Project description:The global transcriptome of the wild type Lactobacillus acidophilus NCFM strain (NCK56) was measured during exponential growth on 11 prebiotic carbohydrates and glucose to identify the specific gene cluster differentially upregulated in response to each carbohydrate.
Project description:We used a whole genome array containing 97.4 % of the annotated genes of Lactobacillus acidophilus NCFM, a probiotic culture that belongs to the lactic acid bacteria group, to identify genes that are differentially expressed under several stress conditions. Keywords: Stress response
Project description:Lactic acid bacteria have been used as starter strains in the production of fermented dairy products for centuries. Lactobacillus acidophilus is a widely recognized probiotic bacteria commonly added to yogurt and used in dietary supplements. In this study, a whole genome microarray was employed to monitor gene expression of L. acidophilus cells propagated in 11% skim milk (SM) during early, mid and late logarithmic phase, and stationary phase. Approximately 21% of 1,864 ORFs were differentially expressed at least in one time point. Genes differentially expressed in SM included several members of the proteolytic enzyme system. Expression of prtP (proteinase precursor) and prtM (maturase) increased over time as well as several peptidases and transport systems. Expression of Opp1 (oligopeptide transport system 1) was highest at 4h, while gene expression of Opp2 increased over time reaching its highest level at 12h, suggesting that the two systems have different specificities. Expression of a two-component regulatory system (2CRS), previously shown to regulate acid tolerance and proteolytic activity, also increased during the early log and early stationary phases of growth. Expression of the genes involved in lactose utilization increased immediately (5 min) upon exposure to milk. The acidification activity, survival under storage conditions, and adhesion to mucin and Caco-2 tissue culture cells of selected mutants containing insertionally inactivated genes differentially expressed in the wild-type strain during growth in milk were examined for any potential links between probiotic properties and bacterial growth and survival in milk. Some of the most interesting genes found to be expressed in milk were correlated with signaling (AI-2) and adherence to mucin and intestinal epithelial cells, in vitro.
Project description:This study reports an over 20-fold increase in the adhesive ability of Lactobacillus acidophilus NCFM to Caco-2 cells following a 1 hour incubation of cells that were concentrated ten-fold, immediately prior to adhesion. Microarray analysis of the global transcriptional response with and without exposure to the adhesion adaptive conditions revealed several genes potentially involved with adhesion to the intestinal epithelial cells and a classic stress response. Interestingly, putative genes linked to the synthesis of an interspecies signaling molecule, autoinducer-2 (AI-2), were overexpressed. Examination of the L. acidophilus NCFM genome revealed the complete pathway for AI-2 synthesis. AI-2 activity was detected in L. acidophilus NCFM during stationary growth phase using the Vibrio harveyi BB170 assay system. Using site-specific integration, an isogenic mutation was created in luxS and the resulting derivative of L. acidophilus NCFM did not produce AI-2. A 58 % decrease in adherence to Caco-2 cells was also observed by the LuxS- mutant when the cells were used for adhesion directly from logarithmic phase cultures. However, the LuxS- mutant strain still responded to adhesion adaptive conditions with significantly increased adherence indicating that additional factors contribute to the amplified adhesion response. Keywords: Culture response to specific environmental conditions
Project description:Metabolomic and lipidomic profiling of Lactobacillus acidophilus and Lactobacillus gasseri to identify unique differences in their biochemistry that could potentially influence their ability to serve as probiotic agents for oxalate diseases.
Project description:Lactobacillus helveticus is a rod-shaped lactic acid bacterium that is widely used in the manufacture of fermented dairy foods and for production of bioactive peptides from milk proteins. Although L. helveticus is commonly associated with milk environments, phylogenetic studies show it is closely related to an intestinal species, Lactobacillus acidophilus, which has been shown to impart probiotic health benefits to humans. This relationship has fueled a prevailing hypothesis that L. helveticus is a highly specialized derivative of L. acidophilus which has adapted to acidified whey. However, L. helveticus has also been sporadically recovered from non-dairy environments, which argues the species may not be as highly specialized as is widely believed. This study employed genome sequence analysis and comparative genome hybridizations to investigate genomic diversity among L. helveticus strains collected from cheese, whey, and whiskey malt, as well as commercial cultures used in manufacture of cheese or bioactive dairy foods. Results revealed considerable variability in gene content between some L. helveticus strains, and indicated the species should not be viewed as a strict dairy-niche specialist. In addition, comparative genomic analyses provided new insight on several industrially and ecologically important attributes of L. helveticus that may facilitate commercial strain selection.