Isolation, Characterization, and Identification of Zinc-Solubilizing Bacteria (ZSB) from Wetland Rice Fields in Peninsular Malaysia

Abstract

Micronutrients, such as zinc (Zn), are essential for the growth and development of a wide range of crops. To overcome Zn deficiency in the soil, Zn-solubilizing bacteria (ZSB) have recently been employed. In the present study, samples from the rice fields in the state of Selangor, Malaysia, were collected to isolate, characterize, and identify the ZSB. A total of 88 strains were isolated, and only 9 strains were able to solubilize the insoluble Zn on zinc oxide (ZnO)-, zinc carbonate (ZnCO3)-, and zinc phosphate (Zn3(PO4)2)-amended Tris-minimal media agar and broth assays. The highest Zn solubilization (20.99%) was measured for the TM23 isolate when exposed to Zn3(PO4)2-modified media culture, whereas ZnCO3 showed the lowest (3.35%) Zn solubilization by ZSB. In addition, nine isolated ZSB also exhibited plant-growth-promoting (PGP) traits, including nitrogen fixation ability, siderophore production, indole acetic acid production (35.28–65.48 mL−1), phosphate solubilization (27.69–77.38%), enzyme hydrolysis, and production of organic acids. Most of the isolated strains (88) were Gram-negative, except for TM54, which was Gram-positive. The four potential ZSB isolates based on 16RS rDNA sequence analysis were identified as Serratia sp. and Acinetobacter sp. Hence, this study’s findings suggest that these isolates could be prospective candidates to overcome Zn deficiencies and reduce the consumption of chemical fertilizers in agricultural areas.