Project description:In this study, we investigated the transcriptional response of the human isolate L. reuteri ATCC 55730 during sourdough fermentation by using whole-genome microarrays. Significant changes of mRNA levels were found for 101 genes involved in diverse cellular processes, e.g., carbohydrate and energy metabolism, cell envelope biosynthesis, exopolysaccharide production, stress responses, signal transduction and cobalamin biosynthesis. Our results evidence extensive changes of the organism’s gene expression to the growth in sourdough as compared to the growth in chemically defined medium, and thus allowed us to uncover pathways involved in the adaptation of L. reuteri to the ecological niche of sourdough. An impact of several genes of L. reuteri for effective growth in sourdough was shown by implementation of mutant strains in sourdough fermentation. This study contributes to the understanding of the molecular fundamentals of L. reuteri’s ecological competitiveness, and provides a basis for further exploration of genetic traits involved in adaptation to the food and/or intestinal environment. Keywords: environment-specific gene expression, sourdough fermentation, chemically defined medium, dye swap
Project description:Lactic acid bacteria (LAB) are of industrial importance in the production of fermented foods, among which sourdough-derived products. Despite their limited metabolic capacity LAB contribute considerably to important characteristics of fermented foods, among which extended shelf-life, microbial safety, improved texture, and enhanced organoleptic properties. Thanks to the considerable amount of LAB genomic information that became available during the last years, transcriptome, and by extension meta-transcriptome studies, are the exquisite research approaches to study whole ecosystem gene expression into more detail. In this study, microarray analyses were performed using RNA sampled during four 10-day spontaneous sourdough fermentations carried out in the laboratory, namely two wheat and two spelt fermentations with daily back-slopping. Hereto, the in-house developed functional gene LAB microarray was used, representing 406 genes that play a key role in sugar and nitrogen metabolism, functional metabolite production, stress responses and health and safety characteristics. The results reveal the activation of different key metabolic pathways, the ability to use different energy sources, and successful acid and oxidative stress responses. Also, a new algorithm was developed to compute a net expression profile for each of the represented genes, thereby exceeding the species level. The labeled aRNA of the sourdough fermentation samples was hybridized using a loop design, i.e. subsequent samples (e.g. 27 h and 51 h, 51 h and 75 h etc.) were hybridized together on the microarray and the loop was closed by hybridizing the last sample with the first.
Project description:Lactic acid bacteria (LAB) are of industrial importance in the production of fermented foods, among which sourdough-derived products. Despite their limited metabolic capacity LAB contribute considerably to important characteristics of fermented foods, among which extended shelf-life, microbial safety, improved texture, and enhanced organoleptic properties. Thanks to the considerable amount of LAB genomic information that became available during the last years, transcriptome, and by extension meta-transcriptome studies, are the exquisite research approaches to study whole ecosystem gene expression into more detail. In this study, microarray analyses were performed using RNA sampled during four 10-day spontaneous sourdough fermentations carried out in the laboratory, namely two wheat and two spelt fermentations with daily back-slopping. Hereto, the in-house developed functional gene LAB microarray was used, representing 406 genes that play a key role in sugar and nitrogen metabolism, functional metabolite production, stress responses and health and safety characteristics. The results reveal the activation of different key metabolic pathways, the ability to use different energy sources, and successful acid and oxidative stress responses. Also, a new algorithm was developed to compute a net expression profile for each of the represented genes, thereby exceeding the species level. The labeled aRNA of the sourdough fermentation samples was hybridized using a loop design, i.e. subsequent samples (e.g. 27 h and 51 h, 51 h and 75 h etc.) were hybridized together on the microarray and the loop was closed by hybridizing the last sample with the first.
Project description:This SuperSeries is composed of the following subset Series: GSE15686: Meta-transcriptome analysis of a natural wheat sourdough ecosystem during a 10-day spontaneous laboratory fermentation (I) GSE15691: Meta-transcriptome analysis of a natural spelt sourdough ecosystem during a 10-day spontaneous laboratory fermentation (I) GSE15692: Meta-transcriptome analysis of a natural spelt sourdough ecosystem during a 10-day spontaneous laboratory fermentation (II) GSE15693: Meta-transcriptome analysis of a natural wheat sourdough ecosystem during a 10-day spontaneous laboratory fermentation (II) Refer to individual Series
Project description:The microbial community and enzymes in fermented rice using defined microbial starter, containing Rhizopus oryzae, Saccharomycopsis fibuligera, Saccharomyces cerevisiae and Pediococcus pentosaceus, play an important role in quality of the fermented rice product and its biological activities including melanogenesis inhibitory activity. The microbial metaproteome revealed large-scale proteins expressed by the microbial community to better understand the role of microbiota in the fermented rice.