Shams Tabrez Khan

Zn‐deficiency causes immense losses to agriculture and leads to various human health issues adding to the burden on the global healthcare system. Growing zinc‐dense cereals using Zn‐biofertilizer is one of the most enticing solutions to the problem. In this study a Zn‐biofertilizer containing a consortium of Zn‐solubilizing strains of Streptomyces sp., Pseudomonas sp. and Zinc oxide nanoparticles as source of Zn was prepared. Strains showing an excellent Zn‐solubilization efficiency (>200%), additional plant‐growth‐promoting traits, abiotic stress tolerance, and root colonization were selected. Seven experiments, mainly comparing the influence of bulk and nano‐ZnO as Zn‐sources in combination with the prepared Zn‐biofertilizer on wheat plant growth and grain Zn‐fortification were performed. When wheat plants were grown in the presence of prepared biofertilizer and nano‐ZnO a significant increase in plant vegetative growth and grain yield was observed. A 35.1%, 60.5% and 67.2% increase in total‐ plant length, fresh and dry‐weight respectively, was observed compared to the control. Similarly, wheat grains per spike, grain yield, and grain protein increased by 17.0%, 13.9%, and 47.5%, respectively. The Atomic Absorption Spectroscopy and SEM–EDX of wheat grains grown with biofertilizer and nano‐ZnO reveal a high Zn‐content (43.0 ± 0.5 mg kg ⁻¹ ) in the grains. The AAS analysis of the blood from Wistar rats fed with Zn‐dense wheat flour obtained in the study shows a higher Zn‐content (7.79 ± 0.18 μg ml ⁻¹ ) in the blood than those fed with control flour. This study conclusively proves that the prepared Zn‐biofertilizer with ZnO‐nanoparticles can improve the Zn‐content of wheat, consequently increasing blood Zn‐content in rats.

The decline of new antibiotics and the emergence of multidrug resistance in pathogens necessitates a revisit of strategies used for lead compound discovery. This study proposes to induce the production of bioactive compounds with sub-lethal concentrations of silver nanoparticles (Ag-NPs). A total of Forty-two Actinobacteria isolates from four Saudi soil samples were grown with and without sub-lethal concentration of Ag-NPs (50 µg ml⁻¹). The spent broth grown with Ag-NPs, or without Ag-NPs were screened for antimicrobial activity against four bacteria. Interestingly, out of 42 strains, broths of three strains grown with sub-lethal concentration of Ag-NPs exhibit antimicrobial activity against Staphylococcus aureus and Micrococcus luteus. Among these, two strains S4-4 and S4-21 identified as Streptomyces labedae and Streptomyces tirandamycinicus based on 16S rRNA gene sequence were selected for detailed study. The change in the secondary metabolites profile in the presence of Ag-NPs was evaluated using GC–MS and LC–MS analyses. Butanol extracts of spent broth grown with Ag-NPs exhibit strong antimicrobial activity against M. luteus and S. aureus. While the extracts of the controls with the same concentration of Ag-NPs do not show any activity. GC-analysis revealed a clear change in the secondary metabolite profile when grown with Ag-NPs. Similarly, the LC–MS patterns also differ significantly. Results of this study, strongly suggest that sub-lethal concentrations of Ag-NPs influence the production of secondary metabolites by Streptomyces. Besides, LC–MS results identified possible secondary metabolites, associated with oxidative stress and antimicrobial activities. This strategy can be used to possibly induce cryptic biosynthetic gene clusters for the discovery of new lead compounds.

Zinc-deficiency, a global health challenge affects one-third of the world population. Zinc solubilizing bacteria (ZSB) increases plant vegetative growth, grain’s Zn-content ensuring improved dietary Zn-supply offering an efficient and cost-effective solution. This study aimed at understanding that how the presence of two soil abundant nanoparticles silver and titanium dioxide in the rhizosphere influences the activity of ZSB and plant’s vegetative growth. Two ZSB strains D-7 and D-117 with good zinc solubilization efficiency of 254 and 260%, respectively were used with ZnO-NPs for Zn fortification of Mung bean in the presence of various doses of TiO₂ and Ag-NPs. Two sets of pots, were used, one containing ZSB, Mung bean seeds, ZnO-NPs (20 mg kg^− 1 soil) and various doses of nanoparticles. ZSB-free pots were used as control. The plants were studied for change in rate of seed germination, vegetative growth (shoot and root length, fresh and dry weight), photosynthetic pigment and Zn-content. Lower dose of nanomaterials (50 and 100 mg kg^− 1 soil) slightly promoted the plant growth compared to control. While, higher doses (200 and 400 mg kg^− 1 soil) inhibited the growth. A maximum decrease of shoot length, root length, fresh-weight, and dry-weight of 37.5, 62.3, 57.1, and 53.2%, respectively was observed with 400 mg kg^− 1 soil of Ag-NPs. In the presence of ZSB the decrease was 34.8, 21.3, 41.6, and 37.9, respectively with the same concentration of Ag-NPs. Results presented in this study demonstrate that ZSB alleviate the toxicity of the nanoparticles and improves Zn content in Mung bean.

Introduction: Agricultural productivity in the arid hot desert climate of UAE is limited by the unavailability of water, high temperature, and salt stresses. Growing enough food under abiotic stresses and decreasing reliance on imports in an era of global warming are a challenge. Biochar with high water and nutrient retention capacity and acid neutralization activity is an attractive soil conditioner. This study investigates the microbial community in the arid soil of Dubai under shade house conditions irrigated with saline water and the shift in the microbial community, following 1 year of amendment with indigenously prepared biochar from date palm waste.Methods: Amplicon sequencing was used to elucidate changes in bacterial, archaeal, and fungal community structures in response to long-term biochar amendment. Samples were collected from quinoa fields receiving standard NPK doses and from fields receiving 20 and 30 tons ha⁻¹ of biochar, in addition to NPK for 1 year. Water holding capacity, pH, electrical conductivity, calcium, magnesium, chloride, potassium, sodium, phosphorus, total carbon, organic matter, and total nitrogen in the soil from biochar-treated and untreated controls were determined.Results and discussion: The results show that soil amendment with biochar helps retain archaeal and bacterial diversity. Analysis of differentially abundant bacterial and fungal genera indicates enrichment of plant growth-promoting microorganisms. Interestingly, many of the abundant genera are known to tolerate salt stress, and some observed genera were of marine origin. Biochar application improved the mineral status and organic matter content of the soil. Various physicochemical properties of soil receiving 30 tons ha⁻¹ of biochar improved significantly over the control soil. This study strongly suggests that biochar helps retain soil fertility through the enrichment of plant growth-promoting microorganisms.

A staggering number of nanomaterials-based products are being engineered and produced commercially. Many of these engineered nanomaterials (ENMs) are finally disposed into the soil through various routes in enormous quantities. Nanomaterials are also being specially tailored for their use in agriculture as nano-fertilizers, nano-pesticides, and nano-based biosensors, which is leading to their accumulation in the soil. The presence of ENMs considerably affects the soil microbiome, including the abundance and diversity of microbes. In addition, they also influence crucial microbial processes, such as nitrogen fixation, mineralization, and plant growth promoting activities. ENMs conduct in soil is typically dependent on various properties of ENMs and soil. Among nanoparticles, silver and zinc oxide have been extensively prepared and studied owing to their excellent industrial properties and well-known antimicrobial activities. Therefore, at this stage, it is imperative to understand how these ENMs influence the soil microbiome and related processes. These investigations will provide necessary information to regulate the applications of ENMs for sustainable agriculture and may help in increasing agrarian production. Therefore, this review discusses several such issues.

Understanding the microbial communities in anaerobic digesters, especially bacteria and archaea, is key to its better operation and regulation. Microbial communities in the anaerobic digesters of the Gulf region where climatic conditions and other factors may impact the incoming feed are not documented. Therefore, Archaeal and Bacterial communities of three full-scale anaerobic digesters, namely AD1, AD3, and AD5 of the Jebel Ali Sewage water Treatment Plant (JASTP) were analyzed by Illumina sequencing of 16S rRNA genes. Among bacteria, the most abundant genus was fermentative bacteriaAcetobacteroides(Blvii28). Other predominant bacterial genera in the digesters included thermophilic bacteria (FervidobacteriumandCoprothermobacter) and halophilic bacteria likeHaloterrigenaandSediminibacter. This can be correlated with the climatic condition in Dubai, where the bacteria in the incoming feed may be thermophilic or halophilic as much of the water used in the country is desalinated seawater. The predominant Archaea include mainly the members of the phyla Euryarchaeota and Crenarchaeota belonging to the genusMethanocorpusculum,Metallosphaera,Methanocella, andMethanococcus. The highest population ofMethanocorpusculum(more than 50% of total Archaea), and other hydrogenotrophic archaea, is in agreement with the high population of bacterial generaAcetobacteroides(Blvii28) andFervidobacterium, capable of fermenting organic substrates into acetate and H₂.Coprothermobacter, which is known to improve protein degradation by establishing syntrophy with hydrogenotrophic archaea, is also one of the digesters’ dominant genera. The results suggest that the microbial community in three full-scale anaerobic digesters is different. To best of our knowledge this is the first detailed report from the UAE.