Project description:Background: Lactobacillus plantarum is found in a variety of fermented foods and as such, consumed for centuries. Some strains are natural inhabitants of the human gastro-intestinal tract and like other Lactobacillus species, L. plantarum has been extensively studied for its immunomodulatory properties and its putative health-promoting effects (probiotic). Being the first line of host defense intestinal epithelial cells (IEC) are key players in the recognition and initiation of responses to gut microorganisms. Results: Using high-density oligonucleotide microarrays we examined the gene expression profiles of differentiated Caco-2 cells exposed to various doses of L. plantarum. In addition, the effects were correlated to monolayer permeability studies and measurement of lactic acid production. A transcriptional dose-dependent IEC response to L. plantarum was found. Incubation of Caco-2 with a low bacterial dose induced a specific response, not due to cytotoxicity or production of lactic acid, including modulation of cell cycle and cell signaling functions. Exposure of Caco-2 cells to larger amounts of bacteria, accompanied by the production of lactic acid and glucose depletion, provoked increased permeability and supposed non-specific defense responses. Conclusions: These results suggest that IEC are able to sense and react to the presence of gut bacteria. This study provides the first description of global transcriptional response of human IEC to a commensal lactic acid bacterium, and it shows the importance of choosing physiological bacterial doses to prevent the observation of non-specific host reactions. Caco-2 cells were exposed for 10h to Lactobacillus. Fourteen samples are analyzed: 4 control Caco-2, 4 Caco-2 exposed to a low dose (10) of Lactobacillus, 4 Caco-2 exposed to a medium dose (100) of Lactobacillus, 2 Caco-2 exposed to a high dose (1000) of Lactobacillus. All 14 RNA samples are labeled with Cy5 and hybridized to a common reference (undifferentiated Caco-2, untreated) RNA labeled with Cy3

Project description:Lactobacillus plantarum is a common inhabitant of mammalian gastrointestinal tracts and specific strains belonging to this species are marketed as probiotics intended to confer beneficial health effects. To assist in determining the physiological status and host-microbe interactions of L. plantarum in the digestive tract we assessed changes in the transcriptome of L. plantarum WCFS1 during colonization of the cecum of germ-free mice. According to the transcript profiles L. plantarum WCFS1 was metabolically active and not under severe stress in this intestinal compartment. Carbohydrate metabolism was the most strongly affected functional gene category whereby many genes encoding diverse sugar transport and degradation pathways were induced in mice even compared to L. plantarum grown in a mouse chow-derived laboratory medium. This suggests that the ability of L. plantarum WCFS1 to consume diverse energy sources including plant-associated and host-derived carbohydrates was increased during its residence in the digestive tract. Many of these genes were also induced in L. plantarum colonizing germ-free mice fed a humanized Western-style diet. Similarly a core set of genes encoding cell surface-related properties were differentially expressed in mice. This set includes genes required for the D-alanylation and glycosylation of lipoteichoic acids that were strongly down-regulated in mice. In total L. plantarum exhibits a distinct in vivo transcriptome directed towards adaptation to the mouse intestinal environment. Keywords: cell type comparison Six-week old germ-free C57 Black-6 male mice were inoculated with a single dose of 109 CFU of exponential-phase L. plantarum WCFS1 cells. The mice were sacrificed 15 days later, after sufficient time had passed for several turnovers of the intestinal epithelium and its overlying mucosal layer. Four mice were fed on Chow diet and two mice were fed on western style diet. RNA was isolated from the cecum of these mice. The transcriptome of L. plantarum in these mice was compared to that of L. plantarum grown on MRS broth, Chow broth, or on chemically defined media with either glucose or lactose as carbon- and energy source.

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