Lactococcus Lactis MG1363 Research Articles

Expression of Concern: Effects of Lactococcus lactis MG1363 producing fusion proteins of bovine lactoferricin-lactoferrampin on growth, intestinal morphology and immune function in weaned piglet.

Expression of Concern: Effects of Lactococcus lactis MG1363 producing fusion proteins of bovine lactoferricin-lactoferrampin on growth, intestinal morphology and immune function in weaned piglet.

Analysis of the effects of specific growth rate of Lactococcus lactis MG1363 on aerobic metabolism and its application to high-density culture

Lactic acid bacteria (LAB) are known to produce a large amount of lactate when cultured under non-aerated conditions, which inhibits their growth at high concentrations. Our previous studies have shown that LAB can be cultured without lactate production under aerated conditions at a low specific growth rate. In this study, we investigated the effects of specific growth rate on cell yield and the specific production rates of metabolites in aerated fed-batch cultures of Lactococcus lactis MG1363. The results showed that lactate and acetoin production could be suppressed at specific growth rates below 0.2 h-1, whereas acetate production was the highest at a specific growth rate of 0.2 h-1. When LAB was cultured at a specific growth rate of 0.25 h-1 with the addition of 5mg/L heme to assist ATP production by respiration, lactate and acetate production was suppressed, and cell concentration reached 19g-dry-cell/L (5.6× 10ˆ10cfu/mL) with a high cell yield of 0.42 ± 0.02g-dry-cell/g-glucose.

Avidumicin, a novel cyclic bacteriocin, produced by Cutibacterium avidum shows anti-Cutibacterium acnes activity.

The prevalence of antimicrobial-resistant Cutibacterium acnes in acne patients has increased owing to inappropriate antimicrobial use. Commensal skin bacteria may play an important role in maintaining the balance of the skin microbiome by producing antimicrobial substances. Inhibition of Cu. acnes overgrowth can prevent the development and exacerbation of acne vulgaris. Here, we evaluated skin bacteria with anti-Cu. acnes activity. Growth inhibition activity against Cu. acnes was tested using 122 strains isolated from the skin of healthy volunteers and acne patients. Comparative genomic analysis of the bacterium with or without anti-Cu. acnes activity was conducted. The anti-Cu. acnes activity was confirmed by cloning an identified gene cluster and chemically synthesized peptides. Cu. avidum ATCC25577 and 89.7% of the Cu. avidum clinical isolates (26/29 strains) inhibited Cu. acnes growth. The growth inhibition activity was also found against other Cutibacterium, Lactiplantibacillus, and Corynebacterium species, but not against Staphylococcus species. The genome sequence of Cu. avidum showed a gene cluster encoding a novel bacteriocin named avidumicin. The precursor protein encoded by avdA undergoes post-translational modifications, supposedly becoming a circular bacteriocin. The anti-Cu. acnes activity of avidumicin was confirmed by Lactococcus lactis MG1363 carrying avdA. The C-terminal region of the avidumicin may be essential for anti-Cu. acnes activity. A commensal skin bacterium, Cu. avidum, producing avidumicin has anti-Cu. acnes activity. Therefore, avidumicin is a novel cyclic bacteriocin with a narrow antimicrobial spectrum. These findings suggest that Cu. avidum and avidumicin represent potential alternative agents in antimicrobial therapy for acne vulgaris.

Growth differentiation factor 11 delivered by dairy Lactococcus lactis strains modulates inflammation and prevents mucosal damage in a mice model of intestinal mucositis.

Mucositis is an inflammation of the gastrointestinal mucosa that debilitate the quality of life of patients undergoing chemotherapy treatments. In this context, antineoplastic drugs, such as 5-fluorouracil, provokes ulcerations in the intestinal mucosa that lead to the secretion of pro-inflammatory cytokines by activating the NF-κB pathway. Alternative approaches to treat the disease using probiotic strains show promising results, and thereafter, treatments that target the site of inflammation could be further explored. Recently, studies reported that the protein GDF11 has an anti-inflammatory role in several diseases, including in vitro and in vivo results in different experimental models. Hence, this study evaluated the anti-inflammatory effect of GDF11 delivered by Lactococcus lactis strains NCDO2118 and MG1363 in a murine model of intestinal mucositis induced by 5-FU. Our results showed that mice treated with the recombinant lactococci strains presented improved histopathological scores of intestinal damage and a reduction of goblet cell degeneration in the mucosa. It was also observed a significant reduction of neutrophil infiltration in the tissue in comparison to positive control group. Moreover, we observed immunomodulation of inflammatory markers Nfkb1, Nlrp3, Tnf, and upregulation of Il10 in mRNA expression levels in groups treated with recombinant strains that help to partially explain the ameliorative effect in the mucosa. Therefore, the results found in this study suggest that the use of recombinant L. lactis (pExu:gdf11) could offer a potential gene therapy for intestinal mucositis induced by 5-FU.

Polymerase chain reaction for molecular detection of the genes involved in the production of riboflavin in lactic acid bacteria

Some lactic acid bacteria (LAB) strains have the ability to synthesize riboflavin, a trait linked to the presence of ribG, ribB, ribA and ribH genes in the rib operon. Multiple sequence alignments of these genes showed that these sequences are not identical in different LAB species, so primers designed to detect these genes in one species do not always work with others. Therefore, we designed degenerate primers based on sequences from Lactococcus lactis MG1363, Levilactobacillus brevis ATCC 367 and Limosilactobacillus fermentum IFO3956, and established optimal PCR conditions for the detection of rib genes in different LAB species. Simultaneously, we selected riboflavin-producing LAB strains from our bacterial collection belonging to the species L. brevis, L. fermentum, L. lactis, Leuconostoc mesenteroides and Lactiplantibacillus plantarum, and we were able to detect ribG, ribB, ribA and ribH genes in these strains by PCR using the designed primers. Thus, the development of degenerate primers and optimal PCR conditions for the detection of ribG, ribB, ribA and ribH genes in LAB allowed the detection and the selection of potential riboflavin-producing strains of different species, which could be good candidates for the development of riboflavin-enriched functional foods.

Extracellular recombinant production of 4,6 and 4,3 α-glucanotransferases in Lactococcus lactis

4,6 α-Glucanotransferase (4,6-α-GTase) and 4,3 α-glucanotransferases (4,3-α-GTase) produced by Lactic Acid Bacteria (LAB) in the GH70 enzyme family have become important due to their catalytic effect on starch and maltodextrins. Their high level of production is necessary for their application at industrial scale. In this respect, both enzymes were expressed extracellularly using Lactococcus lactis as GRAS host. 4,6-α-GTase and 4,3-α-GTase genes from Limosilactobacillus reuteri E81 and Limosilactobacillus fermentum PFC282 respectively were transformed into the plasmid pLEB124 vector having the signal peptide usp45 under the P45 continuous promoter and successfully expressed in Lactococcus lactis MG1363. Western blot screening showed that the relevant enzymes were able to be successfully secreted extracellularly. The Vmax and Km of 4,6-α-GTase were 2.58 µmol min−1 and 0054 mg min−1 whereas 3369 µmol min−1 and 0032 mg min−1 for 4,3-α-GTase respectively. NMR analysis demonstrated the formation of new bonds within the corresponding enzymes. Also, both enzymes were active on maltose, maltoheptaose, maltohexaose and starch and produced malto-oligosaccarides observed by TLC analysis. In conclusion, this study demonstrated first time the extracellular production of 4,6-α-GTase and 4,3-α-GTase with GRAS status that can be useful for starch retrogradation delay and glycaemic index reduction.

High-Resolution Chrono-Transcriptome of Lactococcus lactis Reveals That It Expresses Proteins with Adapted Size and pI upon Acidification and Nutrient Starvation.

ABSTRACTWhole-genome transcriptional analyses performed on microorganisms are traditionally based on a small number of samples. To map transient expression variations, and thoroughly characterize gene expression throughout the growth curve of the widely used model organism Lactococcus lactis MG1363, gene expression data were collected with unprecedented time resolution. The resulting gene expression patterns were globally analyzed in several different ways to demonstrate the richness of the data and the ease with which novel phenomena can be discovered. When the culture moves from one growth phase to another, gene expression patterns change to such an extent that we suggest that those patterns can be used to unequivocally distinguish growth phases from each other. Also, within the classically defined growth phases, subgrowth phases were distinguishable with a distinct expression signature. Apart from the global expression pattern shifts seen throughout the growth curve, several cases of short-lived transient gene expression patterns were clearly observed. These could help explain the gene expression variations frequently observed in biological replicates. A method was devised to estimate a measure of unnormalized/absolute gene expression levels and used to determine how global transcription patterns are influenced by nutrient starvation or acidification of the medium. Notably, we inferred that L. lactis MG1363 produces proteins with on average lower pIs and lower molecular weights as the medium acidifies and nutrients get scarcer.IMPORTANCE This data set is a rich resource for microbiologists interested in common mechanisms of gene expression, regulation and in particular the physiology of L. lactis. Thus, similar to the common use of genome sequence data by the scientific community, the data set constitutes an extensive data repository for mining and an opportunity for bioinformaticians to develop novel tools for in-depth analysis.

Food grade microbial synthesis of the butter aroma compound butanedione using engineered and non-engineered Lactococcus lactis

The design-build-test-learn (DBTL) cycle has been implemented in metabolic engineering processes for optimizing the production of valuable compounds, including food ingredients. However, the use of recombinant microorganisms for producing food ingredients is associated with different challenges, e.g., in the EU, a content of more than 0.9% of such ingredients requires to be labeled. Therefore, we propose to expand the DBTL cycle and use the “learn” module to guide the development of non-engineered strains for clean label production. Here, we demonstrate how this approach can be used to generate engineered and natural cell factories able to produce the valuable food flavor compound - butanedione (diacetyl). Through comprehensive rerouting of the metabolism of Lactococcus lactis MG1363 and re-installment of the capacity to metabolize lactose and dairy protein, we managed to achieve a high titer of diacetyl (6.7 g/L) in pure dairy waste. Based on learnings from the engineering efforts, we successfully achieved the production of diacetyl without using recombinant DNA technology. We accomplish the latter by process optimization and by relying on high-throughput screening using a microfluidic system. Our results demonstrate the great potential that lies in combining metabolic engineering and natural approaches for achieving efficient production of food ingredients.

Heterologous production of equol by lactic acid bacteria strains in culture medium and food

The isoflavones daidzin and genistin, present in soybeans, can be transformed by the intestinal microbiota into equol and 5-hydroxy-equol, compounds with enhanced availability and bioactivity, although these are only produced by a fraction of the population. Hence, there is an interest in the production of these compounds, although, to date, few bacteria with biotechnological interest and applicability in food have been found able to produce equol. In order to obtain lactic acid bacteria able to produce equol, the daidzein reductase (dzr), dihydrodaidzein reductase (ddr), tetrahydrodaidzein reductase (tdr) and dihydrodaidzein racemase (ifcA) genes, from Slackia isoflavoniconvertens DSM22006, were cloned into the vector pNZ:TuR, under a strong constitutive promoter (TuR). Lactococcus lactis MG1363, Lacticaseibacillus casei BL23, Lactiplantibacillus plantarum WCFS1, Limosilactobacillus fermentum INIA 584L and L. fermentum INIA 832L, harbouring pNZ:TuR.tdr.ddr, were able to produce equol from dihydrodaidzein, while L. fermentum strains showed also production of 5-hydroxy-equol from dihydrogenistein. The metabolization of daidzein and genistein by the combination of strains harbouring pNZ:TuR.dzr and pNZ:TuR.tdr.ddr showed similar results, and the addition of the correspondent strain harbouring pNZ:TuR.ifcA resulted in an increase of equol production, but only in the L. fermentum strains. This pattern of equol and 5-hydroxy-equol production by L. fermentum strains was also confirmed in cow's milk supplemented with daidzein and genistein and incubated with the different combination of strains harbouring the constructed plasmids. Bacteria generally recognized as safe (GRAS), such as the lactic acid bacteria species used in this work, harbouring these plasmids, would be of value for the development of fermented vegetal foods enriched in equol and 5-hydroxy-equol.

Metabolism of flavonoids and lignans by lactobacilli and bifidobacteria strains improves the nutritional properties of flaxseed-enriched beverages

Flaxseed (Linum usitatissimum L.) is of interest as functional food because of the presence of compounds in its composition with potential health benefits, such as fatty acid omega-3, fiber, lignans and flavonoids. The bioactivity of lignans and flavonoids depends greatly on bacterial metabolism. Previously, lactobacilli and bifidobacteria strains were described to produce enterolignans and bioactive flavonoids (herbacetin, quercetin, quercetagetin, kaempferol, naringenin and eriodictyol) from flaxseed extracts and/or from secoisolariciresinol (SECO) in culture medium. In this work, cow's milk and soy beverage were supplemented with flaxseed extracts and fermented with selected lactobacilli and bifidobacteria strains. Lacticaseibacillus rhamnosus INIA P224, Limosilactobacillus mucosae INIA P508 and Lactiplantibacillus plantarum ESI 144 were capable of producing enterolactone (ENL) in both beverages supplemented with flaxseed, in addition to matairesinol and the flavonoids daidzein, genistein, glycitein, quercetin, naringenin, kaempferol and eriodictyol. On the other hand, Bifidobacterium breve INIA P367, Bifidobacterium pseudocatenulatum INIA P815 and Bifidobacterium pseudocatenulatum INIA P946 were able to produce quercetin, quercetagetin and high concentrations of herbacetin and SECO, in addition to pinoresinol, matairesinol, daidzein, genistein, naringenin, kaempferol and eriodictyol. The co-incubation of Lacticaseibacillus paracasei INIA P74 and Ligilactobacillus salivarius INIA P183 with Lactococcus lactis MG1363 harboring the food grade vector pLEB590.gly913, facilitated the production of ENL in soy beverage enriched with flaxseed. In this work, it is demonstrated how lactobacilli and bifidobacteria strains can improve the nutritional properties of flaxseed-enriched beverages, providing metabolites of great interest for human health.

Lactococcus-based vaccine against brucellosis: IgG immune response in mice with rOmp16-IL2 fusion protein.

This study was designed to introduce the recombinant Lactococcus lactis MG1363 as a cell factory candidate for production of recombinant Brucella melitensis Omp16-Human IL2 (r-Omp16-IL2) and to suggest it as a promising safe, non-pathogenic mucosal live vaccine against brucellosis. Three groups of BALB/c mice (10 mice per group) were intragastrically administrated with phosphate-buffered saline (PBS), L. lactis harboring the empty pAMJ2008 plasmid and with L. lactis expressing rOmp-IL2. The first two groups were classified as control groups and the third one is indicated as treatment group. Another group was injected by the intraperitoneal (i.p.) route with purified rOmp16-IL2 protein. The total serum IgG of each group was assessed with indirect ELISAs at two days before immunization and also two weeks after the last immunization. Results showed that BALB/c mice intragastrically administrated with L. lactis expressing rOmp-IL2 had dominant IgG response compared to the control (PBS administrated) group (P < 0.05). The level of IgG was significantly increased by intraperitoneally injection of recombinant Omp-IL2 in adjuvant compared to the intragastrically administration of PBS and L. lactis/pAMJ2008 as control groups, and also compared to L. lactis/pAMJ2008-rOmp-IL2 (P < 0.05). Our findings provide the use of L. lactis rOmp16-IL2 as a new promising alternative safe strategy than presently live attenuated vaccines toward developing an oral vaccine or subunit-based vaccine against brucellosis.

Recombinant Lactococcus lactis Carrying IL-4 and IL-10 Coding Vectors Protects against Type 1 Diabetes in NOD Mice and Attenuates Insulitis in the STZ-Induced Model.

Type 1 diabetes (T1D) is an autoimmune disease that culminates in beta cell destruction in the pancreas and, subsequently, deficiency in insulin production. Cytokines play a crucial role in the development of diabetes, orchestrating the recruitment and action of immune cells, to not only destroy insulin-producing cells but also preserve them. Therefore, the aim of this study was to investigate the effect of orally administered Lactococcus lactis MG1363 FnBPA+ strains carrying plasmids encoding IL-4 and IL-10 in the streptozotocin- (STZ-) induced diabetes model and in nonobese diabetic (NOD) mice. The STZ-induced mice that were treated with combined bacterial strains carrying plasmids encoding IL-4 and IL-10 showed lower incidence of diabetes and more preserved pancreatic islets than the mice that received the individual bacterial strains. Combined administration of L. lactis MG1363 FnBPA+ (pValac::dts::IL-4) and L. lactis MG1363 FnBPA+ (pValac::IL-10) resulted in protection against diabetes in NOD mice. It was shown that the combined treatment with recombinant bacterial by oral route prevented hyperglycemia and reduced the pancreatic islets-destruction in NOD mice. In addition, increased levels of IL-4 and IL-10 in serum and pancreatic tissue revealed a systemic effect of the treatment and also favored an anti-inflammatory microenvironment. Reduced concentrations of IL-12 in pancreas were essential to the regulation of inflammation, resulting in no incidence of diabetes in treated NOD mice. Normal levels of intestinal sIgA after long-term treatment with the L. lactis strains carrying plasmids encoding IL-4 and IL-10 indicate the development of oral tolerance and corroborate the use of this potent tool of mucosal delivery. For the first time, L. lactis MG1363 FnBPA+ strains carrying eukaryotic expression vectors encoding IL-4 and IL-10 are tested in STZ-induced and NOD mouse models. Therefore, our study demonstrates this innovative strategy provides immunomodulatory potential for further investigations in T1D and other autoimmune diseases.

A Lactococcal Phage Protein Promotes Viral Propagation and Alters the Host Proteomic Response During Infection.

The lactococcal virulent phage p2 is a model for studying the Skunavirus genus, the most prevalent group of phages causing milk fermentation failures in cheese factories worldwide. This siphophage infects Lactococcus lactis MG1363, a model strain used to study Gram-positive lactic acid bacteria. The structural proteins of phage p2 have been thoroughly described, while most of its non-structural proteins remain uncharacterized. Here, we developed an integrative approach, making use of structural biology, genomics, physiology, and proteomics to provide insights into the function of ORF47, the most conserved non-structural protein of unknown function among the Skunavirus genus. This small phage protein, which is composed of three α-helices, was found to have a major impact on the bacterial proteome during phage infection and to significantly reduce the emergence of bacteriophage-insensitive mutants.

Therapeutic effect of GLP-1 engineered strain on mice model of Alzheimer\u2019s disease and Parkinson\u2019s disease

Alzheimer’s disease (AD) and Parkinson’s disease (PD) are neurodegenerative diseases (NDD) characterized by progressive degeneration of the central nervous system, and few medications are available to halt the progression of AD and PD. In the present study, an engineered strain MG136-pMG36e-GLP-1 was used to evaluate its neuroprotective effect on AD and PD mice, via the probiotics effects of Lactococcus lactis MG1363 and the constantly produced Glucagon-like peptide-1 (GLP-1) by the engineered strain. Our results indicated that oral administration of MG136-pMG36e-GLP-1 significantly reduced lipopolysaccharide (LPS)-induced memory impairment and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced motor dysfunction through the toll-like receptor4 (TLR4)/nuclear factor-kappa B (NFκB) and protein kinase B (AKT)/Glycogen synthase kinase-3β (GSK3β) signaling pathway. High-throughput sequencing results showed that MG1363-pMG36e-GLP-1 reduced the abundance of the pathogens Enterococcus, Proteus, and increased the abundance of the probiotics Akkermansia muciniphila. These results suggest that the engineered strain may be a new intervention for treating AD and PD by reducing the occurrence of neuroinflammation.

Application of recombinant lactic acid bacteria and bifidobacteria able to enrich soy beverage in dihydrodaidzein and dihydrogenistein

Dihydrodaidzein (DHD) and dihydrogenistein (DHG) are intermediate compounds in the production of equol and 5-hydroxy-equol from daidzein and genistein by certain intestinal bacteria. In this work, we explored the heterologous expression of the daidzein reductase gene from Slackia isoflavoniconvertens DSM22006, responsible for the formation of DHD and DHG, in nine lactic acid bacteria and Bifidobacterium strains under a strong constitutive promoter in the plasmid pNZ:TuR.dzr. All the transformed strains showed high production of DHD and DHG both from pure daidzein and genistein and from the isoflavone glycosides present in soy beverage. In addition, Lactococcus lactis MG1363 pNZ:TuR.dzr, expressing the recombinant daidzein reductase, incremented the production of equol by equol-producing intestinal microbiotas in a colonic environment. Nevertheless, other recombinant strains tested showed the opposite effect to L. lactis MG1363 pNZ:TuR.dzr in the production of equol by intestinal microbiota. Here, we describe for the first time the production of 5-hydroxy-equol by human intestinal microbiota, both from genistein and DHG. The use of DHD and DHG as substrates, compared to daidzein and genistein, resulted in an increment of equol and 5-hydroxy-equol production by intestinal microbiota. The recombinant strains developed would be of value for the development of fermented soy beverage enriched in DHD and DHG with the aim of facilitate equol and 5-hydroxy-equol production by intestinal microbiota.

Expression of a β-glucosidase in bacteria with biotechnological interest confers them the ability to deglycosylate lignans and flavonoids in vegetal foods.

Lignans and flavonoids are found in plants in their glycosylated forms and need to be hydrolyzed to aglycones to become bioavailable. Putative β-glucosidase genes from Lactobacillus mucosae INIA P508 were inserted into the plasmid pNZ:TuR. The strain Lactococcus lactis MG1363 harboring the plasmid pNZ:TuR.glu913 showed high β-glucosidase activity and was able to transform secoisolariciresinol diglucoside (SDG) into secoisolariciresinol (SECO). Lactic acid bacteria and Bifidobacterium strains harboring pNZ:TuR.glu913 were incubated with a soy beverage supplemented with flax seed extracts. SDG was almost completely consumed by the transformed strains, while concentration of SECO greatly increased. Moreover, these strains showed high deglycosylation of the isoflavone glycosides daidzin and genistin. In addition, other lignan and flavonoid aglycones were produced, i.e. matairesinol, pinoresinol, quercetin, and eriodyctiol. These deglycosylase activities were maintained when this glucosidase gene was cloned in a food grade vector, pLEB590, and transformed into L. lactis MG1363. This is the first report of the use of a food grade plasmid that confers the ability to efficiently catalyze the deglycosylation of lignans, isoflavonoids, flavones, and flavanones. The recombinant bacteria of this study would be of value for the development of fermented vegetal foods enriched in bioavailable forms of lignans and flavonoids.

β-Glucan is a major growth substrate for human gut bacteria related to Coprococcus eutactus.

A clone encoding carboxymethyl cellulase activity was isolated during functional screening of a human gut metagenomic library using Lactococcus lactis MG1363 as heterologous host. The insert carried a glycoside hydrolase family 9 (GH9) catalytic domain with sequence similarity to a gene from Coprococcus eutactus ART55/1. Genome surveys indicated a limited distribution of GH9 domains among dominant human colonic anaerobes. Genomes of C. eutactus-related strains harboured two GH9-encoding and four GH5-encoding genes, but the strains did not appear to degrade cellulose. Instead, they grew well on β-glucans and one of the strains also grew on galactomannan, galactan, glucomannan and starch. Coprococcus comes and Coprococcus catus strains did not harbour GH9 genes and were not able to grow on β-glucans. Gene expression and proteomic analysis of C. eutactus ART55/1 grown on cellobiose, β-glucan and lichenan revealed similar changes in expression in comparison to glucose. On β-glucan and lichenan only, one of the four GH5 genes was strongly upregulated. Growth on glucomannan led to a transcriptional response of many genes, in particular a strong upregulation of glycoside hydrolases involved in mannan degradation. Thus, β-glucans are a major growth substrate for species related to C. eutactus, with glucomannan and galactans alternative substrates for some strains.

Quantifying and Engineering Mucus Adhesion of Probiotics.

Mucus in the gastrointestinal (GI) tract is the primary point-of-interaction between humans and their gut microbiota. This intimates that mucus not only ensures protection against endogenous and exogenous opportunists but also provisions for the human microbiota to reside and flourish. With the emergence of living therapeutics, engineered microbes can deliver and produce increasingly complex medicine, and controlling the mucoadhesive properties of different microbial chassis can dictate dose-response in a patient. Here we present a redesigned, in vitro, plate-based assay to measure the mucus adhesion of various probiotics. Cell-mucus interactions were isolated by immobilizing mucus to the plate surface. Binding parameters were derived for each probiotic strain by measuring cell adhesion over a wide range of cell concentrations, providing dose-dependent adhesion metrics. Surface proteins and cell components known to influence mucoadhesion were then heterologously expressed or altered in Lactococcus lactis MG1363 and Escherichia coli Nissle 1917 to control mucus-binding capacity, avidity, and cooperativity.

Expression of Helicobacter pylori CagL gene in Lactococcus lactis MG1363 and evaluation of its immunogenicity as an oral vaccine in mice

Helicobacter pylori is a gram negative pathogen which commonly colonizes in the human gastric mucosa from early childhood and persists throughout life. CagL is a 27-kDa protein that is located at the tip of T4SS pili and highly conserved among pathogenic H. pylori strains. Lactic acid bacteria especially Lactococcus lactis (L. lactis) could serve as an antigen-delivering vehicle for the development of edible vaccine. In this study H. pylori CagL gene was cloned in pAMJ2008 vector and transferred to Lactococcus lactis MG1363 as the host for CagL antigen production. This recombinant bacterium was orally subjected to mice, and the immune response to CagL was evaluated by ELISA. Intracellular expression of CagL protein was confirmed by Western blot analysis. Mucosal immunization of mice with the recombinant L. lactis significantly stimulated CagL-Specific antibodies: IgA, IgG, cytokine IL-17 and IFN-γ. Moreover, the specific anti-CagL IgA response was detected in the feces of immunized mice. These results indicate that CagL of H. pylori was successfully expressed in L. lactis and the recombinant bacteria can be potentially used as an edible vaccine against H. pylori infection.

Ampicillin-treated Lactococcus lactis MG1363 populations contain persisters as well as viable but non-culturable cells

Lactococcus lactis is used as cell-factory and strain selections are regularly performed to improve production processes. When selection regimes only allow desired phenotypes to survive, for instance by using antibiotics to select for cells that do not grow in a specific condition, the presence of more resistant subpopulations with a wildtype genotype severely slows down the procedure. While the food grade organism L. lactis is not often exposed to antibiotics we characterized its response to ampicillin in more detail, to better understand emerging population heterogeneity and how this might affect strain selection procedures. Using growth-dependent viability assays we identified persister subpopulations in stationary and exponential phase. Growth-independent viability assays revealed a 100 times larger subpopulation that did not grow on plates or in liquid medium, but had an intact membrane and could maintain a pH gradient. Over one third of these cells restored their intracellular pH when we induced a temporary collapse, indicating that this subpopulation was metabolically active and in a viable but non-culturable state. Exposure of L. lactis MG1363 to ampicillin therefore results in a heterogeneous population response with different dormancy states. These dormant cells should be considered in survival-based strain selection procedures.