Today, the dramatic changes in types of food consumed have led to an increased burden of chronic diseases. Therefore, the emphasis of food research is not only to ensure quality food that can supply adequate nutrients to prevent nutrition related diseases, but also to ensure overall physical and mental-health. This has led to the concept of functional foods and nutraceuticals (FFNs), which can be ideally produced and delivered through plants. Metabolomics can help in getting the most relevant functional information, and thus has been considered the greatest -OMICS technology to date. However, metabolomics has not been exploited to the best potential in plant sciences. The technology can be leveraged to identify the health promoting compounds and metabolites that can be used for the development of FFNs. This article reviews (i) plant-based FFNs-related metabolites and their health benefits; (ii) use of different analytic platforms for targeted and non-targeted metabolite profiling along with experimental considerations; (iii) exploitation of metabolomics to develop FFNs in plants using various biotechnological tools; and (iv) potential use of metabolomics in plant breeding. We have also provided some insights into integration of metabolomics with latest genome editing tools for metabolic pathway regulation in plants.
Forty-three yeast isolates derived from various fermented foods, alcoholic beverages and traditional inocula of Western Himalayas were characterized by using traditional and molecular techniques. Traditional characterization identified these isolates as belonging to seven genera and eight species. Twenty-three yeast isolates were identified as Saccharomyces cerevisiae, six as Debaromyces hansenii, five as Issatchenkia orientalis, four as Saccharomyces fermentati, two as Schizosaccharomyces pombe and one each as Endomyces fibuliger, Brettanomyces bruxellensis and Candida tropicalis. The molecular characterization using four marker systems i.e. universal rice primers (URP), randomly amplified polymorphic DNA (RAPD), inter simple sequence repeat (ISSR) and delta typing was carried out, which revealed strainal level differences along with geographical origin clustering of various yeast isolates which otherwise could not be revealed through conventional characterization. URP markers were found to be best for revealing the genetic polymorphism hidden among forty-three yeast isolates followed by delta typing, RAPD and ISSR. In the above study, URP 6R and URP 9F were found to be species specific thereby producing specific banding pattern for a specific species.
Diazotrophs are nitrogen-fixing bacteria which possess the nifH gene that codes for the nitrogenase enzyme involved in reduction of atmospheric dinitrogen to ammonia. Seventy-two diazotrophic bacteria were isolated using eight nitrogen-free media from wheat rhizospheric soil. The diazotrophic population was found to be negatively related to soil nitrogen, whereas a positive correlation was observed with organic carbon and electrical conductivity of soil. The isolates were initially identified on the basis of cultural, morphological, and biochemical characterisation. Various diazotrophic isolates were screened for functional activities. Thirty-seven isolates were acetylene reduction assay positive, among which 28 isolates exhibited nitrogenase activity ranging from 22.3 to 72.0 nmol C2H4/h. The majority of isolates were able to produce indole acetic acid ranging from 11.2 to 23.0 µg/mL and only a few diazotrophs could solubilise phosphate. These isolates showed amplification with two nifH primers (nifH1 and nifH2), thereby confirming their diazotrophic potential. The positive nifH isolates were further characterised using restriction fragment length polymorphism of 16S rDNA to reveal diversity among them. Based on UPGMA clustering and partial sequencing of 16S rDNA, the isolates were identified as Azotobacter sp., Azospirillum sp., Stenotrophomonas maltophilia, Stenotrophomonas sp., Sphingomonas paucimobilis, Rhizobium larrymoorei, Pseudomonas aeruginosa, and Xanthomonas oryzae.
Plant rhizo-microbiome comprises complex microbial communities that colonize at the interphase of plant roots and soil. Plant growth-promoting rhizobacteria (PGPR) in the rhizosphere provide important ecosystem services ranging from the release of essential nutrients for enhancing soil quality and improving plant health to imparting protection to plants against rising biotic and abiotic stresses. Hence, PGPR serve as restoring agents to rejuvenate soil health and mediate plant fitness in the facet of changing climate. Though it is evident that nutrient availability in soil is managed through inter-linked mechanisms, how PGPR expedite these processes remain less recognized. Promising results of PGPR inoculation on plant growth are continually reported in controlled environmental conditions, however, their field application often fails due to competition with native microbiota and low colonization efficiency in roots. The development of highly efficient and smart bacterial synthetic communities by integrating bacterial ecological and genetic features provides better opportunities for successful inoculant formulations. This review provides an overview of the interplay between nutrient availability and disease suppression governed by rhizobacteria in soil followed by the role of synthetic bacterial communities in developing efficient microbial inoculants. Moreover, an outlook on the beneficial activities of rhizobacteria in modifying soil characteristics to sustainably boost agroecosystem functioning is also provided.
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