Phosphate solubilization, indole-3-acetic acid synthesis and nitrogen fixation ability of various indigenous microorganism communities from different agriecosystem habitats

Abstract

Bio-fertilizer formulation from indigenous microorganism communities (IMOCs) is great suitable methods applied widely in the eastern part of world for the extraction of minerals, enhancement of agriculture and waste management although its functionalities have been unknown. The aim of this study was to assess phosphate solubility, indole-3-acetic acid (IAA) biosynthesis and nitrogen fixation efficacy of various IMOCs from different farming systems within Soc Trang province of Vietnam. Phosphate solubilization and synthesis IAA abilities of collected IMOCs were investigated in National Botanical Research Institute's Phosphate (NBRIP) liquid media containing tricalcium phosphate (TCP) as the sole P source. This medium was supplemented with and without tryptophan (100 mg/L) for IAA synthesis capability evaluation while nitrogen fixation ability was tested in liquid N-free Burks media. Besides, nifH functional gene involving in nitrogen fixation was also detected by specific polF/polR primers. The results showed that all surveyed IMOCs were found to solubilize TCP with a various extent, and the maximum amount of P2O5 solubilized was over 2,000 mg/L. In regard to the IAA biosynthesis, all IMOCs were able to biosynthesize considerably IAA with the highest IAA amount of 56.6 mg/L. All surveyed IMOCs had potential in nitrogen fixation when the primer amplified nifH gene successfully from DNA of collected IMO, and eight out of 15 IMOCs proved their nitrogen fixation with quantity varied between 1.0 and 6.5 mg/L N. In conclusion, all collected IMOCs had beneficial functions for plants like phosphate solubility, IAA synthesis and biological nitrogen fixation which can be exploited for enhancing soil fertility and plant growth.