Project description:Alkali stress is an important means of inactivating undesirable pathogens in a wide range of situations, ranging from environmental cleaning of food processing environments, to the phagolysosomal killing of cells engulfed by mammalian phagocytes. Unfortunately, L. monocytogenes can launch an alkaline tolerance response (AlTR), significantly increasing persistence of the pathogen in such environments. This study compared the transcriptome patterns of alkali stressed and non alkali stressed L. monocytogenes 10403S cells, to elucidate the mechanisms by which this important pathogen adapts and/or grows during short or long-term alkali stress. Transcription profiles associated with alkali shock (AS) responses were obtained by DNA microarray analysis of mid-exponential cells suspended in pH 9 media for 15, 30 or 60 min. Transcription profiles associated with alkali adaptation (AA) were obtained by DNA microarray analysis of cells grown to mid-exponential phase in pH 9 media . Comparison of AS and AA transcription profiles with profiles from control (pH 7.0) cells identified over 2,000 genes that were differentially expressed under alkaline conditions. Rapid (15min) changes in expression included upregulation of genes encoding for multiple metabolic pathways, (including those associated with Na+/H+ antiporters), ABC transporters of functional compatible solutes such as carnitine, motility and virulence-associated genes as well as the σB controlled stress resistance network. Slower (30min and more) responses to AS and adaptation during growth in alkaline conditions (AA), included modest changes in mRNA concentrations, and genes involved in proton export. Keywords: Time course study of gene expression response to alkaline shock and adaptation
