Phosphate solubilizing bacteria with glucose dehydrogenase gene for phosphorus uptake and beneficial effects on wheat

PLoS One. 2018 Sep 21;13(9):e0204408. doi: 10.1371/journal.pone.0204408. eCollection 2018.

Abstract

The aim of this study was to isolate, characterize and use phosphate solubilizing bacteria to enhance the bioavailability of insoluble Ca-phosphate for wheat plants. For this purpose, 15 phosphorus solubilizing bacteria (PSB) were isolated from wheat rhizospheric soils of Peshawar and southern Punjab region, Pakistan. These isolates were identified using light microscopy and 16S rRNA gene. Among the isolated bacteria, two strains (Pseudomonas sp. MS16 and Enterobacter sp. MS32) were the efficient P solubilizers based on their P solubilization activity determined qualitatively (solubilization index 3.2-5.8) as well as quantitatively (136-280 μg mL-1). These two strains produced indole-3-acetic acid (25.6-28.1 μg mL-1), gibberellic acid (2.5-11.8), solubilized zinc compounds (SI 2.8-3.3) and showed nitrogenase and 1-Aminocyclopropane-1-carboxylic acid deaminase activity in vitro. Phosphate solubilization activity of Pseudomonas sp. MS16 was further validated by amplification, sequencing and phylogenetic analysis of glucose dehydrogenase (gcd) gene (LT908484) responsible for P solubilization. Response Surface Methodology for large-scale production was used to find optimal conditions (Temperature 22.5°C, pH 7) for P solubilization. Glucose was found to support higher P solubilization in vitro. In an in vitro experiment, PSB treated wheat seedlings improved germination and seedling vigor (11% increases) as compared to un-inoculated control. Rhizoscanning of these seedlings showed an increase in various root growth parameters. Wheat inoculation with selected strain MS16 showed pronounced effect on grain yield in pot (38.5% increase) and field (17-18% increase) experiments compared to non-inoculated control. Root colonization by PSB through Florescent in situ Hybridization and Confocal Laser Scanning Microscopy confirmed their rhizosphere competence in soil. BOX-PCR confirmed the re-isolated colonies of Pseudomonas sp. MS16. The results indicated that gluconic acid producing Pseudomonas sp. MS16 from un-explored soils may be cost effective and environment friendly candidate to improve plant growth and phosphorous uptake by wheat plants.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacteria / enzymology
  • Bacteria / genetics*
  • Bacteria / metabolism*
  • Biological Transport
  • Glucose 1-Dehydrogenase / genetics*
  • Glucose 1-Dehydrogenase / metabolism
  • Phosphates / chemistry*
  • Phosphates / metabolism*
  • Phosphorus / metabolism*
  • Rhizosphere
  • Safety
  • Solubility
  • Triticum / microbiology*

Substances

  • Phosphates
  • Phosphorus
  • Glucose 1-Dehydrogenase

Grants and funding

The research work was partially supported by the grant of Higher Education Commission (HEC) funded project No. 3813 but there is no allocation of HEC project funds for charges of manuscript publication. Our institute (National Institute for Biotechnology & Genetic Engineering) does not financially support the authors to pay manuscript publication and processing charges. Furthermore, the corresponding author does not have any other grant from which this article processing charges can be paid. There was no additional external funding received for this study.