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. 2021 Sep 23;26(19):5758.
doi: 10.3390/molecules26195758.

Psychrotolerant Mesorhizobium sp. Isolated from Temperate and Cold Desert Regions Solubilizes Potassium and Produces Multiple Plant Growth Promoting Metabolites

Zahoor Ahmad Baba  1 , Basharat Hamid  1 , Tahir Ahmad Sheikh  2 , Saad H Alotaibi  3 , Hesham A El Enshasy  4   5 , Mohammad Javed Ansari  6 , Ali Tan Kee Zuan  7 , R Z Sayyed  8
Affiliations

Psychrotolerant Mesorhizobium sp. Isolated from Temperate and Cold Desert Regions Solubilizes Potassium and Produces Multiple Plant Growth Promoting Metabolites

Zahoor Ahmad Baba et al. Molecules. .

Abstract

Soil potassium (K) supplement depends intensively on the application of chemical fertilizers, which have substantial harmful environmental effects. However, some bacteria can act as inoculants by converting unavailable and insoluble K forms into plant-accessible forms. Such bacteria are an eco-friendly approach for enhancing plant K absorption and consequently reducing utilization of chemical fertilization. Therefore, the present research was undertaken to isolate, screen, and characterize the K solubilizing bacteria (KSB) from the rhizosphere soils of northern India. Overall, 110 strains were isolated, but only 13 isolates showed significant K solubilizing ability by forming a halo zone on solid media. They were further screened for K solubilizing activity at 0 °C, 1 °C, 3 °C, 5 °C, 7 °C, 15 °C, and 20 °C for 5, 10, and 20 days. All the bacterial isolates showed mineral K solubilization activity at these different temperatures. However, the content of K solubilization increased with the upsurge in temperature and period of incubation. The isolate KSB (Grz) showed the highest K solubilization index of 462.28% after 48 h of incubation at 20 °C. The maximum of 23.38 µg K/mL broth was solubilized by the isolate KSB (Grz) at 20 °C after 20 days of incubation. Based on morphological, biochemical, and molecular characterization (through the 16S rDNA approach), the isolate KSB (Grz) was identified as Mesorhizobium sp. The majority of the strains produced HCN and ammonia. The maximum indole acetic acid (IAA) (31.54 µM/mL) and cellulase (390 µM/mL) were produced by the isolate KSB (Grz). In contrast, the highest protease (525.12 µM/mL) and chitinase (5.20 µM/mL) activities were shown by standard strain Bacillus mucilaginosus and KSB (Gmr) isolate, respectively.

Keywords: Mesorhizobium sp.; cellulase; plant growth promoting traits; potassium solubilization; rhizosphere.

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Conflict of interest statement

The authors declare that they have no conflict of interest that could influence the reported work.

Figures

Figure 1
Figure 1
KSB showing solubilization on Aleksandrov’s agar media at 10 °C.
Figure 2
Figure 2
Phylogenetic tree of K-solubilizing KSB (Grz) strain based on 16S rDNA sequences.
See this image and copyright information in PMC

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