Characterization of Novel Species of Potassium-Dissolving Purple Nonsulfur Bacteria Isolated from In-Dyked Alluvial Upland Soil for Maize Cultivation

Abstract

Potassium (K) is immobilized within the clay minerals, making it unavailable for plant use. Therefore, the current study aimed to (i) select isolates of purple nonsulfur bacteria that can dissolve K (K-PNSB) and (ii) evaluate the production of plant-growth-promoting substances by the K-PNSB isolates. The results revealed that from in-dyked alluvial soils in hybrid maize fields, 61 K-PNSB isolates were obtained under the pH 5.50 conditions. The total dissolved K content (Kdis) by the 61 K-PNSB isolates fluctuated from 56.2 to 98.6 mg L−1. Therein, three isolates, including M-Sl-09, M-So-11, and M-So-14 had Kdis of 48.1–48.8 mg L−1 under aerobic dark condition (ADC) and 47.6–49.7 mg L−1 under microaerobic light condition (MLC). Moreover, these three isolates can also fix nitrogen (19.1–21.5 mg L−1 and 2.64–7.24 mg L−1), solubilize Ca-P (44.3–46.8 mg L−1 and 0.737–6.965 mg L−1), produce indole-3-acetic acid (5.34–7.13 and 2.40–3.23 mg L−1), 5-aminolevulinic acid (1.85–2.39 and 1.53–2.47 mg L−1), siderophores (1.06–1.52 and 0.92–1.26 mg L−1), and exopolymeric substances (18.1–18.8 and 52.0–56.0%), respectively, under ADC and MLC. The bacteria were identified according to their 16S rDNA as Cereibacter sphaeroides M-Sl-09, Rhodopseudomonas thermotolerans M-So-11, and Rhodospeudomonas palustris M-So-14. These potential bacteria should be further investigated as a plant-growth-promoting biofertilizer.