Inorganic Phosphate Solubilization by a Novel Isolated Bacterial Strain Enterobacter sp. ITCB-09 and Its Application Potential as Biofertilizer

Katia I Cob-Rivera,Gustavo Enrique Mendoza-Arroyo,Benito Dzib-Castillo,Antonio O Chab-Ruiz,Rodrigo Enrique Tun-Che,Manuel Jesús Chan-Bacab,Juan Carlos Camacho-Chab,Benjamín Otto Ortega-Morales,Ruth Noemi Aguila-Ramírez,René Efraín Canché Solís

doi:10.3390/agriculture10090383

Abstract

The excessive use of fertilizers in agriculture is mainly due to the recognized plant requirements for soluble phosphorus. This problem has limited the implementation of sustainable agriculture. A viable alternative is to use phosphate solubilizing soil microorganisms. This work aimed to isolate inorganic phosphorus-solubilizing bacteria from the soils of agroecosystems, to select and identify, based on sequencing and phylogenetic analysis of the 16S rRNA gene, the bacterium with the highest capacity for in vitro solubilization of inorganic phosphate. Additionally, we aimed to determine its primary phosphate solubilizing mechanisms and to evaluate its effect on Habanero pepper seedlings growth. A total of 21 bacterial strains were isolated by their activity on Pikovskaya agar. Of these, strain ITCB-09 exhibited the highest ability to solubilize inorganic phosphate (865.98 µg/mL) through the production of organic acids. This strain produced extracellular polymeric substances and siderophores that have ecological implications for phosphate solubilization. 16S rRNA gene sequence analysis revealed that strain ITCB-09 belongs to the genus Enterobacter. Enterobacter sp. ITCB-09, especially when immobilized in beads, had a positive effect on Capsicum chinense Jacq. seedling growth, indicating its potential as a biofertilizer.

Highlights

Phosphorus is present in soils as inorganic and, to a lesser extent, as organic compounds [1]
Bacterial solubilization of inorganic phosphate has been mainly associated with the release of low molecular weight organic acids, such as citric, oxalic, malic and gluconic, which chelate phosphate-bound cations through their hydroxyl and carboxyl groups, converting them into bioavailable forms [4,5]
Another less reported mechanism is the production of siderophores, low molecular weight secondary metabolites produced by bacteria under iron deficiency

Summary

Introduction

Phosphorus is present in soils as inorganic (with aluminum, calcium, iron, manganese) and, to a lesser extent, as organic compounds (organic matter) [1]. The mechanisms of microorganism-mediated phosphate solubilization and mineralization in soils, as well as their importance for plant growth, have been widely researched [3]. Mineralization involves enzymatic degradation of organic phosphorus releasing soluble forms [6,7,8], being phosphatases (phytases) that commonly carry out this activity in bacteria and fungi [9,10]. Another less reported mechanism is the production of siderophores, low molecular weight secondary metabolites produced by bacteria under iron deficiency. Some studies have described that bacteria can synthesize EPS in soils through the change in homeostasis during phosphate solubilization [14]

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Conclusion