Introduction of Spontaneous Mutations Using Streptomycin as a Method for Lactic Acid Bacteria Breeding.

The chapter presents a technique for inducing spontaneous mutations using antibiotics that target microbial ribosomes and/or RNA polymerase, employed in bacterial breeding. In contrast to UV-based mutagenesis, this method allows control of the mutation sites, specifically targeting the rpsL gene. The outlined methodology introduces spontaneous mutations using streptomycin in Lacticaseibacillus rhamnosus GG ATCC 53103 (LGG), a widely studied lactic acid bacterium. Streptomycin has been shown to induce mutations in the rpsL gene, particularly altering lysine residues at position 56 or 101. It has also been reported to affect bacterial morphology and surface protein composition, thereby enhancing adhesion to human mucin.

The effect of arginine on the growth of probiotics.

OBJECTIVE(S): The study objective was to examine the effect of arginine (Arg) supplementation on the growth of probiotics. METHODS: Lacticaseibacillus rhamnosus GG, Lactiplantibacillus plantarum, and Lactobacillus acidophilus were identified as potential probiotics. L. rhamnosus GG and L. plantarum were selected for further experimentation. The probiotics were co-treated with 0.9 % NaCl (negative control), 0.5 % Arg, and 1.0 % Arg in a 1:1 ratio for 24 h at 5 % CO2, 37 °C. The probiotics were tested for growth profiles, spectroscopic turbidity assay, metabolic assays (XTT and WST-8), live/dead cell assessment using confocal laser scanning microscopy (CLSM), and colony forming units (CFU). RESULTS: The growth profiles of L. rhamnosus GG and L. plantarum were found to be similar, whereas L. acidophilus showed minimal or no transition from the initial lag phase. In the turbidity assay, the end-point absorbance for L. rhamnosus GG with 1.0 % Arg was significantly lower than 0.9 % NaCl and 0.5 % Arg (p < 0.05). For metabolic assays and CFU, increasing concentrations of Arg increased the viable cells for L. rhamnosus GG (p < 0.05), but decreased viability for L. plantarum (p < 0.05). Metabolic assays with dual-species bacterial suspensions indicated that Arg co-treatment inhibited viable proportions compared to control (p < 0.05). The dead cell proportion was significantly lower than live cell proportion for all tested interventions and probiotics (p < 0.05). CONCLUSION: Increasing concentrations of Arg promote the growth of L. rhamnosus GG, while conversely inhibiting the growth of L. plantarum. Therefore, the effect of prebiotic Arg on probiotics is concentration-dependent, leading to a selective promotion or inhibition of growth. CLINICAL SIGNIFICANCE: The present study results show that Arg supplementation can selectively enhance the growth of L. rhamnosus GG while inhibit the growth of L. plantarum. This underscores the need to consider strain-specific responses in probiotic formulations when developing Arg-based synbiotics for modulating biofilms and creating ecologically homeostatic biofilm microenvironments.

Lactobacilli decrease the susceptibility of Salmonella Typhimurium to azithromycin.

Bacteria are involved in numerous interactions during infection and among host-associated microbial populations. Salmonella enterica serovar Typhimurium is a foodborne pathogen of great importance as well as a model organism to study interactions within a microbial community. In this study, we found that S. Typhimurium becomes tolerant to azithromycin when co-cultured with lactobacilli strains. Similarly, acidified media, from cell-free supernatant of lactobacilli cultures for instance, also induced the tolerance of S. Typhimurium to azithromycin. The addition of membrane disruptors restored the normal sensitivity to azithromycin in acidified media, but not when lactobacilli were present. These results suggested that the acidification of the media led to modification in envelope homeostasis, but that a different mechanism promoted the tolerance to azithromycin in the presence of lactobacilli strains. To further understand how lactobacilli strains modify the sensitivity of S. Typhimurium to azithromycin, a high-throughput assay was performed using the single-gene deletion collection of the S. Typhimurium (1) in co-culture with Lacticaseibacillus rhamnosus and (2) in sterile acidic conditions (pH 5.5 media only). As expected, both screens identified genes involved in envelope homeostasis and membrane permeability. Our results also suggest that changes in the metabolism of S. Typhimurium induce the tolerance observed in the presence of L. rhamnosus. Our results thus highlight two different mechanisms by which lactobacilli induce the tolerance of S. Typhimurium to azithromycin.IMPORTANCEThis study provides valuable insights into the intricate interactions between bacteria during infections and within host-associated microbial communities. Specifically, it sheds light on the significant role of lactobacilli in inducing antibiotic tolerance in Salmonella enterica serovar Typhimurium, a critical foodborne pathogen and model organism for microbial community studies. The findings not only uncover the mechanisms underlying this antibiotic tolerance but also reveal two distinct pathways through which strains of lactobacilli might influence Salmonella's response to antibiotics. Understanding these mechanisms has the potential to enhance our knowledge of bacterial infections and may have implications for the development of strategies to combat antibiotic resistance in pathogens, such as Salmonella. Furthermore, our results underscore the necessity to explore beyond the direct antimicrobial effects of antibiotics, emphasizing the broader microbial community context.

Eugenia uniflora (pitanga) juice as a new alternative vehicle for Limosilactobacillus fermentum ATCC 23271: evaluation of antioxidant and anti-infective effects.

Probiotic-containing foods are among the most appreciated functional foods; however, probiotic-based dairy products cannot be consumed by people who are lactose intolerant, allergic to milk, or vegetarian or vegan individuals. Thus, new non-dairy matrices have been tested for probiotics delivery. This study evaluated the growth and viability of Limosilactobacillus fermentum ATCC 23271 and Lacticaseibacillus rhamnosus ATCC 9595 in Pitanga juice (Eugenia uniflora L.). The effects of the fermentation on the antioxidant and anti-infective properties of the juice were also analyzed. The E. uniflora juice allowed lactobacilli growth without supplementation, reaching rates around 8.4 Log CFU/mL and producing organic acids (pH values < 4) after 72 h of fermentation. The strain remained viable after 35 days of refrigerated storage. Fermentation by these bacteria increases the antioxidant capacity of the juice. The central composite rotational design was employed to evaluate the effects of bacterial inoculum and pulp concentration on growth and organic acids production by L. fermentum ATCC 23271. The strain was viable and produced organic acids in all tested combinations. L. fermentum-fermented juice and its cell-free supernatant significantly increased the survival of Tenebrio molitor larvae infected by enteroaggregative Escherichia coli 042. The results obtained in this study provide more insights into the potential of Pitanga juice to develop a functional non-dairy probiotic beverage with antioxidant and anti-infective properties.

Polysaccharide Hydrogels for the Protection of Dairy-Related Microorganisms in Adverse Environmental Conditions.

Adverse environmental conditions are severely limiting the use of microorganisms in food systems, such as probiotic delivery, where low pH causes a rapid decrease in the survival of ingested bacteria, and mixed-culture fermentation, where stepwise changes and/or metabolites of individual microbial groups can hinder overall growth and production. In our study, model probiotic lactic acid bacteria (L. plantarum ATCC 8014, L. rhamnosus GG) and yeasts native to dairy mixed cultures (K. marxianus ZIM 1868) were entrapped in an optimized (cell, alginate and hardening solution concentration, electrostatic working parameters) Ca-alginate system. Encapsulated cultures were examined for short-term survival in the absence of nutrients (lactic acid bacteria) and long-term performance in acidified conditions (yeasts). In particular, the use of encapsulated yeasts in these conditions has not been previously examined. Electrostatic manufacturing allowed for the preparation of well-defined alginate microbeads (180-260 µm diameter), high cell-entrapment (95%) and viability (90%), and uniform distribution of the encapsulated cells throughout the hydrogel matrix. The entrapped L. plantarum maintained improved viabilities during 180 min at pH 2.0 (19% higher when compared to the free culture), whereas, L. rhamnosus appeared to be less robust. The encapsulated K. marxianus exhibited double product yields in lactose- and lactic acid-modified MRS growth media (compared to an unfavorable growth environment for freely suspended cells). Even within a conventional encapsulation system, the pH responsive features of alginate provided superior protection and production of encapsulated yeasts, allowing several applications in lacto-fermented or acidified growth environments, further options for process optimization, and novel carrier design strategies based on inhibitor charge expulsion.

Preventive Effect and Molecular Mechanism of Lactobacillus rhamnosus JL1 on Food-Borne Obesity in Mice.

Probiotics can prevent obesity and related metabolic complications. In our study, the protective effect and molecular mechanism of Lactobacillus rhamnosus JL1 (separated from the feces of healthy infants) on high-fat diet mice were investigated. After 10 weeks of dietary intervention with L. rhamnosus JL1 intervention, the body weight of the JL1 group (23.78 g) was significantly lower than that of the HFD group (26.59 g, p < 0.05) and the liver index was reduced. Serum biochemical analysis showed that the TC, TG and LDL-C contents of JL1 group mice were significantly decreased (p < 0.05). Histological images of the mice livers showed that the degree of lipid action and damage of hepatic cells were improved. L. rhamnosus JL1 activated the AMPK pathway, and reduced the gene expression of PPAR-γ, LXR-α and SREBP-1C. In addition, the protein expression of PPAR-γ and LXR-α were reduced. After dietary intervention with L. rhamnosus JL1, the concentration of acetic acid, propionic acid, and butyric acid were increased significantly, especially the concentration of butyric acid, which was 63.16% higher than that of the HFD group (p < 0.05). In conclusion, this study provided a theoretical reference for the development and application of probiotics derived from healthy infant feces in health products and functional foods.

Influence of Proton Pump Inhibitors and Histamine Receptor 2 Antagonists on Blastocystis ST3 and Selected Microorganisms of Intestinal Microbiota In Vitro.

INTRODUCTION: Proton pump inhibitors (PPIs) and histamine receptor 2 (H2) antagonists are commonly prescribed medications. Association between PPIs and alteration of the gut microbiota has been reported. Blastocystis, the most common intestinal protozoan worldwide, occurs in both healthy and symptomatic people with gastrointestinal or cutaneous disorders, with controversial pathogenicity. The current study was aimed to investigate the influence of PPIs and H2 blockers on the in vitro proliferation of selected intestinal bacteria, fungi, and protozoa. METHODS: Cultures of Lactobacillus rhamnosus, Escherichia coli, Enterococcus faecium, Candida albicans, and Blastocystis subtype 3 were treated with different concentrations of respective medications in vitro, and the numbers of microorganisms were quantified and compared. RESULTS: Pantoprazole and esomeprazole exerted a significant inhibition on Blastocystis and C. albicans, especially at higher concentrations, which were even more effective than metronidazole. On the other hand, treatment with pantoprazole caused an increase in proliferation of L. rhamnosus and E. coli. There was no influence of H2 blockers on the examined microorganisms. DISCUSSION: PPIs, such as pantoprazole, can be a potential treatment in the prophylaxis or eradication of Blastocystis and C. albicans.

Fucoidan as a marine-origin prebiotic modulates the growth and antibacterial ability of Lactobacillus rhamnosus.

Fucoidan has received much attention in healthy food and biomedicine owing to their unique (bio)physicochemical properties, particularly antibacterial and antiviral. Pathogenic microorganisms and probiotics are coexisting in many tissues (e.g., gut, oral, and vagina). However, the effect of fucoidan on probiotics has not been examined. Herein, fucoidan sterilized by different methods (i.e., 0.22 µm filter and high-temperature autoclave) is applied to explore its effect on the responses of Lactobacillus rhamnosus. It is found that high-temperature autoclave treatment causes the depolymerization of fucoidan. Further, the proliferation, morphology, and metabolism of probiotics are greatly dependent on the concentrations of fucoidan. The formation of probiotic biofilm is reduced with an increased concentration of fucoidan. Moreover, the antibacterial ability of probiotics initially increases and then decreases with an increased concentration of fucoidan. Thus, fucoidan could serve as a new marine-origin prebiotic, offering new insight into probiotic modulation and its application in inhibiting bacterial infections.

Combined effect of arginine and fluoride on the growth of Lactobacillus rhamnosus GG.

The objectives of the in vitro study were: (1) to investigate the effect of combining L-arginine (Arg) and NaF on the growth of Lactobacillus rhamnosus GG (LRG); and (2) to identify an optimum synergistic concentration for the synbiotic (Arg + LRG)-fluoride (SF) therapy. 1% Arg + 2000-ppm NaF (A-SF) and 2% Arg + 2000-ppm NaF (B-SF) demonstrated antagonism against LRG (FIC > 4.0). Both XTT (2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide) and WST-8 (2-(2-methoxy-4-nitrophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium, monosodium salt) assays showed that A-SF and B-SF enhanced the growth of LRG when compared to 2000-ppm NaF and LRG control. Colony forming units, bacterial weight, and biofilm thickness of A-SF and B-SF were significantly higher than 2000-ppm NaF and LRG control. Biofilm imaging depicted that 2000-ppm NaF inhibited biofilm formation; while 1%/2% Arg, A-SF, and B-SF increased biofilm growth of LRG. Lactic acid formation was the lowest for 2000-ppm NaF, followed by A-SF and then B-SF. The SF buffer potential after 24 h was the highest for B-SF, and then A-SF. Biofilm pH for B-SF was closest to neutral. Fluoride, Arg and LRG bioavailability remained unaffected in B-SF. The relative gene expression for arcA, argG, and argH was significantly higher for B-SF than the respective controls. In conclusion, combining 2% Arg, 2000-ppm NaF, and LRG provides an optimum synbiotic-fluoride synergism.

Lactobacillus rhamnosus sepsis associated with probiotic therapy in an extremely preterm infant: Pathogenesis and a review for clinicians.

BACKGROUND: Necrotizing enterocolitis (NEC) is one of the most serious complications in preterm infants. Probiotics have been used to prevent NEC. Safety is a major concern for this practice. METHODS: We reported a female preterm infant who received oral Lactobacillus rhamnosus GG but developed sepsis 12 days after the treatment. Cultures of blood and the catheter tip yielded L. rhamnosus. Next-generation sequencing was performed to analyze isolates from blood, stool, catheter, and product capsules. We also determined the capacities of these isolates to form biofilms. A literature review was performed. RESULTS: The patient was treated with ampicillin and piperacillin/tazobactam, and she subsequently recovered without complications. The analysis of genome sequences indicated that all the isolates belonged to the clone of L. rhamnosus GG (ATCC 53103), suggesting that sepsis was a catheter-related infection caused by the oral probiotic. L. rhamnosus GG (ATCC 53103) and the probiotic strain tested formed biofilms under all growth conditions. Isolates from the blood and catheter tip also formed biofilms, but the stool isolate did not. The capacity of intrinsic biofilm formation in L. rhamnosus GG depended on environmental factors and the type of culture medium. Literature review of L. rhamnosus GG sepsis in preterm and young infants found that nearly 60% of the patients had a suspected or confirmed infected catheter. CONCLUSION: The study showed that the capacity of L. rhamnosus GG to form biofilms, especially in the presence of glucose, is a critical factor leading to the probiotic-related sepsis in preterm infants.

Antimicrobial efficacy of nisin-loaded bacterial cellulose nanocrystals against selected meat spoilage lactic acid bacteria.

This study aimed to explore the potential of bacterial cellulose nanocrystals (BCNs) loaded with nisin against selected meat spoilage lactic acid bacteria (LAB) in vitro. BCNs were produced by H2SO4 hydrolysis, and nisin-loaded BCNs were produced through the complexation method. All nanocrystals were assessed for their zeta-potential, encapsulation efficiency and antimicrobial activity. Different nisin concentrations were tested and the most effective nanocrystals were further characterised. BCNs had an average zeta-potential of - 43 mV and all nisin-loaded BCNs produced with 5 mg/ml BCNs suspension had zeta-potential values ≥- 30 mV. The encapsulation efficiency of nisin varied from 80.5 to 93.3 % and crystallinity of BCNs was not influenced by nisin encapsulation. Microbial inactivation was achieved by BCN loaded with 2.0 and 2.5 mg/ml nisin. Therefore, nisin-loaded BCNs may be used as antimicrobial agents in active food packaging.

Isolation and characterization of lactic acid bacteria from human milk.

Human milk is the main source of nutrition for infants and the transmission of various microorganisms. The lactic acid bacteria (LAB) in breast milk allow for the establishment of the gut microflora of infants. In this study, we aimed to assess the probiotic potential of LAB strains isolated from breast milk of healthy Chinese women. Two strains, Lacticaseibacillus rhamnosus (formerly Lactobacillus rhamnosus) LHL6 and LHL7, were selected and identified through morphology observation, Gram staining, and 16S rDNA phylogenetic analysis. Using Limosilactobacillus fermentum (formerly Lactobacillus fermentum) CECT5716 as the standard reference strain, the screened strains were characterized for aspects of growth, production of lactic acid and H2O2, antibiotic susceptibility, survival under simulated gastrointestinal conditions, and tolerance to cadmium (Cd). In de Man, Rogosa, and Sharpe (MRS) broth, LHL6 and LHL7 showed longer lag phases than CECT5716 but higher specific growth rates. For the production of lactic acid and H2O2, LHL7 performed better than LHL6 and CECT5716, indicating better antimicrobial ability. Strain LHL7 generated 9.99 mg/L H2O2, considerably higher than 1.25 mg/L for LHL6 and 2.33 mg/L for CECT5716. According to European Food Safety Authority minimum inhibitory concentrations, all of the investigated strains were resistant to chloramphenicol, streptomycin, and kanamycin. However, unlike LHL6 and CECT5716, LHL7 was susceptible to ampicillin and resistant to tetracycline. Resistance to azithromycin, cephalexin, and penicillin G were similar for all 3 strains, whereas CECT5716 was resistant to a higher concentration of roxithromycin. All 3 strains were able to survive in a simulated gastric-like solution, but a low percentage survived in the presence of 0.4% bile salt and 7% pancreatin. Encapsulation with protectants may enhance the survival rate. All 3 strains were tolerant to 500 mg/L Cd in MRS broth and to 1,000 mg/L Cd on MRS agar medium. In summary, 2 novel strains of LAB were obtained that have similar characteristics to the reference strain CECT5716. This work identified potential probiotic candidates for application in the food and pharmaceutical industries and facilitated identification of further probiotics.

Next-generation multiparameter flow cytometry assay improves the assessment of oxidative stress in probiotics.

Stability of probiotic products' potency throughout shelf life is essential to ensure systematic delivery of the dosages required to provide clinically-proven health benefits. Due to the oxygen sensitivity of gut-derived microorganisms, methods for the rapid and accurate monitoring of oxidative stress in probiotics are greatly needed as they can be instrumental to both bioprocess optimization and quality control. This study introduces a next-generation flow cytometry method multiplexing the CellROX® Green and Propidium Iodide probes for the simultaneous measurement of free total reactive oxygen species (ROS) and membrane integrity, respectively. The multiparameter method was compared to the single-parameter assays, measuring either ROS or membrane integrity, for the ability to evaluate the fitness of Lactobacillus rhamnosus GG (LGG) after freeze drying, spray drying and H2O2-mediated oxidative stress. Each stand-alone assay detected only three cell populations, showing either differential membrane integrity (Syto 24+/PI-, Syto 24+/PI+, Syto 24-/PI+) or ROS levels (ROS-, low-ROS, high-ROS), and no correlation could be drawn between these groups. Conversely, the multiparameter method detected up to five physiologically distinct cell populations and allowed the integrated assessment of their membrane integrity and oxidative stress. It also revealed a much larger fitness heterogeneity in LGG as each group of low-ROS and high-ROS cells was found to be formed by a healthier population with an intact membrane (L-ROS/PI-, H-ROS/PI-) and a population with damaged membrane (L-ROS/PI+, H-ROS/PI+). As the CRG probe only detects free unreacted ROS, these populations are suggested to reflect the dynamic lifecycle of ROS formation, accumulation and reactive depletion leading to oxidative damage of macromolecules and consequent cell death. With the stand-alone CRG assay being unable to detect ROS lifecycle, the multiparameter method here presented delivers a superior profiling of the heterogeneity generated by oxidative stress in bacteria and enables a more correct interpretation of CRG fluorescence data. We provide recent examples from literature where the use of a single-parameter fluorescence approach may have led to misinterpret oxidative stress data and eventually draw erroneous conclusions.

Milk Fat Globule Membrane Protects Lactobacillus rhamnosus GG from Bile Stress by Regulating Exopolysaccharide Production and Biofilm Formation.

The milk fat globule membrane (MFGM) is a complex, highly conserved structure surrounding fat droplets secreted into mammalian milk. This study evaluated the impact of MFGM on Lactobacillus rhamnosus GG (LGG). MFGM-10 (2.5 g/L, 5 g/L, and 10 g/L) did not affect LGG growth in MRS medium but enhanced the ability of LGG to survive in the presence of 0.5% porcine bile. In the presence of MFGM-10 (5 g/L) and bile (0.5%), there were less complex polysaccharides in the media and less capsular polysaccharides associated with the LGG cells compared to the bile exposure alone (p < 0.05). The expression of four EPS genes was modulated by bile stress and MFGM. Biofilm thickness was increased (p < 0.05) during bile stress with MFGM compared to other treatments. Furthermore, MFGM increased LGG survival during transit in the murine GI tract. Future experiments will determine the impact of MFGM on LGG probiotic functionality.

In vitro mechanism of antibacterial action of a citrus essential oil on an enterotoxigenic Escherichia coli and Lactobacillus rhamnosus.

AIM: This study investigated the in vitro mechanism of action of a commercial citrus EO, Brazilian orange terpenes (BOT), on an enterotoxigenic Escherichia coli (ETEC) isolated from pig gut and on Lactobacillus rhamnosus. METHODS AND RESULTS: Firstly, bacteria were exposed sequentially to BOT every 3 h (three times) at sub-minimal inhibitory concentrations and results showed that sequential exposure to BOT provoked a higher reduction of bacteria viability than a single exposure and the reduction of ETEC viability was higher compared to that of L. rhamnosus. Then, evaluation of the BOT effects on the cell membrane permeability and integrity, indicated that BOT increased the membrane permeability and caused disruptive effects on the integrity of bacterial cells as reflected by an increase of the relative electric conductivity and the release of essential cell constituents. Interestingly, BOT effects were more pronounced on the ETEC than on L. rhamnosus. This was ratified by scanning electron microscopy, which showed more noticeable morphological damages and disturbances on ETEC cells than on the L. rhamnosus cells. Limonene was detected as the major compound in BOT by polar/nonpolar GC-MS (78·65%/79·38%). CONCLUSIONS: Results revealed that the probable mechanism of the selective antibacterial action of the citrus EO, BOT, can be described as altering more remarkable the permeability and integrity of the cytoplasmic membrane as well as the external structure of ETEC cells than L. rhamnosus cells. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provides information about the mechanism of antibacterial action displayed by a citrus EO, a by-product of the citrus processing industry, as a natural alternative to antibiotics used in pig production sector to combat pathogens such as ETECs.

Conscious uncoupling of riboswitch functions.

Riboswitches alter gene expression in response to ligand binding, coupling sensing and regulatory functions to help bacteria respond to their environment. The structural determinants of ligand binding in the prequeuosine (7-aminomethyl-7-deazaguanine, preQ1) bacterial riboswitches have been studied, but the functional consequences of structural perturbations are less known. A new article combining biophysical and cell-based readouts of 15 mutants of the preQ1-II riboswitch from Lactobacillus rhamnosus demonstrates that ligand binding does not ensure successful gene regulation, providing new insights into these shapeshifting sequences.

Viability of Lactobacillus rhamnosus GG microencapsulated in alginate/chitosan hydrogel particles during storage and simulated gastrointestinal digestion: role of chitosan molecular weight.

Sodium alginate hydrogel particles coated with cationic biopolymers have been shown to be one of the promising means for probiotic encapsulation and protection. In this study, we aimed to systematically explore the effect of molecular weight of chitosan coating on the functional performance of sodium alginate hydrogel particles for improving the viability of Lactobacillus rhamnosus GG (LGG). We first electrostatically deposited three different molecular weights of chitosan coatings, i.e., chitosan oligosaccharide (COS), low molecular weight chitosan (LMW-chitosan) and medium molecular weight chitosan (MMW-chitosan) on sodium alginate hydrogel particles. Both SEM and FTIR results indicated that chitosan was successfully deposited onto the surface of the hydrogel particles. We then evaluated the effect of chitosan MW on the viability of LGG encapsulated in the hydrogels during long-term storage and simulated gastrointestinal digestion. Among them, the hydrogel particles coated with COS prevented the viability loss of LLG during long-term storage at different temperatures (4, 25 and 37 °C). However, we did not find any improvement in the viability of the encapsulated LGG by all three chitosan coatings during simulated digestion.

Apple polysaccharide could promote the growth of Bifidobacterium longum.

It is widely accepted that regulating microbiome could improve human health. We previously observed apple polysaccharide (AP) reversed high-fat-induced microbial dysbiosis, but the mechanism remains to be elucidated. In this study, the function of AP in vitro was evaluated in Bifidobacterium longum (B. longum) and Lactobacillus rhamnosus (L. rhamnosus). The effects of AP on the composition of fecal bacteria of normal SD rats were investigated by qPCR, TA cloning and 16S sequencing. 0.125-2% AP showed no significant effect on the growth of B. longum and L. rhamnosus. DNA concentration of fecal bacteria cultured with 1% AP was significantly higher than that of control group. qPCR revealed that the number of Bifidobacterium and Lactobacillus in fecal flora incubated by 1% AP was significantly higher than that of control group. Three strains of escherichia coli (E. coli) in fecal bacteria were screened out and analyzed. AP can be utilized by one E. coli and the metabolic products of AP could enhance the proliferation of B. longum. These data suggest that AP could promote the growth of B. longum indirectly, and provide another basis to understand the health care function of apple.

Linoleic acid inhibits Lactobacillus activity by destroying cell membrane and affecting normal metabolism.

BACKGROUND: The reason why dietary polyunsaturated fatty acids (PUFAs) affect the activity of Lactobacillus remains unclear. In this study, linoleic acid was used to study the mechanism underlying its inhibition function against Lactobacillus activity. RESULTS: The growth curve of Lactobacillus rhamnosus LGG and the metabolite content in bacterial liquid were determined at varying linoleic acid concentration. The degree of cell membrane damage of L. rhamnosus LGG was determined by flow cytometry and fluorescence microscopy, and the cell structure was observed by scanning electron microscopy and transmission electron microscopy. The effect of linoleic acid on Lactobacillus activity was assessed in a simulated gut environment. Results showed that L. rhamnosus LGG grew slowly, cell metabolites leaked into the liquid, cell membrane was damaged, and the cell structure changed at a linoleic acid concentration of 50 µg mL-1 . CONCLUSION: The mechanism of action of linoleic acid on Lactobacillus showed that that linoleic acid destroyed the cell membrane of bacteria, thereby affecting the normal metabolism of the bacteria and ultimately leading to their death. © 2019 Society of Chemical Industry.

Effects of oral probiotic supplements on vaginal microbiota during pregnancy: a randomised, double-blind, placebo-controlled trial with microbiome analysis.

OBJECTIVE: To determine the effects on the vaginal microbiota of an oral probiotic preparation administered from early pregnancy. DESIGN: Randomised, double blind, placebo-controlled trial. SETTING: Four maternity units in the UK. POPULATION: Women aged 16 years or older recruited at 9-14 weeks' gestation. METHODS: Participants were randomly allocated to receive oral capsules of probiotic containing Lactobacillus rhamnosus GR-1 and Lactobacillus reuteri RC-14 each at 2.5 × 109 colony-forming units (CFUs) or placebo once daily from recruitment until the end of pregnancy. MAIN OUTCOME MEASURE: Rates of bacterial vaginosis (BV, defined as Nugent score ≥7) at 18-20 weeks' gestation compared by logistic regression adjusted for possible confounders. RESULTS: The primary analysis included 78% (238/304) of participants who initially consented (probiotic group 123, placebo group 115). Of these participants, 95% (227/238) reported an intake of 93% or more of the required number of capsules. The rates of BV did not differ between groups at 18-20 weeks' gestation (15% (19/123) in the probiotic group vs. 9% (10/115) in the placebo group, adjusted odds ratio 1.82, 95% confidence interval 0.64-5.19). There were also no differences between the groups in the proportion of women colonised with the probiotic strains, Escherichia coli, group B streptococci or other vaginal microbiota. There were no differences in the alpha diversity or composition of the bacterial communities between or within the probiotic and placebo groups at 9-14 and 18-20 weeks' gestation. CONCLUSIONS: Oral probiotics taken from early pregnancy did not modify the vaginal microbiota. TWEETABLE ABSTRACT: The oral probiotic preparation used in this study does not prevent BV in pregnant women.