scholarly journals Weak acid and alkali stress regulate phosphatidylinositol bisphosphate synthesis in Saccharomyces cerevisiae

2006 ◽  
Vol 395 (1) ◽  
pp. 73-80 ◽  
Author(s):  
Mehdi Mollapour ◽  
John P. Phelan ◽  
Stefan H. Millson ◽  
Peter W. Piper ◽  
Frank T. Cooke
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Stress Responses ◽  
Acid Stress ◽  
Weak Acid ◽  
Weak Acids ◽  
Extracellular Medium ◽  
Food Preservatives ◽  
Active Efflux ◽  
Signalling Molecules ◽  
Spoilage Yeasts

Weak organic acids are used as food preservatives to inhibit the growth of spoilage yeasts, including Saccharomyces cerevisiae. Long-term adaptation to weak acids requires the increased expression of the ATP-binding cassette transporter Pdr12p, which catalyses the active efflux of the weak acids from the cytosol; however, very little is known about the signalling events immediately following application of weak acid stress. We have investigated the effects of weak acids on two stress-responsive signalling molecules, PtdIns(3,5)P2 and PtdIns(4,5)P2, which in S. cerevisiae are synthesized by Fab1p and Mss4p respectively. At low extracellular pH, benzoic acid, sorbic acid and acetic acid all cause a transient reduction in PtdIns(3,5)P2 accumulation and a more persistent rise in PtdIns(4,5)P2 levels. The increase in PtdIns(4,5)P2 levels is accompanied by a reorganization of the actin cytoskeleton. However, changes in PtdInsP2 levels are independent of weak acid-induced Pdr12p expression. In contrast, changing the extracellular medium to alkaline pH provokes a prolonged and substantial rise in PtdIns(3,5)P2 levels. As PtdIns(3,5)P2 synthesis is required for correct vacuole acidification, it is possible that levels of this molecule are modulated to maintain intracellular pH homoeostasis in response to weak acid and alkali stresses. In conclusion, we have expanded the repertoire of stress responses that affect PtdInsP2 levels to include weak acid and alkali stresses.

scholarly journals The SPI1 Gene, Encoding a Glycosylphosphatidylinositol-Anchored Cell Wall Protein, Plays a Prominent Role in the Development of Yeast Resistance to Lipophilic Weak-Acid Food Preservatives

2006 ◽  
Vol 72 (11) ◽  
pp. 7168-7175 ◽  
Author(s):  
T. Simões ◽  
N. P. Mira ◽  
A. R. Fernandes ◽  
Isabel Sá-Correia
Keyword(s):  
Cell Wall ◽  
Transcription Factor ◽  
Acetic Acid ◽  
Benzoic Acid ◽  
Acid Stress ◽  
Weak Acid ◽  
Cell Wall Protein ◽  
Weak Acids ◽  
Food Preservatives ◽  
Cell Wall Porosity

ABSTRACT The Saccharomyces cerevisiae SPI1 gene encodes a member of the glycosylphosphatidylinositol-anchored cell wall protein family. In this work we show results indicating that SPI1 expression protects the yeast cell from damage caused by weak acids used as food preservatives. This is documented by a less extended period of adaptation to growth in their presence and by a less inhibited specific growth rate for a parental strain compared with a mutant with SPI1 deleted. Maximal protection exerted by Spi1p against equivalent concentrations of the various weak acids tested was registered for the more lipophilic acids (octanoic acid, followed by benzoic acid) and was minimal for acetic acid. Weak-acid adaptation was found to involve the rapid activation of SPI1 transcription, which is dependent on the presence of the Msn2p transcription factor. Activation of SPI1 transcription upon acetic acid stress also requires Haa1p, whereas this recently described transcription factor has a negligible role in the adaptive response to benzoic acid. The expression of SPI1 was found to play a prominent role in the development of yeast resistance to 1,3-β-glucanase in benzoic acid-stressed cells, while its involvement in acetic acid-induced resistance to the cell wall-lytic enzyme is slighter. The results are consistent with the notion that Spi1p expression upon weak-acid stress leads to cell wall remodeling, especially for the more lipophilic acids, decreasing cell wall porosity. Decreased cell wall porosity, in turn, reduces access to the plasma membrane, reducing membrane damage, intracellular acidification, and viability loss.

Plasma membrane H+ and K+ transporters are involved in the weak-acid preservative response of disparate food spoilage yeasts

Microbiology ◽  
2005 ◽  
Vol 151 (6) ◽  
pp. 1995-2003 ◽  
Author(s):  
Neil Macpherson ◽  
Lana Shabala ◽  
Henrietta Rooney ◽  
Marcus G. Jarman ◽  
Julia M. Davies
Keyword(s):  
Plasma Membrane ◽  
Benzoic Acid ◽  
Acid Stress ◽  
Weak Acid ◽  
Uptake System ◽  
Food Spoilage ◽  
Adaptive Responses ◽  
Spoilage Yeasts ◽  
Food Spoilage Yeasts

The food spoilage yeasts Zygosaccharomyces bailii and Saccharomyces cerevisiae have been proposed to resist weak-acid preservative stress by different means; Z. bailii by limiting influx of preservative combined with its catabolism, S. cerevisiae by active extrusion of the preservative weak-acid anion and H+. Measurement of H+ extrusion by exponential-phase Z. bailii cells suggest that, in common with S. cerevisiae, this yeast uses a plasma membrane H+-ATPase to expel H+ when challenged by weak-acid preservative (benzoic acid). Simultaneous measurement of Z. bailii net H+ and K+ fluxes showed that net K+ influx accompanies net H+ efflux during acute benzoic acid stress. Such ionic coupling is known for S. cerevisiae in short-term preservative stress. Both yeasts significantly accumulated K+ on long-term exposure to benzoic acid. Analysis of S. cerevisiae K+ transporter mutants revealed that loss of the high affinity K+ uptake system Trk1 confers sensitivity to growth in preservative. The results suggest that cation accumulation is an important factor in adaptation to weak-acid preservatives by spoilage yeasts and that Z. bailii and S. cerevisiae share hitherto unsuspected adaptive responses at the level of plasma membrane ion transport.

scholarly journals Editing of misaminoacylated tRNA controls the sensitivity of amino acid stress responses in Saccharomyces cerevisiae

2017 ◽  
Vol 45 (7) ◽  
pp. 3985-3996 ◽  
Author(s):  
Kyle Mohler ◽  
Rebecca Mann ◽  
Tammy J. Bullwinkle ◽  
Kyle Hopkins ◽  
Lin Hwang ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Amino Acid ◽  
Stress Responses ◽  
Acid Stress

scholarly journals Quantitative Analysis of the Modes of Growth Inhibition by Weak Organic Acids in Saccharomyces cerevisiae

2012 ◽  
Vol 78 (23) ◽  
pp. 8377-8387 ◽  
Author(s):  
Azmat Ullah ◽  
Rick Orij ◽  
Stanley Brul ◽  
Gertien J. Smits
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Organic Acids ◽  
Growth Inhibition ◽  
Organic Anion ◽  
Acid Stress ◽  
Yeast Cells ◽  
Plasma Membrane Atpase ◽  
Weak Acids ◽  
Content Type ◽  
Weak Organic Acids

ABSTRACTWeak organic acids are naturally occurring compounds that are commercially used as preservatives in the food and beverage industries. They extend the shelf life of food products by inhibiting microbial growth. There are a number of theories that explain the antifungal properties of these weak acids, but the exact mechanism is still unknown. We set out to quantitatively determine the contributions of various mechanisms of antifungal activity of these weak acids, as well as the mechanisms that yeast uses to counteract their effects. We analyzed the effects of four weak organic acids differing in lipophilicity (sorbic, benzoic, propionic, and acetic acids) on growth and intracellular pH (pHi) inSaccharomyces cerevisiae. Although lipophilicity of the acids correlated with the rate of acidification of the cytosol, our data confirmed that not initial acidification, but rather the cell's ability to restore pHi, was a determinant for growth inhibition. This pHirecovery in turn depended on the nature of the organic anion. We identified long-term acidification as the major cause of growth inhibition under acetic acid stress. Restoration of pHi, and consequently growth rate, in the presence of this weak acid required the full activity of the plasma membrane ATPase Pma1p. Surprisingly, the proposed anion export pump Pdr12p was shown to play an important role in the ability of yeast cells to restore the pHiupon lipophilic (sorbic and benzoic) acid stress, probably through a charge interaction of anion and proton transport.

scholarly journals Intracellular pH Response to Weak Acid Stress in Individual Vegetative Bacillus subtilis Cells

2016 ◽  
Vol 82 (21) ◽  
pp. 6463-6471 ◽  
Author(s):  
Rachna Pandey ◽  
Norbert O. E. Vischer ◽  
Jan P. P. M. Smelt ◽  
Johan W. A. van Beilen ◽  
Alexander Ter Beek ◽  
...  
Keyword(s):  
Organic Acid ◽  
Single Cell ◽  
Acid Stress ◽  
Weak Acid ◽  
Food Preservation ◽  
Cell Level ◽  
Food Preservatives ◽  
Content Type ◽  
Weak Organic Acid ◽  
Weak Acid Stress

ABSTRACTIntracellular pH (pHi) critically affects bacterial cell physiology. Hence, a variety of food preservation strategies are aimed at perturbing pHihomeostasis. Unfortunately, accurate pHiquantification with existing methods is suboptimal, since measurements are averages across populations of cells, not taking into account interindividual heterogeneity. Yet, physiological heterogeneity in isogenic populations is well known to be responsible for differences in growth and division kinetics of cells in response to external stressors. To assess in this context the behavior of intracellular acidity, we have developed a robust method to quantify pHiat single-cell levels inBacillus subtilis. Bacilli spoil food, cause disease, and are well known for their ability to form highly stress-resistant spores. Using an improved version of the genetically encoded ratiometric pHluorin (IpHluorin), we have quantified pHiin individualB. subtiliscells, cultured at an external pH of 6.4, in the absence or presence of weak acid stresses. In the presence of 3 mM potassium sorbate, a decrease in pHiand an increase in the generation time of growing cells were observed. Similar effects were observed when cells were stressed with 25 mM potassium acetate. Time-resolved analysis of individual bacteria in growing colonies shows that after a transient pH decrease, long-term pH evolution is highly cell dependent. The heterogeneity at the single-cell level shows the existence of subpopulations that might be more resistant and contribute to population survival. Our approach contributes to an understanding of pHiregulation in individual bacteria and may help scrutinizing effects of existing and novel food preservation strategies.IMPORTANCEThis study shows how the physiological response to commonly used weak organic acid food preservatives, such as sorbic and acetic acids, can be measured at the single-cell level. These data are key to coupling often-observed single-cell heterogeneous growth behavior upon the addition of weak organic acid food preservatives. Generally, these data are gathered in the form of plate counting of samples incubated with the acids. Here, we visualize the underlying heterogeneity in cellular pH homeostasis, opening up avenues for mechanistic analyses of the heterogeneity in the weak acid stress response. Thus, microbial risk assessment can become more robust, widening the scope of use of these well-known weak organic acid food preservatives.

scholarly journals Weak Acid Resistance A (WarA), a Novel Transcription Factor Required for Regulation of Weak-Acid Resistance and Spore-Spore Heterogeneity in Aspergillus niger

mSphere ◽  
2020 ◽  
Vol 5 (1) ◽  
Author(s):  
Ivey A. Geoghegan ◽  
Malcolm Stratford ◽  
Mike Bromley ◽  
David B. Archer ◽  
Simon V. Avery
Keyword(s):  
Transcription Factor ◽  
Aspergillus Niger ◽  
Sorbic Acid ◽  
Acid Resistance ◽  
Resistance Mechanisms ◽  
Weak Acid ◽  
Benzoic Acids ◽  
Weak Acids ◽  
Food Preservatives ◽  
Content Type

ABSTRACT Propionic, sorbic, and benzoic acids are organic weak acids that are widely used as food preservatives, where they play a critical role in preventing microbial growth. In this study, we uncovered new mechanisms of weak-acid resistance in molds. By screening a library of 401 transcription factor deletion strains in Aspergillus fumigatus for sorbic acid hypersensitivity, a previously uncharacterized transcription factor was identified and named weak acid resistance A (WarA). The orthologous gene in the spoilage mold Aspergillus niger was identified and deleted. WarA was required for resistance to a range of weak acids, including sorbic, propionic, and benzoic acids. A transcriptomic analysis was performed to characterize genes regulated by WarA during sorbic acid treatment in A. niger. Several genes were significantly upregulated in the wild type compared with a ΔwarA mutant, including genes encoding putative weak-acid detoxification enzymes and transporter proteins. Among these was An14g03570, a putative ABC-type transporter which we found to be required for weak-acid resistance in A. niger. We also show that An14g03570 is a functional homologue of the Saccharomyces cerevisiae protein Pdr12p and we therefore name it PdrA. Last, resistance to sorbic acid was found to be highly heterogeneous within genetically uniform populations of ungerminated A. niger conidia, and we demonstrate that pdrA is a determinant of this heteroresistance. This study has identified novel mechanisms of weak-acid resistance in A. niger which could help inform and improve future food spoilage prevention strategies. IMPORTANCE Weak acids are widely used as food preservatives, as they are very effective at preventing the growth of most species of bacteria and fungi. However, some species of molds can survive and grow in the concentrations of weak acid employed in food and drink products, thereby causing spoilage with resultant risks for food security and health. Current knowledge of weak-acid resistance mechanisms in these fungi is limited, especially in comparison to that in yeasts. We characterized gene functions in the spoilage mold species Aspergillus niger which are important for survival and growth in the presence of weak-acid preservatives. Such identification of weak-acid resistance mechanisms in spoilage molds will help in the design of new strategies to reduce food spoilage in the future.

scholarly journals Weak Acid Resistance A (WarA), a novel transcription factor required for regulation of weak-acid resistance and spore-spore heterogeneity in Aspergillus niger

2019 ◽  
Author(s):  
Ivey A. Geoghegan ◽  
Malcolm Stratford ◽  
Mike Bromley ◽  
David B. Archer ◽  
Simon V. Avery
Keyword(s):  
Transcription Factor ◽  
Aspergillus Niger ◽  
Sorbic Acid ◽  
Acid Resistance ◽  
Resistance Mechanisms ◽  
Weak Acid ◽  
Benzoic Acids ◽  
Food Spoilage ◽  
Weak Acids ◽  
Food Preservatives

ABSTRACTPropionic, sorbic and benzoic acids are organic weak acids that are widely used as food preservatives, where they play a critical role in preventing microbial growth. In this study, we uncovered new mechanisms of weak acid resistance in moulds. By screening a library of 401 transcription-factor deletion strains in Aspergillus fumigatus for sorbic acid hypersensitivity, a previously uncharacterised transcription factor was identified, and named as WarA (Weak Acid Resistance A). The orthologous gene in the spoilage mould Aspergillus niger was identified and deleted. WarA was required for resistance to a range of weak acids, including sorbic, propionic and benzoic acids. A transcriptomic analysis was performed to characterise genes regulated by WarA during sorbic acid treatment in A. niger. Several genes were significantly upregulated in the wild type compared with a ΔwarA mutant, including genes encoding putative weak acid detoxification enzymes and transporter proteins. Among these was An14g03570, a putative ABC-type transporter which we found to be required for weak acid resistance in A. niger. We also show that An14g03570 is a functional homologue of the Saccharomyces cerevisiae protein Pdr12p, and therefore named as PdrA. Lastly, resistance to sorbic acid was found to be highly heterogeneous within genetically-uniform populations of ungerminated A. niger conidia, and we demonstrate that pdrA is a determinant of this heteroresistance. This study has identified novel mechanisms of weak acid resistance in A. niger which could help to inform and improve future food spoilage prevention strategies.IMPORTANCEWeak acids are widely used as food preservatives, as they are very effective at preventing growth of most species of bacteria and fungi. However, some species of moulds can survive and grow in the concentrations of weak acid employed in food and drink products, thereby causing spoilage with resultant risks for food security and health. Current knowledge of weak acid resistance mechanisms in these fungi is limited, especially in comparison to that in yeasts. We characterised gene functions in the spoilage mould species Aspergillus niger which are important for survival and growth in the presence of weak acid preservatives. Such identification of weak acid resistance mechanisms in spoilage moulds will help to design new strategies to reduce food spoilage in the future.

scholarly journals Casein Kinase I Isoform Hrr25 Is a Negative Regulator of Haa1 in the Weak Acid Stress Response Pathway in Saccharomyces cerevisiae

2017 ◽  
Vol 83 (13) ◽  
Author(s):  
Morgan E. Collins ◽  
Joshua J. Black ◽  
Zhengchang Liu
Keyword(s):  
Acetic Acid ◽  
Target Genes ◽  
Acid Stress ◽  
Weak Acid ◽  
Casein Kinase ◽  
Negative Regulator ◽  
Weak Acids ◽  
Casein Kinase I ◽  
Content Type ◽  
Weak Acid Stress

ABSTRACT Haa1 is a transcription factor that adapts Saccharomyces cerevisiae cells to weak organic acid stresses by activating the expression of various genes. Many of these genes encode membrane proteins, such as TPO2 and YRO2. How Haa1 is activated by weak acids is not clear. Here, we show that casein kinase I isoform Hrr25 is an important negative regulator of Haa1. Haa1 is known to be multiply phosphorylated. We found that mutations in HRR25 lead to reduced Haa1 phosphorylation and increased expression of Haa1 target genes and that Hrr25 interacts with Haa1. The other three casein kinase I isoforms, Yck1, Yck2, and Yck3, do not seem to play critical roles in Haa1 regulation. Hrr25 has a 200-residue C-terminal region, including a proline- and glutamine-rich domain. Our data suggest that the C-terminal region of Hrr25 is required for normal inhibition of expression of Haa1 target genes TPO2 and YRO2 and is important for cell growth but is not required for cell morphogenesis. We propose that Hrr25 is an important regulator of cellular adaptation to weak acid stress by inhibiting Haa1 through phosphorylation. IMPORTANCE Our study has revealed the casein kinase I protein Hrr25 to be a negative regulator of Haa1, a transcription factor mediating the cellular response to stresses caused by weak acids. Many studies have focused on the target genes of Haa1 and their roles in weak acid stress responses, but little has been reported on the regulatory mechanism of Haa1. Weak acids, such as acetic acid, have long been used for food preservation by slowing down the growth of fungal species, including S. cerevisiae. In the biofuel industry, acetic acid in the lignocellulosic hydrolysates limits the production of ethanol, which is undesirable. By understanding how Haa1 is regulated, we can make advances in the field of food sciences to better preserve food and engineer acetic acid-resistant strains that will increase productivity in the biofuel industry.

scholarly journals MNL1Regulates Weak Acid–induced Stress Responses of the Fungal PathogenCandida albicans

2008 ◽  
Vol 19 (10) ◽  
pp. 4393-4403 ◽  
Author(s):  
Mark Ramsdale ◽  
Laura Selway ◽  
David Stead ◽  
Jan Walker ◽  
Zhikang Yin ◽  
...  
Keyword(s):  
Stress Responses ◽  
Acid Stress ◽  
Transcriptional Response ◽  
Weak Acid ◽  
Ras Pathway ◽  
Induced Stress ◽  
Pathway Activation ◽  
Weak Acid Stress ◽  
Dying Cells

MNL1, the Candida albicans homologue of an orphan Msn2-like gene (YER130c in Saccharomyces cerevisiae) has no known function. Here we report that MNL1 regulates weak acid stress responses. Deletion of MNL1 prevents the long-term adaptation of C. albicans cells to weak acid stresses and compromises their global transcriptional response under these conditions. The promoters of Mnl1-dependent genes contain a novel STRE-like element (SLE) that imposes Mnl1-dependent, weak acid stress–induced transcription upon a lacZ reporter in C. albicans. The SLE (HHYYCCCCTTYTY) is related to the Nrg1 response element (NRE) element recognized by the transcriptional repressor Nrg1. Deletion of NRG1 partially restores the ability of C. albicans mnl1 cells to adapt to weak acid stress, indicating that Mnl1 and Nrg1 act antagonistically to regulate this response. Molecular, microarray, and proteomic analyses revealed that Mnl1-dependent adaptation does not occur in cells exposed to proapoptotic or pronecrotic doses of weak acid, suggesting that Ras-pathway activation might suppress the Mnl1-dependent weak acid response in dying cells. Our work defines a role for this YER130c orthologue in stress adaptation and cell death.

scholarly journals Arginine Decarboxylase Is Essential for Pneumococcal Stress Responses

Pathogens ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. 286
Author(s):  
Mary Frances Nakamya ◽  
Moses B. Ayoola ◽  
Leslie A. Shack ◽  
Mirghani Mohamed ◽  
Edwin Swiatlo ◽  
...  
Keyword(s):  
Stress Responses ◽  
Critical Role ◽  
Acid Stress ◽  
Arginine Decarboxylase ◽  
Arginine Deiminase ◽  
Dependent Manner ◽  
Cellular Processes ◽  
Opportunistic Human Pathogen ◽  
Thiol Peroxidase ◽  
The Impact

Polyamines such as putrescine, cadaverine, and spermidine are small cationic molecules that play significant roles in cellular processes, including bacterial stress responses and host–pathogen interactions. Streptococcus pneumoniae is an opportunistic human pathogen, which causes several diseases that account for significant morbidity and mortality worldwide. As it transits through different host niches, S. pneumoniae is exposed to and must adapt to different types of stress in the host microenvironment. We earlier reported that S. pneumoniae TIGR4, which harbors an isogenic deletion of an arginine decarboxylase (ΔspeA), an enzyme that catalyzes the synthesis of agmatine in the polyamine synthesis pathway, has a reduced capsule. Here, we report the impact of arginine decarboxylase deletion on pneumococcal stress responses. Our results show that ΔspeA is more susceptible to oxidative, nitrosative, and acid stress compared to the wild-type strain. Gene expression analysis by qRT-PCR indicates that thiol peroxidase, a scavenger of reactive oxygen species and aguA from the arginine deiminase system, could be important for peroxide stress responses in a polyamine-dependent manner. Our results also show that speA is essential for endogenous hydrogen peroxide and glutathione production in S. pneumoniae. Taken together, our findings demonstrate the critical role of arginine decarboxylase in pneumococcal stress responses that could impact adaptation and survival in the host.

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