Identification of heterotrophic zinc mobilization processes among bacterial strains isolated from wheat rhizosphere (Triticum aestivum L).

In this study, wheat rhizosphere soil serial dilutions were plated onto several solid microbiological media supplemented with scarcely soluble Zn oxide (ZnO) and 115 putative Zn solubilizing isolates were directly detected based on the formation of solubilization halo around the colonies. Eight strains were selected based on their Zn solubilization efficiency and siderophore production capacity. These included one Curtobacterium, two Plantibacter, three Pseudomonas, one Stenotrophomonas and one strain of Streptomyces In ZnO liquid solubilization assays, the presence of glucose clearly stimulated organic acid production, leading to media acidification and ZnO solubilization. While solubilization by Streptomyces and Curtobacterium was attributed, respectively, to the accumulated production of seven and eight different organic acids, the other strains solubilized Zn via gluconic, malonic and oxalic acid, exclusively. In contrast, in absence of glucose, ZnO dissolution resulted from protons extrusion (e.g. via ammonia consumption by Plantibacter strains) and complexation processes (i.e. complexation with glutamic acid in cultures of Curtobacterium). Therefore, while gluconic acid production was described as a major Zn solubilization mechanism in literature, this study goes beyond and shows that solubilization mechanisms are various among ZSB and strongly affected by growth conditions.IMPORTANCE Barriers towards a better understanding of the mechanisms underlying Zn solubilization...
Source: Applied and Environmental Microbiology - Category: Microbiology Authors: Tags: Appl Environ Microbiol Source Type: research