Project description:Autoinducer-2 (AI-2)-mediated quorum sensing has been extensively studied in relation to the regulation of microbial behaviour. There are however two potential roles for the AI-2 synthase (LuxS). The first is in the production of AI-2 and the second is as an enzyme in the activated methyl cycle where it catalyses the conversion of S-ribosylhomocysteine to homocysteine. The by-product of the reaction catalysed by LuxS is (S)-4,5-dihydroxy-2,3-pentanedione (DPD), which spontaneously forms the furanones known collectively as AI-2. The mammalian gastrointestinal tract contains a complex collection of bacterial species so a method of interspecies communication might influence community structure and function. Lactobacillus reuteri 100-23 is an autochthonous inhabitant of the rodent forestomach where it adheres to the non-secretory epithelium of the forestomach forming a biofilm. Microarray comparisons of gene expression profiles of the L. reuteri 100-23 wild type and a luxS mutant under different culture conditions revealed altered transcription of genes encoding proteins involved in cysteine biosynthesis, the oxidative stress response and cell wall proteins. Metabolomic analysis revealed that the luxS mutation affected cellular levels of fermentation products, fatty acids and amino acids. Cell density-dependent changes (log phase versus stationary phase growth) in gene transcription were not detected. Overall, the results indicated that AI-2 was unlikely to be involved in gene regulation in L. reuteri 100-23 in a classical quorum-sensing type manner. Analysis of the microarray data was obtained from two or more independent biological replicates.
Project description:Lactobacillus reuteri 100-23 is an autochthonous inhabitant of the rodent gastrointestinal system that adheres to the non-secretory epithelium of the forestomach and forms biofilms. Microarray analysis of the expression profile of L. reuteri 100-23 cells harvested from the stomach of ex-Lactobacillus-free mice, compared to those of L. reuteri 100-23 in laboratory culture, revealed an in vivo upregulation of a urease gene cluster by greater than 50-fold. Genes for urease production were absent in all publically available Lactobacillus genome sequences except L. reuteri 100-23 and have recently been identified as specific to rodent strains of L. reuteri (Frese et al. 2011). In the current study, the urease enzyme was shown to be functional. Supplementation with 2% urea allowed L. reuteri 100-23 to increase the pH of the culture medium. A mutant strain of L. reuteri 100-23 was developed by insertional inactivation of the ureC gene, which encodes the largest subunit of the urease enzyme. The mutant strain was unable to hydrolyze urea to increase the pH of culture medium, and did not survive acid stress at pH 2.5 for 6 h, even in the presence of urea. In contrast, the wild type strain was still viable after 6 h when 2% urea supplementation was included. When mice free of lactobacilli were inoculated with a mixture of equal numbers of wild type L. reuteri 100-23 and ureC mutant cells, the wild type constituted 99% of the resulting Lactobacillus population in the stomach, caecum and jejunum after one week (108 cells/gram of sample). This study has therefore shown the importance of a functional urease enzyme in the ecological fitness of L. reuteri 100-23.
Project description:Autoinducer-2 (AI-2)-mediated quorum sensing has been extensively studied in relation to the regulation of microbial behaviour. There are however two potential roles for the AI-2 synthase (LuxS). The first is in the production of AI-2 and the second is as an enzyme in the activated methyl cycle where it catalyses the conversion of S-ribosylhomocysteine to homocysteine. The by-product of the reaction catalysed by LuxS is (S)-4,5-dihydroxy-2,3-pentanedione (DPD), which spontaneously forms the furanones known collectively as AI-2. The mammalian gastrointestinal tract contains a complex collection of bacterial species so a method of interspecies communication might influence community structure and function. Lactobacillus reuteri 100-23 is an autochthonous inhabitant of the rodent forestomach where it adheres to the non-secretory epithelium of the forestomach forming a biofilm. Microarray comparisons of gene expression profiles of the L. reuteri 100-23 wild type and a luxS mutant under different culture conditions revealed altered transcription of genes encoding proteins involved in cysteine biosynthesis, the oxidative stress response and cell wall proteins. Metabolomic analysis revealed that the luxS mutation affected cellular levels of fermentation products, fatty acids and amino acids. Cell density-dependent changes (log phase versus stationary phase growth) in gene transcription were not detected. Overall, the results indicated that AI-2 was unlikely to be involved in gene regulation in L. reuteri 100-23 in a classical quorum-sensing type manner.
Project description:Lactobacillus reuteri 100-23 is an autochthonous inhabitant of the rodent gastrointestinal system that adheres to the non-secretory epithelium of the forestomach and forms biofilms. Microarray analysis of the expression profile of L. reuteri 100-23 cells harvested from the stomach of ex-Lactobacillus-free mice, compared to those of L. reuteri 100-23 in laboratory culture, revealed an in vivo upregulation of a urease gene cluster by greater than 50-fold. Genes for urease production were absent in all publically available Lactobacillus genome sequences except L. reuteri 100-23 and have recently been identified as specific to rodent strains of L. reuteri (Frese et al. 2011). In the current study, the urease enzyme was shown to be functional. Supplementation with 2% urea allowed L. reuteri 100-23 to increase the pH of the culture medium. A mutant strain of L. reuteri 100-23 was developed by insertional inactivation of the ureC gene, which encodes the largest subunit of the urease enzyme. The mutant strain was unable to hydrolyze urea to increase the pH of culture medium, and did not survive acid stress at pH 2.5 for 6 h, even in the presence of urea. In contrast, the wild type strain was still viable after 6 h when 2% urea supplementation was included. When mice free of lactobacilli were inoculated with a mixture of equal numbers of wild type L. reuteri 100-23 and ureC mutant cells, the wild type constituted 99% of the resulting Lactobacillus population in the stomach, caecum and jejunum after one week (108 cells/gram of sample). This study has therefore shown the importance of a functional urease enzyme in the ecological fitness of L. reuteri 100-23. Analysis of the microarray data was obtained from two independent biological replicates.
Project description:Comparison of gene expression between L. reuteri ATCC PTA 6475 and PocR mutant grown in semi-defined medium after 24h of growth at 37C in anaerobic condition
Project description:Transcriptional profiling of Lactobacillus reuteri ATCC 55730 mid-log cultures before vs after exposure to 0.5% bovine bile (oxgall). Two sets of array experiments were performed. One set compared the expression profiles of L. reuteri ATCC 55730 cells before bile exposure vs cells that had been exposed to 0.5% bile for 15 minutes (bile shock). The other set compared the expression profiles of L. reuteri ATCC 55730 cells before bile exposure vs cells that had begun growing again in the presence of 0.5% bile (bile adaptation). Keywords: Stress response
Project description:This SuperSeries is composed of the following subset Series: GSE24415: Comparison of gene expression of L. reuteri ATCC PTA 6475 at different growth phase in a LDMIII GSE24570: Comparison of gene expression of L. reuteri ATCC 55730 at different growth phase in LDMIII medium Refer to individual Series
Project description:Comparison of gene expression between L. reuteri DSM 17938 and L. reuteri DSM 17938::pocR mutant grown in semi-defined medium after 24h of growth at 37C in anaerobic condition. PocR is an AraC-like transcriptional regulator, and changes in gene expression between mutant and wild-type strains would indicate genes involved in the PocR regulon.
Project description:This SuperSeries is composed of the following subset Series: GSE11860: The impact of glycerol on the metabolism of Lactobacillus reuteri - Exploratory experiment GSE11861: The impact of glycerol on the metabolism of Lactobacillus reuteri - Main experiment Refer to individual Series