Effects of acid stress on gene transcription of L.lactis strain G423
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ABSTRACT: Bacteria that live in the acidic environment face number of growth-related challenges from the intracellular pH changes. In order to survive under acidic environment, Lactic acid bacteria must employ multiple genes and proteins to regulate the relative pathways.
Project description:Bacteria that live in the acidic environment face number of growth-related challenges from the intracellular pH changes. In order to survive under acidic environment, Lactic acid bacteria must employ multiple genes and proteins to regulate the relative pathways.
Project description:Acetylation of lysine residues is conserved across organisms and plays important roles in various cellular functions. Maintaining intracellular pH homeostasis is crucial for the survival of enteric bacteria in acidic gastric tract. However, it remains unkown whether bacteria can utilize reversible protein acetylation system to adapt to acidic environment. Here we demonstrate that the protein acetylation/deacetylation is critical for Salmonella Typhimurium to survive in acidic environment. We first used RNA-seq to analyze the transcriptome patterns under acid stress, and found that the transcriptional levels of genes involved in NAD+/NADH metabolism were significantly changed, leading to the increase of intracellular NAD+/NADH ratio. Moreover, acid stress down-regulated the transcriptional level of pat (encoding an acetyltranseferase) and genes encoding adenylate cyclase and cAMP-regulatory protein (CRP) which regulates pat positively. Acid signal also affects TCA cycle to promote the consumption of Ac-CoA, which reduced the donor of acetylation. Lowered acetylation level is not only bacterial’s response to acid stress, but also positively regulates the survival rate of S. Typhimurium. The deletion mutant of pat had more stable intracellular pH, which paralleled with higher survival rate after acid treatment compared with the wild type strain and deletion mutant of cobB. Our data suggest that bacteria can down-regulate protein acetylation level to prevent intracellular pH further falling in acid stress, and this work may provide a new perspective to understand the bacterial acid resistance mechanism. To use RNA-seq to analyze the transcriptome patterns under acid stress
Project description:Acetylation of lysine residues is conserved across organisms and plays important roles in various cellular functions. Maintaining intracellular pH homeostasis is crucial for the survival of enteric bacteria in acidic gastric tract. However, it remains unkown whether bacteria can utilize reversible protein acetylation system to adapt to acidic environment. Here we demonstrate that the protein acetylation/deacetylation is critical for Salmonella Typhimurium to survive in acidic environment. We first used RNA-seq to analyze the transcriptome patterns under acid stress, and found that the transcriptional levels of genes involved in NAD+/NADH metabolism were significantly changed, leading to the increase of intracellular NAD+/NADH ratio. Moreover, acid stress down-regulated the transcriptional level of pat (encoding an acetyltranseferase) and genes encoding adenylate cyclase and cAMP-regulatory protein (CRP) which regulates pat positively. Acid signal also affects TCA cycle to promote the consumption of Ac-CoA, which reduced the donor of acetylation. Lowered acetylation level is not only bacterial’s response to acid stress, but also positively regulates the survival rate of S. Typhimurium. The deletion mutant of pat had more stable intracellular pH, which paralleled with higher survival rate after acid treatment compared with the wild type strain and deletion mutant of cobB. Our data suggest that bacteria can down-regulate protein acetylation level to prevent intracellular pH further falling in acid stress, and this work may provide a new perspective to understand the bacterial acid resistance mechanism.
Project description:Cytokines interact with their receptors in the extracellular space to control immune responses. How the physicochemical properties of the extracellular space influence cytokine signaling is incompletely elucidated. Here, we show that the activity of interleukin (IL)-2, a critical cytokine in T cell immunity, is profoundly affected by pH, limiting IL-2 signaling within the acidic environment of tumors. Generation of lactic acid by tumors limits STAT5 activation, effector differentiation and anti-tumor immunity by CD8+ T cells and renders high-dose IL-2 therapy poorly effective. Directed evolution enabled selection of a pH-selective IL-2 mutein (Switch-2). Switch-2 binds the IL-2 receptor subunit IL-2Ra with higher affinity, triggers STAT5 activation and drives CD8+ T cell effector function more potently at acidic pH than at neutral pH. Consequently, high-dose Switch-2 therapy induces potent immune activation and tumor rejection with reduced on-target toxicity in normal tissues. Finally, we find that sensitivity to pH is a generalizable property of a diverse range of cytokines with broad relevance to immunity and immunotherapy in healthy and diseased tissues.
Project description:Cytokines interact with their receptors in the extracellular space to control immune responses. How the physicochemical properties of the extracellular space influence cytokine signaling is incompletely elucidated. Here, we show that the activity of interleukin (IL)-2, a critical cytokine in T cell immunity, is profoundly affected by pH, limiting IL-2 signaling within the acidic environment of tumors. Generation of lactic acid by tumors limits STAT5 activation, effector differentiation and anti-tumor immunity by CD8+ T cells and renders high-dose IL-2 therapy poorly effective. Directed evolution enabled selection of a pH-selective IL-2 mutein (Switch-2). Switch-2 binds the IL-2 receptor subunit IL-2Ra with higher affinity, triggers STAT5 activation and drives CD8+ T cell effector function more potently at acidic pH than at neutral pH. Consequently, high-dose Switch-2 therapy induces potent immune activation and tumor rejection with reduced on-target toxicity in normal tissues. Finally, we find that sensitivity to pH is a generalizable property of a diverse range of cytokines with broad relevance to immunity and immunotherapy in healthy and diseased tissues.
Project description:Metals at high concentrations can exert toxic effects on microorganisms. It has been widely reported that lowering environmental pH reduces effects of cadmium toxicity in bacteria. Understanding the effects of pH-mediated cadmium toxicity on bacteria would be useful for minimizing cadmium toxicity in the environment and gaining insight into the interactions between organic and inorganic components of life. Growth curve analysis confirmed that cadmium was less toxic to Escherichia coli at pH 5 than at pH 7 in M9 minimal salts medium. To better understand the cellular mechanisms by which lowering pH decreases cadmium toxicity, we used DNA microarrays to characterize global gene expression patterns in E. coli in response to cadmium exposure at moderately acidic (5) and neutral (7) values of pH. Higher expression of several stress response genes including hdeA, otsA, and yjbJ at pH 5 after only 5 minutes was observed and may suggest that acidic pH more rapidly induces genes that confer cadmium resistance. Genes involved in transport were more highly expressed at pH 7 than at pH 5 in the presence of cadmium. Of the genes that showed an interaction between pH and cadmium effects, 46% encoded hypothetical proteins, which may have novel functions involved in mitigating cadmium toxicity.
Project description:Following phagocytosis by macrophages, Mycobacterium tuberculosis (Mtb) senses the intracellular environment and remodels its gene expression for growth in the phagosome. Abramovitch et.al. in this current study identified an Acid and Phagosome Regulated (aprABC) locus that is unique to the Mtb complex and whose gene expression is induced during growth in acidic environments in vitro and in macrophages. The authors propose a model where phoP senses the acidic pH of the phagosome and induces aprABC expression to fine-tune processes unique for intracellular adaptation of Mtb complex bacteria. This study uses microarray analyses to compare transcriptional responses of wild type Mycobacterium tuberculosis (CDC1551) to aprABC locus deletion mutants and the phoP transposon mutant. The bacteria were grown to early log phase in vented T-75 standing flasks containing 12 mL of pH 7.0 7H9 OADC medium. Transcript levels of the wild type bacteria were compared to the following mutants: aprABC null, aprBC null, aprC null, phoP::Tn mutant.
Project description:Oal anaerobic bacteria have to face constant oxidative stress in order to survive in the inflammatory environment of the periodontal pocket. In this study, we analyzed the transcriptome profiles of P. gingivalis and Filifactor in monoculture as compared to P. gingivalis+F.alocis coculture under H2O2 stress condtions, to analyze the genes responsible for enhanced survival of P. gingivalis in presence of F. alocis under oxidative-stress conditions.
Project description:Penicillium citrinum X9-4, which was isolated from infected grapes by our laboratory, produced the highest amount of OTA at pH 5 in culture media, and toxin-production was restrained under acidic environment (pH 3). It revealed the possible mechanism of OTA biosynthesis and metabolic regulation in P. citrinum by transcriptomics, and investigated the reason of OTA biosynthesis was restrained in P. citrinum when cultured under acidic environment.
Project description:Following phagocytosis by macrophages, Mycobacterium tuberculosis (Mtb) senses the intracellular environment and remodels its gene expression for growth in the phagosome. Abramovitch et.al. in this current study identified an Acid and Phagosome Regulated (aprABC) locus that is unique to the Mtb complex and whose gene expression is induced during growth in acidic environments in vitro and in macrophages. The authors propose a model where phoP senses the acidic pH of the phagosome and induces aprABC expression to fine-tune processes unique for intracellular adaptation of Mtb complex bacteria.