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Remodeling of the Streptococcus agalactiae transcriptome in response to growth temperature

ABSTRACT: To understand the extent to which GBS modify gene expression in response to temperatures encountered in the various hosts, we conducted a whole genome transcriptome analysis of organisms grown at 30°C and 40°C. We identified extensive transcriptome remodeling at various stages of growth, especially in the stationary phase (significant transcript changes occurred for 25% of the genes). A large proportion of genes involved in metabolism was up-regulated at 30°C in stationary phase, which reflects a slowing of bacterial metabolism in the early stages of its shift to growth at lower temperature followed by an acceleration in the later stages. Conversely, genes up-regulated at 40°C relative to 30°C include those encoding virulence factors such as hemolysins and extracellular secreted proteins with LPXTG motifs. Over-expression of hemolysins was linked to larger zones of hemolysis and enhanced hemolytic activity at 40°C. A key theme identified by our study was that genes involved in purine metabolism and iron acquisition were significantly up-regulated at 40°C.

ORGANISM(S): Streptococcus agalactiae

PROVIDER: GSE11666 | GEO | 2008/09/01

SECONDARY ACCESSION(S): PRJNA106181

REPOSITORIES: GEO

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Project description:Gene expression profiles of bakerâs yeast during initial dough-fermentation were investigated using liquid fermentation media to obtain insights at the molecular level into rapid adaptation mechanisms of bakerâs yeast. Results showed that onset of fermentation caused drastic changes in gene expression profiles within 15 min. Genes involved in the tricarboxylic acid (TCA) cycle were down-regulated and genes involved in glycolysis were up-regulated, indicating a metabolic shift from respiration to fermentation. Genes involved in ethanol production (PDC genes and ADH1), in glycerol synthesis (GPD1 and HOR2), and in low-affinity hexose transporters (HXT1 and HXT3) were up-regulated at the beginning of model dough-fermentation. Among genes up-regulated at 15 min, several genes classified as transcription were down-regulated within 30 min. These down-regulated genes are involved in messenger RNA splicing and ribosomal protein biogenesis, in zinc finger transcription factor proteins, and in transcriptional regulator (SRB8, MIG1). In contrast, genes involved in amino acid metabolism and in vitamin metabolism, such as arginine biosynthesis, riboflavin biosynthesis, and thiamin biosynthesis, were subsequently up-regulated after 30 min. Interestingly, the genes involved in the unfolded protein response (UPR) pathway were also subsequently up-regulated. Our study presents the first overall description of the transcriptional response of bakerâs yeast during dough-fermentation, and will thus help clarify genomic responses to various stresses during commercial fermentation processes. Experiment Overall Design: Saccharomyces cerevisiae T128 was used as a model of typical commercial bakerâs yeast used in Japan. After 18 h cultivation, cells in stationary phase were collected by centrifugation (2,700 ï g for 5 min). Some of the cell pellets were suspended in 900 ml of sterilized water. Cells for no-fermentation control were harvested after the fed-butch cultivation and stored until RNA extraction. Cell pellets (11,700 OD units) were suspended in 390 ml of lequid fermentation (LF) medium in a 500-ml flask and then fermented for 300 min. To investigate gene expression profiles during initial stages of dough-fermentation, cell samples for DNA microarray analysis were obtained from each culture medium at 15 min, 30 min, and 60 min. Cells in stationary phase were then collected by centrifugation (2,700ï g for 5 min), and stored until RNA extraction.

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Remodeling of the Streptococcus agalactiae transcriptome in response to growth temperature

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