bacteria and Their Potential Benefits for Humans and Farmed Animals

Lactic acid bacteria (LAB) synthesize exopolysaccharides (EPS), which are structurally diverse biopolymers with a broad range of technological properties and bioactivities. There is scientific evidence that these polymers have health-promoting properties. Most commercialized probiotic microorganisms for consumption by humans and farmed animals are LAB and some of them are EPS-producers indicating that some of their beneficial properties could be due to these polymers. Probiotic LAB are currently used to improve human health and for the prevention and treatment of specific pathologic conditions. They are also used in food-producing animal husbandry, mainly due to their abilities to promote growth and inhibit pathogens via different mechanisms, among which the production of EPS could be involved. Thus, the aim of this review is to discuss the current knowledge of the characteristics, usage and biological role of EPS from LAB, as well as their postbiotic action in humans and animals, and to predict the future contribution that they could have on the diet of food animals to improve productivity, animal health status and impact on public health.

The role of probiotic exopolysaccharides in adhesion to mucin in different gastrointestinal conditions

The presence of exopolysaccharides (EPS), a type of biomacromolecules, on the surface of probiotics play an important role in mucoadhesion, and it can be severely influenced by environments during gastrointestinal transit. In this study, the impact of gastrointestinal factors on surface properties of two probiotics (Lactobacillus rhamnosus GG and Pediococcus pentosaceus LI05) was investigated. Probiotic suspensions had relatively high viscosities and exhibited pronounced shear-thinning behavior due to the presence of EPS. The ζ-potential of both probiotics was relatively low and was not believed to play an important role in mucoadhesion. Compared to the control, the adhesive forces tended to decrease in the presence of gastric acids but increase in the presence of bile salts, since bile salts led to a thicker more open EPS layer compared to gastric acids. Although the functional groups of EPS in both probiotics are similar according to the study by FT-IR spectroscopy, the molecular weight of purified EPS in LI05 was much higher, ranging from 10,112 Da to 477,763 Da, which may contribute to higher rupture length in LI05 group. These results suggest that probiotic-mucin interactions are governed by the compositions and changes in the EPS of the probiotics in different gastrointestinal conditions, which contribute to a better understanding of the mucoadhesive behavior of the probiotics in the GIT.

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Simulated gastrointestinal fluids affected property of EPS, influencing the probiotic mucoadhesion.

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Higher molecular weight of EPS may contribute to enhanced rupture length.

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The morphology changes of probiotic EPS enhanced mucoadhesion by controlling the exposure of pili.

The potential role of adherence factors in probiotic function in the gastrointestinal tract of adults and pediatrics: a narrative review of experimental and human studies

Numerous studies point to the important role of probiotic bacteria in gastrointestinal health. Probiotics act through mechanisms affecting enteric pathogens, epithelial barrier function, immune signaling, and conditioning of indigenous microbiota. Once administered, probiotics reach the gastrointestinal tract and interact with the host through bacterial surface molecules, here called adhesion factors, which are either strain- or specie-specific. Probiotic adhesion, through structural adhesion factors, is a mechanism that facilitates persistence within the gastrointestinal tract and triggers the initial host responses. Thus, an understanding of specific probiotic adhesion mechanisms could predict how specific probiotic strains elicit benefits and the potential of adherence factors as a proxy to predict probiotic function. This review summarizes the present understanding of probiotic adherence in the gastrointestinal tract. It highlights the bacterial adhesion structure types, their molecular communication with the host and the consequent impact on intestinal diseases in both adult and pediatric populations. Finally, we discuss knockout/isolation studies as direct evidence for adhesion factors conferring anti-inflammatory and pathogen inhibition properties to a probiotic.What is known: Probiotics can be used to treat clinical conditions.Probiotics improve dysbiosis and symptoms.Clinical trials may not confirm in vitro and animal studies.What is new: Adhesion structures may be important for probiotic function.Need to systematically determine physical characteristics of probiotics before selecting for clinical trials.Probiotics may be genetically engineered to add to clinical efficacy.

Overexpression of Capsular Polysaccharide Biosynthesis Protein in Lactobacillus plantarum P1 to Enhance Capsular Polysaccharide Production for Di-n-butyl Phthalate Adsorption

Exopolysaccharides (EPSs) such as capsular polysaccharide (CPS) are important bioactive carbohydrate compounds and are often used as bioenrichment agents and bioabsorbers to remove environmental pollutants like di-n-butyl phthalate (DBP). Among the EPS-producing bacteria, lactic acid bacteria (LAB) have gained the most attention. As generally recognized as safe (GRAS) microorganisms, LAB can produce EPSs having many different structures and no health risks. However, EPS production by LAB does not meet the needs of large-scale application on an industrial scale. Here, the capA gene (encoding CPS biosynthesis protein) was overexpressed in Lactobacillus plantarum P1 to improve the production of EPSs and further enhance the DBP adsorption capability. Compared with P1, the CPS production in capA overexpressed strain was increased by 11.3 mg/l, and the EPS thickness was increased from 0.0786 ± 0.0224 μm in P1 to 0.1160 ± 0.0480 μm in P1-capA. These increases caused the DBP adsorption ratio of P1-capA to be doubled. Overall, the findings in this study provide a safe method for the adsorption and removal of DBP.

Genomic Stability and Phenotypic Characteristics of Industrially Produced Lacticaseibacillus rhamnosus GG in a Yogurt Matrix

Lacticaseibacillus rhamnosus GG is a widely marketed probiotic with well-documented probiotic properties. Previously, deletion of the mucus-adhesive spaCBA-srtC1 genes in dairy isolates was reported. In this study, we examined the genome preservation of industrially produced L. rhamnosus GG (DSM 33156) cofermented in yogurts. In total, DNA of 66 samples, including 60 isolates, was sequenced. Population samples and 59 isolates exhibited an intact genome. One isolate exhibited loss of spaCBA-srtC1. In addition, we examined phenotypes related to the probiotic properties of L. rhamnosus GG either from frozen pellets or cofermented in yogurt. L. rhamnosus GG from frozen pellets induced a response in intestinal barrier function in vitro, in contrast to frozen pellets of the starter culture. Yogurt matrix, containing only the starter culture, induced a response, but cofermentation with L. rhamnosus GG induced a higher response. Conversely, only the starter culture stimulated cytokine secretion in dendritic cells, and it was observed that the addition of L. rhamnosus GG to the starter culture reduced the response. We conclude that the L. rhamnosus GG genome is preserved in yogurt and that common in vitro probiotic effects of L. rhamnosus GG are observed when examined in the yogurt matrix. IMPORTANCE Lacticaseibacillus rhamnosus GG is a well-documented probiotic strain recognized for its high acid and bile tolerance and properties of adhesion to enterocytes and mucus. The strain exhibits SpaCBA pili, which have been demonstrated to play an important role in adhesion and therefore are relevant for persistence in the gastrointestinal tract. Recently we demonstrated that the genome and phenotypes of L. rhamnosus GG are preserved throughout an industrial production pipeline. However, as gene deletions in L. rhamnosus GG were previously reported for isolates from dairy products, a key question on the genomic stability of L. rhamnosus GG in a yogurt matrix remained. The aim of this study was to analyze genome stability and phenotypic characteristics of L. rhamnosus GG in yogurt. We found that the genome of L. rhamnosus GG is well conserved when the organism is cofermented in yogurt. Some phenotypic characteristics are consistent in all product matrixes, while other characteristics are modulated.

Lyophilized alginate-based microspheres containing Lactobacillus fermentum D12, an exopolysaccharides producer, contribute to the strain's functionality in vitro

Lactobacillus (Limosilactobacillus) fermentum D12 is an exopolysaccharide (EPS) producing strain whose genome contains a putative eps operon. Whole-genome analysis of D12 was performed to disclose the essential genes correlated with activation of precursor molecules, elongation and export of the polysaccharide chain, and regulation of EPS synthesis. These included the genes required for EPS biosynthesis such as epsA, B, C, D and E, also gt, wzx, and wzy and those involved in the activation of the precursor molecules galE, galT and galU. Both the biosynthesis and export mechanism of EPS were proposed based on functional annotation. When grown on MRS broth with an additional 2% w/v glucose, L. fermentum D12 secreted up to 200 mg/L of a mixture of EPSs, whose porous structure was visualized by scanning electron microscopy (SEM). Structural information obtained by ¹HNMR spectroscopy together with composition and linkage analyses, suggested the presence of at least two different EPSs, a branched heteropolysaccharide containing t-Glcp and 2,6-linked Galf, and glycogen. Since recent reports showed that polysaccharides facilitate the probiotic-host interactions, we at first sought to evaluate the functional potential of L. fermentum D12. Strain D12 survived simulated gastrointestinal tract (GIT) conditions, exhibited antibacterial activity against enteropathogenic bacteria, adhered to Caco-2 cells in vitro, and as such showed potential for in vivo functionality. The EPS crude extract positively influenced D12 strain capacity to survive during freeze-drying and to adhere to extracellular matrix (ECM) proteins but did not interfere Caco-2 and mucin adherence when added at concentrations of 0.2, 0.5, and 1.0 mg/mL. Since the viable bacterial count of free D12 cells was 3 logarithmic units lower after the exposure to simulated GIT conditions than the initial count, the bacterial cells had been loaded into alginate for viability improvement. Microspheres of D12 cells, which were previously analyzed at SEM, significantly influenced their survival during freeze-drying and in simulated GIT conditions. Furthermore, the addition of the prebiotic substrates mannitol and lactulose improved the viability of L. fermentum D12 in freeze-dried alginate microspheres during 1-year storage at 4 °C compared to the control.

Liposome encapsulated surfactant abetted copper nanoparticles alleviates biofilm mediated virulence in pathogenic Pseudomonas aeruginosa and MRSA

In the present study lipopeptide biosurfactant with high emulsification capacity produced by human skin bacterium Paenibacillus thiaminolyticus was purified and subjected to FTIR and NMR spectral analysis which gave evidence of the active characteristics of the surfactant. To augment the antivirulent potential further, the mixer of copper and copper oxide nanoparticles (CuNPs) was synthesized, and characterized by UV–Visible spectroscopy, SEM-EDAX, TEM, and Zeta analysis. Here, we attempted to enhance the antimicrobial and antibiofilm activity with the assistance of encapsulated preparation of lipopeptide and CuNPs in multilamellar liposomes. The proposed mechanism of action of lipopeptide and CuNPs liposomal preparation negatively influences the cell metabolism, secreted virulence such as staphyloxanthin, pyocyanin, and extracellular polysaccharides. The significant decline in the growth of MRSA and P. aeruginosa in both planktonic form and biofilm by lipopeptide and CuNPs treatment were visualized using scanning electron microscopy and High content screening imaging system. In vivo studies revealed that treatment with lipopeptide and CuNPs in multilamellar liposomes extended the lifespan of infected Caenorhabditis elegans by about 75%. Therefore, this study typifies lipopeptide and CuNPs could credibly be a substantial substitute over conventional antibiotics in averting the biofilm associated pathogenesis of MRSA and P. aeruginosa.

Oxidative stress tolerance and antioxidant capacity of lactic acid bacteria as probiotic: a systematic review

Lactic acid bacteria (LAB) are the most frequently used probiotics in fermented foods and beverages and as food supplements for humans or animals, owing to their multiple beneficial features, which appear to be partially associated with their antioxidant properties. LAB can help improve food quality and flavor and prevent numerous disorders caused by oxidation in the host. In this review, we discuss the oxidative stress tolerance, the antioxidant capacity related herewith, and the underlying mechanisms and signaling pathways in probiotic LAB. In addition, we discuss appropriate methods used to evaluate the antioxidant capacity of probiotic LAB. The aim of the present review is to provide an overview of the current state of the research associated with the oxidative stress tolerance and antioxidant capacity of LAB.

Gastrointestinal stress as innate defence against microbial attack

The human gastrointestinal (GI) tract has been bestowed with the most difficult task of protecting the underlying biological compartments from the resident commensal flora and the potential pathogens in transit through the GI tract. It has a unique environment in which several defence tactics are at play while maintaining homeostasis and health. The GI tract shows myriad number of environmental extremes, which includes pH variations, anaerobic conditions, nutrient limitations, elevated osmolarity etc., which puts a check to colonization and growth of nonfriendly microbial strains. The GI tract acts as a highly selective barrier/platform for ingested food and is the primary playground for balance between the resident and uninvited organisms. This review focuses on antimicrobial defense mechanisms of different sections of human GI tract. In addition, the protective mechanisms used by microbes to combat the human GI defence systems are also discussed. The ability to survive this innate defence mechanism determines the capability of probiotic or pathogen strains to confer health benefits or induce clinical events respectively.

Characterization of robust Lactobacillus plantarum and Lactobacillus pentosus starter cultures for environmentally friendly low-salt cucumber fermentations

Seven candidates for starter cultures for cucumber fermentations belonging to the Lactobacillus pentosus and Lactobacillus plantarum species were characterized based on physiological features desired for pickling. The isolates presented variable carbohydrate utilization profile on API^® 50CHL test strips. The L. pentosus strains were unable to utilize d-xylose in MRS broth or the M medium. The lactobacilli were unable to produce histamine, tyramine, putrescine, and cadaverine in biogenic amine broth containing the necessary precursors. Production of d-lactic acid by the lactobacilli, detected enzymatically, was stimulated by growth in MRS broth as compared to cucumber juice medium (CJM). The lactobacilli utilized malic acid in the malate decarboxylase medium. Exopolyssacharide biosynthesis related genes were amplified from the lactobacilli. A sugar type-dependent-ropy phenotype was apparent for all the cultures tested in MRS and CJM. The genes associated with bacteriocin production were detected in the lactobacilli, but not the respective phenotypes. The antibiotic susceptibility profile of the lactobacilli mimics that of other L. plantarum starter cultures. It is concluded that the lactobacilli strains studied here are suitable starter cultures for cucumber fermentation. PRACTICAL APPLICATION: The availability of such starter cultures enables the implementation of low salt cucumber fermentations that can generate products with consistent biochemistry and microbiological profile.

Lactobacillus rhamnosus GG promotes M1 polarization in murine bone marrow-derived macrophages by activating TLR2/MyD88/MAPK signaling pathway

Lactobacillus rhamnosus GG (LGG) is increasingly applied in functional food products and acts as a probiotic model in nutritious and clinical studies. Increasing evidences have revealed the immune modulation of LGG on macrophages. The aim of this study is to investigate the effect of LGG on macrophage polarization of murine bone marrow-derived macrophages (BMDMs). BMDMs were treated with 10⁸ colony-forming units (CFU)/ml LGG for 1.5, 3, and 6 hr. Results showed that LGG obviously upregulated the mRNA expression of M1-associated cytokines (p < .05), including interleukin-1 beta (IL-1β), IL-6, tumor necrosis factor-alpha (TNF-α), and inducible nitric oxide synthase (iNOS), whereas had no effect on the expression of M2-associated markers (p > .05), including arginase 1 (Arg1), mannose receptor, and chitinase-like protein 3 (YM1). Furthermore, LGG markedly increased the expression of pro-inflammatory cytokines (IL-12p40, cyclooxygenase-2 [COX-2], and interferon-γ [IFN-γ]) (p < .05) and anti-inflammatory cytokines (IL-10, IL-4, and transforming growth factor-β [TGF-β]) (p < .05). In addition, we also found that TLR2/MyD88/MAPK signaling pathway was required for LGG-induced M1 macrophage polarization and M1-related cytokines expression. Together, these findings demonstrate that probiotic LGG facilitates M1 polarization of BMDMs, suggesting that LGG may have an immunotherapeutic potential in regulating the host defense against pathogen invasion.

Postbiotics-parabiotics: the new horizons in microbial biotherapy and functional foods

Probiotics have several health benefits by modulating gut microbiome; however, techno-functional limitations such as viability controls have hampered their full potential applications in the food and pharmaceutical sectors. Therefore, the focus is gradually shifting from viable probiotic bacteria towards non-viable paraprobiotics and/or probiotics derived biomolecules, so-called postbiotics. Paraprobiotics and postbiotics are the emerging concepts in the functional foods field because they impart an array of health-promoting properties. Although, these terms are not well defined, however, for time being these terms have been defined as here. The postbiotics are the complex mixture of metabolic products secreted by probiotics in cell-free supernatants such as enzymes, secreted proteins, short chain fatty acids, vitamins, secreted biosurfactants, amino acids, peptides, organic acids, etc. While, the paraprobiotics are the inactivated microbial cells of probiotics (intact or ruptured containing cell components such as peptidoglycans, teichoic acids, surface proteins, etc.) or crude cell extracts (i.e. with complex chemical composition)". However, in many instances postbiotics have been used for whole category of postbiotics and parabiotics. These elicit several advantages over probiotics like; (i) availability in their pure form, (ii) ease in production and storage, (iii) availability of production process for industrial-scale-up, (iv) specific mechanism of action, (v) better accessibility of Microbes Associated Molecular Pattern (MAMP) during recognition and interaction with Pattern Recognition Receptors (PRR) and (vi) more likely to trigger only the targeted responses by specific ligand-receptor interactions. The current review comprehensively summarizes and discussed various methodologies implied to extract, purify, and identification of paraprobiotic and postbiotic compounds and their potential health benefits.

Strain-specific differences in behaviour among Lacticaseibacillus rhamnosus cell wall mutants during direct compression

The human body harbours a large variety of microbial communities. It is already well-known that these communities play an important role in human health. Therefore, microbial imbalances can be responsible for several health disorders by different mechanisms. In recent years, probiotic bacteria have been increasingly applied to restore imbalances and stimulate microbiome functions such as immune modulation. Tablets are the dosage form of choice for oral probiotics. Nevertheless, a probiotic tablet with a sufficient amount of viable cells remains a challenge due to the stress of the compression process. Recent research demonstrated that the applied pressure and tableting properties play an important role in the survival of Lacticaseibacillus rhamnosus GG during direct compression. This study focused on the importance of the cell surface molecules in the protection of this prototype probiotic strain during direct compression. Spray-dried powders of L. rhamnosus GG and its exopolysaccharide-deficient mutant and lipoteichoic acid mutant were blended with two different filler-binders and compacted at various compression pressures. Under each tableting condition, the survival rate and tableting properties were analysed. The results demonstrated that the cell surface molecules play an important role in the behaviour of L. rhamnosus GG during direct compression. Specifically, the long, galactose-rich exopolysaccharides of L. rhamnosus served a protective shield during tablet production, promoting the survival rate of this probiotic strain. The D-alanylation of the lipoteichoic acids plays also an important role. When the D-alanyl ester content was completely absent, the survival rate was less affected by the tableting properties. Moreover, this research revealed that the sensitivity to the tableting properties is species and strain dependent.

Evaluation of the Probiotic Properties and the Capacity to Form Biofilms of Various Lactobacillus Strains

Over the last 20 years, Lactobacillus species inhabiting the gastrointestinal tract (GIT) have received much attention, and their health-promoting properties are now well-described. Probiotic effects cannot be generalized, and their uses cover a wide range of applications. It is thus important to proceed to an accurate selection and evaluation of probiotic candidates. We evaluate the probiotic potential of six strains of Lactobacillus in different in vitro models representing critical factors of either survival, efficacy, or both. We characterized the strains for their ability to (i) modulate intestinal permeability using transepithelial electrical resistance (TEER), (ii) form biofilms and resist stressful conditions, and (iii) produce beneficial host and/or bacteria metabolites. Our data reveal the specificity of Lactobacillus strains to modulate intestinal permeability depending on the cell type. The six isolates were able to form spatially organized biofilms, and we provide evidence that the biofilm form is beneficial in a strongly acidic environment. Finally, we demonstrated the ability of the strains to produce γ-aminobutyric acid (GABA) that is involved in the gut-brain axis and beneficial enzymes that promote the bacterial tolerance to bile salts. Overall, our study highlights the specific properties of Lactobacillus strains and their possible applications as biofilms.

Future of Probiotics and Prebiotics and the Implications for Early Career Researchers

The opportunities in the fields of probiotics and prebiotics to a great degree stem from what we can learn about how they influence the microbiota and interact with the host. We discuss recent insights, cutting-edge technologies and controversial results from the perspective of early career researchers innovating in these areas. This perspective emerged from the 2019 meeting of the International Scientific Association for Probiotics and Prebiotics - Student and Fellows Association (ISAPP-SFA). Probiotic and prebiotic research is being driven by genetic characterization and modification of strains, state-of-the-art in vitro, in vivo, and in silico techniques designed to uncover the effects of probiotics and prebiotics on their targets, and metabolomic tools to identify key molecules that mediate benefits on the host. These research tools offer unprecedented insights into the functionality of probiotics and prebiotics in the host ecosystem. Young scientists need to acquire these diverse toolsets, or form inter-connected teams to perform comprehensive experiments and systematic analysis of data. This will be critical to identify microbial structure and co-dependencies at body sites and determine how administered probiotic strains and prebiotic substances influence the host. This and other strategies proposed in this review will pave the way for translating the health benefits observed during research into real-life outcomes. Probiotic strains and prebiotic products can contribute greatly to the amelioration of global issues threatening society. The intent of this article is to provide an early career researcher's perspective on where the biggest opportunities lie to advance science and impact human health.

Immunomodulatory Roles of Polysaccharide Capsules in the Intestine

The interplay between the immune system and the microbiota in the human intestine dictates states of health vs. disease. Polysaccharide capsules are critical elements of bacteria that protect bacteria against environmental and host factors, including the host immune system. This review summarizes the mechanisms by which polysaccharide capsules from commensal and pathogenic bacteria in the gut microbiota modulate the innate and adaptive immune systems in the intestine. A deeper understanding of the roles of polysaccharide capsules in microbiota-immune interactions will provide a basis to harness their therapeutic potential to advance human health.

Identification of Genes Required for Glucan Exopolysaccharide Production in Lactobacillus johnsonii Suggests a Novel Biosynthesis Mechanism

Exopolysaccharides are key components of the surfaces of their bacterial producers, contributing to protection, microbial and host interactions, and even virulence. They also have significant applications in industry, and understanding their biosynthetic mechanisms may allow improved production of novel and valuable polymers. Four categories of bacterial exopolysaccharide biosynthesis have been described in detail, but novel enzymes and glycosylation mechanisms are still being described. Our findings that a putative bactoprenol glycosyltransferase and flippase are essential to homopolysaccharide biosynthesis in Lactobacillus johnsonii FI9785 indicate that there may be an alternative mechanism of glucan biosynthesis to the glucansucrase pathway. Disturbance of this synthesis leads to a slow-growth phenotype. Further elucidation of this biosynthesis may give insight into exopolysaccharide production and its impact on the bacterial cell.

Lactobacillus johnsonii FI9785 makes two capsular exopolysaccharides—a heteropolysaccharide (EPS2) encoded by the eps operon and a branched glucan homopolysaccharide (EPS1). The homopolysaccharide is synthesized in the absence of sucrose, and there are no typical glucansucrase genes in the genome. Quantitative proteomics was used to compare the wild type to a mutant where EPS production was reduced to attempt to identify proteins associated with EPS1 biosynthesis. A putative bactoprenol glycosyltransferase, FI9785_242 (242), was less abundant in the Δeps_cluster mutant strain than in the wild type. Nuclear magnetic resonance (NMR) analysis of isolated EPS showed that deletion of the FI9785_242 gene (242) prevented the accumulation of EPS1, without affecting EPS2 synthesis, while plasmid complementation restored EPS1 production. The deletion of 242 also produced a slow-growth phenotype, which could be rescued by complementation. 242 shows amino acid homology to bactoprenol glycosyltransferase GtrB, involved in O-antigen glycosylation, while in silico analysis of the neighboring gene 241 suggested that it encodes a putative flippase with homology to the GtrA superfamily. Deletion of 241 also prevented production of EPS1 and again caused a slow-growth phenotype, while plasmid complementation reinstated EPS1 synthesis. Both genes are highly conserved in L. johnsonii strains isolated from different environments. These results suggest that there may be a novel mechanism for homopolysaccharide synthesis in the Gram-positive L. johnsonii.

IMPORTANCE Exopolysaccharides are key components of the surfaces of their bacterial producers, contributing to protection, microbial and host interactions, and even virulence. They also have significant applications in industry, and understanding their biosynthetic mechanisms may allow improved production of novel and valuable polymers. Four categories of bacterial exopolysaccharide biosynthesis have been described in detail, but novel enzymes and glycosylation mechanisms are still being described. Our findings that a putative bactoprenol glycosyltransferase and flippase are essential to homopolysaccharide biosynthesis in Lactobacillus johnsonii FI9785 indicate that there may be an alternative mechanism of glucan biosynthesis to the glucansucrase pathway. Disturbance of this synthesis leads to a slow-growth phenotype. Further elucidation of this biosynthesis may give insight into exopolysaccharide production and its impact on the bacterial cell.

The Effect of Donor Human Milk Fortification on The Adhesion of Probiotics In Vitro

Preterm delivery complications are the primary cause of death among children under the age of five. Preventive strategies include the use of pasteurized donor human milk (DHM), its fortification with human milk fortifiers (protein supplements), and supplementation with probiotics. Our aim was to examine the impact of DHM and fortified DHM (FDHM) on the mucus adhesion properties of two widely used probiotics. The study covered two forms of human milk fortifier, liquid and powdered, with or without probiotics and storage at 4 °C for 24 h. To test the adhesion properties of the probiotic strains, DHM+probiotics and FDHM+probiotics were prepared and added to immobilized mucus isolated from the stool of healthy Finnish infants. The probiotic adhesion was then measured by liquid scintillation. Our results suggest that addition of liquid or powdered human milk fortifier in donor human milk had no impact on probiotic adhesion. In addition, given the increased adhesion of probiotics suspended in buffer, other matrices should be further studied. These factors need to be considered when designing future intervention strategies using probiotics in preterm infants.

Impact of spray-drying on the pili of Lactobacillus rhamnosus GG

The preservation of the viability of microorganisms in probiotic formulations is the most important parameter ensuring the adequate concentration of live microorganisms at the time of administration. The formulation and processing techniques used to produce these probiotic formulations can influence the preservation of the microbial viability. However, it is also required that the bacteria maintain their key probiotic capacities during processing, formulation and shelf life. In this study, we investigated the impact of spray-drying on different cell wall properties of the model probiotic strain Lactobacillus rhamnosus GG, including its adherence to intestinal epithelial cells. The dltD gene knock-out mutant, L. rhamnosus GG CMPG5540, displaying modified cell wall lipoteichoic acids, showed significantly increased colony-forming units after spray-drying and subsequent storage under standard conditions compared to wild-type L. rhamnosus GG. In contrast, disruption of the biosynthesis of exopolysaccharides or pili expression did not impact survival. However, spray-drying did significantly affect the adherence capacity of L. rhamnosus GG. Scanning electron microscopy confirmed that the pili, key surface factors for adherence to intestinal cells and mucus, were sheared off during the spray-drying process. These data thus highlight that both the functionality and viability of probiotics should be assessed during the spray-drying process and subsequent storage.

Growth Mode and Carbon Source Impact the Surfaceome Dynamics of Lactobacillus rhamnosus GG

Bacterial biofilms have clear implications in disease and in food applications involving probiotics. Here, we show that switching the carbohydrate source from glucose to fructose increased the biofilm formation and the total surface-antigenicity of a well-known probiotic, Lactobacillus rhamnosus GG. Surfaceomes (all cell surface-associated proteins) of GG cells grown with glucose and fructose in planktonic and biofilm cultures were identified and compared, which indicated carbohydrate source-dependent variations, especially during biofilm growth. The most distinctive differences under these conditions were detected with several surface adhesins (e.g., MBF, SpaC pilus protein and penicillin-binding proteins), enzymes (glycoside hydrolases, PrsA, PrtP, PrtR, and HtrA) and moonlighting proteins (glycolytic, transcription/translation and stress-associated proteins, r-proteins, tRNA synthetases, Clp family proteins, PepC, PepN, and PepA). The abundance of several known adhesins and candidate moonlighters, including enzymes acting on casein-derived peptides (ClpP, PepC, and PepN), increased in the biofilm cells grown on fructose, from which the surface-associated aminopeptidase activity mediated by PepC and PepN was further confirmed by an enzymatic assay. The mucus binding factor (MBF) was found most abundant in fructose grown biofilm cells whereas SpaC adhesin was identified specifically from planktonic cells growing on fructose. An additional indirect ELISA indicated both growth mode- and carbohydrate-dependent differences in abundance of SpaC, whereas the overall adherence of GG assessed with porcine mucus indicated that the carbon source and the growth mode affected mucus adhesion. The adherence of GG cells to mucus was almost completely inhibited by anti-SpaC antibodies regardless of growth mode and/or carbohydrate source, indicating the key role of the SpaCBA pilus in adherence under the tested conditions. Altogether, our results suggest that carbon source and growth mode coordinate mechanisms shaping the proteinaceous composition of GG cell surface, which potentially contributes to resistance, nutrient acquisition and cell-cell interactions under different conditions. In conclusion, the present study shows that different growth regimes and conditions can have a profound impact on the adherent and antigenic features of GG, thereby providing new information on how to gain additional benefits from this probiotic.

The relationship between the structural characteristics of lactobacilli-EPS and its ability to induce apoptosis in colon cancer cells in vitro

Colon cancer is one of the most common cancer around the world. Exopolysaccharides (EPSs) produced by lactobacilli as potential prebiotics have been found to have an anti-tumor effect. In this study, lyophilized EPSs of four Lactobacillus spp. for their impact on apoptosis in colon cancer cells (HT-29) was evaluated using flow cytometry. The relationship between capability of a lactobacilli-EPS to induce apoptosis and their monosaccharide composition, molecular weight (MW), and linkage type was investigated by HPLC, SEC, and NMR, respectively. Changes in apoptotic-markers were examined by qPCR and Western Blotting. EPSs were capable of inhibiting proliferation in a time-dependent manner and induced apoptosis via increasing the expression of Bax, Caspase 3 and 9 while decreasing Bcl-2 and Survivin. All EPSs contained mannose, glucose, and N-acetylglucosamine with different relative proportions. Some contained arabinose or fructose. MW ranged from 102-104Da with two or three fractions. EPS of L. delbrueckii ssp. bulgaricus B3 having the highest amount of mannose and the lowest amount of glucose, showed the highest apoptosis induction. In conclusion, lactobacilli-EPSs inhibit cell proliferation in HT-29 via apoptosis. Results suggest that a relationship exists between the ability of EPS to induce apoptosis and its mannose and glucose composition.

Thirty Years of Lactobacillus rhamnosus GG: A Review

Lactobacillus rhamnosus GG (LGG) was the first strain belonging to the genus Lactobacillus to be patented in 1989 thanks to its ability to survive and to proliferate at gastric acid pH and in medium containing bile, and to adhere to enterocytes. Furthermore LGG is able to produces both a biofilm that can mechanically protect the mucosa, and different soluble factors beneficial to the gut by enhancing intestinal crypt survival, diminishing apoptosis of the intestinal epithelium, and preserving cytoskeletal integrity. Moreover LGG thanks to its lectin-like protein 1 and 2 inhibits some pathogens such as Salmonella species. Finally LGG is able to promote type 1 immune-responsiveness by reducing the expression of several activation and inflammation markers on monocytes and by increasing the production of interleukin-10, interleukin-12 and tumor necrosis factor-α in macrophages. A large number of research data on Lactobacillus GG is the basis for the use of this probiotic for human health. In this review we have considered predominantly randomized controlled trials, meta-analysis, Cochrane Review, guide lines of Scientific Societies and anyway studies whose results were evaluated by means of relative risk, odds ratio, weighted mean difference 95% confidence interval. The effectiveness of LGG in gastrointestinal infections and diarrhea, antibiotic and Clostridium difficile associated diarrhea, irritable bowel syndrome, inflammatory bowel disease, respiratory tract infections, allergy, cardiovascular diseases, nonalcoholic fatty liver disease, nonalcoholic steatohepatitis, cystic fibrosis, cancer, elderly end sport were analyzed.

Structure and biological activities of a hexosamine-rich cell wall polysaccharide isolated from the probiotic Lactobacillus farciminis

Lactobacillus farciminis CIP 103136 is a bacterial strain with recognized probiotic properties. However, the mechanisms underlying such properties have only been partially elucidated. In this study, we isolated and purified a cell-wall associated polysaccharide (CWPS), and evaluated its biological role in vitro. The structure of CWPS and responses from stimulation of (i) human macrophage-like THP-1 cells, (ii) human embryonal kidney (HEK293) cells stably transfected with Toll-like receptors (TLR2 or TLR4) and (iii) human colonocyte-like T84 intestinal epithelial cells, upon exposure to CWPS were studied. The structure of the purified CWPS from L. farciminis CIP 103136 was analyzed by nuclear magnetic resonance (NMR), MALDI-TOF-TOF MS, and methylation analyses in its native form and following Smith degradation. It was shown to be a novel branched polysaccharide, composed of linear backbone of trisaccharide repeating units of: [→6αGlcpNAc1 → 4βManpNAc1 → 4βGlcpNAc1→] highly substituted with single residues of αGlcp, αGalp and αGlcpNAc. Subsequently, the lack of pro- or anti-inflammatory properties of CWPS was established on macrophage-like THP-1 cells. In addition, CWPS failed to modulate cell signaling pathways dependent of TLR2 and TLR4 in transfected HEK-cells. Finally, in T84 cells, CWPS neither influenced intestinal barrier integrity under basal conditions nor prevented TNF-α/IFN-γ cytokine-mediated epithelium impairment.

Aciduric Strains of Lactobacillus reuteri and Lactobacillus rhamnosus, Isolated from Human Feces, Have Strong Adhesion and Aggregation Properties

Human feces were streaked onto MRS Agar adjusted to pH 2.5, 3.0, and 6.4, respectively, and medium supplemented with 1.0% (w/v) bile salts. Two aciduric strains, identified as Lactobacillus reuteri HFI-LD5 and Lactobacillus rhamnosus HFI-K2 (based on 16S rDNA and recA sequences), were non-hemolytic and did not hydrolyze mucin. The surface of Lactobacillus reuteri HFI-LD5 cells has a weak negative charge, whereas Lactobacillus rhamnosus HFI-K2 has acidic and basic properties, and produces exopolysaccharides (EPS). None of the strains produce bacteriocins. Both strains are resistant to several antibiotics, including sulfamethoxazole-trimethoprim and sulphonamides. The ability of Lactobacillus reuteri HFI-LD5 and Lactobacillus rhamnosus HFI-K2 to grow at pH 2.5 suggests that they will survive passage through the stomach. EPS production may assist in binding to intestinal mucus, especially in the small intestinal tract, protect epithelial cells, and stimulate the immune system. Lactobacillus reuteri HFI-LD5 and Lactobacillus rhamnosus HFI-K2 may be used as probiotics, especially in the treatment of small intestinal bacterial overgrowth (SIBO).

Anti-proliferative, pro-apoptotic and anti-oxidative activity of Lactobacillus and Bifidobacterium strains: A review of mechanisms and therapeutic perspectives

Lactobacillus and Bifidobacterium strains, their isolated constituents and substances that they secrete exert various anti-cancer actions, resulting from their anti-proliferative, pro-apoptotic and anti-oxidant properties. They can express and secrete anti-oxidant enzymes, bind reactive oxygen species, release small molecular weight anti-oxidants and chelate transition metals, preventing detrimental actions of many carcinogens. Lactobacillus and Bifidobacterium can interact with proteins regulating the cell cycle inhibiting proliferation of cancer cells, which often are intrinsically resistant to apoptosis. Lactobacilli and bifidobacteria can break this resistance through activation of pro-caspases and downregulation of the anti-apoptotic Bcl-2 and upregulation of pro-apoptotic Bax proteins. Anti-cancer effects of these bacteria can be also associated with their multi-pathways action in the microbiota. However, exact mechanism of their anti-cancer action is poorly known and needs further studies, which are justified by the important role of these bacteria in cancer biology as well as their potential preventive and therapeutic use.

Interactions of Surface Exopolysaccharides From Bifidobacterium and Lactobacillus Within the Intestinal Environment

Exopolysaccharides (EPS) are surface carbohydrate polymers present in most bacteria acting as a protective surface layer but also interacting with the surrounding environment. This review discusses the roles of EPS synthesized by strains of Lactobacillus and Bifidobacterium, many of them with probiotic characteristics, in the intestinal environment. Current knowledge on genetics and biosynthesis pathways of EPS in lactic acid bacteria and bifidobacteria, as well as the development of genetic tools, has created possibilities to elucidate the interplay between EPS and host intestinal mucosa. These include the microbiota that inhabits this ecological niche and the host cells. Several carbohydrate recognition receptors located in the intestinal epithelium could be involved in the interaction with bacterial EPS and modulation of immune response; however, little is known about the receptors recognizing EPS from lactobacilli or bifidobacteria and the triggered response. On the contrary, it has been clearly demonstrated that EPS play a relevant role in the persistence of the producing bacteria in the intestinal tract. Indeed, some authors postulate that some of the beneficial actions of EPS-producing probiotics could be related to the formation of a biofilm layer protecting the host against injury, for example by pathogens or their toxins. Nevertheless, the in vivo formation of biofilms by probiotics has not been proved to date. Finally, EPS produced by probiotic strains are also able to interact with the intestinal microbiota that populates the gut. In fact, some of these polymers can be used as carbohydrate fermentable source by some gut commensals thus being putatively involved in the release of bacterial metabolites that exert positive benefits for the host. In spite of the increasing knowledge about the role that these surface molecules play in the interaction of probiotic bacteria with the gut mucosal actors, both intestinal receptors and microbiota, the challenging issue is to demonstrate the functionality of EPS in vivo, which will open an avenue of opportunities for the application of EPS-producing probiotics to improve health.