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

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.

From Isolation of Phosphate Solubilizing Microbes to Their Formulation and Use as Biofertilizers: Status and Needs

“…These bacteria deserve special attention due to their ability to adapt to diverse ecosystems such as desert soil, marine soil, rock phosphate deposit etc. (Nafis et al, 2019;Qu et al, 2019). Therefore, future research should focused on this group which still has a hidden repertoire that can be explored to develop quality bio-fertilizers.…”

“…Biofertilizers are commonly defined as "Preparation containing live microbes which helps in enhancing the soil fertility either by fixing atmospheric nitrogen, solubilizing phosphorus or decomposing organic wastes or by augmenting plant growth by producing growth hormones with their biological activities" (Chaparro et al, 2014;Okur, 2018). Many strains, some of which have interesting biotechnological potential have been isolated from the extensive research programs on plant-beneficial microorganisms (Sivasakthivelan and Saranraj, 2013;Umesha et al, 2018;Nafis et al, 2019). Nitrogen fixers, potassium and phosphorus solubilizers, or their combinations with molds fungi are the organisms commonly used as components of biofertilizers (Mohammadi and Sohrabi, 2012;Pathak and Kumar, 2016).…”

Desert Microbes for Boosting Sustainable Agriculture in Extreme Environments

“…Second, Actinobacteria: bacterial members belonging to this phyla, show strong versatility of growing under extreme selective conditions such as salinity, low and high pH, low water availability, extreme temperatures, radiation, and pressure, they embrace a complete spectrum of members living in extreme ecosystems (e.g., alkaliphilic, acidotolerant, thermotolerant, and halotolerant strains) (Mohammadipanah and Wink, 2016). On the genus level, Actinobacteria harbor some of plant growth promoting conferring genera such as Streptomyces, Saccharomonospora, and Nocardioides (Yandigeri et al, 2012;Nafis et al, 2019). Finally, it is clear that desert habitats exert selective pressures on their soil and plant associated bacterial communities to choose the best-adapted phyla to help them thrive in such extreme conditions.…”

Industrially Important Enzyme and Plant Growth Promoter Potential of Soil Actinomycetes

“…Among the actinomycetes isolates, six isolates were negative for IAA production.The reason for thismay be the producing level of IAA not at the detectable sensitivity range of the test used.The range of IAA concentration produced by the isolates was 5-66.15 µg/mL (Table 02). IAA production of Actonomycetes from extream niches in Morocco was 6.70-75.54 µg/mL (Nafis et al, 2019). Approximately similar range of IAA production also can be seen in soil Actinomycetes.…”