scholarly journals A highly active phosphate-insensitive phosphatase is widely distributed in nature

2021 ◽  
Author(s):  
Ian Dennis Edmund Alan Lidbury ◽  
David Scanlan ◽  
Andrew Robert Joseph Murphy ◽  
Joseph Christie-Oleza ◽  
Maria del Mar Aguilo-Ferretjans ◽  
...  
Keyword(s):  
Sole Carbon Source ◽  
Growth Conditions ◽  
Global Ocean ◽  
Phosphorus Cycle ◽  
Highly Active ◽  
Flavobacterium Johnsoniae ◽  
Phosphate Availability ◽  
Alkaline Conditions ◽  
Major Route ◽  
Important Enzyme

The regeneration of bioavailable phosphate from immobilised organophosphorus represents a key process in the global phosphorus cycle and is facilitated by enzymes known as phosphatases. Most bacteria possess at least one of three major phosphatases, known as PhoA, PhoX and PhoD, whose activity is optimal under alkaline conditions. The production and activity of these three phosphatase families is negatively regulated by phosphate availability and thus these enzymes play a major role in scavenging phosphorus only during times of phosphate scarcity. Here, we reveal a previously overlooked phosphate-insensitive phosphatase, PafA, prevalent in Bacteroidetes, which is highly abundant in nature and represents a major route for the remineralisation of phosphate in the environment. Using Flavobacterium johnsoniae as the model, we reveal PafA is highly active towards phosphomonoesters. Unlike other major phosphatases, PafA is fully functional in the presence of its metabolic product, phosphate, and is essential for growth on phosphorylated carbohydrates as a sole carbon source. PafA, which is constitutively produced under all growth conditions tested, rapidly remineralises phosphomonoesters producing significant quantities of bioavailable phosphate that can cross feed into neighbouring cells. pafA is both abundant and highly expressed in the global ocean and abundant in plant rhizospheres, highlighting a new and important enzyme in the global phosphorus cycle with applied implications for agriculture as well as biogeochemical cycling. We speculate PafA expands the metabolic niche of Bacteroidetes by enabling utilisation of abundant organophosphorus substrates in the presence of excess phosphate, when other microbes are rendered incapable.

scholarly journals TheBeauveria bassianaGas3 β-Glucanosyltransferase Contributes to Fungal Adaptation to Extreme Alkaline Conditions

2018 ◽  
Vol 84 (15) ◽  
Author(s):  
Zhibing Luo ◽  
Tongbing Zhang ◽  
Pengfei Liu ◽  
Yuting Bai ◽  
Qiyan Chen ◽  
...  
Keyword(s):  
Cell Wall ◽  
Pathogenic Fungus ◽  
Growth Conditions ◽  
Alkaline Ph ◽  
Ph Responsive ◽  
Content Type ◽  
Cell Wall Remodeling ◽  
Alkaline Conditions ◽  
Increased Sensitivity ◽  
Ph Dependent

ABSTRACTFungal β-1,3-glucanosyltransferases are cell wall-remodeling enzymes implicated in stress response, cell wall integrity, and virulence, with most fungal genomes containing multiple members. The insect-pathogenic fungusBeauveria bassianadisplays robust growth over a wide pH range (pH 4 to 10). A random insertion mutant library screening for increased sensitivity to alkaline (pH 10) growth conditions resulted in the identification and mapping of a mutant to a β-1,3-glucanosyltransferase gene (Bbgas3).Bbgas3expression was pH dependent and regulated by the PacC transcription factor, which activates genes in response to neutral/alkaline growth conditions. Targeted gene knockout ofBbgas3resulted in reduced growth under alkaline conditions, with only minor effects of increased sensitivity to cell wall stress (Congo red and calcofluor white) and no significant effects on fungal sensitivity to oxidative or osmotic stress. The cell walls of ΔBbgas3aerial conidia were thinner than those of the wild-type and complemented strains in response to alkaline conditions, and β-1,3-glucan antibody and lectin staining revealed alterations in cell surface carbohydrate epitopes. The ΔBbgas3mutant displayed alterations in cell wall chitin and carbohydrate content in response to alkaline pH. Insect bioassays revealed impaired virulence for the ΔBbgas3mutant depending upon the pH of the media on which the conidia were grown and harvested. Unexpectedly, a decreased median lethal time to kill (LT50, i.e., increased virulence) was seen for the mutant using intrahemocoel injection assays using conidia grown at acidic pH (5.6). These data show that BbGas3 acts as a pH-responsive cell wall-remodeling enzyme involved in resistance to extreme pH (>9).IMPORTANCELittle is known about adaptations required for growth at high (>9) pH. Here, we show that a specific fungal membrane-remodeling β-1,3-glucanosyltransferase gene (Bbgas3) regulated by the pH-responsive PacC transcription factor forms a critical aspect of the ability of the insect-pathogenic fungusBeauveria bassianato grow at extreme pH. The loss ofBbgas3resulted in a unique decreased ability to grow at high pH, with little to no effects seen with respect to other stress conditions, i.e., cell wall integrity and osmotic and oxidative stress. However, pH-dependent alternations in cell wall properties and virulence were noted for the ΔBbgas3 mutant. These data provide a mechanistic insight into the importance of the specific cell wall structure required to stabilize the cell at high pH and link it to the PacC/Pal/Rim pH-sensing and regulatory system.

scholarly journals Intervention of Bro1 in pH-Responsive Rim20 Localization in Saccharomyces cerevisiae

2010 ◽  
Vol 9 (4) ◽  
pp. 532-538 ◽  
Author(s):  
Jacob H. Boysen ◽  
Shoba Subramanian ◽  
Aaron P. Mitchell
Keyword(s):  
Target Genes ◽  
Fluorescent Protein ◽  
Growth Conditions ◽  
Yeast Cells ◽  
Endosomal Trafficking ◽  
The Novel ◽  
Pathway Activation ◽  
Alkaline Conditions ◽  
Acidic Conditions ◽  
Green Fluorescent

ABSTRACT Yeast cells contain two Bro1 domain proteins: Bro1, which is required for endosomal trafficking, and Rim20, which is required for the response to the external pH via the Rim101 pathway. Rim20 associates with endosomal structures under alkaline growth conditions, when it promotes activation of Rim101 through proteolytic cleavage. We report here that the pH-dependent localization of Rim20 is contingent on the amount of Bro1 in the cell. Cells that lack Bro1 have increased endosomal Rim20-green fluorescent protein (GFP) under acidic conditions; cells that overexpress Bro1 have reduced endosomal Rim20-GFP under acidic or alkaline conditions. The novel endosomal association of Rim20-GFP in the absence of Bro1 requires ESCRT components including Vps27 but not specific Rim101 pathway components such as Dfg16. Vps27 influences the localization of Bro1 but is not required for RIM101 pathway activation in wild-type cells, thus suggesting that Rim20 enters the Bro1 localization pathway when a vacancy exists. Despite altered localization of Rim20, the lack of Bro1 does not bypass the need for signaling protein Dfg16 to activate Rim101, as evidenced by the expression levels of the Rim101 target genes RIM8 and SMP1. Therefore, endosomal association of Rim20 is not sufficient to promote Rim101 activation.

scholarly journals pH-Dependent Degradation of Diclofenac by a Tunnel-Structured Manganese Oxide

Water ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 2203
Author(s):  
Ching-Yao Hu ◽  
Yu-Jung Liu ◽  
Wen-Hui Kuan
Keyword(s):  
Formation Control ◽  
High Performance ◽  
Degradation Kinetics ◽  
Removal Rate ◽  
Solution Ph ◽  
Mn Oxide ◽  
Highly Active ◽  
Alkaline Conditions ◽  
Acidic Conditions ◽  
Key Parameter

The mechanism of diclofenac (DIC) degradation by tunnel-structured γ-MnO2, with superior oxidative and catalytic abilities, was determined in terms of solution pH. High-performance liquid chromatography with mass spectroscopy (HPLC–MS) was used to identify intermediates and final products of DIC degradation. DIC can be efficiently oxidized by γ-MnO2 in an acidic medium, and the removal rate decreased significantly under neutral and alkaline conditions. The developed model can successfully fit DIC degradation kinetics and demonstrates electron transfer control under acidic conditions and precursor complex formation control mechanism under neutral to alkaline conditions, in which the pH extent for two mechanisms exactly corresponds to the distribution percentage of ionized species of DIC. We also found surface reactive sites (Srxn), a key parameter in the kinetic model for mechanism determination, to be exactly a function of solution pH and MnO2 dosage. The main products of oxidation with a highly active hydroxylation pathway on the tunnel-structured Mn-oxide are 5-iminoquinone DIC, hydroxyl-DIC, and 2,6-dichloro-N-o-tolylbenzenamine.

scholarly journals Electrodeposited PdNi on a Ni rotating disk electrode highly active for glycerol electrooxidation in alkaline conditions

2021 ◽  
pp. 139714
Author(s):  
Jai White ◽  
Athira Anil ◽  
Daniel Martín-Yerga ◽  
Germán Salazar-Alvarez ◽  
Gunnar Henriksson ◽  
...  
Keyword(s):  
Rotating Disk ◽  
Rotating Disk Electrode ◽  
Disk Electrode ◽  
Glycerol Electrooxidation ◽  
Highly Active ◽  
Alkaline Conditions

scholarly journals Response of hya Expression to External pH in Escherichia coli

1999 ◽  
Vol 181 (17) ◽  
pp. 5250-5256 ◽  
Author(s):  
Paul W. King ◽  
Alan E. Przybyla
Keyword(s):  
Escherichia Coli ◽  
Alkaline Medium ◽  
Ph Value ◽  
Peak Level ◽  
Growth Conditions ◽  
Anaerobic Growth ◽  
Uptake Hydrogenase ◽  
Expression Levels ◽  
Alkaline Conditions ◽  
External Ph

ABSTRACT The hya operon of Escherichia coli is composed of the genes which synthesize uptake hydrogenase isoenzyme 1 (Hyd1). Although hya expression and Hyd1 synthesis occur only under anaerobic conditions, Hyd1 is not essential for growth. In this study we used a hya′-′lacZ fusion to characterize parameters of anaerobic growth that maximize hya expression in an attempt to further elucidate Hyd1 function. We found that the expression pattern of hya followed a decline of external pH. In buffered media where the pH value was set, the onset ofhya expression initiated earlier in growth and reached a greater peak level in acidic than in alkaline medium. When cultures expressing hya were shifted from acidic to alkaline conditions, hya expression was arrested; shifting from alkaline to acidic conditions stimulated hya expression. Maximal expression of hya under all growth conditions required the sigma factor RpoS and transcriptional regulators AppY and ArcA. In the absence of RpoS or AppY, the response of hyaexpression onset to external pH was evident and maximal hyalevels remained greater in acidic than in alkaline medium. However, the absence of ArcA led to a diminished response of expression onset to external pH and the loss of elevated expression at an acidic external pH. The fermentation end product formate slightly alteredhya expression levels but was not required forhya to respond to external pH. In contrast tohya expression, the onset of hyb operon expression, encoding uptake hydrogenase isoenzyme 2, was constitutive with respect to external pH. However, external pH did affecthyb expression levels, which, in contrast tohya, were maximal in alkaline rather than acidic medium.

scholarly journals Satellite-detected fluorescence reveals global physiology of ocean phytoplankton

2008 ◽  
Vol 5 (6) ◽  
pp. 4235-4270 ◽  
Author(s):  
M. J. Behrenfeld ◽  
T. K. Westberry ◽  
E. S. Boss ◽  
R. T. O'Malley ◽  
D. A. Siegel ◽  
...  
Keyword(s):  
Field Studies ◽  
Growth Conditions ◽  
Global Ocean ◽  
Physiological Status ◽  
Light Use Efficiency ◽  
Fluorescence Measurements ◽  
Ocean Productivity ◽  
Natural Iron ◽  
Use Efficiency ◽  
Ocean Ecosystem

Abstract. Phytoplankton photosynthesis links global ocean biology and climate-driven fluctuations in the physical environment. These interactions are largely expressed through changes in phytoplankton physiology, but physiological status has proven extremely challenging to characterize globally. Phytoplankton fluorescence does provide a rich source of physiological information long exploited in laboratory and field studies, and is now observed from space. Here we use satellite-based fluorescence measurements to evaluate light-absorption and energy-dissipation processes influencing phytoplankton light use efficiency and demonstrate its utility as a global physiological indicator of iron-limited growth conditions. This new tool provides a path for monitoring climate-phytoplankton physiology interactions, improving descriptions of light use efficiency in ocean productivity models, evaluating nutrient-stress predictions in ocean ecosystem models, and appraising phytoplankton responses to natural iron enrichments or purposeful iron fertilizations activities.

scholarly journals Bacterial catabolism of threonine. Threonine degradation initiated by l-threonine acetaldehyde-lyase (aldolase) in species of Pseudomonas

1977 ◽  
Vol 166 (2) ◽  
pp. 209-216 ◽  
Author(s):  
Stephen C. Bell ◽  
John M. Turner
Keyword(s):  
Reductase Activity ◽  
Growth Conditions ◽  
Serine Hydroxymethyltransferase ◽  
Threonine Aldolase ◽  
Highly Active ◽  
Activity Ratios ◽  
Exclusion Chromatography ◽  
Mammalian Origin ◽  
Aldolase Activity ◽  
Single Enzyme

1. The route of l-threonine degradation was studied in four strains of the genus Pseudomonas able to grow on the amino acid and selected because of their high l-threonine aldolase activity. Growth and manometric results were consistent with the cleavage of l-threonine to acetaldehyde+glycine and their metabolism via acetate and serine respectively. 2. l-Threonine aldolases in these bacteria exhibited pH optima in the range 8.0–8.7 and Km values for the substrate of 5–10mm. Extracts exhibited comparable allo-l-threonine aldolase activities, Km values for this substrate being 14.5–38.5mm depending on the bacterium. Both activities were essentially constitutive. Similar activity ratios in extracts, independent of growth conditions, suggested a single enzyme. The isolate Pseudomonas D2 (N.C.I.B. 11097) represents the best source of the enzyme known. 3. Extracts of all the l-threonine-grown pseudomonads also possessed a CoA-independent aldehyde dehydrogenase, the synthesis of which was induced, and a reversible alcohol dehydrogenase. The high acetaldehyde reductase activity of most extracts possibly resulted in the underestimation of acetaldehyde dehydrogenase. 4. l-Serine dehydratase formation was induced by growth on l-threonine or acetate+glycine. Constitutively synthesized l-serine hydroxymethyltransferase was detected in extracts of Pseudomonas strains D2 and F10. The enzyme could not be detected in strains A1 and N3, probably because of a highly active ‘formaldehyde-utilizing’ system. 5. Ion-exchange and molecular exclusion chromatography supported other evidence that l-threonine aldolase and allo-l-threonine aldolase activities were catalysed by the same enzyme but that l-serine hydroxymethyltransferase was distinct and different. These results contrast with the specificities of some analogous enzymes of mammalian origin.

Unveiling the active sites of Ni–Fe phosphide/metaphosphate for efficient oxygen evolution under alkaline conditions

2019 ◽  
Vol 55 (53) ◽  
pp. 7687-7690 ◽  
Author(s):  
Can Huang ◽  
Ying Zou ◽  
Ya-Qian Ye ◽  
Ting Ouyang ◽  
Kang Xiao ◽  
...  
Keyword(s):  
Oxygen Evolution ◽  
Oxygen Evolution Reaction ◽  
Active Sites ◽  
Highly Active ◽  
Alkaline Conditions ◽  
Stable Oxygen

The highly active and stable oxygen evolution reaction (OER) performance of Ni–Fe phosphide/metaphosphate (Ni1−xFex-P/PO3) can originate from in situ generated Fe doped γ-NiOOH.

scholarly journals Regulation of Pyrroloquinoline Quinone-Dependent Glucose Dehydrogenase Activity in the Model Rhizosphere-Dwelling Bacterium Pseudomonas putida KT2440

2016 ◽  
Vol 82 (16) ◽  
pp. 4955-4964 ◽  
Author(s):  
Ran An ◽  
Luke A. Moe
Keyword(s):  
Gene Expression ◽  
Pseudomonas Putida ◽  
Sole Carbon Source ◽  
Phosphate Solubilization ◽  
Specific Activity ◽  
Glucose Dehydrogenase ◽  
Growth Conditions ◽  
Pyrroloquinoline Quinone ◽  
Soluble Phosphate ◽  
Content Type

ABSTRACTSoil-dwelling microbes solubilize mineral phosphates by secreting gluconic acid, which is produced from glucose by a periplasmic glucose dehydrogenase (GDH) that requires pyrroloquinoline quinone (PQQ) as a redox coenzyme. While GDH-dependent phosphate solubilization has been observed in numerous bacteria, little is known concerning the mechanism by which this process is regulated. Here we use the model rhizosphere-dwelling bacteriumPseudomonas putidaKT2440 to explore GDH activity and PQQ synthesis, as well as gene expression of the GDH-encoding gene (gcd) and PQQ biosynthesis genes (pqqoperon) while under different growth conditions. We also use reverse transcription-PCR to identify transcripts from thepqqoperon to more accurately map the operon structure. GDH specific activity and PQQ levels vary according to growth condition, with the highest levels of both occurring when glucose is used as the sole carbon source and under conditions of low soluble phosphate. Under these conditions, however, PQQ levels limitin vitrophosphate solubilization. GDH specific activity data correlate well withgcdgene expression data, and the levels of expression of thepqqFandpqqBgenes mirror the levels of PQQ synthesized, suggesting that one or both of these genes may serve to modulate PQQ levels according to the growth conditions. Thepqqgene cluster (pqqFABCDEG) encodes at least two independent transcripts, and expression of thepqqFgene appears to be under the control of an independent promoter and terminator.IMPORTANCEPlant growth promotion can be enhanced by soil- and rhizosphere-dwelling bacteria by a number of different methods. One method is by promoting nutrient acquisition from soil. Phosphorus is an essential nutrient that plants obtain through soil, but in many cases it is locked up in forms that are not available for plant uptake. Bacteria such as the model bacteriumPseudomonas putidaKT2440 can solubilize insoluble soil phosphates by secreting gluconic acid. This chemical is produced from glucose by the activity of the bacterial enzyme glucose dehydrogenase, which requires a coenzyme called PQQ. Here we have studied how the glucose dehydrogenase enzyme and the PQQ coenzyme are regulated according to differences in bacterial growth conditions. We determined that glucose dehydrogenase activity and PQQ production are optimal under conditions when the bacterium is grown with glucose as the sole carbon source and under conditions of low soluble phosphate.

Sign in / Sign up

Export Citation Format

Share Document