Genomic and proteomic comparisons of bacteriocins in probiotic species Lactobacillus and Bifidobacterium and inhibitory ability of Escherichia coli MG 1655

Bifidobacteria in Fermented Dairy Foods: A Health Beneficial Outlook

Bifidobacteria, frequently present in the human gastrointestinal tract, play a crucial role in preserving gut health and are mostly recognized as beneficial probiotic microorganisms. They are associated with fermenting complex carbohydrates, resulting in the production of short-chain fatty acids, bioactive peptides, exopolysaccharides, and vitamins, which provide energy and contribute to gut homeostasis. In light of these findings, research in food processing technologies has harnessed probiotic bacteria such as lactobacilli and bifidobacteria for the formulation of a wide range of fermented dairy products, ensuring their maximum survival and contributing to the development of distinctive quality characteristics and therapeutic benefits. Despite the increased interest in probiotic dairy products, introducing bifidobacteria into the dairy food chain has proved to be complicated. However, survival of Bifidobacterium species is conditioned by strain of bacteria used, metabolic interactions with lactic acid bacteria (LAB), fermentation parameters, and the temperature of storage and preservation of the dairy products. Furthermore, fortification of dairy foods and whey beverages with bifidobacteria have ability to change physicochemical and rheological properties beyond economic value of dairy products. In summary, this review underscores the significance of bifidobacteria as probiotics in diverse fermented dairy foods and accentuates their positive impact on human health. By enhancing our comprehension of the beneficial repercussions associated with the consumption of bifidobacteria-rich products, we aim to encourage individuals to embrace these probiotics as a means of promoting holistic health.

Bifidobacterium longum subsp. infantis as widespread bacteriocin gene clusters carrier stands out among the Bifidobacterium

Bifidobacterium is the dominant genus, particularly in the intestinal tract niche of healthy breast-fed infants, and many of these strains have been proven to elicit positive effects on infant development. In addition to its effective antimicrobial activity against detrimental microorganisms, it helps to improve the intestinal microbiota balance. The isolation and identification of bacteriocins from Bifidobacterium have been limited since the mid-1980s, leading to an underestimation of its ability for bacteriocin production. Here, we employed a silicon-based search strategy to mine 354 putative bacteriocin gene clusters (BGCs), most of which have never been reported, from the genomes of 759 Bifidobacterium strains distributed across 9 species. Consistent with previous reports, most Bifidobacterium strains did not carry or carry only a single BGC; however, Bifidobacterium longum subsp. infantis, in contrast to other Bifidobacterium species, carried numerous BGCs, including lanthipeptides, lasso peptides, thiopeptides, and class IId bacteriocins. The antimicrobial activity of the crude bacteriocins and transcription analysis confirmed its potential for bacteriocin biosynthesis. Additionally, we investigated the association of bacteriocins with the phylogenetic positions of their homologs from other genera and niches. In conclusion, this study re-examines a few Bifidobacterium species traditionally regarded as a poor source of bacteriocins. These bacteriocin genes impart a competitive advantage to Bifidobacterium in colonizing the infant intestinal tract. IMPORTANCE Development of the human gut microbiota commences from birth, with bifidobacteria being among the first colonizers of the newborn intestinal tract and dominating it for a considerable period. To date, the genetic basis for the successful adaptation of bifidobacteria to this particular niche remains unclear since studies have mainly focused on glycoside hydrolase and adhesion-related genes. Bacteriocins are competitive factors that help producers maintain colonization advantages without destroying the niche balance; however, they have rarely been reported in Bifidobacterium. The advancement in sequencing methods and bacteriocin databases enables the use of a silicon-based search strategy for the comprehensive and rapid re-evaluation of the bacteriocin distribution of Bifidobacterium. Our study revealed that B. infantis carries abundant bacteriocin biosynthetic gene clusters for the first time, presenting new evidence regarding the competitive interactions of Bifidobacterium in the infant intestinal tract.

Isolation, characterization, and mode of action of a class III bacteriocin produced by Lactobacillus helveticus 34.9

Traditionally fermented foods and beverages are still produced and consumed at a large scale in Romania. They are rich sources for novel lactic acid bacteria with functional properties and with potential application in food industry or health. Lactobacillus helveticus 34.9, isolated from a home-made fermented milk is able to inhibit the growth of other bacteria, such as other lactic acid bacteria, but also strains of Bacillus subtilis, Bacillus cereus, Staphylococcus aureus, and Halobacillus hunanensis, a halobacterium isolated from the degraded wall of a Romanian monastery. L. helveticus 34.9 produces a large bacteriocin (35 KDa), active in a wide pH range, but inactivated by heat and proteinase K treatment. It shares about 20% sequence coverage with helveticin J, as determined by LC-MS analysis. Bacteriocin production was enhanced under stress conditions, especially when combined stresses were applied. Its mode of action and degree of inhibition depended on the concentration and on the indicator strain that was used; L. delbrueckii subsp. bulgaricus LMG 6901^T cells from a suspension were killed, but the viability of H. hunanensis 5Hum cells was only reduced to 60%, within 8 h. However, the bacteriocin was able to prevent the bacterial growth of both indicator strains when added to the cultivation medium prior inoculation. Scanning electron microscopy images revealed morphological changes induced by the bacteriocin treatment in both sensitive strains, but more severe in the case of L. delbrueckii subsp. bulgaricus. Due to the broad antibacterial spectrum and its production under various stress conditions, the bacteriocin or the producing strain may find application in health, food and non-food related fields, including in the restoration of historical buildings.

Effects of Multi-Strain Probiotics and Perilla frutescens Seed Extract Supplementation Alone or Combined on Growth Performance, Antioxidant Indices, and Intestinal Health of Weaned Piglets

Simple Summary

Weaning piglets face stressors from changes in feed and environment, which affects their growth. To resolve this problem, we explored the separate effects of multi-strain probiotics and Perilla frutescens seed extract and their combined effect on weaning piglets. We found multi-strain probiotics or Perilla frutescens seed extract both improved the gain to feed ratio and antioxidant capacity. In addition, multi-strain probiotics improved jejunal villus height and the villus height/crypt depth ratio. Perilla frutescens seed extract improved ileal villus height. The interactive effects were observed in jejunal villus height and the villus height/crypt depth ratio, ileal villus height, and the gene expression of IL-1β and mucin2 in the intestinal mucosa. This study shows that using either multi-strain probiotics or Perilla frutescens seed extract alone is more effective than their combined use in weaning piglets.

Abstract

This study examined the effects of multi-strain probiotics (BL) and Perilla frutescens seed extract (PSE), alone or in combination, on weaning piglets. In total, 96 weaning piglets were allocated into four treatments: CON group (the basal diet), PSE group (basal diet + 1g/kg PSE), BL group (basal diet + 2 g/kg BL), and BL+PSE group (basal diet +1 g/kg PSE + 2 g/kg BL) according to a 2 × 2 factorial arrangement. The supplementation of BL or PSE improved the gain to feed ratio. Dietary BL reduced diarrhea occurrence and Escherichia coli, but increased Lactobacillus counts in the ileal digesta. Dietary PSE tended to increase Lactobacillus counts in the ileal digesta. Interactive effects were found in terms of ileal villus height, the gene expression of IL-1β, and malondialdehyde in the ileal mucosa. Dietary BL lowered malondialdehyde in the spleen, liver, and jejunal mucosa but increased the total antioxidant capacity (T-AOC) in the liver and ileum mucosa. The supplementation of PSE improved superoxide dismutase in serum and T-AOC in the liver, and reduced MDA in liver, spleen, and jejunum mucosa. Taken together, BL or PSE showed positive effects, improving growth and intestinal morphology and enhancing antioxidant capacity. However, their interaction showed no beneficial effects on the antioxidant indices and the intestinal morphology of weaned piglets.

In Silico Genomic and Metabolic Atlas of Limosilactobacillus reuteri DSM 20016: An Insight into Human Health

Probiotics are bacterial strains that are known to provide host health benefits. Limosilactobacillus reuteri is a well-documented lactic acid bacterium that has been cultured from numerous human sites. The strain investigated was L. reuteri DSM 20016, which has been found to produce useful metabolites. The strain was explored using genomic and proteomic tools, manual searches, and databases, including KEGG, STRING, BLAST Sequence Similarity Search, and UniProt. This study located over 200 key genes that were involved in human health benefit pathways. L. reuteri DSM 20016 has metabolic pathways to produce acetate, propionate, and lactate, and there is evidence of a pathway for butanoate production through a FASII mechanism. The bacterium produces histamine through the hdc operon, which may be able to suppress proinflammatory TNF, and the bacterium also has the ability to synthesize folate and riboflavin, although whether they are secreted is yet to be explored. The strain can bind to human Caco2 cells through srtA, mapA/cnb, msrB, and fbpA and can compete against enteric bacteria using reuterin, which is an antimicrobial that induces oxidative stress. The atlas could be used for designing metabolic engineering approaches to improve beneficial metabolite biosynthesis and better probiotic-based cures.

Study of intestinal microbial flora of local chickens to investigate the effect of probiotics Bacillus subtilis and Bacillus coagulans on the expression of ctxM and luxS pathogenic genes in isolates of Escherichia coli

Background and objective: Antibiotics are widely used worldwide. However, due to the emergence of antibiotic resistance in a wide range of microorganisms, their use worldwide has failed. Probiotics are suggested as complementary and alternative medicine. The present study aimed to investigate the effects of probiotics isolated from local chickens on the expression of luxS and ctxM genes in resistant Escherichia coli.

Materials and methods: 300 fecal samples were taken from patients referring to Imam Khomeini Hospital in Tehran during May–September 2016 and Escherichia coli samples were isolated using specific culture media and biochemical tests and then the presence of luxS and ctxM genes were identified using PCR with specific primers. In order to extract the probiotics forming spores, the intestinal contents of 10 poultry that had not used any antibiotics and probiotics were cultured, isolated, and identified using biochemical and PCR methods. Commercial strains of Bacillus subtilis and Bacillus coagulans were purchased to compare their effects with native bacteria. These strains were then co-cultured with resistant Escherichia coli strains containing ctxM and luxS genes. Real-time PCR was used to evaluate the effect of these probiotics on gene expression

Results: The results indicated that 40 isolates (7.5%) of Escherichia coli were obtained from the 300 fecal samples. Thirteen samples (32.5%) were outpatients and 27 (67.5%) were inpatients. All isolates were isolated from men and women aged 21–62. Four Escherichia coli strains were isolated from patients carrying ctxM and luxS genes. Isolation of Bacillus coagulans and Bacillus subtilis from samples was confirmed by biochemical and molecular experiments. The commercial and native strains of Bacillus coagulans reduced the expression of the luxS and ctxM genes by 3.60, 3.30, 1.58, and 2.70 times respectively. Also, the commercial and native strains of Bacillus subtilis decreased the expression of the luxS and ctxM genes by 1.37, 1.10, 2.20, and 2.80 times respectively. The results of statistical analysis showed a significant relationship between the presence of native and commercial probiotics in culture and reduced expression of ctxM and luxS genes.

Conclusion: According to the results, supplements of Bacillus coagulans and Bacillus subtilis increase the effect of antibiotics resistance in Escherichia coli by reducing the expression of resistance genes.

Enterocin: Promising Biopreservative Produced by Enterococcus sp

Food preservation is a method used to handle and treat food products to slow down food spoilage and subsequently reduce the risk of foodborne illness. Nowadays, the demand for natural preservatives over chemical preservatives in food is increasing due to the awareness of consuming healthy food products without the risk of harmful side effects. Thus, the research and development of preservation techniques, referred to as biopreservation, is growing rapidly. In biopreservation methods, microorganisms that are known as lactic acid bacteria (LAB) and their antimicrobial substances are used to extend shelf life and maintain the nutritional value of foods. Among the most studied LAB are from the genus Enterococcus, which produces a bacteriocin called enterocin. Bacteriocins are ribosomal-synthesized antimicrobial peptides that are capable of inhibiting the growth of pathogenic bacteria that cause spoilage in food. LAB is generally regarded as safe (GRAS) for human consumption. The current application of LAB, notably Enterococcus sp. in the biopreservation of meat and meat-based products was highlighted in this review. This report also includes information on the effects of enzymes, temperature, and pH on the stability of bacteriocin produced by Enterococcus sp. An extensive compilation of numerous industry procedures for preserving meat has also been emphasized, highlighting the benefits and drawbacks of each method.

A Novel Bacteriocin Against Shigella flexneri From Lactiplantibacillus plantarum Isolated From Tilapia Intestine: Purification, Antibacterial Properties and Antibiofilm Activity

Few bacteriocins with antibacterial activity against Shigella flexneri have been reported. Here, a novel bacteriocin (LFX01) produced by Lactiplantibacillus plantarum strain LF-8 from the intestine of tilapia was purified and extensively characterized. LFX01 possesses a molecular weight of 1049.56 Da and an amino acid sequence of I-T-G-G-P-A-V-V-H-Q-A. LFX01 significantly inhibited S. flexneri strain 14 (S. flexneri_14) growth. Moreover, it exhibited excellent stability under heat and acid-base stress, and presented sensitivity to a variety of proteases, such as proteinase K, pepsin, and trypsin. The minimum inhibitory concentration (MIC) of LFX01 against S. flexneri_14 was 12.65 μg/mL, which was smaller than that of most of the previously found bacteriocins. Furthermore, LFX01 significantly inhibited (p < 0.05) S. flexneri_14 cells and decreased their cell viability. In addition, LFX01 could significantly (p < 0.05) inhibit biofilm formation of S. flexneri_14. Scanning electron microscopy analysis presented that the cell membrane permeability of S. flexneri_14 was demolished by LFX01, leading to cytoplasmic contents leakage and cell rupture death. In summary, a novel bacteriocin of lactic acid bacteria (LAB) was found, which could effectively control S. flexneri in both planktonic and biofilm states.