Construction of a food-grade gene editing system based on CRISPR-Cas9 and its application in Lactococcus lactis NZ9000.

Clustered regularly interspaced short palindromic repeats-associated protein 9 (CRISPR/Cas9) system has been widely used in gene editing of various organisms. However, food-grade gene editing systems in lactic acid bacteria are still preliminary. Red/ET-dependent homologous recombination or CRISPR-based systems have been developed to gene editing in Lactococcus lactis, but these methods are overall inefficient. In the present study, a recombinant system based on CRISPR/Cas9 technology combined with Red/ET was developed using the plasmid pMG36e derived from Lactococcus lactis. Then, the developed recombinant system was applied to Lactococcus lactis. Knockout efficiency was significantly higher using the developed system (91%). In addition, this system showed the potential to be used as a high-throughput method for hierarchical screening. Finally, a gene-edited strain was obtained, and no antibiotics or exogenous genes were introduced using the developed gene editing system. Thus, the efficient system in lactic acid bacteria was constructed and optimized.

Study on Lactiplantibacillus plantarum R6-3 from Sayram Ketteki to prevent chronic unpredictable mild stress-induced depression in mice through the microbiota-gut-brain axis.

The prevention, mitigation and treatment of depression has become a global issue that needs to be solved urgently. Sayram Ketteki, a traditional natural fermented yoghurt from the region with the world's fourth highest life expectancy, has been known as the "longevity secret", whose longevity and anti-depression factors are speculated to come from its rich microorganisms. Therefore, for the first time, we systematically studied in depth the microbes of Sayram Ketteki, screened a new edible probiotic strain, Lactiplantibacillus plantarum R6-3, and explored its anti-depression effect in chronic unpredictable mild stress (CUMS)-induced depression in mice. It is encouraging that L. plantarum R6-3 was significantly superior to the classic anti-depressant drug, fluoxetine, in the performance of promoting sucrose preference test (SPT) behavior by 18% (p < 0.001), lowering the serum CORT content by 5.6% (p < 0.05), accelerating the brain-derived neurotrophic factor (BDNF) level by 5.9% (p < 0.01), increasing the serum IL-10 concentration by 2.3% (p < 0.05), up-regulating the expression of BDNF and phosphorylated-ERK by 74% (p < 0.01) and 45% (p < 0.001), respectively, and facilitating the secretion of fecal short-chain fatty acids (SCFAs), including n-butyric, n-valeric, and isovaleric acid by 47% (p < 0.01), 42% (p < 0.05) and 38% (p < 0.05), respectively. Through the microbiota-gut-brain axis, L. plantarum R6-3 promoted the secretion of intestinal SCFAs through regulation of the composition and function of the gut microbiota, and activated the production of the monoamine neurotransmitter, renewed the level of brain neurotrophic factor, and suppressed the hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis by adjusting the hippocampal BDNF/TrkB/ERK/CREB signaling pathway, thereby improving the immune and oxidative stress status, protecting hippocampal tissue from damage, maintaining a healthy weight and preventing CUMS-induced depressive behavior in mice. It has great prospects for the development of natural functional foods, the prevention and treatment of depression and in innovative microecological preparations.

Copper inhibits postacidification of yogurt and affects its flavor: A study based on the Cop operon.

Yogurt and its related products are popular worldwide. During transportation and storage, Lactobacillus delbrueckii ssp. bulgaricus in yogurt continues to metabolize to form lactic acid, the postacidification phenomenon of yogurt. Postacidification of yogurt is a widespread phenomenon in the dairy industry. Many scholars have done research on controlling the postacidification process, but few report on the molecular mechanisms involved. In this study, we used a molecular-assisted approach to screen food additives that can inhibit postacidification and analyzed its effects on yogurt quality as well as its regulatory mechanism from multi-omics perspectives in combination. The copper ion was found to upregulate the expression of the LDB_RS05285 gene, and the copper transporter-related genes were regulated by copper. Based on the metabolic-level analysis, copper was found to promote lactose hydrolysis, accumulate a large amount of glucose and galactose, inhibit the conversion of glucose to lactic acid, and reduce the production of lactic acid. The significantly greater abundance of l-isoleucine and l-phenylalanine increased the abundance of 3-methylbutyraldehyde (∼1.2 times) and benzaldehyde (∼7.9 times) to different degrees, which contributed to the formation of the overall flavor of yogurt. Copper not only stabilizes the acidity of yogurt, but also it improves the flavor of yogurt. Through this established method involving quantitative and correlation analyses at the transcriptional and metabolic levels, this study provides guidance for the research and development of food additives that inhibit postacidification of yogurt and provide a reference for studying the changes of metabolites during storage of yogurt.

Niacin inhibits post-acidification of yogurt based on the mining of LDB_RS00370 biomarker gene.

The post-acidification of yogurt results in short shelf life, undesirable flavor, and sour taste, making it unacceptable to consumers. Many scholars have proposed several solutions to this problem. However, the existing methods of inhibiting post-acidification cannot fundamentally solve this problem. So exploring the molecular mechanism behind post-acidification can be a better approach to finding the solution. Therefore, we first evaluated the correlation between 69 candidate genes for post-acidification and changes in the acidity of yogurt fermented with different Lactobacillus bulgaricus, and mined a biomarker LDB_RS00370 for post-acidification. Subsequently, this biomarker was used for large-scale screening of food additives that could inhibit post-acidification, and niacin was found to be the most representative one. Finally, the mechanism of niacin inhibiting post-acidification of yogurt was analyzed by RNA-seq, which revealed that post-acidification might be inhibited by affecting protein synthesis and glycolysis. This study opens up a novel perspective on molecular prediction of the post-acidification process, which could provide guidance for precautions to be taken in yogurt production.

Mechanism of gastrointestinal adaptability and antioxidant function of infant-derived Lactobacillus plantarum BF_15 through genomics.

Lactobacillus plantarum is an essential probiotic in the human gastrointestinal tract. L. plantarum BF_15, a functional probiotic isolated from the feces of breast-fed infants, has been reported in many in vitro and in vivo studies with strong gastrointestinal adaptability and outstanding anti-oxidative activities. Therefore, the whole genome of L. plantarum BF_15 was sequenced. Several genes, encoding the gastrointestinal adaptability-related proteins, were identified, including genes related to gastrointestinal environment-induced stress resistance, adhesive performance, and ability to transport and metabolize resistant starch and oligosaccharides. Genes related to alleviating oxidative stress were also found. Further functional verification was carried out by RT-qPCR on the 10 and 12 key adhesion and antioxidant genes. Overall, this study might provide a critical basis for L. plantarum BF_15 as a potential candidate for probiotics. Supplementary Information: The online version contains supplementary material available at 10.1007/s10068-022-01132-w.

Risk factors for postoperative delirium in ICU patients with severe illness based on systematic review and meta-analysis.

BACKGROUND: Meta-analysis was performed on risk factors for postoperative delirium in intensive care unit (ICU) patients to provide theoretical guidance for the prevention of postoperative delirium in ICU patients. METHODS: We conducted a search of Chinese databases using a combination of "meta-analysis", "risk factors for delirium", and "ICU patients with severe illness". "Meta analysis", "Risk factors of delirium", and "ICU severe patients" were used as search terms for English databases. The quality of the literature was evaluated using RevMan 5.3 software for Cochrane reviews. RESULTS: Ten literatures were included, and funnel plots were drawn, most of which were asymmetric and might have publication bias. However, the experimental results of each risk factor were relatively stable, so the experimental conclusions were relatively reliable. Of the 10 studies, there were 7 literatures on age factor, 95% confidence interval (CI): 2.29-9.01. There were 9 studies on gender factors, 95% CI: 0.73-1.40. There were 3 studies on drinking factors, 95% CI: -0.04 to 0.08. There were 3 studies on Acute Physiology and Chronic Health Evaluation-II (APACHE- II) scoring factors, 95% CI: 4.54-5.15. There were 4 studies on mechanical ventilation factors, 95% CI: 3.24-11.16. There were 3 studies on mechanical ventilation time factors, 95% CI: -39.92 to 154.97. There were 3 studies on sedative factors, 95% CI: 0.23-15.50. DISCUSSION: Different risk factors can influence the incidence of postoperative delirium in ICU patients with severe illness, which provides theoretical guidance for clinical prevention of delirium incidence.

Global transcriptomic analysis of Lactobacillus delbrueckii subsp. bulgaricus ATCC11842 reveals the role of LDB_RS05285 in the post-acidification of yogurt.

During the storage of yogurt, acid-resistant bacteria continue to produce lactic acid (i.e., post-acidification process), leading to undesirable taste and flavor. Many methods have been proposed to inhibit post-acidification. However, the specific genes involved during this biological process have not yet been systematically studied. Hence, herein, we assessed the culture starter Lactobacillus delbrueckii subsp. bulgaricus ATCC11842 with regards to its transcriptomes under in vitro acid- and cold-culture conditions. Through differential gene expression analysis, we screened out 69 candidate genes that persistently responded to acid with or without cold stress. qPCR was then used to determine the in situ expression levels of these candidate genes at different stages of yogurt fermentation and storage. Genes whose expression levels did not change much from the end of fermentation to the early stage of yogurt storage were more likely to be post-acidification genes, as such stability indicated that they were not affected by cold stress. LDB_RS05285 was determined to be one such gene; the overexpression of this gene showed that the increase of gene expression could reduce the acid production of the strain without affecting normal growth. Therefore, the genetic manipulation techniques that increased the expression level of the LDB_RS05285 gene might have the potential to inhibit the post-acidification of yogurt. Thus, LDB_RS05285 plays an important role in the post-acidification process and would become a new target for regulating yogurt post-acidification.

Food-grade expression of nattokinase in Lactobacillus delbrueckii subsp. bulgaricus and its thrombolytic activity in vitro.

OBJECTIVES: To produce nattokinase in a food-grade expression system and evaluate its thrombolytic activity in vitro. RESULTS: No nattokinase activity from reconstituted strains was observed in simulated gastric juice, but the enzyme was stable in intestinal fluid, the relative activity of which was found to be 60% after 4 h. Due to the nattokinase being produced intracellularly by recombinant bacterial strains, the persistence of the bacteria in gastric juice ensured transmission of the nattokinase into intestinal juice. Because of subsequent disintegration of the bacteria, the highest nattokinase activity was observed after 3 h at approximately 32%, following its carriage within the recombinant strains to the intestinal fluid. CONCLUSIONS: This study demonstrated that nattokinase from recombinant strains exhibited good thrombolytic activity in vitro and may be used by the dairy fermentation industry for the development of novel thrombolytic functional foods.

Probiotics, prebiotics, and synbiotics regulate the intestinal microbiota differentially and restore the relative abundance of specific gut microorganisms.

Fermented milk is an effective carrier for probiotics, the consumption of which improves host health. The beneficial effects of probiotics, prebiotics, and synbiotics on gut dysbiosis have been reported previously. However, the way in which specific probiotics, prebiotics, and synbiotics regulate intestinal microbes remains unclear. Therefore, the probiotics Lactobacillus rhamnosus AS 1.2466 and Lactobacillus delbrueckii ssp. bulgaricus ATCC 11842 and the prebiotics xylooligosaccharide and red ginseng extracts were fed to mice to determine their effects on the intestinal microbiota. Then, mice were administered xylooligosaccharide and L. rhamnosus (synthesis) by gavage, and the number of L. rhamnosus was determined in the intestine at different times. The results show that probiotics and prebiotics can quickly reduce the Firmicutes/Bacteroidetes ratio, inhibit harmful bacteria (such as Klebsiella and Escherichia coli), and accelerate the recovery of beneficial intestinal microorganisms (such as Lactobacillus). In a complex intestinal microecology, different probiotics and prebiotics have different effects on specific intestinal microorganisms that cannot be recovered in the short term. In addition, after 20 d of intragastric xylooligosaccharide addition at 0.12 g/kg of body weight, L. rhamnosus colonization in the mouse ileum was 7.48 log cfu/mL, which was higher than in the low-dose group, prolonging colonization time and increasing the number of probiotics in the intestine. Therefore, this study demonstrated that probiotics and prebiotics can promote the balance of intestinal microbiota by regulating specific microbes in the intestine, and the effects of a suitable combination of synbiotics are beneficial, laying the foundation for the development of new dairy products rich in synbiotics.

Colonization and immunoregulation of Lactobacillus plantarum BF_15, a novel probiotic strain from the feces of breast-fed infants.

Immunosuppression is a manifestation imbalance in the immune system, often during unhealthy states. In recent years, lactic acid bacteria (LAB) have been found to be important components of the body's innate immune system, and indispensable to maintaining normal immune function. Lactobacillus plantarum BF_15, a novel strain isolated from the feces of breast-fed infants, which has shown potential as an immunomodulator in vitro. In the present study, with the Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis (PCR-DGGE) based on RNA-polymerase beta subunit encoding gene (rpoB) to analyze the colonization of L. plantarum BF_15 in the intestine of mice. In addition, Lactobacillus rhamnosus GG (LGG) as a positive control strain, by measuring immune-related indexes and the diversity of intestinal microbiota, the effects of BF_15 on immunoregulation and intestinal microbiota dysbiosis were investigated to elucidate whether the attenuation of immunosuppression is related to the modulation of intestinal microbiota. Results did indeed support this notion that BF_15 did colonize murine intestines well, in which it could still be detected in mice feces 14 days after stopping the probiotic administration. Moreover, BF_15 found to protect mice against reduction in the levels of several immune-related indicators, including the thymus and spleen indexes, splenic lymphocyte proliferation, toe swelling degree, serum hemolysin-antibody level, and macrophage phagocytosis index, triggered by high-dose (200 mg kg-1) intraperitoneal administration of cyclophosphamide (CTX). In addition, the strain was also found to effectively balance intestinal microbiota dysbiosis in the mice. Collectively, these results indicated that L. plantarum BF_15 can not only successfully colonize murine intestines, but also can effectively alleviate CTX-induced immunosuppression, once established, by rebalancing the intestinal microbiota. This, therefore, provides strong evidence for the view that BF_15 has the potential to become a highly effective immunomodulating probiotic in human microbiota as well.

Adhesion and Colonization of the Probiotic Lactobacillus rhamnosus Labeled by Dsred2 in Mouse Gut.

The health-promoting effects of the probiotic strain Lactobacillus rhamnosus are based on its adherence and colonization ability. However, little is known about its adhesion and colonization rates. Lactobacillus rhamnosus in mouse intestinal mucosa a mutant of the red fluorescence protein (RFP) DSred2 was used to tag L. rhamnosus to observe the adhesion and distribution of L. rhamnosus in mouse intestinal mucosa. A mutant of the red fluorescence protein (RFP) Dsred2 was used to tag L. rhamnosus to allow us to observe and distinguish it in the mouse intestine. Seven-week-old female BALB/c mice were fed once (at day 0) with an oral administration of the labeled L. rhamnosus, and the number of labeled bacteria was detected in different regions of the intestinal tract at 3 h and at day 1, 2, 3, 4, 5, 6, 7, and 15 after administration. The labeling process changed the morphology of L. rhamnosus, as it appeared after observation under the microscope, but did not change its basic probiotic properties in vitro. In vivo, labeled L. rhamnosus reached the colonization peak at the fourth day after gavage. From the distribution point of view, the number of colonization strains increased from the proximal to the distal small intestine (duodenum < jejunum < ileum) and the number of strains in the colon was less than the distal small intestine (ileum). The labeling protocol actually allowed the detection of the distribution and adhesion of this bacterium to the intestine, thus demonstrating that the health-promoting effects of this probiotic are satisfied. This study provides a scientific basis in the use of probiotics such as L. rhamnosus in functional foods.

Blocking CXCR1/2 contributes to amelioration of lipopolysaccharide-induced sepsis by downregulating substance P.

OBJECTIVES: C-X-C chemokine receptor types 1/2 (CXCR1/2) is known to be activated in liver damage in acute-on-chronic liver failure; however, the role in lipopolysaccharide (LPS)-induced sepsis is unknown. The current study was designed to determine whether or not CXCR1/2 blockade with reparixin ameliorates acute lung injury (ALI) by affecting neuropeptides in a LPS-induced sepsis mouse model. MATERIALS AND METHODS: Male C57BL/6 mice (10 to 14-week old) were divided into sham, LPS, sham-R, and LPS-R groups. Bronchoalveolar lavage fluid (BALF) was collected and evaluated. The lung histopathology was assessed by immunocytochemistry staining. Western blot analysis was used to measure myeloperoxidase, substance P (SP), and vasoactive intestinal peptide. RESULTS: LPS-induced animal models were ameliorated by cotreatment with a CXCR1/2 antagonist. Moreover, the protective effects of CXCR1/2 antagonists were attributed to the increased secretion of pro-opiomelanocortin and decreased the secretion of SP. Reparixin decreased the expression of necroptosis cell death markers induced by LPS. CONCLUSION: The results of this study indicate that blockade of CXCR1/2 may represent a promising therapeutic strategy for the treatment of sepsis-associated ALI through regulation of neuropeptides and necroptosis.