Comparative genomics of the lactic acid bacteria

Lactic acid-producing bacteria are associated with various plant and animal niches and play a key role in the production of fermented foods and beverages. We report nine genome sequences representing the phylogenetic and functional diversity of these bacteria. The small genomes of lactic acid bacteria encode a broad repertoire of transporters for efficient carbon and nitrogen acquisition from the nutritionally rich environments they inhabit and reflect a limited range of biosynthetic capabilities that indicate both prototrophic and auxotrophic strains. Phylogenetic analyses, comparison of gene content across the group, and reconstruction of ancestral gene sets indicate a combination of extensive gene loss and key gene acquisitions via horizontal gene transfer during the coevolution of lactic acid bacteria with their habitats.     

Molecular approaches for identification and characterization of lactic acid bacteria

The last few years have produced a revolution in the development of very sensitive, rapid, automated, molecular detection methods for a variety of various species of lactic acid bacteria (LAB) associated with food and dairy products. Nowadays many such strains of LAB are considered probiotics. The genome-based methods are useful in identifying bacteria as a complementary or alternative tool to phenotypical methods. Over the years, identification methodologies using primers that target different sequences, such as the 16S ribosomal RNA (rRNA)-encoding gene, the 16S-23S rRNA intergenic spacer region, the 23S rRNA-encoding, recA and ldhD genes; randomly amplified polymorphic DNA, restriction fragment length polymorphism, denaturing gradient gel electrophoresis, temperature gradient gel electrophoresis, amplification rDNA restriction analysis, restriction enzyme analysis, rRNA, pulse field gel electrophoresis and amplification fragment length polymorphism have played a significant role in probiotic bacteriology. Hence, the aim of this review is to provide an overview of some rapid and reliable polymerase chain reaction-based molecular methods used for identifying and differentiating closely related species and strains of LAB associated with food and industry.     

Emerging roles of lactic acid bacteria in protection against colorectal cancer

Colorectal cancer(CRC)is the third leading cause of cancer deaths worldwide and the fourth most common cancer diagnosed among men and women in the United States.Considering the risk factors of CRC,dietary therapy has become one of the most effective approaches in reducing CRC morbidity and mortality.The use of probiotics is increasing in popularity for both the prevention and treatment of a variety of diseases.As the most common types of microbes used as probiotics,lactic acid bacteria(LAB)are comprised of an ecologically diverse group of microorganisms united by formation of lactic acid as the primary metabolite of sugar metabolism.LAB have been successfully used in managing diarrhea,food allergies,and inflammatory bowel disease.LAB also demonstrated a host of properties in preventing colorectal cancer development by inhibiting initiation or progression through multiple pathways.In this review,we discuss recent insights into cellular and molecular mechanisms of LAB in CRC prevention including apoptosis,antioxidant DNA damages,immune responses,and epigenetics.The emerging experimental findings from clinical trials as well as the proposed mechanisms of gut microbiota in carcinogenesis will also be briefly discussed.     

Correlation between in vitro and in vivo immunomodulatory properties of lactic acid bacteria

AIM To investigate the correlation between in vitro and in vivo immunomodulation potential of the probiotic strain and its ability to prevent experimental colitis in mice.METHODS In vitro immunomodulation was assessed by measuring interleukin (IL)-12p70, IL-10, tumor necrosis factor alpha (TNFα) and interferon γ (IFNγ) release by human peripheral blood mononuclear cells (PBMCs) after 24 h stimulation with 13 live bacterial strains. A murine model of acute TNBS-colitis was next used to evaluate the prophylactic protective capacity of the same set of strains.RESULTS A strain-specific in vivo protection was observed. The strains displaying an in vitro potential to induce higher levels of the anti-inflammatory cytokine IL-10 and lower levels of the inflammatory cytokine IL-12, offered the best protection in the in vivo colitis model. In contrast, strains leading to a low IL-10/IL-12 cytokine ratio could not significantly attenuate colitis symptoms.CONCLUSIONThese results show that we could predict the in vivo protective capacity of the studied lactic acid bacteria (LAB) based on the cytokine profile we established in vitro. The PBMC-based assay we used may thus serve as a useful primary indicator to narrow down the number of candidate strains to be tested in murine models for their anti-inflammatory potential.     

Polyunsaturated fatty acid saturation by gut lactic acid bacteria affecting host lipid composition

In the representative gut bacterium Lactobacillus plantarum, we identified genes encoding the enzymes involved in a saturation metabolism of polyunsaturated fatty acids and revealed in detail the metabolic pathway that generates hydroxy fatty acids, oxo fatty acids, conjugated fatty acids, and partially saturated trans-fatty acids as intermediates. Furthermore, we observed these intermediates, especially hydroxy fatty acids, in host organs. Levels of hydroxy fatty acids were much higher in specific pathogen-free mice than in germ-free mice, indicating that these fatty acids are generated through polyunsaturated fatty acids metabolism of gastrointestinal microorganisms. These findings suggested that lipid metabolism by gastrointestinal microbes affects the health of the host by modifying fatty acid composition.Dietary fats are metabolized not only by humans but also by microbes in our gastrointestinal tracts. Microorganisms in the gastrointestinal tract interact with their host in many ways and contribute significantly to the maintenance of host health (1). Lipid metabolism by gastrointestinal microbes generates multiple fatty acid species, such as conjugated fatty acids and trans-fatty acids, that can affect host lipid metabolism (2). However, lipid metabolism by gastrointestinal microbes has not been explored in detail. Saturation metabolism of polyunsaturated fatty acids, a representative mode of lipid metabolism by gastrointestinal microbes, is a detoxifying metabolism of anaerobic bacteria, such as lactic acid bacteria, that reside in colon and intestine. This process transforms growth-inhibiting free polyunsaturated fatty acids into less toxic free saturated fatty acids (3). This saturation metabolism generates characteristic fatty acids (e.g., conjugated fatty acids and trans-fatty acids, which are well known to present in ruminant-derived foods and exert various physiological activities).“Conjugated fatty acid” is a collective term for positional and geometric isomers of fatty acids with conjugated double bonds. In particular, conjugated linoleic acids (CLAs), such as cis-9,trans-11-CLA and trans-10,cis-12-CLA, reduce carcinogenesis (4), atherosclerosis (5), and body fat (6). With regard to lipid metabolism, CLA is a potent peroxisome proliferator-activated receptor (PPAR)α agonist (7), and treatment with CLA increases the catabolism of lipids in the liver of rodents (8). Based on these findings, CLA is now commercialized as a functional food for control of body weight, especially in the United States and European countries.On the other hand, consumption of trans-fatty acids increases the risk of coronary heart disease by increasing LDL and reducing HDL cholesterol levels (9). Consequently, trans-fatty acids are considered to be harmful for health, and nutritional authorities have recommended that consumption of trans-fatty acids be reduced to trace amounts (10). Therefore, it is important to control fatty acid saturation processes that generate these fatty acids (11); however, the precise metabolic pathway and enzymes involved have not been clearly identified.Our analyses on conjugated fatty acid synthesis in representative gut bacteria, the lactic acid bacteria (12–15), demonstrated that Lactobacillus plantarum AKU 1009a (AKU Culture Collection, Faculty of Agriculture, Kyoto University) can transform the cis-9,cis-12 diene structure of C18 fatty acids such as linoleic acid, α-linolenic acid, and γ-linolenic acid into the conjugated diene structures cis-9,trans-11 and trans-9,trans-11 (16–21). In addition, this strain can saturate these conjugated dienes into the trans-10 monoene. Our subsequent metabolic analysis indicated that 10-hydroxy-12-octadecenoic acid is an intermediate of CLA synthesis, and further investigations of hydroxy fatty acid metabolism by lactic acid bacteria revealed that CLA is produced from hydroxy fatty acids such as ricinoleic acid in castor oil (22–25). In cell-free extracts from this strain, we identified the enzymes involved in CLA synthesis (26). Three enzymes, CLA-HY, CLA-DH, and CLA-DC, are necessary for synthesis of conjugated fatty acids such as CLA. Only the combined action of these three enzymes can generate CLA from linoleic acid, with 10-hydroxy-cis-12-octadecenoic acid arising as an intermediate (Fig. 1B, 3). The reactions catalyzed by each enzyme, however, were not revealed in those studies. Through genomic analysis in L. plantarum WCFS1, we found that cla-dh (GenBank accession no. {"type":"entrez-nucleotide","attrs":{"text":"NC_004567","term_id":"380031102","term_text":"NC_004567"}}NC_004567; region: 59613-60473) and cla-dc (GenBank accession no. {"type":"entrez-nucleotide","attrs":{"text":"NC_004567","term_id":"380031102","term_text":"NC_004567"}}NC_004567; region: 60505-61350) are located in a cluster with another gene, cla-er (GenBank accession no. {"type":"entrez-nucleotide","attrs":{"text":"NC_004567","term_id":"380031102","term_text":"NC_004567"}}NC_004567; region: 61378-62031) (Fig. 1A). In light of this, we tried to identify the function of the gene product (CLA-ER) together with those of CLA-HY, CLA-DH, and CLA-DC.Open in a separate windowFig. 1.Gene clusters for polyunsaturated fatty acid metabolism and GC chromatograms. (A) Gene clusters for fatty acid metabolic enzymes in L. plantarum. (B) GC chromatograms of substrate (1); reaction with CLA-HY (2); reaction with CLA-HY, CLA-DH, and CLA-DC together with FAD and NADH (3); and reaction with CLA-HY, CLA-DH, CLA-DC, and CLA-ER together with FAD and NADH (4). I.S., internal standard.     

Controlled trial of antimycobacterial therapy in Crohn's disease

In order to study the effect of clofazimine, a powerful antimycobacterial and antiinflammatory agent, 49 patients with active Crohn's disease were randomized to either corticosteroids plus clofazimine 100 mg daily (N = 25) or to steroids and matching placebo (N = 24). A total of 28 patients (58%) went into disease remission (clofazimine 16, placebo 12; P = NS) with a fall in disease activity score from 10.5 +/- 4.4 to 3.3 +/- 3.5. Patients were treated for a further eight months with clofazimine or placebo and 18 of 28 maintained their remission and completed the study (clofazimine 12, placebo 6; P = NS). Side effects were minor and consisted of skin rash and increased pigmentation. Clofazimine as a solitary antimycobacterial agent appears ineffective in inducing remission in Crohn's disease but may have a role in either disease maintenance or combination chemotherapy.     

Reporter systems for in vivo tracking of lactic acid bacteria in animal model studies

Bioluminescence (BLI) and fluorescence imaging (FI) allow for non-invasive detection of viable microorganisms from within living tissue and are thus ideally suited for in vivo probiotic studies. Highly sensitive optical imaging techniques detect signals from the excitation of fluorescent proteins, or luciferase-catalyzed oxidation reactions. The excellent relation between microbial numbers and photon emission allow for quantification of tagged bacteria in vivo with extreme accuracy. More information is gained over a shorter period compared to traditional pre-clinical animal studies. The review summarizes the latest advances in in vivo bioluminescence and fluorescence imaging and points out the advantages and limitations of different techniques. The practical application of BLI and FI in the tracking of lactic acid bacteria in animal models is addressed.     

Reporter systems for in vivo tracking of lactic acid bacteria in animal model studies

Bioluminescence (BLI) and fluorescence imaging (FI) allow for non-invasive detection of viable microorganisms from within living tissue and are thus ideally suited for in vivo probiotic studies. Highly sensitive optical imaging techniques detect signals from the excitation of fluorescent proteins, or luciferase-catalyzed oxidation reactions. The excellent relation between microbial numbers and photon emission allow for quantification of tagged bacteria in vivo with extreme accuracy. More information is gained over a shorter period compared to traditional pre-clinical animal studies. The review summarizes the latest advances in in vivo bioluminescence and fluorescence imaging and points out the advantages and limitations of different techniques. The practical application of BLI and FI in the tracking of lactic acid bacteria in animal models is addressed.     

Improvement of an experimental colitis in rats by lactic acid bacteria producing superoxide dismutase

The use of superoxide dismutases (SODs) in inflammatory diseases is hampered by their short circulatory half-life. To determine whether a bacterial supply of SOD into the colon might improve an experimental colitis, the effects of oral treatment with live recombinant lactic acid bacteria producing different amounts of SOD and those of colonic infusion of SOD were compared. Wistar rats were fitted with a catheter in the proximal colon through which TNBS was administered to induce colitis. Animals received a continuous intracolonic infusion of bovine SOD (40 U per rat per day) for 4 days after TNBS or were treated orally with live recombinant Lactococcus lactis or Lactobacillus plantarum strains (10 colony-forming units (CFU)/d), producing or not producing SOD, for 4 days before and after TNBS. SOD activity of bacterial extracts was 0, 26, 74, and 624 units/10 CFU for L. plantarum, L. lactis, L. lactis SOD, and L. plantarum SOD, respectively. Four days after TNBS, macroscopic and microscopic damage, myeloperoxidase (MPO) activity, and nitrotyrosine immunostaining were evaluated. TNBS induced macroscopic and microscopic damages, an increase in MPO activity, and intense immunostaining for nitrotyrosine. Macroscopic damage and MPO activity were reduced by bovine SOD. These parameters and microscopic damages also were reduced by L. lactis, L. lactis SOD, and L. plantarum SOD, but not by L. plantarum. Nitrotyrosine immunostaining was attenuated after treatment with the 4 bacterial strains. Although not all of the anti-inflammatory effects could be attributed directly to SOD, our results suggest that SOD-producing lactic acid bacteria open a novel approach in inflammatory bowel disease treatment.     

Lack of inhibitory effects of lactic acid bacteria on 1,2-dimethylhydrazine-induced colon tumors in rats

AIM: A myriad of healthful effects has been attributed to the probiotic lactic acid bacteria, perhaps the most controversial issue remains that of anticancer activity. This study was aimed at investigating the putative anti-cancer effects of lactic acid bacteria strains on the progression of colon tumor in 1,2-dimethylhydrazine (DMH)-treated animals. METHODS: The strain of lactic acid bacteria used in this study was lactic acid bacteria NZ9000 that conformed to the characteristics of plasmid free. Sixty male Wistar rats were given subcutaneous injections of DMH at a dose of 40 mg/kg body wt or saline once a week for 10 weeks. The rats were divided into 6 experimental groups. After the last DMH injection, animals in groups 1 and 4 were gavaged with 1 ml of lactic acid bacteria at a dose of 5 X 10(9) per day or vehicle until sacrifice at the end of week 22 or week 52. Animals in groups 1-3 were killed at the end of week 22 for histopathological examination. The whole period of experimental observation was 52 weeks. RESULTS: By the end of 22nd week, final average body weights of the rats treated with DMH alone and all animals receiving lactic acid bacteria were significantly decreased compared with the vehicle control (P<0.05). No differences in tumor incidence, multiplicity, dimensions and stage in the colonic mucosa were observed among the groups. At week 52, the survival rate of the rats administered lactic acid bacteria was lower than that of the rats treated with DMH that were fed on control fluids of non-lactococcus lactis. The mean survival time of lactic acid bacteria-treated animals was 39 weeks. CONCLUSION: These results indicate that lactic acid bacteria lacks inhibitory effects on the progression of colon tumor in DMH-treated animals, and does not support the hypothesis that alteration of colonic flora may exert an influence on the progression of colon tumor.     

A meta-analysis of antimycobacterial therapy for Crohn's disease

OBJECTIVE: Various therapies have been studied for the treatment of Crohn's disease, including antimycobacterial therapy. Meta-analysis was used to evaluate the effect of antimycobacterial therapy in patients with Crohn's disease. METHODS: Randomized, controlled trials comparing antimycobacterial therapy with placebo were identified. Key outcome data were abstracted and the results were pooled to yield odds ratios for maintenance of remission in treated versus control groups. RESULTS: A total of eight randomized trials were identified. Six trials were fully published and were included in the primary analysis. Two trials used antimycobacterial therapy in combination with corticosteroids to induce remission in patients with active Crohn's disease, followed by maintenance therapy with antimycobacterial agents. In these trials, control patients received corticosteroids to induce remission but no antimycobacterial therapy. Pooling of these trials yielded an odds ratio of maintenance of remission in treatment versus control of 3.37 (95% confidence interval [CI], 1.38-8.24) in favor of antimycobacterial therapy. The remaining four trials used antimycobacterial therapy combined with standard therapy in patients with Crohn's disease. In these trials, control patients received standard therapy alone. Pooling of these trials yielded an odds ratio of maintenance of remission in treatment versus control of 0.69 (95% CI, 0.39-1.21) in favor of standard therapy. CONCLUSIONS: These results suggest that antimycobacterial therapy is effective in maintaining remission in patients with Crohn's disease after a course of corticosteroids combined with antimycobacterial therapy to induce remission. Treatment of Crohn's disease with antimycobacterial therapy does not seem to be effective without a course of corticosteroids to induce remission. Because of the small number of studies included in this meta-analysis, the results should be interpreted with caution.     

Effect of lactic acid producing bacteria on the human intestinal microflora during ampicillin treatment

20 healthy volunteers participated in a double blind study concerning the effect of lactic acid producing bacteria on the intestinal microflora during ampicillin treatment. 10 volunteers received 500 mg ampicillin tablets t.i.d. together with capsules containing lactic acid producing bacteria (Lactobacillus acidophilus and Bifidobacterium bifidum) for 7 days, and the other 10 volunteers were given 500 mg ampicillin tablets together with placebo capsules t.i.d. for 7 days. Both groups of volunteers continued the intake of the capsules t.i.d. for another 14 days after the ampicillin administration had been completed. The number of enterococci, streptococci and corynebacteria decreased during ampicillin administration but returned to normal levels after 14 days. Yeasts increased during the antibiotic treatment but returned to the same levels as before treatment within 14 days. Escherichia coli strains were suppressed in most volunteers during ampicillin administration. The numbers of anaerobic gram-positive cocci and rods decreased in most subjects during ampicillin treatment but were normalized within 2 weeks. Bacteroides strains were recovered in higher numbers in the lactic acid producing bacteria group compared to the placebo group. The volunteers receiving lactic acid producing bacteria were recolonized slightly faster than those having placebo. There were adverse effects observed in 3 subjects receiving ampicillin plus placebo. In the lactic acid producing bacteria group, one subject had diarrhoea on day 3 to on day 3 to day 7.     

Prevalence of antibiotic resistance in lactic acid bacteria isolated from the faeces of broiler chicken in Malaysia

Background

Probiotics are commonly used as feed additive to substitute antibiotic as growth promoter in animal farming. Probiotic consists of lactic acid bacteria (LAB), which enhance the growth and health of the animal. Probiotic also have higher possibility to become pathogenic bacteria that may carry antibiotic resistant gene that can be transmitted to other LAB species. The aim of this study was to identify the LAB species in the faeces of broiler chicken and to determine the prevalence of antibiotic resistant in LAB of broiler chicken.

Methods

Sixty faeces samples were collected from wet markets located in Klang Valley of Malaysia for the isolation of LAB using de-Mann Rogosa Sharpe medium. Thirteen species of LAB were obtained in this study and the identification of LAB was performed by using API test kit on the basis of carbohydrate fermentation profile. Antibiotic susceptibility assay was then carried out to determine the prevalence of LAB antibiotic resistance.

Results

Lactococcus lactis subsp lactis was found in nine out of sixty faecal samples. Lactobacillus paracasei was the second common LAB species isolated from chicken faecal. No significant difference (P > 0.05) was found between the occurrence of Lactobacillus brevis, Lactobacillus curvatus, Lactobacillus plantarum, Leuconostoc lactis mesenteroides subsp mesenteroides/dectranium and Pediococcus pentosaceus isolated from 5 different locations. Most of the isolated LAB was resistant to antibiotic and high variability of the antibiotic resistance was observed among the LAB against 15 types of antibiotics. Penicillin, amoxicillin, chloramphenicol, and ampicillin had significant higher (P< 0.05) inhibitory zone than nalidixic acid, gentamycin, sulphamethoxazole, kanamycin, and streptomycin.

Conclusions

Many species of LAB were isolated from the faecal samples of broiler chicken that resistance to the common antibiotics used in the farm. The development of resistant against antibiotics in LAB can be attributed to the long term exposure of antibiotic as growth promoter and therapeutic agents. Thus, it is essential to advise farmer the safety measure of antibiotic application in animal farming. Additionally, the supplementation of probiotic in animal feeding also needs more attention and close monitoring.     

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

ABSTRACT

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

Effects of lactic acid bacteria on the uptake and distribution of the food mutagen Trp-P-2 in mice

BACKGROUND: Lactic acid bacteria have been reported to have antimutagenic and anticarcinogenic properties in vivo and in vitro. Lactobacillus acidophilus and Bifidobacterium longum have earlier been shown to bind the food mutagen Trp-P-2 in vitro. METHODS: The influence of oral supplementation with L. acidophilus NCFB 1748 and B. longum BB 536 on the uptake and distribution of 14C-labelled Trp-P-2 in several mouse tissues was quantified by liquid scintillation measurements and examined by tape section autoradiography (gives an unbiased qualitative registration of differences in overall tissue distribution) in the present investigation. Furthermore, the effect of 13-naphthoflavone (BNF), a cytochrome P4501A (CYP1A)-inducing agent, on the distribution of 14C-labelled Trp-P-2 was examined. RESULTS: After oral (6 mg/kg; 5 microCi) or iv (1.2 mg/kg; 1 microCi) administration of 14C-labelled Trp-P-2, high levels of radioactivity were observed in the bile, urine and contents of the gastrointestinal tract. Lower levels were present in the liver, lung, kidney, intestines, brown fat, submaxillary salivary gland and thymus. In mice supplemented with lactic acid bacteria there was a significantly decreased level (29%-73%) of radioactivity in the lung, thymus, liver, kidney, submaxillary salivary gland and small intestine as compared with controls. In mice pretreated with BNF, a low but distinct localization of radioactivity in the lung was observed, whereas no similar localization occurred in controls. CONCLUSIONS: The results suggest that (i) there is a decreased bioavailability of the Trp-P-2 in the majority of the tissues examined in bacteria supplemented mice and (ii) there is a low but distinct CYP1A-dependent activation of Trp-P-2 in the lung of BNF-treated mice.     

Amino acid metabolism in lactic acidosis

Individual plasma amino acid levels have been determined in six patients with severe lactic acidosis. A consistently distorted pattern was observed whether the disorder was due to shock or was of the idiopathic type. A sixfold elevation in mean alanine concentration was observed, and a significant correlation of alanine with pyruvate concentrations was demonstrated. Since alanine is normally released from muscle and stoichiometrically extracted by liver, normal formation of alanine from pyruvate is suggested by the findings. However, uptake and metabolism of alanine by isolated, perfused rat liver was significantly inhibited by perfusate concentrations of lactate and pyruvate equivalent to those observed in the patients. Thus the high levels of alanine in lactic acidosis are viewed as consistent with normal or increased peripheral release combined with impaired hepatic disposal. The levels of fifteen of the nineteen amino acids measured were elevated. Of the remaining four, three were intermediates of the urea cycle.