Saffron, a Potential Bridge between Nutrition and Disease Therapeutics: Global Health Challenges and Therapeutic Opportunities.

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.

Assessing phytotoxicity and cyto-genotoxicity of two insecticides using a battery of in-vitro biological assays.

Intensive use of chemical pesticides in agriculture poses environmental risks and may have negative impacts on agricultural productivity. The potential phytotoxicity of two chemical pesticides, chlorpyrifos (CPS) and fensulfothion (FSN), were evaluated using Cicer arietinum and Allium cepa as model crops. Different concentrations (0-100 µgmL-1) of both CPS and FSN decreased germination and biological attributes of C. arietinum. High pesticide doses significantly (p ≤ 0.05) caused membrane damage by producing thiobarbituric acid reactive substances (TBARS) and increasing proline (Pro) content. Pesticides elevated ROS levels and substantially increased the superoxide anions and H2O2 concentrations, thus aggravating cell injury. Plants exposed to high pesticide dosages displayed significantly higher antioxidant levels to combat pesticide-induced oxidative stress. Ascorbate peroxidase (APX), guaiacol peroxidase (GPX), catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD) increased by 48%, 93%, 71%, 52% and 94%, respectively, in C. arietinum roots exposed to 100 µgFSNmL-1. Under CLSM, pesticide-exposed C. arietinum and 2',7'-dichlorodihydrofluorescein diacetate (2'7'-DCF) and 3,3'-diaminobenzidine stained roots exhibited increased ROS production in a concentration-dependent manner. Additionally, enhanced Rhodamine 123 (Rhd 123) and Evan's blue fluorescence in roots, as well as changes in mitochondrial membrane potential (ΔΨm) and cellular apoptosis, were both associated with high pesticide dose. Allium cepa chromosomal aberration (CAs) assay showed a clear reduction in mitotic index (MI) and numerous chromosomal anomalies in root meristematic cells. Additionally, a-dose-dependent increase in DNA damage in root meristematic cells of A. cepa and conversion of the super-coiled form of DNA to open circular in pBR322 plasmid revealed the genotoxic potential of pesticides. The application of CPS and FSN suggests phytotoxic and cyto-genotoxic effects that emphasize the importance of careful monitoring of current pesticide level in soil before application and addition at optimal levels to soil-plant system. It is appropriate to prepare both target-specific and slow-release agrochemical formulations for crop protection with concurrent safeguarding of agroecosystems.

Phytogenically Synthesized Zinc Oxide Nanoparticles (ZnO-NPs) Potentially Inhibit the Bacterial Pathogens: In Vitro Studies.

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.

Core microbiota of wheat rhizosphere under Upper Indo-Gangetic plains and their response to soil physicochemical properties.

Wheat is widely cultivated in the Indo-Gangetic plains of India and forms the major staple food in the region. Understanding microbial community structure in wheat rhizosphere along the Indo-Gangetic plain and their association with soil properties can be an important base for developing strategies for microbial formulations. In the present study, an attempt was made to identify the core microbiota of wheat rhizosphere through a culture-independent approach. Rhizospheric soil samples were collected from 20 different sites along the upper Indo-Gangetic plains and their bacterial community composition was analyzed based on sequencing of the V3-V4 region of the 16S rRNA gene. Diversity analysis has shown significant variation in bacterial diversity among the sites. The taxonomic profile identified Proteobacteria, Chloroflexi, Actinobacteria, Bacteroidetes, Acidobacteria, Gemmatimonadetes, Planctomycetes, Verrucomicrobia, Firmicutes, and Cyanobacteria as the most dominant phyla in the wheat rhizosphere in the region. Core microbiota analysis revealed 188 taxa as core microbiota of wheat rhizosphere with eight genera recording more than 0.5% relative abundance. The order of most abundant genera in the core microbiota is Roseiflexus> Flavobacterium> Gemmatimonas> Haliangium> Iamia> Flavisolibacter> Ohtaekwangia> Herpetosiphon. Flavobacterium, Thermomonas, Massilia, Unclassified Rhizobiaceae, and Unclassified Crenarchaeota were identified as keystone taxa of the wheat rhizosphere. Correlation studies revealed, pH, organic carbon content, and contents of available nitrogen, phosphorus, and iron as the major factors driving bacterial diversity in the wheat rhizosphere. Redundancy analysis has shown the impact of different soil properties on the relative abundance of different genera of the core microbiota. The results of the present study can be used as a prelude to be developing microbial formulations based on core microbiota.

The Exogenous Application of 24-Epibrassinolide (24-EBL) Increases the Cd and Pb Resilience in Zea mays (L.) by Regulating the Growth and Physiological Mechanism.

Heavy metals (HMs) at a concentration above the threshold level act as environmental pollutants and very often threaten the agricultural productivity globally. Finding affordable and environmentally sustainable deliverables to address this issue is therefore a top focus. Phytohormones alleviate the HMs-induced toxicity and positively influence the plant growth. Considering the importance of phytohormones, the present study aimed to assess the effect of 24-epibrassinolide (24-EBL; 10 µM) as seed soaking treatment on growth performance of Zea mays (L.) contaminated separately with increasing concentrations (50-400 mg.kg-1) of lead (Pb) and cadmium (Cd). With increasing metal concentrations, growth and plant biometric criteria were reduced. For instance, Cd at 400 mg.kg-1 soil reduced the germination efficiency (56%), root (77%) and shoot (69%) dry weight, total chlorophyll (64%), and carotenoid content (45%). Contrarily, both HMs caused increase in stress biomarkers and antioxidant enzymes in seedling. However, exogenous administration of 24-EBL significantly enhanced the growth attributes, photosynthetic pigments, proline, MDA, and antioxidant enzyme activity while reducing the harmful effects of HMs stress on Z. mays. For instance, 24-EBL (10 µM) improved the germination percentage, root biomass, chl a, chl b, total chlorophyll, and carotenoid content by 16, 21, 17, 34, 18, and 15%, respectively, in 50 mg.Pb.kg-1 soil-treated Z. mays plants. Furthermore, the amounts of proline, MDA, and antioxidant enzymes in foliage of Z. mays were interestingly and dramatically lowered by 24-EBL application. Uptake of metals in plant organs was significantly reduced when 24-EBL was applied to Pb- and Cd-treated Z. mays. The recent findings help us better understand how 24-EBL regulates growth and development of Z. mays as well as how it boosts HMs' resilience, which could increase the possibility of employing 24-EBL to increase Z. mays productivity. Thus, the present findings confirmed the potentiality of pre-soaking the seed in 24-EBL solution that neutralizes the toxic effects of heavy metals in Z. mays plants. Therefore, it is suggested that applying phytohormones including 24-EBL in removal of heavy metal stress in plants is the best possible solution in sustainable agriculture.

Genotoxicity assessment of textile waste contaminated soil and characterization of textile dye degradation by a novel indigenous bacterium Ochrobactrum intermedium BS39.

The harmful effects of textile wastewater irrigation practices on the crop productivity and soil nutrient levels are primarily related with the accumulation of recalcitrant azo dyes in the soil. Therefore, toxicity assessment of the textile waste contaminated soil along with the development of a powerful soil bioremediation strategy is a challenging task for the researchers. Present study aimed to evaluate potential toxicity of the textile wastewater irrigated soil collected from Panki industrial site 5, Kanpur, India employing Ames Salmonella/mammalian microsome test, Escherichia coli DNA repair defective mutation assay and Allium cepa chromosomal aberration assay. The results of the Ames test and DNA repair defective mutation test showed that all the organic extracts of the contaminated soil samples induced different degrees of DNA damage, indicating the existence of mutagenicity and genotoxicity. Additionally, in A. cepa root cells, the contaminated soil altered mitotic index and caused chromosomal abnormalities. Results of the study demonstrated potential health risks related with the irrigation of textile wastewater. Keeping in view of the above scenario, the study led to the isolation and characterization of a novel indigenous bacterium capable of tolerating very high concentration of reactive black 5 dye (500 µg-mL-1) and salt (20 gL-1) with concurrently high efficiency of the dye degradation i.e., 93% decolorization at temperature of 37 °C and in pH range of 5-9. Based on the 16S rRNA gene sequencing, the bacterium was identified as Ochrobactrum intermedium. Further, dye degradation products were identified as sodium-2-hydrosulfonylethyl sulphate and sodium-3-aminonaphthalene-2-sulfonate by Gas Chromatography-Mass spectrometry; and this isolate can be exploited for bioremediation of textile waste contaminated soils.

Genotoxic hazard and oxidative stress induced by wastewater irrigated soil with special reference to pesticides and heavy metal pollution.

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.

Bacillus mojavensis, a Metal-Tolerant Plant Growth-Promoting Bacterium, Improves Growth, Photosynthetic Attributes, Gas Exchange Parameters, and Alkalo-Polyphenol Contents in Silver Nanoparticle (Ag-NP)-Treated Withania somnifera L. (Ashwagandha).

Discharge of nanoparticles (NPs) into aquatic and terrestrial ecosystems during manufacturing processes and from various commercial goods has become a significant ecotoxicological concern. After reaching soil systems, NPs cause deleterious effects on soil fertility, microbial activity, and crop productivity. Taking into consideration the medicinal importance of Withania somnifera (L.) (ashwagandha), the present study assessed the potential hazards of silver nanoparticles (Ag-NPs) and the toxicity amelioration by a metal-tolerant plant growth-promoting rhizobacterium (PGPR). Bacillus mojavensis BZ-13 (NCBI accession number MZ950923) recovered from metal-polluted rhizosphere soil, tolerated an exceptionally high level of Ag-NPs. The growth-regulating substances synthesized by B. mojavensis were increased with increasing concentrations (0-1000 µg mL-1) of Ag-NPs. Also, strain BZ-13 had the ability to form biofilm, produce alginate and exopolysaccharides (EPSs), as well maintain swimming and swarming motilities in the presence of Ag-NPs. Soil application of varying concentrations of Ag-NPs resulted in a dose-related reduction in growth and biochemical features of ashwagandha. In contrast, following soil inoculation, B. mojavensis relieved the Ag-NPs-induced phytotoxicity and improved plant productivity. Root, shoot length, dry biomass, and leaf area increased by 13, 17, 37, 25%, respectively, when B. mojavensis was applied with 25 mg/kg Ag-NPs when compared to noninoculated controls. Furthermore, the soil plant analysis development (SPAD) index, photosystem efficiency (Fv/Fm), PS II quantum yield (FPS II), photochemical quenching (qP), non-photochemical quenching (NpQ), and total chlorophyll and carotenoid content of BZ-13-inoculated plants in the presence of 25 mg Ag-NPs/kg increased by 33, 29, 41, 47, 35, 26, and 25%, respectively, when compared to noninoculated controls that were exposed to the same amounts of NPs. In addition, a significant (p ≤ 0.05) increase in 48, 18, 21, and 19% in withaferin-A (alkaloids), flavonoids, phenols, and tannin content, respectively, was recorded when plants were detached from bacterized and Ag-NP-treated plants. Leaf gas exchange parameters were also modulated in the case of inoculated plants. Furthermore, bacterial inoculation significantly decreased proline, lipid peroxidation, antioxidant enzymes, and Ag-NP's absorption and build-up in phyto-organs. In conclusion, soil inoculation with B. mojavensis may possibly be used as an alternative to protect W. somnifera plants in soil contaminated with nanoparticles. Therefore, phytohormone and other biomolecule-synthesizing and NP-tolerant PGPR strains like B. mojavensis might serve as an agronomically significant and cost-effective remediation agent for augmenting the yield and productivity of medicinally important plants like ashwagandha raised in soil contaminated with nanoparticles in general and Ag-NPs in particular.

PGPR Kosakonia Radicincitans KR-17 Increases the Salt Tolerance of Radish by Regulating Ion-Homeostasis, Photosynthetic Molecules, Redox Potential, and Stressor Metabolites.

Among abiotic stresses, salinity is a significant limiting factor affecting agricultural productivity, survival, and production, resulting in significant economic losses. Considering the salinity problem, the goal of this study was to identify a halotolerant beneficial soil bacterium to circumvent salinity-induced phytotoxicity. Here, strain KR-17 (having an irregular margin; a mucoid colony; Gm-ve short rod; optimum temperature, 30°C; pH 7.0; no any pigmentation; showed a positive response to citrate utilization, catalase, starch, sucrose, lactose, and dextrose, etc.) recovered from rhizosphere soils of the potato-cultivating field, tolerated surprisingly a high (18% NaCl; 3.-M concentration) level of salt and identified as Kosakonia radicincitans (Accession No. OM348535). This strain was discovered to be metabolically active, synthesized essential PGP bioactive molecules like indole-3-acetic acid (IAA), siderophore (iron-chelating compounds), ACC deaminase, and ammonia, the quantity of which, however, increased with increasing NaCl concentrations. Here, Raphanus sativus L. (radish) was taken as a model crop to evaluate the adverse impact of NaCl, as well as salinity alleviation by halotolerant K. radicincitans. Salinity-induced toxicity to R. sativus was increased in a dose-dependent way, as observed both in vitro and in vivo conditions. Maximum NaCl levels (15%) demonstrated more extreme harm and considerably reduced the plant's biological features. However, membrane damage, relative leaf water content (RLWC), stressor metabolites, and antioxidant enzymes were increased as NaCl concentration increased. In contrast, halotolerant K. radicincitans KR-17 relieved salinity stress and enhanced the overall performance of R. sativus (L.) by increasing germination efficiency, dry biomass, and leaf pigments even in salt-challenged conditions. Additionally, KR-17 inoculation significantly (p ≤ 0.05) improved plant mineral nutrients (Na, K, Ca, Mg, Zn, Fe, Cu, P, and N). Following inoculation, strain KR-17 enhanced the protein, carbohydrates, root pigments, amino acids (AsA and Lys), lipids, and root alkaloids in R. sativus (L.). Besides these, due to PGPR seed priming in NaCl-stressed/non-stressed conditions, membrane damage, RLWC, stressor metabolites, and antioxidant defense enzymes were dramatically reduced. The strong biofilm-forming capacity of K. radicincitans could result in both in vitro and in vivo colonization under NaCl stress. Conclusively, halotolerant K. radicincitans KR-17 may probably be investigated affordably as the greatest way to increase the production of radish under salinity-stressed soils.

Stress-Tolerant Endophytic Isolate Priestia aryabhattai BPR-9 Modulates Physio-Biochemical Mechanisms in Wheat (Triticum aestivum L.) for Enhanced Salt Tolerance.

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.

Bio-priming with a consortium of Streptomyces araujoniae strains modulates defense response in chickpea against Fusarium wilt.

Wilt caused by Fusarium oxysporum f. sp. ciceris (Foc) is one of the major diseases of chickpea affecting the potential yield significantly. Productivity and biotic stress resilience are both improved by the association and interaction of Streptomyces spp. with crop plants. In the present study, we evaluated two Streptomyces araujoniae strains (TN11 and TN19) for controlling the wilt of chickpea individually and as a consortium. The response of Foc challenged chickpea to inoculation with S. araujoniae TN11 and TN19 individually and as a consortium was recorded in terms of changes in physio-biochemical and expression of genes coding superoxide dismutase (SOD), peroxidase, and catalase. Priming with a consortium of TN11 and TN19 reduced the disease severity by 50-58% when challenged with Foc. Consortium primed-challenged plants recorded lower shoot dry weight to fresh weight ratio and root dry weight to fresh weight ratio as compared to challenged non-primed plants. The pathogen-challenged consortium primed plants recorded the highest accumulation of proline and electrolyte leakage. Similarly, total chlorophyll and carotenoids were recorded highest in the consortium treatment. Expression of genes coding SOD, peroxidase, and catalase was up-regulated which corroborated with higher activities of SOD, peroxidase, and catalase in consortium primed-challenged plants as compared to the challenged non-primed plants. Ethyl acetate extracts of TN11 and TN19 inhibited the growth of fungal pathogens viz., Fusarium oxysporum f. sp. ciceris. Macrophomina phaseolina, F. udum, and Sclerotinia sclerotiarum by 54-73%. LC-MS analyses of the extracts showed the presence of a variety of antifungal compounds like erucamide and valinomycin in TN11 and valinomycin and dinactin in TN19. These findings suggest that the consortium of two strains of S. araujoniae (TN11 and TN19) can modulate defense response in chickpea against wilt and can be explored as a biocontrol strategy.

Influence of host genotype in establishing root associated microbiome of indica rice cultivars for plant growth promotion.

Rice plants display a unique root ecosystem comprising oxic-anoxic zones, harboring a plethora of metabolic interactions mediated by its root microbiome. Since agricultural land is limited, an increase in rice production will rely on novel methods of yield enhancement. The nascent concept of tailoring plant phenotype through the intervention of synthetic microbial communities (SynComs) is inspired by the genetics and ecology of core rhizobiome. In this direction, we have studied structural and functional variations in the root microbiome of 10 indica rice varieties. The studies on α and ß-diversity indices of rhizospheric root microbiome with the host genotypes revealed variations in the structuring of root microbiome as well as a strong association with the host genotypes. Biomarker discovery, using machine learning, highlighted members of class Anaerolineae, α-Proteobacteria, and bacterial genera like Desulfobacteria, Ca. Entotheonella, Algoriphagus, etc. as the most important features of indica rice microbiota having a role in improving the plant's fitness. Metabolically, rice rhizobiomes showed an abundance of genes related to sulfur oxidation and reduction, biofilm production, nitrogen fixation, denitrification, and phosphorus metabolism. This comparative study of rhizobiomes has outlined the taxonomic composition and functional diversification of rice rhizobiome, laying the foundation for the development of next-generation microbiome-based technologies for yield enhancement in rice and other crops.

Green synthesis of cerium oxide nanoparticles using Acorus calamus extract and their antibiofilm activity against bacterial pathogens.

The emergence of multidrug resistance in bacterial pathogens has increased drastically and it has become prevalent in clinical infections. In last few decades, there is a large gap in the discovery of new antibiotics with novel mode of action. The situation of antimicrobial resistance has become so alarming that if not action is taken, infectious diseases will become major cause of global mortality and morbidity by 2050. The growing interest of researchers in nanotechnology and their possible application in healthcare is being seen as a new hope in discovery of novel antimicrobial agents. Among various approaches employed for the nanoparticle synthesis, biological methods are considered more advantageous and environment friendly. Biofilms are considered as novel target for the development of new antimicrobial entities. In this study, cerium oxide nanoparticles (CeO2 -NPs) were synthesized using Acorus calamus aqueous extract and tested for the antibiofilm activity both against Gram +ve and Gram -ve bacteria. The average size of synthesized CeO2 -NPs was found to be 22.03 nm. The biofilms of the test bacteria were inhibited by more than 75% by the treatment with CeO2 -NPs. The quantitative biofilm data were further verified by light microscopy, electron microscopy, and confocal microscopy. The confocal and electron microscopic analysis confirmed that treatment with CeO2-NPs reduced the development and colonization of the bacteria on solid support. Moreover, it was found that the colonization and biofilm development by test bacteria were fairly reduced on the glass surface. Moreover, a dose-dependent inhibition of preformed biofilms was also found. The exopolysaccharides (EPS) production by the test bacteria were substantially reduced by the supplementation of CeO2 -NPs in culture media. The findings of this study highlight the efficacy of cerium oxide nanoparticles against bacterial pathogens that may be exploited for the development of new alternative antimicrobial agent.

Heavy Metals Induced Modulations in Growth, Physiology, Cellular Viability, and Biofilm Formation of an Identified Bacterial Isolate.

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.

Effective inhibition and eradication of pathogenic biofilms by titanium dioxide nanoparticles synthesized using Carum copticum extract.

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.

Mutagenicity, genotoxicity and oxidative stress induced by pesticide industry wastewater using bacterial and plant bioassays.

Atomic absorption spectrophotometer and gas chromatography analysis revealed the presence of heavy metals, organochlorine and organophosphate pesticides in industrial wastewater. XAD, Dichloromethane and n-Hexane extracted wastewater were analysed for genotoxic potential using Ames Salmonella/mammalian microsome test. The XAD concentrated sample displayed remarkable mutagenic activity compared to solvent assisted liquid-liquid extraction. Strain TA98 was found utmost sensitive towards all extracts. Wastewater induced chromosomal aberrations in roots of Allium cepa showed significant (p < 0.05) decrease in mitotic index. Seeds of Vigna radiata germinated on soft agar plates treated with different concentration of wastewater showed significant reduction in germination (52 %), seedling vigor index (76 %), radicle length (56 %), plumule length (47 %), biomass of radicle (64 %) and plumule (57%) at highest wastewater concentration. Propidium iodide stained V. radiata roots showed oxidative stress induced by wastewater under CLS microscopy. Further, genotoxicity of wastewater was confirmed by plasmid nicking assay using pBR322 plasmid.