Heterologous expression of phosphoenolpyruvate carboxylase enhances the phosphate solubilizing ability of fluorescent pseudomonads by altering the glucose catabolism to improve biomass yield

2010 ◽  
Vol 101 (2) ◽  
pp. 679-687 ◽  
Author(s):  
Aditi Buch ◽  
G. Archana ◽  
G. Naresh Kumar
Keyword(s):  
Heterologous Expression ◽  
Phosphoenolpyruvate Carboxylase ◽  
Biomass Yield ◽  
Fluorescent Pseudomonads ◽  
Glucose Catabolism ◽  
Phosphate Solubilizing

scholarly journals Enhanced citric acid biosynthesis in Pseudomonas fluorescens ATCC 13525 by overexpression of the Escherichia coli citrate synthase gene

Microbiology ◽  
2009 ◽  
Vol 155 (8) ◽  
pp. 2620-2629 ◽  
Author(s):  
Aditi D. Buch ◽  
G. Archana ◽  
G. Naresh Kumar
Keyword(s):  
Escherichia Coli ◽  
Citric Acid ◽  
Acid Secretion ◽  
Pseudomonas Fluorescens ◽  
Phosphoenolpyruvate Carboxylase ◽  
Citrate Synthase ◽  
Acid Biosynthesis ◽  
Acid Yield ◽  
Glucose Catabolism ◽  
Citric Acid Biosynthesis

Citric acid secretion by fluorescent pseudomonads has a distinct significance in microbial phosphate solubilization. The role of citrate synthase in citric acid biosynthesis and glucose catabolism in pseudomonads was investigated by overexpressing the Escherichia coli citrate synthase (gltA) gene in Pseudomonas fluorescens ATCC 13525. The resultant ∼2-fold increase in citrate synthase activity in the gltA-overexpressing strain Pf(pAB7) enhanced the intracellular and extracellular citric acid yields during the stationary phase, by about 2- and 26-fold, respectively, as compared to the control, without affecting the growth rate, glucose depletion rate or biomass yield. Decreased glucose consumption was paralleled by increased gluconic acid production due to an increase in glucose dehydrogenase activity. While the extracellular acetic acid yield increased in Pf(pAB7), pyruvic acid secretion decreased, correlating with an increase in pyruvate carboxylase activity and suggesting an increased demand for the anabolic precursor oxaloacetate. Activities of two other key enzymes, glucose-6-phosphate dehydrogenase and isocitrate dehydrogenase, remained unaltered, and the contribution of phosphoenolpyruvate carboxylase and isocitrate lyase to glucose catabolism was negligible. Strain Pf(pAB7) demonstrated an enhanced phosphate-solubilizing ability compared to the control. Co-expression of the Synechococcus elongatus PCC 6301 phosphoenolpyruvate carboxylase and E. coli gltA genes in P. fluorescens ATCC 13525, so as to supplement oxaloacetate for citrate biosynthesis, neither significantly affected citrate biosynthesis nor caused any change in the other physiological and biochemical parameters measured, despite approximately 1.3- and 5-fold increases in citrate synthase and phosphoenolpyruvate carboxylase activities, respectively. Thus, our results demonstrate that citrate synthase is rate-limiting in enhancing citrate biosynthesis in P. fluorescens ATCC 13525. Significantly low extracellular citrate levels as compared to the intracellular levels in Pf(pAB7) suggested a probable limitation of efficient citrate transport.

scholarly journals Multifarious native plant growth promoting fluorescent pseudomonads associated with rhizosphere of Aloe barbadensis miller

2016 ◽  
Author(s):  
Anuradha Rai ◽  
Pradeep K Rai ◽  
Jay S Singh ◽  
Surendra Singh
Keyword(s):  
Plant Growth ◽  
Acc Deaminase ◽  
Fluorescent Pseudomonads ◽  
Plant Production ◽  
Geographical Information ◽  
Phosphate Solubilizing Bacteria ◽  
Aloe Barbadensis ◽  
Plant Growth Promoting ◽  
Growth Promoting ◽  
Phosphate Solubilizing

Medicinal plants provide an enormous bioresource of potential use in modern medicine and agriculture. Phosphorous deficiency is a major constraint to plant production. Sustainable agriculture could be promoted by harnessing the plant beneficial bacteria particularly the fluorescent pseudomonads associated with the rhizosphere of plants, to mobilize soil inorganic phosphate and also to increase its bioavailability to the plants. Total five hundred seven fluorescent Pseudomonas isolates were obtained from four different Aloe barbadensis (Miller) growing locations of Varanasi. These Pseudomonas strains were further evaluated in vitro for their ability to solubilize phosphate and to produce indole acetic acid (IAA), hydrogen cyanide (HCN), siderophore and aminocyclopropane (ACC) deaminase. Total 119 fluorescent Pseudomonas isolates from the rhizospheric soil (RS) and 25 isolates from the endorhizosperic (ER) region solubilized phosphate.Whereas 53 (36.8%) Pseudomonas isolates produced IAA and siderophore, 36(25%) and 31 (21.5%) isolates, however, produced HCN and ACC deaminase. Out of 119 phosphate solubilizing bacteria (PSB) from RS region, 51 (42.9%) isolates and 9 (36%) isolates out of 25 PSBs from ER region lacked plant growth promoting traits (PGPTs). Among the phosphate solubilizing fluorescent pseudomonads showing PGPT, 59 isolates have multiple traits and showed more than two types of PGPT. A positive correlation exists between siderophore and ACC deaminase producers. Clustering by principal component analysis (PCA) showed that RS was the most important factor influencing the ecological distribution and physiological characterization of PGPT- possessing PSB. Geographical Information System (GIS) and Kriging Interpolation method was used to map and establish spatial variation of soil properties of the study site.

scholarly journals Increased ethylene production by overexpressing phosphoenolpyruvate carboxylase in the cyanobacterium Synechocystis PCC 6803

2020 ◽  
Vol 13 (1) ◽  
Author(s):  
Claudia Durall ◽  
Pia Lindberg ◽  
Jianping Yu ◽  
Peter Lindblad
Keyword(s):  
Heterologous Expression ◽  
Ethylene Production ◽  
Phosphoenolpyruvate Carboxylase ◽  
Carbon Fixation ◽  
Tca Cycle ◽  
Central Carbon Metabolism ◽  
Gene Encoding ◽  
Carbon Supply ◽  
Phosphoenolpyruvate Synthase ◽  
Pcc 6803

Abstract Background Cyanobacteria can be metabolically engineered to convert CO2 to fuels and chemicals such as ethylene. A major challenge in such efforts is to optimize carbon fixation and partition towards target molecules. Results The efe gene encoding an ethylene-forming enzyme was introduced into a strain of the cyanobacterium Synechocystis PCC 6803 with increased phosphoenolpyruvate carboxylase (PEPc) levels. The resulting engineered strain (CD-P) showed significantly increased ethylene production (10.5 ± 3.1 µg mL−1 OD−1 day−1) compared to the control strain (6.4 ± 1.4 µg mL−1 OD−1 day−1). Interestingly, extra copies of the native pepc or the heterologous expression of PEPc from the cyanobacterium Synechococcus PCC 7002 (Synechococcus) in the CD-P, increased ethylene production (19.2 ± 1.3 and 18.3 ± 3.3 µg mL−1 OD−1 day−1, respectively) when the cells were treated with the acetyl-CoA carboxylase inhibitor, cycloxydim. A heterologous expression of phosphoenolpyruvate synthase (PPSA) from Synechococcus in the CD-P also increased ethylene production (16.77 ± 4.48 µg mL−1 OD−1 day−1) showing differences in the regulation of the native and the PPSA from Synechococcus in Synechocystis. Conclusions This work demonstrates that genetic rewiring of cyanobacterial central carbon metabolism can enhance carbon supply to the TCA cycle and thereby further increase ethylene production.

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