In efforts to improve plant productivity and enhance defense mechanisms against biotic and abiotic stresses, endophytic bacteria have been used as an alternative to chemical fertilizers and pesticides. In the current study, 25 endophytic microbes recovered from plant organs of Triticum aestivum L. (wheat) were assessed for biotic (phyto-fungal pathogens) and abiotic (salinity, drought, and heavy metal) stress tolerance. Among the recovered isolates, BPR-9 tolerated maximum salinity (18% NaCl), drought (15% PEG-6000), and heavy metals (µg mL⁻¹): Cd (1200), Cr (1000), Cu (1000), Pb (800), and Hg (30). Based on phenotypic and biochemical characteristics, as well as 16S rDNA gene sequencing, endophytic isolate BPR-9 was recognized as Priestia aryabhattai (accession no. OM743254.1). This isolate was revealed as a powerful multi-stress-tolerant crop growth promoter after extensive in-vitro testing for plant growth-promoting attributes, nutrient (phosphate, P; potassium, K; and zinc, Zn) solubilization efficiency, extracellular enzyme (protease, cellulase, amylase, lipase, and pectinase) synthesis, and potential for antagonistic activity against important fungal pathogens viz. Alternaria solani, Rhizoctonia solani, Fusarium oxysporum, and Ustilaginoidea virens. At elevated salt levels, increases were noted in indole-3-acetic acid; siderophores; P, K, and Zn-solubilization; ACC deaminase; and ammonia synthesized by Priestia aryabhattai. Additionally, under in-vitro plant bioassays, wheat seedlings inoculated with P. aryabhattai experienced superior growth compared to non-inoculated seedlings in high salinity (0–15% NaCl) environment. Under NaCl stress, germination rate, plant length, vigor indices, and leaf pigments of wheat seedlings significantly increased following P. aryabhattai inoculation. Furthermore, at 2%-NaCl, B. aryabhattai greatly and significantly (p ≤ 0.05) decreased relative leaf water content, membrane damage, and electrolyte leakage compared with the non-inoculated control. Catalase, superoxide dismutase, and peroxidase activity increased by 29, 32, and 21%, respectively, in wheat seedlings exposed to 2% NaCl and inoculated with the bacteria. The present findings demonstrate that endophytic P. aryabhattai strains might be used in the future as a multi-stress reducer and crop growth promoter in agronomically important crops including cereals.

The release of untreated tannery effluents comprising biotoxic heavy metal (HM) compounds into the ecosystem is one of our society’s most serious environmental and health issues. After discharge, HM-containing industrial effluents reach agricultural soils and thus negatively affect the soil microbial diversity. Considering these, we assessed the effect of HMs on identified soil beneficial bacteria. Here, the effects of four heavy metals (HMs), viz., chromium (Cr), cadmium (Cd), nickel (Ni), and lead (Pb), on cellular growth, physiology, cell permeability, and biofilm formation of Enterobacter cloacae MC9 (accession no.: MT672587) were evaluated. HMs in a concentration range of 25–200 μg mL^–1 were used throughout the study. Among HMs, Cd in general had the maximum detrimental effect on bacterial physiology. With increasing concentrations of HMs, bacterial activities consistently decreased. For instance, 200 μgCr mL^–1 concentration greatly and significantly (p ≤ 0.05) reduced the synthesis of indole-3-acetic acid (IAA) by 70% over control. Furthermore, 200 μg mL^–1 Cd maximally and significantly (p ≤ 0.05) reduced the synthesis of 2,3-dihydroxybenzoic acid (2,3-DHBA), salicylic acid (SA), 1-aminocyclopropane 1-carboxylate (ACC) deaminase, and extra polymeric substances (EPSs) of E. cloacae MC9 by 80, 81, 77, and 59%, respectively, over control. While assessing the toxic effect of HMs on the P-solubilizing activity of E. cloacae, the toxicity pattern followed the order Cr (mean value = 94.6 μg mL^–1) > Cd (mean value = 127.2 μg mL^–1) > Pb (mean value = 132.4 μg mL^–1) > Ni (mean value = 140.4 μg mL^–1). Furthermore, the colony-forming unit (CFU) count (Log₁₀) of strain MC9 was completely inhibited at 150, 175, and 200 μg mL^–1 concentrations of Cr and Cd. The confocal laser scanning microscopic (CLSM) analysis of HM-treated bacterial cells showed an increased number of red-colored dead cells as the concentration of HMs increased from 25 to 200 μg mL^–1. Likewise, the biofilm formation ability of strain MC9 was maximally (p ≤ 0.05) inhibited at higher concentrations of Cd. In summary, the present investigation undoubtedly suggests that E. cloacae strain MC9 recovered from the HM-contaminated rhizosphere endowed with multiple activities could play an important role in agricultural practices to augment crop productivity in soils contaminated with HMs. Also, there is an urgent need to control the direct discharge of industrial waste into running water to minimize heavy metal pollution. Furthermore, before the application of HMs in agricultural fields, their appropriate field dosages must be carefully monitored.

The usefulness of nanoparticles (NPs) in biological applications, such as nanomedicine, is becoming more widely acknowledged. Zinc oxide nanoparticles (ZnO-NPs) are a type of metal oxide nanoparticle with an extensive use in biomedicine. Here, ZnO-NPs were synthesized using Cassia siamea (L.) leaf extract and characterized using state-of-the-art techniques; UV–vis spectroscopy, XRD, FTIR, and SEM. At sub-minimum inhibitory concentration (MIC) levels, the ability of ZnO@Cs-NPs to suppress quorum-mediated virulence factors and biofilm formation against clinical MDR isolates (Pseudomonas aeruginosa PAO1 and Chromobacterium violaceum MCC-2290) was tested. The ½MIC of ZnO@Cs-NPs reduced violacein production by C. violaceum. Furthermore, ZnO@Cs-NPs sub-MIC significantly inhibited virulence factors such aspyoverdin, pyocyanin, elastase, exoprotease, rhamnolipid, and the swimming motility of P. aeruginosa PAO1 by 76.9, 49.0, 71.1, 53.3, 89.5, and 60%, respectively. Moreover, ZnO@Cs-NPs also showed wide anti-biofilm efficacy, inhibiting a maximum of 67 and 56% biofilms in P. aeruginosa and C. violaceum, respectively. In addition, ZnO@Cs-NPs suppressed extra polymeric substances (EPS) produced by isolates. Additionally, under confocal microscopy, propidium iodide-stained cells of P. aeruginosa and C. violaceum show ZnO@Cs-NP-induced impairment in membrane permeability, revealing strong anti-bacterial efficacy. This research demonstrates that newly synthesized ZnO@Cs-NPs demonstrate a strong efficacy against clinical isolates. In a nutshell, ZnO@Cs-NPs can be used as an alternative therapeutic agent for managing pathogenic infections.

Most bacteria exist in nature in the form of biofilms. One of the key survival strategies by bacteria to withstand chemical and physical stresses is by forming biofilms on biotic and abiotic surfaces. A different set of genes are expressed in biofilms compared to the planktonic mode of bacterial growth. According to data from the National Institutes of Health (NIH) and Centers for Disease Control and Prevention (CDC), nearly 80 percent of all human infections are encouraged by biofilms and roughly 65 percent of all hospital-acquired infections are associated with biofilms. Hence, considering the role of biofilms in clinical settings, there is an urgent need for the discovery/development of novel antibiofilm agents. In this study, we have tested the effect of freshly prepared titanium dioxide nanoparticles (TiO₂-NPs) synthesized using Carum copticum extract on biofilms, both against Gram +ve and Gram −ve bacteria. Being environment friendly in nature, the green route of nanoparticle synthesis is believed to be advantageous over chemical synthesis of metal nanoparticles. The synthesized nanoparticles were found to be predominantly spherical or spheroidal in shape with an average size of 12.01 ± 5.58 nm. As evident from data, more than 70% inhibition of biofilms of test bacteria was achieved in the presence of TiO₂-NPs. Electron microscopic analysis revealed that the adherence and colonization of bacteria on the glass surface were remarkably reduced by the treatment of TiO₂-NPs. The EPS secretion of E. coli ATCC 25922 and P. aeruginosa PAO1 were inhibited by 62.08 and 74.94%, respectively. The EPS secretion of S. aureus MTCC 3160 was least inhibited (<55%) compared to other test bacteria. Moreover, TiO₂-NPs successfully eradicated the preformed biofilms of E. coli ATCC 25922, P. aeruginosa PAO1, and S. aureus MTCC 3160 by 60.09, 64.14, and 48.30%, respectively. The findings demonstrate the efficacy of green synthesized titanium dioxide nanoparticles in inhibiting and eradicating the biofilms of bacterial pathogens and they may be further exploited for the development of a new alternative antibiofilm agent.

Plants are an important source of essential bioactive compounds that not only have a beneficial role in human health and nutrition but also act as drivers for shaping gut microbiome. However, the mechanism of their functional attributes is not fully understood despite their significance. One such important plant is Crocus sativus, also known as saffron, which possesses huge medicinal, nutritional, and industrial applications like food and cosmetics. The importance of this plant is grossly attributed to its incredible bioactive constituents such as crocins, crocetin, safranal, picrocrocin, and glycosides. These bioactive compounds possess a wide range of therapeutic activities against multiple human ailments. Since a huge number of studies have revealed negative unwanted side effects of modern-day drugs, the scientific communities at the global level are investigating a large number of medicinal plants to explore natural products as the best alternatives. Taken into consideration, the available research findings indicate that saffron has a huge scope to be further explored to establish alternative natural-product-based drugs for health benefits. In this review, we are providing an update on the role of bioactive compounds of saffron as therapeutic agents (human disorders and antimicrobial activity) and its nutritional values. We also highlighted the role of omics and metabolic engineering tools for increasing the content of key saffron bioactive molecules for its mass production. Finally, pre-clinical and clinical studies seem to be necessary to establish its therapeutic potential against human diseases.

Due to enhancement of industrial growth and urbanization, soil contamination is increasing prominently. Therefore, it is important to examine possible adverse effects of industrial waste. Soil samples were might to be polluted with several heavy-metals and pesticides. Gas chromatographic results showed occurrence of high-level of organochlorine and organophosphate pesticides in studied soil samples. Genotoxicity of soil extracts was assessed using environmental-risk assessment models. Soil samples were extracted in hexane and dichloromethane solvents and were evaluated for genotoxic potential by prokaryotic (Ames test, plasmid nicking assay and E. coli K-12 DNA repair defective mutants) and eukaryotic (Allium cepa root chromosomal aberration and Vigna radiata seed-germination test) bioassays. Strain TA98 was found the most susceptible among soil extracts. The mutagenicity of hexane soil extract from wastewater irrigation was found to be higher than that of DCM samples in terms of mutagenic index, mutagenic potential, and induction factor for Ames strains. The damage in DNA repair defective mutants of hexane extracts were found higher compared to DCM extracts at dose of 20 μl/ml of culture. Survival in polA, lexA and recA mutants were 39%, 47% and 55% while treated with hexane extract. Allium cepa test, mitotic index was decreased in dose-dependent way and various kinds of chromosomal aberrations were found. Vigna radiata seeds germination and other parameters were also affected when treated with wastewater irrigated (WWI) soil. Oxidative stress in V. radiata roots were also showed under CLS microscope. Genotoxicity of WWI soil extract was also confirmed by plasmid nicking test. Our study provides possible explanation for the assessment of potential health and environmental hazards of the industrial region.