Actinobacteria from Extreme Niches in Morocco and Their Plant Growth-Promoting Potentials

Ahmed Nafis,Abdelkhalek El Alaoui,Mohamed Hafidi,Yedir Ouhdouch,Anas Raklami,Bernard R Glick,Noura Bechtaoui,Lahcen Hassani,Fatima El Khalloufi,Lamfeddal Kouisni

doi:10.3390/d11080139

Abstract

The objectives of this study were to assess actinobacterial diversity in five Moroccan extreme habitats and to evaluate their plant growth-promoting (PGP) activities. The soil samples were collected from different locations, including soils contaminated with heavy metals, from a high altitude site, from the desert, and from a marine environment. In total, 23 actinobacteria were isolated, 8 from Merzouga sand soil; 5 from Cannabis sativa rhizospheric soil; 5 from Toubkal mountain; 4 from a Draa sfar mining site; and 1 from marine soil. Based on their genotypic classification using 16S rRNA gene sequences, 19 of all belonged to the genus Streptomyces (82%) while the rest are the members of the genera Nocardioides (4.5%), Saccharomonospora (4.5%), Actinomadura (4.5%), and Prauserella (4.5%). Isolates Streptomyces sp. TNC-1 and Streptomyces sp. MNC-1 showed the highest level of phosphorus solubilization activity with 12.39 and 8.56 mg/mL, respectively. All 23 isolates were able to solubilize potassium, and 91% of them could grow under nitrogen-free conditions. The ability of the isolated actinobacteria to form indole-3-acetic acid (IAA) ranged from 6.70 to 75.54 μg/mL with Streptomyces sp. MNC-1 being the best IAA producer. In addition, all of the actinobacteria could produce siderophores, with Saccharomonospora sp. LNS-1 synthesizing the greatest amount (138.92 μg/mL). Principal coordinate analysis revealed that Streptomyces spp. MNC-1, MNT-1, MNB-2, and KNC-5; Saccharomonospora sp. LNS-1; and Nocardioides sp. KNC-3 each showed a variety of high-level plant growth-promoting activities. The extreme environments in Morocco are rich with bioactive actinobacteria that possess a variety of plant growth-promoting potentials that can further benefit green and sustainable agriculture.

Highlights

Microorganisms can colonize various ecological niches, including extremophilic habitats, due to their adaptive features, including structural as well as functional adaptations [1]
We isolated 23 actinobacteria from five soil samples collected from various Moroccan ecosystems (Table 2)
We isolated some rare actinobacteria belonging to Nocardioides (4.5%), Saccharomonospora (4.5%), Actinomadura (4.5%)

Summary

Introduction

Microorganisms can colonize various ecological niches, including extremophilic habitats, due to their adaptive features, including structural as well as functional adaptations [1]. Diversity 2019, 11, 139 such as high mountain peaks, arid deserts, and polymetallic mines, but the actinobacterial diversity of these extreme habitats is lacking. Actinobacteria which occur in both terrestrial and aquatic habitats are among the most common groups of Gram-positive filamentous bacteria with high guanine-cytosine (G-C) content in their genomes and are able to form spores [4]. They have been found to colonize various ecosystems, including extreme environments, and to produce extensive secondary metabolites with major importance for biotechnology and agriculture [5]

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