Anti‐infectious activity of synbiotics in a novel mouse model of methicillin‐resistant Staphylococcus aureus infection

The anti‐infectious activity of synbiotics against methicillin‐resistant Staphylococcus aureus (MRSA) infection was evaluated using a novel lethal mouse model. Groups of 12 mice treated with multiple antibiotics were infected orally with a clinical isolate of MRSA at an inoculum of 10⁸ CFU on day 7 after starting the antibiotics. A dose of 400 mg/kg 5‐fluorouracil (5‐FU) was injected intraperitoneally on day 7 after the infection. A dose of 10⁸ CFU Bifidobacterium breve strain Yakult and 10 mg of galactooligosaccharides (GOS) were given orally to mice daily with the antibiotic treatment until day 28. The intestinal population levels of MRSA in the mice on multiple antibiotics were maintained stably at 10⁸ CFU/g of intestinal contents after oral MRSA infection and the subsequent 5‐FU treatment killed all the mice in the group within 14 days. B. breve administration saved most of the mice, but the synbiotic treatment saved all of the mice from lethal MRSA infection. The synbiotic treatment was effective for the treatment of intestinal infection caused by four MRSA strains with different toxin productions. There was a large difference among the six Bifidobacteria strains that were naturally resistant to the antibacterial drugs used. B. breve in combination with GOS is demonstrated to have valuable preventive and curative effects against even fatal MRSA infections.     

Ethyl pyruvate attenuates ventilation‐induced diaphragm dysfunction through high‐mobility group box‐1 in a murine endotoxaemia model

Mechanical ventilation (MV) can save the lives of patients with sepsis. However, MV in both animal and human studies has resulted in ventilator‐induced diaphragm dysfunction (VIDD). Sepsis may promote skeletal muscle atrophy in critically ill patients. Elevated high‐mobility group box‐1 (HMGB1) levels are associated with patients requiring long‐term MV. Ethyl pyruvate (EP) has been demonstrated to lengthen survival in patients with severe sepsis. We hypothesized that the administration of HMGB1 inhibitor EP or anti‐HMGB1 antibody could attenuate sepsis‐exacerbated VIDD by repressing HMGB1 signalling. Male C57BL/6 mice with or without endotoxaemia were exposed to MV (10 mL/kg) for 8 hours after administrating either 100 mg/kg of EP or 100 mg/kg of anti‐HMGB1 antibody. Mice exposed to MV with endotoxaemia experienced augmented VIDD, as indicated by elevated proteolytic, apoptotic and autophagic parameters. Additionally, disarrayed myofibrils and disrupted mitochondrial ultrastructures, as well as increased HMGB1 mRNA and protein expression, and plasminogen activator inhibitor‐1 protein, oxidative stress, autophagosomes and myonuclear apoptosis were also observed. However, MV suppressed mitochondrial cytochrome C and diaphragm contractility in mice with endotoxaemia (P < 0.05). These deleterious effects were alleviated by pharmacologic inhibition with EP or anti‐HMGB1 antibody (P < 0.05). Our data suggest that EP attenuates endotoxin‐enhanced VIDD by inhibiting HMGB1 signalling pathway.     

Oral administration of Bifidobacterium longum prevents gut-derived Pseudomonas aeruginosa sepsis in mice

Aims: The aim of the study was to evaluate the efficacy of probiotics on gut‐derived sepsis caused by Pseudomonas aeruginosa in immunocompromised mice. Methods and Results: After oral inoculation of P. aeruginosa, mice were treated with cyclophosphamide to induce leucopenia and translocation of the intestinal P. aeruginosa into blood, thereby producing gut‐derived sepsis. In this model, administration of 1 × 10⁹ CFU of Bifidobacterium longum strain BB536 for 10 days significantly (P < 0·01) increased the survival rate compared with groups of mice administered either with Bifidobacterium breve strain ATCC 15700 or excipients contained in the probiotic bacterial powder. Administration of B. longum significantly decreased viable counts of P. aeruginosa in the liver and blood compared with other groups. Culture of intestinal contents revealed a significantly lower viable count of P. aeruginosa in the jejunum of B. longum‐treated mice compared with other groups of mice. Furthermore, in vitro data demonstrated that B. longum possessed apparently higher adherent activity to Caco‐2 cell monolayers and significantly suppressed the adherence of P. aeruginosa to the monolayers of cells compared with other groups. Conclusion: Oral administration of B. longum protects mice against gut‐derived sepsis caused by P. aeruginosa, and the effect may be due to interference of P. aeruginosa adherence to intestinal epithelial cells. Significance and Impact of this Study: This study demonstrated that oral administration of B. longum BB536 is effective to protect against opportunistic infection with drug‐resistant bacteria such as P. aeruginosa. The results suggest that probiotics may play an important role even in the immunocompromised patients.     

α‐Haemolysin production,as a single factor,causes fulminant sepsis in a model of Escherichia coli‐induced bacteraemia

α‐Haemolysin (HlyA) from uropathogenic Escherichia coli has been demonstrated to be a significant virulence factor for ascending urinary tract infections. Once the E. coli reach the well‐vascularised kidneys, there is a high risk of bacteraemia and a subsequent septic host response. Despite this, HlyA has the potential to accelerate the host response both directly and via its ability to facilitate adenosine triphosphate release from cells. It has not been settled whether HlyA aggravates bacteraemia into a septic state. To address this, we used an E. coli strain in a model of acute urosepsis that was either transfected with a plasmid containing the full HlyA operon or one with deletion in the HlyA gene. Here, we show that HlyA accelerates the host response to E. coli in the circulation. Mice exposed to HlyA‐producing E. coli showed massively increased proinflammatory cytokines, a substantial fall in circulating thrombocytes, extensive haematuria, and intravascular haemolysis. This was not seen in mice exposed to either E. coli that do not secrete HlyA or vehicle controls. Consistent with the massive host response to the bacteria, the mice exposed to HlyA‐producing E. coli died exceedingly early, whereas mice exposed to E. coli without HlyA production and vehicle controls survived the entire observation period. These data allow us to conclude that HlyA is a virulence factor that accelerates a state of bacteraemia into fulminant sepsis in a mouse model.     

Identification of mitochondrial function‐associated lncRNAs in septic mice myocardium

The present study aimed to analyze long noncoding RNA (lncRNA) and messenger RNA (mRNA) expression profiles in septic mice heart and to identify potential lncRNAs and mRNAs that be responsible for cardiac mitochondrial dysfunction during sepsis. Mice were treated with 10 mg/kg of lipopolysaccharides to induce sepsis. LncRNAs and mRNAs expression were evaluated by using lncRNA and mRNA microarray or real‐time polymerase chain reaction technique. LncRNA‐mRNA coexpression network assay, Gene Ontology (GO) analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis were performed. The results showed that 1275 lncRNAs were differentially expressed in septic myocardium compared with those in the control group. A total of 2769 mRNAs were dysregulated in septic mice heart, most of which are mainly related to the process of inflammation, mitochondrial metabolism, oxidative stress, and apoptosis. Coexpression network analysis showed that 14 lncRNAs were highly correlated with 11 mitochondria‐related differentially expressed mRNA. Among all lncRNAs and their cis‐acting mRNAs, 41 lncRNAs‐mRNA pairs (such as NONMMUG004378 and Apaf1 gene) were enriched in GO terms and KEGG pathways. In summary, we gained some specific lncRNAs and their potential target mRNAs that might be involved in mitochondrial dysfunction in septic myocardium. These findings provide a panoramic view of lncRNA and might allow developing new treatment strategies for sepsis.     

Regulatory effects of Spirulina complex polysaccharides on growth of murine RSV‐M glioma cells through Toll‐like receptor 4

This study is the first to report that Spirulina complex polysaccharides (CPS) suppress glioma growth by down‐regulating angiogenesis via a Toll‐like receptor 4 signal. Murine RSV‐M glioma cells were implanted s.c. into C3H/HeN mice and TLR4 mutant C3H/HeJ mice. Treatment with either Spirulina CPS or Escherichia coli (E. coli) lipopolysaccharides (LPS) strongly suppressed RSV‐M glioma cell growth in C3H/HeN, but not C3H/HeJ, mice. Glioma cells stimulated production of interleukin (IL)‐17 in both C3H/HeN and C3H/HeJ tumor‐bearing mice. Treatment with E. coli LPS induced much greater IL‐17 production in tumor‐bearing C3H/HeN mice than in tumor‐bearing C3H/HeJ mice. In C3H/HeN mice, treatment with Spirulina CPS suppressed growth of re‐transplanted glioma; however, treatment with E. coli LPS did not, suggesting that Spirulina CPS enhance the immune response. Administration of anti‐cluster of differentiation (CD)8, anti‐CD4, anti‐CD8 antibodies, and anti‐asialo GM1 antibodies enhanced tumor growth, suggesting that T cells and natural killer cells or macrophages are involved in suppression of tumor growth by Spirulina CPS. Although anti‐interferon‐γ antibodies had no effect on glioma cell growth, anti‐IL‐17 antibodies administered four days after tumor transplantation suppressed growth similarly to treatment with Spirulina CPS. Less angiogenesis was observed in gliomas from Spirulina CPS‐treated mice than in those from saline‐ or E. coli LPS‐treated mice. These findings suggest that, in C3H/HeN mice, Spirulina CPS antagonize glioma cell growth by down‐regulating angiogenesis, and that this down‐regulation is mediated in part by regulating IL‐17 production.     

CHF5074 restores visual memory ability and pre‐synaptic cortical acetylcholine release in pre‐plaque Tg2576 mice

CHF5074, a new microglial modulator, attenuates memory deficit in Alzheimer's disease transgenic mice. In this study, the effect of an acute or subacute CHF5074 treatment on in vivo novel object recognition test and on [³H]Acetylcholine (ACh) and GABA release in pre‐plaque (7‐month‐old) Tg2576 mice have been compared with those induced by the γ‐secretase inhibitor LY450139 (semagacestat). Vehicle‐treated Tg2576 mice displayed an impairment of recognition memory compared with wild‐type animals. This impairment was recovered in transgenic animals acutely treated with CHF5074 (30 mg/kg), while LY450139 (1, 3, 10 mg/kg) was ineffective. In frontal cortex synaptosomes from vehicle‐treated Tg2576 mice, K⁺‐evoked [³H]ACh release was lower than that measured in wild‐type mice. This reduction was absent in transgenic animals subacutely treated with CHF5074 (30 mg/kg daily for 8 days), while it was slightly, not significantly, amplified by LY450139 (3 mg/kg daily for 8 days). There were no differences between the groups on spontaneous [³H]ACh release as well as spontaneous and K⁺‐evoked GABA release. These results suggest that CHF5074 has beneficial effects on visual memory and cortical cholinergic dysfunctions in pre‐plaque Tg2576 mice. Together with previous findings, these data suggest that CHF5074 could be a possible candidate for early Alzheimer's disease therapeutic regimens.     

Co‐culture engineering for microbial biosynthesis of 3‐amino‐benzoic acid in Escherichia coli

3‐amino‐benzoic acid (3AB) is an important building block molecule for production of a wide range of important compounds such as natural products with various biological activities. In the present study, we established a microbial biosynthetic system for de novo 3AB production from the simple substrate glucose. First, the active 3AB biosynthetic pathway was reconstituted in the bacterium Escherichia coli, which resulted in the production of 1.5 mg/L 3AB. In an effort to improve the production, an E. coli‐E. coli co‐culture system was engineered to modularize the biosynthetic pathway between an upstream strain and an downstream strain. Specifically, the upstream biosynthetic module was contained in a fixed E. coli strain, whereas a series of E. coli strains were engineered to accommodate the downstream biosynthetic module and screened for optimal production performance. The best co‐culture system was found to improve 3AB production by 15 fold, compared to the mono‐culture approach. Further engineering of the co‐culture system resulted in biosynthesis of 48 mg/L 3AB. Our results demonstrate co‐culture engineering can be a powerful new approach in the broad field of metabolic engineering.     

Anti‐inflammatory and anti‐endotoxin properties of peptides derived from the carboxy‐terminal region of a defensin from the tick Ornithodoros savignyi

Antimicrobial peptides are small cationic peptides that possess a large spectrum of bioactivities, including antimicrobial, anti‐inflammatory and antioxidant activities. Several antimicrobial peptides are known to inhibit lipopolysaccharide (LPS)‐induced inflammation in vitro and to protect animals from sepsis. In this study, the cellular anti‐inflammatory and anti‐endotoxin activities of Os and Os‐C, peptides derived from the carboxy‐terminal of a tick defensin, were investigated. Both Os and Os‐C were found to bind LPS in vitro, albeit to a lesser extent than polymyxin B and melittin, known endotoxin‐binding peptides. Binding to LPS was found to reduce the bactericidal activity of Os and Os‐C against Escherichia coli confirming the affinity of both peptides for LPS. At a concentration of 25 µM, the nitric oxide (NO) scavenging activity of Os was higher than glutathione, a known NO scavenger. In contrast, Os‐C showed no scavenging activity. Os and Os‐C inhibited LPS/IFN‐γ induced NO and TNF‐α production in RAW 264.7 cells in a concentration‐dependent manner, with no cellular toxicity even at a concentration of 100 µM. Although inhibition of NO and TNF‐α secretion was more pronounced for melittin and polymyxin B, significant cytotoxicity was observed at concentrations of 1.56 µM and 25 µM for melittin and polymyxin B, respectively. In addition, Os, Os‐C and glutathione protected RAW 264.7 cells from oxidative damage at concentrations as low as 25 µM. This study identified that besides previously reported antibacterial activity of Os and Os‐C, both peptides have in addition anti‐inflammatory and anti‐endotoxin properties. Copyright © 2015 European Peptide Society and John Wiley & Sons, Ltd.     

Studies on the Establishment of Multi-Drug-Resistant Strain BIO-4R of Streptococcus faecalis in the Intestinal Tract of Germ-Free Mice

Germ-free ICR mice were mono- or dicontaminated with a multi-drug-resistant strain BIO-4R of Streptococcus faecalis (BIO-4R) and Escherichia coli 026 : K60 (E. coli) and administered aminobenzyl penicillin (ABPC). BIO-4R was established in the intestinal tract at a level of 10⁸ viable cells per gram of stool on the fourth day following oral inoculation and the BIO-4R population was stably maintained thereafter. The drug resistance of BIO-4R remained unchanged in the intestinal tract of gnotobiotes throughout the experiment. Highly resistant cells of E. coli were isolated from the feces of some dicontaminated mice after ABPC administration. However, it seems that the high resistance of these E. coli is not due to the transfer of resistance of BIO-4R to E. coli. All animals given a large amount of BIO-4R (10⁸ cells) per os survived throughout the study period of two weeks without symptoms.     

Activation of Toll‐like receptor 9 inhibits lipopolysaccharide‐induced receptor activator of nuclear factor kappa‐ B ligand expression in rat B lymphocytes

B lymphocytes express multiple TLRs that regulate their cytokine production. We investigated the effect of TLR4 and TLR9 activation on receptor activator of NF‐κB ligand (RANKL) expression by rat spleen B cells. Splenocytes or purified spleen B cells from Rowett rats were cultured with TLR4 ligand Escherichia coli LPS and/or TLR9 ligand CpG‐oligodeoxynucleotide (CpG‐ODN) for 2 days. RANKL mRNA expression and the percentage of RANKL‐positive B cells were increased in rat splenocytes challenged by E. coli LPS alone. The increases were less pronounced when cells were treated with both CpG‐ODN and E. coli LPS. Microarray analysis showed that expressions of multiple cyclin‐dependent kinase (CDK) pathway‐related genes were up‐regulated only in cells treated with both E. coli LPS and CpG‐ODN. This study suggests that CpG‐ODN inhibits LPS‐induced RANKL expression in rat B cells via regulation of the CDK pathway.     

Laboratory adapted Escherichia coli K‐12 becomes a pathogen of Caenorhabditis elegans upon restoration of O antigen biosynthesis

Escherichia coli has been the leading model organism for many decades. It is a fundamental player in modern biology, facilitating the molecular biology revolution of the last century. The acceptance of E. coli as model organism is predicated primarily on the study of one E. coli lineage; E. coli K‐12. However, the antecedents of today's laboratory strains have undergone extensive mutagenesis to create genetically tractable offspring but which resulted in loss of several genetic traits such as O antigen expression. Here we have repaired the wbbL locus, restoring the ability of E. coli K‐12 strain MG1655 to express the O antigen. We demonstrate that O antigen production results in drastic alterations of many phenotypes and the density of the O antigen is critical for the observed phenotypes. Importantly, O antigen production enables laboratory strains of E. coli to enter the gut of the Caenorhabditis elegans worm and to kill C. elegans at rates similar to pathogenic bacterial species. We demonstrate C. elegans killing is a feature of other commensal E. coli. We show killing is associated with bacterial resistance to mechanical shear and persistence in the C. elegans gut. These results suggest C. elegans is not an effective model of human‐pathogenic E. coli infectious disease.     

Influence of bacteriocin in the control of Escherichia coli infection of broiler chickens in Nigeria

One hundred broiler chickens were divided into four groups. Group A was untreated and challenged with E. coli 02:KH6; group B was infected and treated with bacteriocin in their drinking water; group C was infected and treated by administration of Lactobacillus plantarum F1 culture in skimmed milk, and group D acted as a control. Their weight, feed intake, clinical signs, microscopic lesions, E. coli re-isolation and serum biochemistry were compared. Groups B and C showed fewer symptoms and gross lesions than those from group A, while body weight and feed intakes were similar to the control group. E. coli 02:KH6 was re-isolated in 60% of the livers from group A, compared to 8 and 12% of the livers from group B and C respectively. There was significant increase in the levels of total protein (3.78 ± 0.05 g/100 ml) and globulins (2.53 ± 0.03 g/100 ml) in group A compared to groups B and C. The cholesterol levels in group A (112.56 ± 0.15 mg/100 ml) were significantly reduced compared to those of groups B and C which had 127.25 ± 0.14 and 128.73 ± 0.13 mg/100 ml respectively. The study provides evidence of the potential therapeutic efficacy of bacteriocin in the control of an experimental E. coli infection in broiler chickens.     

Probiotic Bifidobacterium bifidum G9‐1 ameliorates phytohemagglutinin‐induced diarrhea caused by intestinal dysbiosis

Diarrhea is largely caused by dysbiosis accompanying the hyperproliferation of Escherichia coli (E. coli). While current treatments can resolve the symptoms, they cannot suppress the proliferation of pathogenic bacteria in the intestine. Probiotics have numerous beneficial effects on host health, including restoring the balance of the intestinal microbiota. This study investigated the effect of the probiotic Bifidobacterium bifidum G9‐1 (BBG9‐1), which is active in intestinal dysbiosis, in the incidence of diarrhea, in the composition of the intestinal microbiota, and in the intestinal tissue of a rat model of phytohemagglutinin (PHA)‐induced diarrhea. The rats were treated with PHA, with and without BBG9‐1, and the microbiota composition throughout the intestine and stool was examined using high‐throughput 16S rRNA sequencing. In line with previous reports, PHA administration caused diarrhea as well as dysbiosis due to E. coli hyperproliferation. Histological findings indicated that the jejunal villus length was shortened. Rats that received BBG9‐1 showed clear improvements in dysbiosis, diarrhea symptoms, and jejunal villus length. Principal coordinates analysis demonstrated the microbiota profile to be more similar between the BBG9‐1 and normal groups than between the PHA and normal groups. These results indicated that BBG9‐1 suppresses the hyperproliferation of E. coli and restores the jejunal villus length, thereby improving dysbiosis, and in turn, alleviating the symptoms of diarrhea.     

大承气汤对MODS时肠道细菌微生态学影响的实验研究

目的探讨多器官功能不全综合征(MODS)大鼠肠道细菌微生态的变化及其与肠源性内毒素血症和细菌易位的关系,并观察大承气汤的影响。方法32只SD大鼠随机分成4组,对照组、模型组、大承气组和氨苄青霉素组。腹腔注射无菌酵母多糖A制备大鼠MODS模型。各组动物于造模后48 h无菌操作抽取外周静脉血和门静脉血进行内毒素含量测定;取肠系膜淋巴结进行细菌定量培养,取回肠和盲肠内容物进行肠腔内游离内毒素测定;取盲肠内容物进行肠道细菌微生态学分析。结果模型组外周血和门静脉血内毒素水平以及肠腔内游离内毒素含量均明显高于对照组(P<0.05);与对照组相比,模型组肠道菌群出现明显变化。肠球菌、肠杆菌数量明显增加,而双歧杆菌和乳酸杆菌数量出现显著下降,类杆菌数量亦出现明显下降(P<0.05)。模型组厌氧菌总数明显下降而需氧菌总数明显增加,同时厌氧菌总数/需氧菌总数的比值和B/E比值呈相应下降,发生倒置(P<0.05);正常对照组未发现肠道细菌向肠系膜淋巴结的易位,而模型组细菌易位阳性率是83.33%(P<0.05)。与模型组相比,大承气汤组上述各指标均出现明显变化(P<0.05);抗生素组作用不明显(P>0.05)。结论MODS时大鼠肠道细菌微生态出现明显变化,发生肠源性内毒素血症和细菌易位。大承气汤可以调整肠道菌群,恢复肠道微生态平衡,增加机体定植抗力,防治细菌易位和内毒素血症。     

Micro‐computed tomographic evaluation of fetal skeletal changes induced by all‐trans‐retinoic acid in rats and rabbits

BACKGROUND: Our laboratory has been conducting positive control studies to evaluate the utility of micro‐computed tomography (micro‐CT) for qualitative evaluation of fetal skeletal morphology. All‐trans‐retinoic acid (atRA) was used to produce a different spectrum of defects compared to our previous studies with boric acid and hydroxyurea. METHODS: Groups of five mated Crl:CD(SD) female rats each were administered vehicle or atRA (2.5–50 mg/kg) on GD 10, and groups of four mated Dutch Belted rabbits each were dosed with vehicle or atRA (6.25–25 mg/kg) on GD 9. Cesarean sections were performed on GD 21 and 28, respectively. Following external examination the viscera were removed and fetuses scanned in a micro‐CT imaging system. Fetuses were subsequently stained with alizarin red. Skeletal morphology was evaluated by each method without the knowledge of treatment group. Total bone mineral content (BMC) of each fetus was quantitated using the micro‐CT images. RESULTS: In rats there were dose‐related increases in the incidence of extra lumbar vertebra and non‐dose‐related increases in supernumerary ribs at all dose levels. There were decreases in mean number of ossified sacrocaudal vertebra at ≥5 mg/kg, and increases in skull bone malformations at ≥10 mg/kg. Rabbits were less sensitive on a mg/kg basis since skeletal malformations and a decrease in mean number of ossified sacrocaudal vertebra were observed only in the 25‐mg/kg group. Micro‐CT evaluation detected essentially the same incidence of skeletal abnormalities as seen in alizarin red‐stained rat and rabbit fetuses. BMC analysis showed a trend toward slight decreases in atRA‐treated rats, but no notable changes in rabbits. CONCLUSIONS: These results add support to our previous work that demonstrates that micro‐CT imaging can effectively assess rat and rabbit fetal skeletal morphology. Birth Defects Res (Part B) 89:408–417, 2010. © 2010 Wiley‐Liss, Inc.     

Ondansetron enhanced diclofenac‐induced nephrotoxicity in mice

This study was performed to investigate the effect of ondansetron, a serotonin receptor (5‐HT3) antagonist, in the alleviation of diclofenac‐induced kidney injuries. NMRI mice were randomly divided into six groups and treated with (A) untreated control group, (B) diclofenac (100 mg/kg), (C) ondansetron (1 mg/kg), (D to F) ondansetron (0.1, 0.5, and 1 mg/kg, respectively) and diclofenac (100 mg/kg) for last 3 days of experiment. The oxidative stress tests strongly demonstrated the negative synergistic effects of diclofenac and ondansetron, regarding the observation of dose‐dependent enhancement of malondialdehyde concentration, and reduction of glutathione content, and superoxide dismutase and catalase activity. Histopathological analyses revealed dose‐dependent tubular epithelial cells degeneration, outstanding mononuclear cells infiltration, clear necrosis at the papillary region of kidney, dilation, and vascular hyperemia in mice kidney tissues treated with ondansetron and diclofenac. Conclusively, these findings suggested the possible ondansetron‐diclofenac interaction through the induction of oxidative stress.     

Lactobacillus plantarum CS24.2 prevents Escherichia coli adhesion to HT‐29 cells and also down‐regulates enteropathogen‐induced tumor necrosis factor‐α and interleukin‐8 expression

The aim of the present study was to evaluate the potential of Lactobacillus plantarum CS24.2 to antagonize Escherichia coli adhesion and modulate expression of the responses by HT‐29 cells of inflammatory molecules to E. coli adhesion. Experiments were performed under different adhesion conditions and findings compared with the responses of Lactobacillus rhamnosus GG. Tests of competitive adhesion, adhesion inhibition and displacement assays were performed for lactobacilli (L. rhamnosus GG and L. plantarum CS24.2) and E. coli O26:H11 to HT‐29 cells. Both the lactobacilli significantly reduced E. coli adhesion to HT‐29 cells (P < 0.05). The ability of lactobacilli to modulate tumor necrosis factor‐α and interleukin‐8 expression was analyzed in HT‐29 cells stimulated with E. coli using qRT‐PCR. L. plantarum CS24.2 significantly down regulated expression of both the genes induced by E. coli in HT‐29 cells at 6 hr as well as 24 hr, which was more significant than the corresponding findings for L. rhamnosus GG. The present findings suggest that L. plantarum CS24.2 inhibits pathogen adhesion to a similar extent as does the established probiotic strain L. rhamnosus GG. It may also attenuate tumor necrosis factor‐α and interleukin‐8 expression in HT‐29 cells stimulated with E. coli.     

Construction and performance of heterologous polyketide‐producing K‐12‐ and B‐derived Escherichia coli

Aims: Escherichia coli has emerged as a viable heterologous host for the production of complex, polyketide natural compounds. In this study, polyketide biosynthesis was compared between different E. coli strains for the purpose of better understanding and improving heterologous production. Methods and Results: Both B and K‐12 E. coli strains were genetically modified to support heterologous polyketide biosynthesis [specifically, 6‐deoxyerythronolide B (6dEB)]. Polyketide production was analysed using a helper plasmid designed to overcome rare codon usage within E. coli. Each strain was analysed for recombinant protein production, precursor consumption, by‐product production, and 6dEB biosynthesis. Of the strains tested for biosynthesis, 6dEB production was greatest for E. coli B strains. When comparing biosynthetic improvements as a function of mRNA stability vs codon bias, increased 6dEB titres were observed when additional rare codon tRNA molecules were provided. Conclusions: Escherichia coli B strains and the use of tRNA supplementation led to improved 6dEB polyketide titres. Significance and Impact of the Study: Given the medicinal potential and growing field of polyketide heterologous biosynthesis, the current study provides insight into host‐specific genetic backgrounds and gene expression parameters aiding polyketide production through E. coli.