Rapid advances in nanotechnology have led to its emergence as a tool for the development of green synthesized noble metal nanoparticles, especially silver nanoparticles (AgNPs), for applications in diverse fields such as human health, the environment and industry. The importance of AgNPs is because of their unique physicochemical and antimicrobial properties, with a myriad of activities that are applicable in various fields, including the pharmaceutical industry. Countries with high biodiversity require the collection and transformation of information about biological assets into processes, associations, methods and tools that must be combined with the sustainable utilization of biological diversity. Therefore, this review paper discusses the applicable studies of the biosynthesis of AgNPs and their antimicrobial activities towards microorganisms in different areas viz. medicine and agriculture. The confirmed antiviral properties of AgNPs promote their applicability for SARS-CoV-2 treatment, based on assimilating the virus’ activities with those of similar viruses via in vivo studies. In this review, an insight into the cytotoxicity and safety issues of AgNPs, along with their future prospects, is also provided.

A thermosensitive wild-type strain (PP201) of Rhizobium sp. (Cajanus) and its 14 heat-resistant mutants were characterized biochemically with regard to their cell surface (exopolysaccharides (EPSs) and lipopolysaccharides (LPSs)) properties and protein profile. Differences were observed between the parent strain and the mutants in all these parameters under high temperature conditions. At normal temperature (30 degrees C), only half of the mutant strains produced higher amounts of EPSs than the parent strain, but at 43 degrees C, all the mutants produced higher quantities of EPS. The LPS electrophoretic pattern of the parent strain PP201 and the heat-resistant mutants was almost identical at 30 degrees C. At 43 degrees C, the parent strain did not produce LPS but the mutants produced both kinds of LPSs. The protein electrophoretic pattern showed that the parent strain PP201 formed very few proteins at high temperature, whereas the mutants formed additional new proteins. A heat shock protein (Hsp) of 63-74 kDa was overproduced in all mutant strains.

Fourteen heat resistant mutant strains were isolated from a wild-type strain (PP201, Nod + Fix + ) of Rhizobium sp. (Cajanus) by giving it a heat shock of 43 0 C. These mutant strains showed a greater increase in optical density (O.D.) and a higher viable cell count in both rhizospheric and non-rhizospheric soil at high temperature. Symbiotic studies showed that pigeon pea plants inoculated with a few mutant strains had ineffective nodules (Nod + Fix -) under controlled temperature (43 o C) conditions, but under natural high temperature (40 -45 o C) conditions, the host plants infected with all the mutant strains showed higher total shoot nitrogen than the plants inoculated with the parent strain. Four mutant strains (HR-3, HR-6, HR-10 and HR-12) were found to be highly effi cient for all the symbiotic parameters, and thus have the potential to be used as bioinoculants in the North-Western regions of India during the summer season.

Biologically synthesized silver nanoparticles (SNPs) from Alhagi maurorum used as disinfectant, and in callogenesis and organogenesis. Green SNPs 125 and 150 mg/l were the best for explants sterilization. 2.0 mg/l – 6.0 mg/l SNPs when added in MS medium [(BAP (3.0mg/l) + NAA (0.2mg/l) + Kin (1.0 mg/l) + ascorbic acid 50.0 mg/l and 25 mg/l each of citric acid, arginine and adenine sulphate)] showed better calologenesis and organogenesis. Higher concentrations of SNPs resulted in decline of survival percentage, callus initiation and growth of cultured tissues.

Mung bean (Vigna radiata L.) sprout is a popular fresh vegetable, tasty and high in antioxidants. To increase yield and quality after the occurrence of both abiotic and biotic stresses, the application of seaweed extracts is of great importance. Hence, this study was conducted to determine the effect of Ascophyllum nodosum extract (ANE) in the presence of salt on the antioxidant potential of V. radiata sprouts. Different concentrations of ANE viz. 0.00, 0.01, 0.05, 0.10, and 0.50% and NaCl 0, 25, 50, 75, and 100 mM alone and in combinations were tested for researching the antioxidant potential of V. radiata sprouts at 0, 24, and 36 h of sprouting. The DPPH free-radical-scavenging activity of sprouts of V. radiata was found to increase with time and peaked at 24 h of treatment. The A. nodosum extract (0.01%) could reverse the ill effect of the low level of salinity posed by up to 25 mM NaCl. The increasing salinity deteriorated the antioxidant activity using ABTS method of sprouts down to 20.45% of the control at 100 mM NaCl. The total phenolic content (TPC), total flavonoid content (TFC), and reducing power of V. radiata sprouts was found to increase till 36 h of sprouting. A slight increase in TPC, TFC and reducing power was observed when seeds were treated with low concentrations of ANE. The elevation in TPC, TFC and reducing power upon treatment with low concentrations of ANE was also noticed in sprouts in saline combinations. Alpha amylase inhibition activity was found to reach a (67.16% ± 0.9) maximum at 24 h of sprouting at a 0.01% concentration of ANE. Tyrosinase inhibition and alpha glucosidase inhibition was 88.0% ± 2.11 and 84.92% ± 1.2 at 36 h of sprouting, respectively, at 0.01% concentration of ANE. A. nodosum extract is natural, environmentally friendly, and safe, and could be used as one of the strategies to decline stress at a low level and enhance the antioxidant activities in V. radiata sprouts, thus increasing its potential to be developed as an antioxidant-based functional food.

Algae are existing macroscopic materials with substantial benefits, including as important growth regulators and macronutrients and micronutrients for the growth of healthy crop plants. Biofertilizers obtained from algae are identified as novel production fertilizers or innovative biofertilizers without the detrimental impacts of chemicals. Seaweeds contain many water-soluble minerals and nutrients that plants can easily absorb and that are valuable for crop plants’ growth. At present, Ascophyllum nodosum (L.) Le Jolis extract outperforms chemical fertilizers in terms of increasing seed germination, plant development, and yield, as well as protecting plants from severe biotic and abiotic stresses. A. nodosum contains bioactive compounds that exhibit an array of biological activities such as antibiotic, anti-microbial, antioxidant, anti-cancer, anti-obesity, and anti-diabetic activities. A. nodosum extract (AnE) contains alginic acid and poly-uronides that improve soil’s water-carrying ability, morsel structure, aeration, and capillary action, stimulating root systems in plants, increasing microbial activity in soil, and improving mineral absorption and availability. The scientific literature has comprehensively reviewed these factors, providing information about the different functions of A. nodosum in plant growth, yield, and quality, the alleviation of biotic and abiotic stresses in plants, and their effects on the interactions of plant root systems and microbes. The application of AnE significantly improved the germination rate, increased the growth of lateral roots, enhanced water and nutrient use efficiencies, increased antioxidant activity, increased phenolic and flavonoid contents, increased chlorophyll and nutrient contents, alleviated the effects of abiotic and biotic stresses in different crop plants, and even improved the postharvest quality of different fruits.

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