Jujube plant can survive in arid climates and tolerates both biotic and abiotic stresses. Here, we isolated, for the first time in Morocco, nine phosphate solubilizing bacteria strains from jujube rhizosphere, designated J10 to J13, J15, J153 to J156. Genotypic identification based on 16S rDNA sequencing, revealed six strains that belong to Pseudomonas (J10, J12, J13, J15, J153 and J154), two to Bacillus (J11 and J156), and one to Paenibacillus J155. Siderophores were produced by all strains. Proteases activity was missing in Pseudomonas sp. J153 J154, whereas cellulase was restricted only to Pseudomonas sp. J10, Paenibacillus xylanexedens J155 and Bacillus cereus J156. Indole-3- acetic acid and ammonia were also produced by all strains, with a maxima of 204.28 μg mL?1 in Bacillus megaterium J11 and 0.33 μmol mL?1 in Pseudomonas sp. J153, respectively. Pseudomonas sp. J10 and B. cereus J156 grew on plates containing 1,500 μg mL?1 of nickel nitrate, while Pseudomonas sp. J153 withstood 1,500 μg mL?1 of either copper sulfate or cadmium sulfate. Phenotypic analysis of the potential of the isolates to promote early plant growth showed that wheat seeds inoculated with either P. moraviensis J12 or B. cereus J156 remarkably increased germination rate and seedlings growth. Lastly, antibiotic resistance profiling revealed that except for Pseudomonas sp. J11 and B. cereus J156, remaining strains displayed resistance at least to one of tested antibiotics. Collectively, Pseudomonas sp. J10, P. moraviensis J12, Pseudomonas sp. J153 and B. cereus J156, represent potential biofertilizers suitable for soils that are poor in P, and/or heavy metals contaminated.To get more news about tube et jujubes, you can visit hl-juicer.com official website.
Phosphorus (P) is considered one of the most important elements in plant nutrition after nitrogen. It is an essential macronutrient to all major metabolic processes in plants growth e.g., photosynthesis, energy transfer, respiration, and signal transduction (Khan et al., 2010; Rahman et al., 2017). Phosphate solubilizing microorganisms including bacteria play an important role in enhancing soil fertility and plant growth (Miransari Mackenzie, 2010). Therefore, it is paramount to explore management strategies which are considered as an environmentally friendly process and economically feasible procedure to improve crop production and maximize their yields in P-poor soils (Zaidi et al., 2009). Exploration of the biodiversity of rhizobacteria and the optimization/manipulation of microbial interactions in the rhizosphere represents an imperative step towards formulating more efficient microbial inoculants with high P-solubilizing ability (Khan, Zaidi Wani, 2007). Although P is plentiful in soils in both organic and inorganic forms, it is in unavailable forms for root uptake (Sharma et al., 2013). Numerous soil microorganisms particularly those present in plant’s rhizosphere can release the bound forms of P to a soluble form to increase its bioavailability to plants (Narayanasamy, Ghosh Sarkar, 1981; Dubey et al., 1997; Dave Patel, 2003). PSB (phosphate solubilizing bacteria) belong to plant growth promoting rhizobacteria (PGPR) and are capable of solubilizing inorganic P from a variety of sources, such as dicalcium phosphate, tricalcium phosphate, or rock phosphate (Khan et al., 2010). Rhizobacteria are considered to be the best-known beneficial plant-associated bacteria and the most valuable bio-inoculants as they showed promising performances under controlled conditions such as the production of phytohormones, siderophores, phosphate solubilization, and nitrogen fixation (Pérez-Monta?o et al., 2014).
A number of strategies have been documented to improve phosphorus availability in soils including, agronomic practices, organic amendments, composting, arbuscular mycorrhizal fungi, P efficient cultivars, and phosphate solubilizing microbes (Kunwar, Lamichhane Gauchan, 2018). This later strategy is one of the most promising, as it is more sustainable and considered to be eco-friendly (Gyaneshwar et al., 2002). In contrast to other strategies, microbes have multiples benefits to plants as they contribute directly and indirectly to the nutrition, biocontrol of pathogens, and mitigating abiotic stresses (Kunwar, Lamichhane Gauchan, 2018). Strains belonging to the bacterial genera Pseudomonas, Bacillus, Rhizobacterium, and Enterobacter are known as potent P solubilizing microorganisms (Whitelaw, 1999).
Antibiotic resistance is a major concern whose emergence and spreading rates are increasing. It is one of the major problems in deploying bacterial-based biofertilizers (Kang et al., 2017). Antibiotic resistance genes (ARGs) harbored by PGPB can be an inborn or gained property. Intrinsic resistance may be due to the presence of multidrug efflux pumps. This is supported by the phylogenetic analysis of several genes involved in antibiotic resistance which could be due to an evolutionary pattern (D’Costa et al., 2011; Van Goethem et al., 2018). Acquired antibiotic resistance may also reflect the acquisition of new resistance genes from other organisms by horizontal gene transfer from bacteria. The resistance of PGPR to antibiotics is a double-edged sword. On the one hand, resistant bacteria can serve either as markers to monitor bacteria survival in vitro or in vivo (Kluepfel, 1993; Trivedi et al., 2004), and to help them competing in native and open microbial niches (Cray et al., 2013). On the other hand, their application in soil as bio-inoculants may represent potential risks by transferring ARG to other bacteria colonizing the same environment (Ramakrishna, Yadav Li, 2019). However, a potential source of ARGs carried by PGPR and derived biocontrol agents and/or bio-fertilizers is widely forgotten and ignored (Kang et al., 2017). Hence, the urgency of large-scale introduction of the beneficial bacteria into soils can aggravate the situation leading to the spread of ARGs in the environment. In addition to antibiotic resistance, heavy metal pollution is an environmental concern that can have harmful effects on human health when they are taken up in amounts that cannot be processed by the organism (Chauhan Solanki, 2015). Many toxic elements such as Cu2+, Pb2+, Zn2+, Cd2+ and As3+ are generally found in detectable quantities in wastewater (Pescod, 1992). Some of these elements are necessary for plant growth, but a high concentration of them in wastewater becomes an obstacle (Pescod, 1992), which leads to the remediation of contaminated environments via sustainable methods (Pizarro-Tobías et al., 2015). Several methods are already being used to clean up the environment from these types of contaminants. The use of microorganisms capable of adsorbing heavy metal ions for bioremediation in contaminated soil is considered as an eco-friendly method and do not produce secondary pollution. Certain PGPR can reduce soil toxicity around plant roots. These PGPR also protect plants from being affected by toxic heavy metals (Gamalero Glick, 2011). Various free-living rhizospheric PGPR can be used in contaminated soils to alleviate lethal effects of heavy-metals (Belimov et al., 2004). Bacillus and Pseudomonas exhibit vital role in the bioremediation of heavy metals (Khan Ahmad, 2006; Niu et al., 2011).
