scholarly journals The Weak Acid Preservative Sorbic Acid Inhibits Conidial Germination and Mycelial Growth of Aspergillus niger through Intracellular Acidification

2004 ◽  
Vol 70 (6) ◽  
pp. 3506-3511 ◽  
Author(s):  
Andrew Plumridge ◽  
Stephan J. A. Hesse ◽  
Adrian J. Watson ◽  
Kenneth C. Lowe ◽  
Malcolm Stratford ◽  
...  
Keyword(s):  
Aspergillus Niger ◽  
Mycelial Growth ◽  
Sorbic Acid ◽  
Weak Acid ◽  
Inoculum Size ◽  
Food Preservation ◽  
Rapid Decline ◽  
Intracellular Acidification ◽  
Ph Homeostasis ◽  
Cytosolic Ph

ABSTRACT The growth of the filamentous fungus Aspergillus niger, a common food spoilage organism, is inhibited by the weak acid preservative sorbic acid (trans-trans-2,4-hexadienoic acid). Conidia inoculated at 105/ml of medium showed a sorbic acid MIC of 4.5 mM at pH 4.0, whereas the MIC for the amount of mycelia at 24 h developed from the same spore inoculum was threefold lower. The MIC for conidia and, to a lesser extent, mycelia was shown to be dependent on the inoculum size. A. niger is capable of degrading sorbic acid, and this ability has consequences for food preservation strategies. The mechanism of action of sorbic acid was investigated using 31P nuclear magnetic resonance (NMR) spectroscopy. We show that a rapid decline in cytosolic pH (pHcyt) by more than 1 pH unit and a depression of vacuolar pH (pHvac) in A. niger occurs in the presence of sorbic acid. The pH gradient over the vacuole completely collapsed as a result of the decline in pHcyt. NMR spectra also revealed that sorbic acid (3.0 mM at pH 4.0) caused intracellular ATP pools and levels of sugar-phosphomonoesters and -phosphodiesters of A. niger mycelia to decrease dramatically, and they did not recover. The disruption of pH homeostasis by sorbic acid at concentrations below the MIC could account for the delay in spore germination and retardation of the onset of subsequent mycelial growth.

scholarly journals The Weak-Acid Preservative Sorbic Acid Is Decarboxylated and Detoxified by a Phenylacrylic Acid Decarboxylase, PadA1, in the Spoilage Mold Aspergillus niger

2007 ◽  
Vol 74 (2) ◽  
pp. 550-552 ◽  
Author(s):  
Andrew Plumridge ◽  
Malcolm Stratford ◽  
Kenneth C. Lowe ◽  
David B. Archer
Keyword(s):  
Aspergillus Niger ◽  
Spore Germination ◽  
Sorbic Acid ◽  
Weak Acid ◽  
Acid Decarboxylase ◽  
Cinnamic Acids ◽  
Inhibit Spore Germination

ABSTRACT Resistance to sorbic and cinnamic acids is mediated by a phenylacrylic acid decarboxylase (PadA1) in Aspergillus niger. A. niger ΔpadA1 mutants are unable to decarboxylate sorbic and cinnamic acids, and the MIC of sorbic acid required to inhibit spore germination was reduced by ∼50% in ΔpadA1 mutants.

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.

Modulation of calcium homeostasis in cultured rat aortic endothelial cells by intracellular acidification

1993 ◽  
Vol 265 (4) ◽  
pp. H1424-H1433 ◽  
Author(s):  
R. C. Ziegelstein ◽  
L. Cheng ◽  
P. S. Blank ◽  
H. A. Spurgeon ◽  
E. G. Lakatta ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Vascular Endothelial Cells ◽  
Cytosolic Calcium ◽  
Ph Sensitive ◽  
Vascular Endothelial ◽  
Intracellular Acidification ◽  
Cytosolic Ph ◽  
Aortic Endothelial Cells ◽  
Endothelial Monolayers ◽  
Aortic Endothelial

Acidosis produces vasodilation in a process that may involve the vascular endothelium. Because synthesis and release of endothelium-derived vasodilatory substances are linked to an increase in cytosolic calcium concentration ([Ca2+]i), we examined the effect of intracellular acidification on cultured rat aortic endothelial cells loaded either with the pH-sensitive probe carboxy-seminaphthorhodafluor-1 or the Ca(2+)-sensitive fluorescent probe indo 1. The basal cytosolic pH (pHi) of endothelial monolayers in a 5% CO2-HCO3- buffer was 7.27 +/- 0.02 and that in a bicarbonate-free solution was 7.22 +/- 0.03. Acidification was induced either by removal of NH4Cl (delta pHi = -0.10 +/- 0.02), changing from a bicarbonate-free to a 5% CO2-HCO3(-)-buffered solution at constant buffer pH (delta pHi = -0.18 +/- 0.03), or changing from a 5% to a 20% CO2-HCO3- solution (delta pHi = -0.27 +/- 0.07). Regardless of the method used, intracellular acidification increased [Ca2+]i as indexed by indo 1 fluorescence. The increase in [Ca2+]i induced by changing from a 5 to a 20% CO2-HCO3- solution was not significantly altered by removal of buffer Ca2+ either before or after depletion of bradykinin- and thapsigargin-sensitive intracellular Ca2+ stores. Thus intracellular acidification of vascular endothelial cells releases Ca2+ into the cytosol either from pH-sensitive intracellular buffer sites, mitochondria, or from bradykinin- and thapsigargin-insensitive intracellular stores. This Ca2+ mobilization may be linked to endothelial synthesis and release of vasodilatory substances during acidosis.

scholarly journals pH-dependent Cargo Sorting from the Golgi

2011 ◽  
Vol 286 (12) ◽  
pp. 10058-10065 ◽  
Author(s):  
Chunjuan Huang ◽  
Amy Chang
Keyword(s):  
Plasma Membrane ◽  
Membrane Proteins ◽  
Atpase Activity ◽  
Secretory Pathway ◽  
Ph Dependence ◽  
Glucose Deprivation ◽  
Ph Homeostasis ◽  
Plasma Membrane Proteins ◽  
Cytosolic Ph ◽  
Cargo Sorting

The vacuolar proton-translocating ATPase (V-ATPase) plays a major role in organelle acidification and works together with other ion transporters to maintain pH homeostasis in eukaryotic cells. We analyzed a requirement for V-ATPase activity in protein trafficking in the yeast secretory pathway. Deficiency of V-ATPase activity caused by subunit deletion or glucose deprivation results in missorting of newly synthesized plasma membrane proteins Pma1 and Can1 directly from the Golgi to the vacuole. Vacuolar mislocalization of Pma1 is dependent on Gga adaptors although no Pma1 ubiquitination was detected. Proper cell surface targeting of Pma1 was rescued in V-ATPase-deficient cells by increasing the pH of the medium, suggesting that missorting is the result of aberrant cytosolic pH. In addition to mislocalization of the plasma membrane proteins, Golgi membrane proteins Kex2 and Vrg4 are also missorted to the vacuole upon loss of V-ATPase activity. Because the missorted cargos have distinct trafficking routes, we suggest a pH dependence for multiple cargo sorting events at the Golgi.

scholarly journals AE anion exchangers in atrial tumor cells

2001 ◽  
Vol 280 (3) ◽  
pp. H937-H945 ◽  
Author(s):  
Panos Papageorgiou ◽  
Boris E. Shmukler ◽  
Alan K. Stuart-Tilley ◽  
Lianwei Jiang ◽  
Seth L. Alper
Keyword(s):  
Tumor Cell Line ◽  
Disulfonic Acid ◽  
Cell Type ◽  
Intracellular Acidification ◽  
Ph Homeostasis ◽  
Rt Pcr ◽  
Anion Exchangers ◽  
Atrial Tumor ◽  
Atrial Cell ◽  
Exchange Activity

Intracellular pH homeostasis and intracellular Cl−concentration in cardiac myocytes are regulated by anion exchange mechanisms. In physiological extracellular Cl−concentrations, Cl−/HCO[Formula: see text] exchange promotes intracellular acidification and Cl−loading sensitive to inhibition by stilbene disulfonates. We investigated the expression of AE anion exchangers in the AT-1 mouse atrial tumor cell line. Cultured AT-1 cells exhibited a substantial basal Na+-independent Cl−/HCO[Formula: see text] (but not Cl−/OH−) exchange activity that was inhibited by DIDS but not by dibenzamidostilbene disulfonic acid (DBDS). AT-1 cell Cl−/HCO[Formula: see text] activity was stimulated two- to threefold by extracellular ATP and ANG II. AE mRNAs detected by RT-PCR in AT-1 cells included brain AE3 (bAE3), cardiac AE3 (cAE3), AE2a, AE2b, AE2c1, AE2c2, and erythroid AE1 (eAE1), but not kidney AE1 (kAE1). Cultured AT-1 cells expressed AE2, cAE3, and bAE3 polypeptides, which were detected by immunoblot and immunocytochemistry. An AE1-like epitope was detected by immunocytochemistry but not by immunoblot. Both bAE3 and cAE3 were present in intact AT-1 tumors. Cultured AT-1 cells provide a useful system for the study of mediators and regulators of Cl−/HCO[Formula: see text] exchange activity in an atrial cell type.

scholarly journals Pectinase production by Aspergillus niger isolated from decomposed apple skin

2013 ◽  
Vol 48 (1) ◽  
pp. 25-32 ◽  
Author(s):  
S Islam ◽  
B Feroza ◽  
AKMR Alam ◽  
S Begum
Keyword(s):  
Aspergillus Niger ◽  
Incubation Temperature ◽  
Nitrogen Sources ◽  
Inoculum Size ◽  
Point Of View ◽  
Media Composition ◽  
Maximal Level ◽  
Pectinolytic Activity ◽  
Pectinase Activity ◽  
Pectinase Production

Pectinase activity among twelve different fungal strains, Aspergillus niger IM09 was identified as a potential one to produce maximal level 831 U/g at pH 4.0. Media composition, incubation temperature, incubation time, substrate concentration, aeration, inoculum size, assay temperature and nitrogen sources were found to effect pectinase activity. Moisture content did not affect the activity significantly. Media composition was varied to optimize the enzyme production in solid state fermentation. It was observed that the highest pectinase activity of 831.0 U/g was found to produce in presence of yeast extract as a nitrogen source in combination with ammonium sulfate in assay media. Aeration showed positive significant effects on pectinase production 755 U/g at 1000 ml flasks. The highest pectinase production was found at 2 g pectin (521 U/g) used as a substrate. Pectinolytic activity was found to have undergone catabolite repression with higher pectin concentration (205 U/g at 5 g pectin). The incubation period to achieve maximum pectinase activity by the isolated strain Aspergillus niger IM09 was 3 days, which is suitable from the commercial point of view. DOI: http://dx.doi.org/10.3329/bjsir.v48i1.15410 Bangladesh J. Sci. Ind. Res. 48(1), 25-32, 2013

scholarly journals Optimal Conditions For Production Acidic D-Xylanase By Aspergillus niger in Submerged Fermentation

2011 ◽  
Vol 5 (3) ◽  
pp. 14-21
Author(s):  
Muhamed Omar Abdulatif ◽  
Hyder H. Assmaeel ◽  
Raghad kadhim Obeid ◽  
Ayat Adnan Abbas
Keyword(s):  
Aspergillus Niger ◽  
Rice Husk ◽  
Enzyme Production ◽  
Inoculum Size ◽  
Optimal Conditions ◽  
Optimum Conditions ◽  
Xylanase Production ◽  
Primary Isolation ◽  
Optimum Ph ◽  
Optimum Period

he Xylanase producing strain Aspergillus niger was isolated from soil on potato dextrose agar in the presence of xylan as its first substrate for primary isolation, and then grown under liquid medium fermentation in the presence of crude xylan (rice husk) to produce D-Xylanase. the optimum conditions were determined as follows: the Optimum pH for xylanase production was found pH 5.0, xylanase was induced by xylan (rice husk) 0.1% and the production was (61.221 U/ml) and nitrogen source Yeast extract recorded highest enzyme production( 89.71 U/ml), and repressed by carbon source xylose the highest enzyme production (88.69 U/ml). The optimum temperature was 40°с for xylanase production was (35.15 U/ml), the optimum period after 7 days of incubation was (52.33 U/ml) ,the optimum substrate concentration 0.1% was (45.95 U/ml), and the optimum inoculum size was 1 x 106 (spore /ml) recorded (57.19 U/ml ).

Sign in / Sign up

Export Citation Format

Share Document