Repression of mineral phosphate solubilizing phenotype in the presence of weak organic acids in plant growth promoting fluorescent pseudomonads.

Two phosphate solubilizing bacteria (PSB), M3 and SP1, were obtained from the rhizosphere of mungbean and sweet potato, respectively and identified as strains of Pseudomonas aeruginosa. Their rock phosphate (RP) solubilizing abilities were found to be due to secretion high amount of gluconic acid. In the presence of malate and succinate, individually and as mixture, the P solubilizing ability of both the strains was considerably reduced. This was correlated with a nearly 80% decrease in the activity of the glucose dehydrogenase (GDH) but not gluconate dehydrogenase (GAD) in both the isolates. Thus, GDH enzyme, catalyzing the periplasmic production of gluconic acid, is under reverse catabolite repression control by organic acids in P. aeruginosa M3 and SP1. This is of relevance in rhizospheric conditions and is a new explanation for the lack of field efficacy of such PSB.

Patel DK ，Murawala P ，Archana G ，Kumar GN ... -  《-》

Metabolic channeling of glucose towards gluconate in phosphate-solubilizing Pseudomonas aeruginosa P4 under phosphorus deficiency.

Buch A ，Archana G ，Naresh Kumar G 《RESEARCH IN MICROBIOLOGY》

Plasmid load adversely affects growth and gluconic acid secretion ability of mineral phosphate-solubilizing rhizospheric bacterium Enterobacter asburiae PSI3 under P limited conditions.

Effect of the metabolic load caused by the presence of plasmids on mineral phosphate-solubilizing (MPS) Enterobacter asburiae PSI3, was monitored with four plasmid cloning vectors and one native plasmid, varying in size, nature of the replicon, copy number and antibiotic resistance genes. Except for one plasmid, the presence of all other plasmids in E. asburiae PSI3 resulted in the loss of the MPS phenotype as reflected by the failure to bring about a drop in pH and release soluble P when grown in media containing rock phosphate (RP) as the sole P source. When 100 μM soluble P was supplemented along with RP, the adverse effects of plasmids on MPS phenotype and on growth parameters was reduced for some plasmid bearing derivatives, as monitored in terms of specific growth rates, glucose consumed, gluconic acids yields and P released. When 10 mM of soluble P as the only P source, was added to the medium all transformants showed growth and pH drop comparable with native strain. It may be concluded that different plasmids impose, to varying extents, a metabolic load in the phosphate-solubilizing bacterium E. asburiae PSI3 and results in diminishing its growth and P-solubilizing ability in P deficient conditions.

Sharma V ，Archana G ，Naresh Kumar G 《-》

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

Buch A ，Archana G ，Naresh Kumar G 《-》

Substrate specificity of glucose dehydrogenase (GDH) of Enterobacter asburiae PSI3 and rock phosphate solubilization with GDH substrates as C sources.

Sharma V ，Kumar V ，Archana G ，Kumar GN ... -  《CANADIAN JOURNAL OF MICROBIOLOGY》