Involvement of a phosphate starvation inducible glucose dehydrogenase in soil phosphate solubilization byEnterobacter asburiae

Enterobacter asburiae PSI3 is a rhizospheric isolate that solubilizes mineral phosphates by the action of a phosphate starvation-inducible GDH (EC 1.1.5.2). We report here that GDH activity of this isolate shows broad substrate range, being able to act on mono and disaccharides. Enterobacter asburiae PSI3 was proficient at bringing about a drop in pH and solubilization of RP with the use of 75 mmol/L of each of the GDH substrate sugars tested as the sole C source. It liberated amounts of P ranging from 450 µmol/L (on arabinose) to 890 µmol/L (on glucose). When grown on a mixture of 7 GDH substrates at concentrations of 15 mmol/L each, the bacterium solubilized RP equivalent to 46% of the value when 75 mmol glucose/L was the C source. HPLC analysis of the culture supernatant under these conditions showed that the acidification of the media is primarily due to the production of organic acids. The significance of these results on the efficacy of E. asburiae PSI3 at solubilizing phosphates under rhizospheric conditions is discussed.Key words: glucose dehydrogenase, substrate specificity, P solubilization, Enterobacter asburiae PSI3.

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Effect of Trichoderma on soil phosphate solubilization and growth improvement of Avicennia marina

Aquatic Botany ◽

10.1016/j.aquabot.2012.09.001 ◽

2013 ◽

Vol 104 ◽

pp. 101-105 ◽

Cited By ~ 40

Author(s):

K. Saravanakumar ◽

V. Shanmuga Arasu ◽

K. Kathiresan

Keyword(s):

Phosphate Solubilization ◽

Avicennia Marina ◽

Soil Phosphate

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Highly Conserved Asp-204 and Gly-776 Are Important for Activity of the Quinoprotein Glucose Dehydrogenase of Escherichia coli and for Mineral Phosphate Solubilization

Journal of Molecular Microbiology and Biotechnology ◽

10.1159/000293819 ◽

2010 ◽

Vol 18 (2) ◽

pp. 109-119 ◽

Cited By ~ 5

Author(s):

Burla Sashidhar ◽

Krishna Kishore Inampudi ◽

Lalitha Guruprasad ◽

Anil Kondreddy ◽

Kodetham Gopinath ◽

...

Keyword(s):

Escherichia Coli ◽

Phosphate Solubilization ◽

Glucose Dehydrogenase ◽

Mineral Phosphate Solubilization ◽

Mineral Phosphate

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Pyrroloquinoline Quinone Biosynthesis GenepqqC, a Novel Molecular Marker for Studying the Phylogeny and Diversity of Phosphate-Solubilizing Pseudomonads

Applied and Environmental Microbiology ◽

10.1128/aem.05434-11 ◽

2011 ◽

Vol 77 (20) ◽

pp. 7345-7354 ◽

Cited By ~ 33

Author(s):

Joana Beatrice Meyer ◽

Michele Frapolli ◽

Christoph Keel ◽

Monika Maurhofer

Keyword(s):

Molecular Marker ◽

Phylogenetic Trees ◽

Phosphate Solubilization ◽

Glucose Dehydrogenase ◽

Housekeeping Genes ◽

Pyrroloquinoline Quinone ◽

Rock Phosphates ◽

Content Type ◽

Strain Collection ◽

Phosphate Solubilizing

ABSTRACTMany root-colonizing pseudomonads are able to promote plant growth by increasing phosphate availability in soil through solubilization of poorly soluble rock phosphates. The major mechanism of phosphate solubilization by pseudomonads is the secretion of gluconic acid, which requires the enzyme glucose dehydrogenase and its cofactor pyrroloquinoline quinone (PQQ). The main aim of this study was to evaluate whether a PQQ biosynthetic gene is suitable to study the phylogeny of phosphate-solubilizing pseudomonads. To this end, two new primers, which specifically amplify thepqqCgene of thePseudomonasgenus, were designed.pqqCfragments were amplified and sequenced from aPseudomonasstrain collection and from a natural wheat rhizosphere population using cultivation-dependent and cultivation-independent approaches. Phylogenetic trees based onpqqCsequences were compared to trees obtained with the two concatenated housekeeping genesrpoDandgyrB. For bothpqqCandrpoD-gyrB, similar main phylogenetic clusters were found. However, in thepqqCbut not in therpoD-gyrBtree, the group of fluorescent pseudomonads producing the antifungal compounds 2,4-diacetylphloroglucinol and pyoluteorin was located outside thePseudomonas fluorescensgroup.pqqCsequences from isolated pseudomonads were differently distributed among the identified phylogenetic groups thanpqqCsequences derived from the cultivation-independent approach. ComparingpqqCphylogeny and phosphate solubilization activity, we identified one phylogenetic group with high solubilization activity. In summary, we demonstrate that the genepqqCis a novel molecular marker that can be used complementary to housekeeping genes for studying the diversity and evolution of plant-beneficial pseudomonads.

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Crc Regulates Succinate-Mediated Repression of Mineral Phosphate Solubilization in Acinetobacter sp. SK2 by Modulating Membrane Glucose Dehydrogenase

Frontiers in Microbiology ◽

10.3389/fmicb.2021.641119 ◽

2021 ◽

Vol 12 ◽

Author(s):

Krishna Bharwad ◽

Niharika Ghoghari ◽

Shalini Rajkumar

Keyword(s):

Glucose Oxidation ◽

Phosphate Solubilization ◽

Glucose Dehydrogenase ◽

Carbon Sources ◽

Shoot Length ◽

Wild Type ◽

Mineral Phosphate Solubilization ◽

Root And Shoot Length ◽

Mineral Phosphate ◽

Encoding Gene

The plant growth-promoting Acinetobacter sp. SK2 isolated from Vigna radiata rhizosphere was characterized for mineral phosphate solubilization (MPS). To understand the contribution of the membrane glucose dehydrogenase (mGDH) and soluble glucose dehydrogenase (sGDH) in glucose oxidation and MPS, insertional inactivation of the corresponding genes was carried out. The disruption of mGDH encoding gene gdhA resulted in complete loss of mGDH activity, which confirmed its role in periplasmic glucose oxidation and gluconate-mediated MPS phenotype. The inactivation of sGDH encoding gene gdhB resulted in loss of sGDH activity, which did not alter the MPS or mGDH activity. Thus, it was also concluded that the sGDH was dispensable in gluconate-mediated MPS. Supplementation of succinate in glucose-containing medium suppressed the activity of mGDH (and sGDH) and therefore repressed the MPS phenotype. The catabolite repression control protein (Crc) of Pseudomonas was implicated in Acinetobacter sp. for a similar function in the presence of preferred and non-preferred carbon sources. To understand the regulatory linkage between Crc and genes for glucose oxidation, crc mutants were generated. The inactivation of crc resulted in increased activity of the mGDH in glucose + succinate-grown cells, indicating derepression. An increase in phosphate solubilization up to 44% in glucose + succinate-grown crc– compared with glucose-grown cells was recorded, which was significantly repressed in the wild-type strain under similar conditions. It is therefore proposed that in Acinetobacter sp. SK2, Crc is involved in the succinate-provoked repression of the MPS phenotype. The gene expression data indicated that Hfq may also have a regulating role in preferential utilization of carbon source by perhaps modulating Crc–Hfq functionality. V. radiata plants inoculated with the wild type improved both root and shoot length by 1.3 to 1.4-fold. However, crc– increased the root and shoot length by 1.6-fold, compared with the uninoculated controls. In mimicking the soil condition (in the presence of multiple carbon sources, e.g., succinate along with glucose), the crc– strain of Acinetobacter sp. SK2 performed better in supporting the growth of V. radiata in pot experiments.

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Differential Contribution of Plant-Beneficial Functions from Pseudomonas kilonensis F113 to Root System Architecture Alterations in Arabidopsis thaliana and Zea mays

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-07-17-0185-r ◽

2018 ◽

Vol 31 (2) ◽

pp. 212-223 ◽

Cited By ~ 10

Author(s):

Jordan Vacheron ◽

Guilhem Desbrosses ◽

Sébastien Renoud ◽

Rosa Padilla ◽

Vincent Walker ◽

...

Keyword(s):

Arabidopsis Thaliana ◽

Type Strain ◽

Wild Type Strain ◽

Phosphate Solubilization ◽

Glucose Dehydrogenase ◽

Root System Architecture ◽

Deletion Mutants ◽

Wild Type ◽

Relative Contribution

Fluorescent pseudomonads are playing key roles in plant-bacteria symbiotic interactions due to the multiple plant-beneficial functions (PBFs) they are harboring. The relative contributions of PBFs to plant-stimulatory effects of the well-known plant growth-promoting rhizobacteria Pseudomonas kilonensis F113 (formerly P. fluorescens F113) were investigated using a genetic approach. To this end, several deletion mutants were constructed, simple mutants ΔphlD (impaired in the biosynthesis of 2,4-diacetylphloroglucinol [DAPG]), ΔacdS (deficient in 1-aminocyclopropane-1-carboxylate deaminase activity), Δgcd (glucose dehydrogenase deficient, impaired in phosphate solubilization), and ΔnirS (nitrite reductase deficient), and a quadruple mutant (deficient in the four PBFs mentioned above). Every PBF activity was quantified in the wild-type strain and the five deletion mutants. This approach revealed few functional interactions between PBFs in vitro. In particular, biosynthesis of glucose dehydrogenase severely reduced the production of DAPG. Contrariwise, the DAPG production impacted positively, but to a lesser extent, phosphate solubilization. Inoculation of the F113 wild-type strain on Arabidopsis thaliana Col-0 and maize seedlings modified the root architecture of both plants. Mutant strain inoculations revealed that the relative contribution of each PBF differed according to the measured plant traits and that F113 plant-stimulatory effects did not correspond to the sum of each PBF relative contribution. Indeed, two PBF genes (ΔacdS and ΔnirS) had a significant impact on root-system architecture from both model plants, in in vitro and in vivo conditions. The current work underscored that few F113 PBFs seem to interact between each other in the free-living bacterial cells, whereas they control in concert Arabidopsis thaliana and maize growth and development.

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

Applied and Environmental Microbiology ◽

10.1128/aem.00813-16 ◽

2016 ◽

Vol 82 (16) ◽

pp. 4955-4964 ◽

Cited By ~ 22

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.

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