Mineral Phosphate Solubilization in Burkholderia tropica Involves an Inducible PQQ-Glucose Dehydrogenase

Abstract

Authors' contributionsThis manuscript is the result of teamwork. Author PRB designed all the experiments and managed the analysis and discussion of results. Author SSG contributed with experiments in flasks and gluconic acid and phosphorous determinations and managed literature searches. Author MLG carried out the supervision of experiments in flasks and bioreactors in relation with enzyme activities measures. Authors GGF and VIG realized all the experiments in bioreactors and enzyme activities measures. Author JLB contributed with the discussion of results, organization and planning of the manuscript.Author MFL developed the experimental design, supervised the experiments and managed the analysis and discussion of results. All authors read and approved the final manuscript. Article InformationABSTRACT Aims: The objective of this work was to provide knowledgement about the mechanism and regulation of the mineral phosphate solubilization in Burkholderia tropica. To this end, the expression of the direct extracellular oxidative pathway in B. tropica was studied using different culture approaches. Bernabeu et al.; BMRJ, 13(4): 1-8, 2016; Article no.BMRJ.24405 2 Study Design: Plate assays and batch cultures in flasks and bioreactor were carried out in this study with B. tropica Mto-293 like target organism. The experiments were achieved at least three times with two repetitions per time. Place and Duration of Study: Departamento de Química, Centro de Investigación y Desarrollo en Fermentaciones Industriales, UNLP, CCT-La Plata-CONICET, between November 2014-2015. Methodology: Qualitative plate assays with different Carbon sources were carried out for the evaluation of Mineral Phosphate Solubilization phenotype. Batch cultures in flasks were carried out with different Carbon, Phosphorus and Nitrogen sources to determine quantitatively soluble phosphorus, gluconic acid and other ketoacids in the supernatants, and also PQQ-linked glucose and gluconate dehydrogenase activities in whole cells. Original Research ArticleCultures with some of the conditions mentioned before were carried out in bioreactor specifically to control pH. Results: This organism was able to produce significant amounts of gluconic acid via the expression of a PQQ-GDH and also showed a significant activity of GaDH. However, the direct oxidative pathway was only observed under conditions of Phosphorus starvation and/or Nitrogen fixation. Conclusion:The Mineral Phosphate Solubilization phenotype for B. tropica can be ascribed to the expression of the direct oxidative pathway which involves the expression of an active PQQ-linked glucose dehydrogenase. Nevertheless, this pathway is not expressed constitutively in this bacterium. Environmental conditions, like low P and N availability, led to an active extracellular glucose oxidation. Therefore, mineral phosphate solubilization in B. tropica involves an inducible pyrroloquinoline quinone-linked glucose dehydrogenase. These findings may contribute to the use of this bacterium as plant growth promoting bacte...

Tracking and plant growth‐promoting effect of Paraburkholderia tropica MTo‐293 applied to Solanum lycopersicum

“…Paraburkholderia tropica [15] has been characterized in vitro and in vivo assays as an epiphytic and endophytic PGPB [8,[16][17][18] able to fix nitrogen, solubilize phosphates, and produce siderophores and antifungal substances, consequently qualifying as a promising bacterium for application as bio-input. Using culturedependent techniques, P. tropica MTo-293 was reported to colonize commercial tomato hybrid seedlings grown under gnotobiotic conditions after inoculation on sprouted seeds [8].…”

Assessment of bacterial inoculant formulated with Paraburkholderia tropica to enhance wheat productivity

“…Paraburkholderia tropica was isolated from the rhizosphere, rhizoplane, and internal tissues of the stem and root of corn plants and from the tissues of sugarcane in different geographical regions (Reis et al 2004). P. tropica possesses different abilities to promote in vitro-plant growth, such as a biologic-nitrogen-fixation capability, an organicacid production facilitating phosphate solubilization, and a production of antifungal substances (Bernabeu et al 2016;Bolívar-Anillo et al 2016;Caballero-Mellado et al 2007;Tenorio-Salgado et al 2013). Bernabeu et al (2015) have reported that P. tropica MTo-293 is able to increase fruit yield in tomato plants by about 15% as compared to uninoculated controls under greenhouse conditions, but the in vivo plant-growth-promoting mechanisms were not discussed.…”