Morphological, Metabolomic and Genomic Evidences on Drought Stress Protective Functioning of the Endophyte Bacillus safensis Ni7.

The metabolomic and genomic characterization of an endophytic Bacillus safensis Ni7 was carried out in this study. This strain has previously been isolated from the xerophytic plant Nerium indicum L. and reported to enhance the drought tolerance in Capsicum annuum L. seedlings. The effects of drought stress on the morphology, biofilm production, and metabolite production of B. safensis Ni7 are analyzed in the current study. From the results obtained, the organism was found to have multiple strategies such as aggregation and clumping, robust biofilm production, and increased production of surfactin homologues under the drought induced condition when compared to non-stressed condition. Further the whole genome sequencing (WGS) based analysis has demonstrated B. safensis Ni7 to have a genome size of 3,671,999 bp, N50 value of 3,527,239, and a mean G+C content of 41.58%. Interestingly the organism was observed to have the presence of various stress-responsive genes (13, 20U, 16U,160, 39, 17M, 18, 26, and ctc) and genes responsible for surfactin production (srfAA, srfAB, srfAC, and srfAD), biofilm production (epsD, epsE, epsF, epsG, epsH, epsI, epsK, epsL, epsM, epsN, and pel), chemotaxis (cheB_1, cheB_2, cheB_3, cheW_1, cheW_2 cheR, cheD, cheC, cheA, cheY, cheV, and cheB_4), flagella synthesis (flgG_1, flgG_2, flgG_3, flgC, and flgB) as supportive to the drought tolerance. Besides these, the genes responsible for plant growth promotion (PGP), including the genes for nitrogen (nasA, nasB, nasC, nasD, and nasE) and sulfur assimilation (cysL_1&L_2, cysI) and genes for phosphate solubilization (phoA, phoP_1& phoP_2, and phoR) could also be predicted. Along with the same, the genes for catalase, superoxide dismutase, protein homeostasis, cellular fitness, osmoprotectants production, and protein folding could also be predicted from its WGS data. Further pan-genome analysis with plant associated B. safensis strains available in the public databases revealed B. safensis Ni7 to have the presence of a total of 5391 gene clusters. Among these, 3207 genes were identified as core genes, 954 as shell genes and 1230 as cloud genes. This variation in gene content could be taken as an indication of evolution of strains of Bacillus safensis as per specific conditions and hence in the case of B. safensis Ni7 its role in habitat adaptation of plant is well expected. This diversity in endophytic bacterial genes may attribute its role to support the plant system to cope up with stress conditions. Overall, the study provides genomic evidence on Bacillus safensis Ni7 as a stress alleviating microbial partner in plants.

Predicting Human Risk with Multidrug Resistant Enterobacter hormaechei MS2 having MCR 9 Gene Isolated from the Feces of Healthy Broiler Through Whole-Genome Sequence-Based Analysis.

The zoonotic spread of antimicrobial resistance (AMR) and the associated infections are becoming a major threat to the human population worldwide. Strategies to identify the potential pathogen dissemination by seemingly healthy livestock are at a nascent stage and it is of significant importance to monitor environmental evolution of AMR. In this study, a multidrug resistant strain (MDR) of Enterobacter hormaechei MS2 isolated from the feces of healthy broiler chicken has been characterized by whole-genome sequencing-based method. Here, the isolate was primarily subjected to antimicrobial susceptibility testing followed genome sequencing and analysis. From the antimicrobial susceptibility testing result, the strain was found to be resistant to multiple classes of drugs including the colistin which is an important  last resort drug used to treat infectious diseases. The resistome prediction of genomic data further revealed the presence of 7 perfect and 26 strict hits including those for MCR-9 and FosA2. The pathogenicity prediction has also demonstrated the strain to have the potential to be a human pathogen with 0.72 probability. The phylogenetic analysis has also supported the zoonotic potential of the strain due to its clustering with isolates from both human and livestock-associated host groups. The results of the study suggest the need for a strong surveillance system to identify the opportunistic zoonotic pathogens to prevent a silent AMR menace mediated by them. Carriage of multi-drug resistant strains in the livestock gut microbiome is also a serious concern as it has high AMR transmissibility through contact and supply chain activities.

Genomic insight into the environmental adaptations and toxigenic features of endophytic Bacillus cereus CaB1 isolated from Capsicum annuum L.

In the study, a previously isolated plant beneficial endophytic B. cereus CaB1 was selected for the detailed analysis by whole-genome sequencing. The WGS has generated a total of 1.9 GB high-quality data which was assembled into a 5,257,162 bp genome with G + C content of 35.2%. Interestingly, CaB1 genome was identified to have 40 genes with plant beneficial functions by bioinformatic analysis. At the same time, it also showed the presence of various virulence factors except the diarrhoeal toxin, cereulide. Upon comparative analysis of CaB1 with other B. cereus strains, it was found to have random distributions of virulence and plant growth promoting traits. The core genome phylogenetic analysis of the Bacillus cereus strains further showed the close relation of plant associated strains with isolates from spoiled food products. The observed genome flexibility of B. cereus thus indicates its ability to make use of diverse hosts, which can result either in beneficial or harmful effects. Supplementary Information: The online version contains supplementary material available at 10.1007/s13205-023-03463-9.

Probiotic Paenibacillus polymyxa HGA4C and Bacillus licheniformis HGA8B combination improved growth performance, enzymatic profile, gene expression and disease resistance in Oreochromisniloticus.

Bacterial consortium containing two bacterial strains such as Paenibacillus polymyxa HGA4C and Bacillus licheniformis HGA8B incorporated in the diet of Oreochromis niloticus at a concentration of 1 × 106 CFU g-1 (PB1) and 1 × 108 CFU g-1 (PB2) revealed the probiotic potentials of the bacterial combination. The probiotic feed enhanced the growth performance, digestive enzymes, and antioxidant enzymes in the liver and intestine. Probiotic mediated growth enhancement was further substantiated by the up-regulation of genes such as GHR-1, GHR-2, IGF-1, and IGF-2 and the up-regulation of immune-related genes viz. TLR-2, IL-10, and TNF-α were also significantly modulated by probiotics supplementation. The intestinal MUC 2 gene expression revealed the mucosal remodification and the disease resistance of the fish challenged with Aeromonas hydrophila (MTCC-1739) was improved by the probiotic supplementation. Based on these results the new probiotic supplementation feed can be possibly marketed to help aquaculture farmers to alleviate many of the problems associated with fish farming.

Chitosan with pendant (E)-5-((4-acetylphenyl)diazenyl)-6-aminouracil groups as synergetic antimicrobial agents.

Conventional antimicrobial agents are losing the war against drug resistance day-by-day. Chitosan biopolymer is one of the alternative materials that lends itself well to this application by fine-tuning its bioactivity using different pendant groups. Herein, we report the synthesis of novel chitosan with pendant (E)-5-((4-acetylphenyl)diazenyl)-6-aminouracil (APAU) groups by forming Schiff base linkages between chitosan and the pendant groups. These chitosan biopolymers with pendant APAU groups form films superior in thermal stability compared to the neat chitosan. Interestingly, APAU alone was inactive against K. pneumoniae, E. coli, S. aureus, T. rubrum and C. albicans. However, novel chitosan samples were active against S. aureus with an MIC of 390 µg mL-1, half that of plain chitosan at 780 µg mL-1. APAU modified chitosan samples, CA80 and CA100 showed an MIC (against K. pneumoniae and E. coli) of 23.4 µg mL-1, superior to plain chitosan's MIC of 187.5 µg mL-1 and is close to commercial Fluconazole's MIC of 11.7 µg mL-1. The activity of chitosan changes with APAU content and at higher concentrations shows a strong synergetic antimicrobial effect.

Rapid detection of mobile resistance genes tetA and tetB from metaplasmid isolated from healthy broiler feces.

Containing antimicrobial resistance is the thought of the moment as it affects the human life from every aspect. Because, the inappropriate use of antibiotics in livestock animals for the growth promotion and prophylactic purpose has already generated significant challenges. The livestock farms which harbor and disseminate drug resistant microorganisms have already been identified as potential source of resistance genes acquired by the sensitive strains. Hence there is high demand for the affordable and effective surveillance method for the detection of antimicrobial resistance genes from livestock. In this study, direct detection of antibiotic resistance from metaplasmid DNA isolated from the poultry feces was conducted. For the initial standardization, plasmid DNA purified from the previously characterized Escherichia coli and Klebsiella pneumoniae were used. The tetA and tetB genes amplified from the purified plasmid DNA were further confirmed by agarose gel electrophoresis and sequencing. Further to this, metaplasmid DNA was purified from 29 different poultry fecal samples and these were further screened for the presence of resistance genes. Among the 29 metaplasmid samples, 8 were positive for tetA gene and 9 were positive for tetB gene. The results of the study indicate the potential of PCR based methods for the rapid screening of poultry samples for the antibiotic stewardship in the livestock sector.

Protective effect of (+)-catechin against lipopolysaccharide-induced inflammatory response in RAW 264.7 cells through downregulation of NF-κB and p38 MAPK.

Catechin, a flavonol belonging to the flavonoid group of polyphenols is present in many plant foods. The present study was done to evaluate the effect of catechin on various inflammatory mediators using lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages. The effect of catechin on total cyclooxygenase (COX) activity, 5-lipoxygenase (5-LOX), myeloperoxidase, nitrite and inducible nitric oxide synthase (iNOS) level, secretion of tumor necrosis factor-α (TNF-α) and interleukin-10 (IL-10) were assessed in LPS-stimulated RAW 264.7 cells. The expression of COX-2, iNOS, TNF-α, nuclear factor-ĸB (NF-κB) and p38 mitogen-activated protein kinase (MAPK) genes were also investigated. The effect was further analyzed using human PBMCs by assessing the level of TNF-α and IL-10. The study demonstrated that the inflammatory mediators such as COX, 5-LOX, nitrite, iNOS, and TNF-α were significantly inhibited by catechin in a concentration-dependent manner whereas IL-10 production was up-regulated in RAW 264.7 cells. Moreover, catechin down-regulated the mRNA level expression of COX-2, iNOS, TNF-α, NF-κB and p38 MAPK. The current study ratifies the beneficial effect of catechin as a dietary component in plant foods to provide protection against inflammatory diseases.

Quinalphos Tolerant Endophytic Bacillus sp. Fcl1 and its Toxicity-Alleviating Effect in Vigna unguiculata.

In order to meet the agricultural requirement for the expanding population, pesticides have been used regularly even with their severe threat. The uncontrolled use of these pesticides can cause irreparable damage to both soil and plant-associated microbiome. Therefore, an environment friendly alternative to enhance plant productivity and yield is highly important. Here comes the importance of endophytic microorganisms with multi-plant beneficial mechanisms to protect plants from the biotic and abiotic stress factors. However, their performance can be negatively affected under pesticide exposure. Hence the present study was conducted to analyse the tolerating ability of a Bacillus sp. Fcl1 which was originally isolated from the rhizome of Curcuma longa towards the pesticide quinalphos and also its ability to reduce the quinalphos-induced toxicity in Vigna unguiculata. The results revealed that the viability of endophytic Bacillus sp. Fcl1 depended on the concentration of quinalphos used for the study. Further, Fcl1 supplementation was found to alleviate the quinalphos-induced toxicity in Vigna unguiculata seedlings. The study is environmentally significant due to the pesticide tolerating and alleviating effect of Bacillus sp. Fcl1 in quinalphos-induced plant toxicity. This could suggest the application of microbes of endophytic origin as an efficient bioinoculant for field application even in the presence of pesticide residues.

Genome sequencing and annotation of multi-virulent Aeromonas veronii XhG1.2 isolated from diseased Xiphophorus hellerii.

The present study was intended to elucidate the genomic basis of antibiotic resistance and hyper-virulence of the fish pathogen Aeromonas veronii XhG1.2 characterized in our previous work. The identity of XhG1.2 was confirmed through 16S rDNA sequence analysis and whole genome sequence analysis. The top-hit species distribution analysis of XhG1.2 sequence data revealed major hits against the Aeromonas veronii. The identification of virulence genes using the VFDB showed the genome of XhG1.2 to have the genes coding for the virulence factors viz. aerolysin, RtxA, T2SS, T3SS and T6SS. The presence of antibiotic resistance predicted through the CARD database analysis showed it to have the CephA3, OXA-12, adeF and pulvomycin resistance genes. By the phylogenetic and comparative genomic analysis, A. veronii species were found to have genes for toxin production. This also confirmed the pathogenicity and drug resistance of A. veronii XhG1.2 and also its potential to cause disease in diverse ornamental fishes.

Environmental Adaptations of an Extremely Plant Beneficial Bacillus subtilis Dcl1 Identified Through the Genomic and Metabolomic Analysis.

Bacterial endophytes ubiquitously colonize the internal tissues of plants and promote the plant growth through diverse mechanisms. The current study describes the mechanistic basis of plant-specific adaptations present in an extremely beneficial endophytic bacterium. Here, the endophytic Bacillus subtilis Dcl1 isolated from the dried rhizome of Curcuma longa was found to have the drought tolerance, IAA and ACC deaminase production and phosphate solubilization properties. The whole genome sequencing and annotation further showed the genome of B. subtilis Dcl1 to have the size of 4,321,654 bp. This also showed the presence of genes for IAA, H2S, acetoin, butanediol, flagella and siderophore production along with phosphate solubilization and biofilm formation for the B. subtilis Dcl1. In addition, the genes responsible for the synthesis of surfactin, iturin, fengycin, bacillibactin, bacillaene, bacilysin, chitinase, chitosanase, protease and glycoside hydrolase could also be annotated from the genome of B. subtilis Dcl1. Identification of genes for the glycine betaine, glutamate and trehalose further indicated the drought stress tolerance features of B. subtilis Dcl1. The presence of the genetic basis to produce the catalase, superoxide dismutase, peroxidases, gamma-glutamyltranspeptidase, glutathione and glycolate oxidase also indicated the plant oxidative stress protective effect of B. subtilis Dcl1. Identification of these properties and the demonstration of its plant probiotic effect in Vigna unguiculata confirmed the applicability of B. subtilis Dcl1 as a biofertilizer, biocontrol and bioremediator agent to enhance the agricultural productivity.

Healthy broilers disseminate antibiotic resistance in response to tetracycline input in feed concentrates.

Wide varieties of antibiotics are used in poultry farms to improve the growth and also to control the infection in broiler chicken. To identify the seriousness of the same in the poultry sector, current study has been designed to analyze the presence of tetracycline in poultry feed and also the tetracycline resistance among the bacteria released through the excreta of poultry. In the study, 27 bacteria belonging to the Escherichiacoli and Klebsiellapneumoniae. were isolated from the faecal samples collected from five different farms. Antibiotic susceptibility analysis showed 77% of E. coli and 100% of the K. pneumoniae. to be resistant to tetracycline. Further, molecular screening for tetA and tetB genes showed 85.18% of isolates to have tetA and 22.22% with tetB. The presence of tetracycline in collected feed samples was also analysed quantitatively by Liquid chromatography-mass spectrometry (LC-MS). Here, three out of five feed samples were found to be positive for tetracycline. The study showed a direct correlation between the antibiotic supplemented feed and the emergence of antimicrobial resistance among the intestinal microflora. The results of the study indicate the need for strict control over antibiotic use in animal feed to limit the rapid evolution and spread of antimicrobial resistance.

Modulation of agriculturally useful rhamnolipid profile of Pseudomonas sp. K6 due to the supplementation with chitosan and gold nanoparticles.

As rhizobacteria have extensively been studied for the production of compounds with biocontrol properties, methods to enhance its production are very important. In this study, nanotechnological method to modulate the rhamnolipid production by Pseudomonas sp. K6 has been demonstrated. For this, Pseudomonas sp. K6 was cultured with different concentrations of chitosan nanoparticles (CNPs) and gold nanoparticles (AuNPs). The rhamnolipid production was further analyzed by CTAB- methylene blue agar assay and also by LC-MS/MS analysis. From the LC-MS/MS result, induction of dirhamnolipid production in K6 could be confirmed when cultured with CNPs (1, 5 and 10 mg/mL) and AuNPs (10, 25, 50 and 100 µg/mL). The monorhamnolipid production by K6 was observed to get enhanced when the K6 culture was supplemented with 2.5 mg/mL CNPs and 10 µg/mL AuNPs. Also, in planta study confirmed the biocontrol ability of rhamnolipid as it suppressed the Sclerotium rolfsii infection in Vigna unguiculata plants. As the rhamnolipids have versatile applications in the agricultural field, the nano-based approach to enhance its production from the biocontrol organism is significant.

Advantage of zinc oxide nanoparticles over silver nanoparticles for the management of Aeromonas veronii infection in Xiphophorus hellerii.

Bacterial pathogens cause significant challenge to the ornamental fish industry. Eventhough antibiotic administration has been recommended to manage fish diseases, there is alarming concern with emergence of antibiotic resistance. This indicates the need for the development of alternative methods with multi-targeted action to manage fish diseases. In the study, silver (AgNPs) and zinc oxide (ZnONPs) nanoparticles have been evaluated for its activity against Aeromonas veronii. Both the AgNPs and ZnONPs were found to have bactericidal activity against A. veronii. In vivo experiments with A. veronii was found to cause severe mortality in Xiphophorus hellerii with a LD50 of 1.4 × 108 CFU/mL. However, treatment with AgNPs and ZnONPs each at a concentration of 1 mg/L was found to enhance the survival rate of X. hellerii to 83.3% and 100% respectively. Further histopathological analysis showed alterations in gill, intestine and liver of X. hellerii due to A. veronii in the infection control. In the case of AgNPs treated group, symptoms of moderate tissue damage could be observed. However, the ZnONPs treated X. hellerii showed normal histological features with minimum tissue damage. The bath dip method further confirmed the protective ability of the zinc oxide nanoparticles (1 mg/L) on X. hellerii.

Antibacterial Potential and Apoptosis Induction by Pigments from the Endophyte Burkholderia sp. WYAT7.

Pigment from the endophyte Burkholderia sp. WYAT7 isolated from the medicinal plant Artemisia nilagirica (Clarke) Pamp. was extracted. The antibacterial efficacy of the crude pigment Y was assessed as a source of antibiotic against both Gram-positive and Gram-negative bacterial pathogens. The pigment Y exhibited a significant level of antibacterial activity against the tested pathogens Salmonella typhi (MTCC 733), Staphylococcus aureus (MTCC 1430), Pseudomonas aeruginosa (MTCC 2453), Klebsiella pneumoniae (MTCC 432), Escherichia coli (MTCC 1610), Salmonella paratyphi (3220), Bacillus subtilis (441) and Acinetobacter baumannii (12,889). The minimum inhibitory concentration of crude pigment extract Y for most of the bacterial pathogens tested was below or equal to 0.25 µg/mL and the minimum bactericidal concentration was below or equal to 0.5 µg/mL. In the cytotoxicity evaluation, crude pigment Y exhibited less toxicity toward normal cells lines (L929). Crude pigment extract Y also showed powerful anticancer activity toward melanoma cancer cells (A375). The IC50 value obtained was 68.08 µg/mL. Acridine orange (AO) and ethidium bromide (EB) double staining of cells treated with the pigment helped in the morphological assessment of nuclear condensation, apoptotic bodies and live cells. The DNA fragmentation analysis and caspase-9 quantification in the pigment-treated A375 cells determined the apoptosis activity mediated by the crude pigment extract Y. The compounds in the crude pigment extract Y was identified by HR-LCMS analysis. Further studies on the active compounds can lead to a rise in new drugs for cancer treatment and also against rising antibacterial resistant pathogens.

Drought-tolerant and plant growth-promoting endophytic Staphylococcus sp. having synergistic effect with silicate supplementation.

Endophytic bacteria have been reported to have symbiotic, mutualistic, commensalistic or trophobiotic relationships with various plant parts. As part of its adaptation, many endophytic organisms are known to exhibit properties with multiple beneficial effects to the plant system. Even though many bacterial genera have been identified to have endophytic association, isolation of those which were previously demonstrated well for human association is quite interesting. In the study, endophytic bacteria Ceb1 isolated from the rhizome of Curcuma longa was identified by 16S rDNA sequencing as Staphylococcus sp. Further, Ceb1 was observed to have the ability to tolerate drought stress. While screening for the plant growth-promoting traits, Ceb1 was found to be positive for IAA production both under drought-stressed and normal conditions as confirmed by HPLC. The Ceb1 priming with Vigna unguiculata was observed to enhance the growth parameters of the plant. Analysis of Ceb1-treated plants by ICP-MS further showed modulation of both macro- and micronutrients. Upon drought stress induction in Vigna unguiculata, Ceb1 was found to provide synergistic plant growth-promoting effect to the plant along with the supplemented silicate sources. Under the changing agroclimatic conditions, exploring the plant stress-alleviating effects of endophytes is highly significant.

Surface functionalization of central venous catheter with mycofabricated silver nanoparticles and its antibiofilm activity on multidrug resistant Acinetobacter baumannii.

The mycofabrication of silver nanoparticles (AgNPs) through green chemistry protocol is an advanced methodological progress in medical nanotechnology. Mycofabricated AgNPs are less toxic due to an aura of biomolecules around the nanoparticles. Hence the mycofabricated AgNPs can be used for clinical applications. The present study explores the antibiofilm activity of mycogenerated AgNPs, which were synthesized by the enzymatic reduction of silver nitrate using the marine algicolous endophytic fungus Penicillium polonicum ARA10. The mycogenerated AgNPs showed very specific and potent bactericidal activity against Acinetobacter baumannii. Anti-A.baumannii activities of mycogenerated AgNPs on planktonic as well as biofilm embedded cells were explored. The physical impact of synthesized AgNPs on A.baumannii was investigated by scanning electron microscopy and fluorescence microscopy. A bionanocomposite coating for the central venous catheter (CVC) was formulated using the mycogenerated AgNPs and polydopamine. The bionanocomposite surface was characterized by field emission scanning electron microscopy, water contact angle measurement, and Raman spectroscopy. The results showed that the mycogenerated AgNPs have potent antibiofilm activity on biofilms of A.baumannii. The scanning electron microscopy (SEM) and fluorescence microscopy images showed noticeable aberrations on the ultrastructure of A.baumannii. The SEM and FE-SEM images of biofilms on the surface of CVC samples proved that the AgNPs at minimum bactericidal concentration could destroy the structure of biofilms and lyses the bacterial cell. Thus, the present study establishes a new way to the development of 'antibacterial surfaces' based on mycogenerated AgNPs.

Bacterial endophytes from Artemisia nilagirica (Clarke) Pamp., with antibacterial efficacy against human pathogens.

A study was conducted to isolate and characterize endophytes from Artemisia nilagirica, a traditional medicinal plant. The plant was collected from Western Ghats, India. Endophytes isolated included Arthrobacter sp. WWAT1, Pseudomonas sp. WYAT2, Microbacterium sp. WYAT3, Psychrobacter sp. WBAT4, Enterobacter sp. WWAT5, Bacillus sp. WBAT6, Kosakonia cowanii WBAT7, Bacillus sp. WBAT8, Bacillus sp. WBAT9, Chromobacterium violaceum WVAT6, Serratia sp.WPAT8 and Burkholderia sp. WYAT7. Of these two bacteria, Chromobacterium violaceum strain WVAT6 and Burkholderia sp. strain WYAT exhibited antibacterial property against human pathogens. Similar to the environmental isolates, Burkholderia sp. WYAT7 showed pleomorphism and produced different enzymes, whereas like clinical strains they showed multidrug resistance, for their survival in different environmental conditions. Chromobacterium violaceum WVAT6 exhibited rod shape morphology and showed multiple drug resistance except to erythromycin, tetracycline and gentamicin antibiotics. Both produced biofilm and enzymes such as protease and lipase. The antimicrobial compounds from these endophytes may find application in the preparation of antimicrobial formulations.

One-step synthesis of eco-friendly boiled rice starch blended polyvinyl alcohol bionanocomposite films decorated with in situ generated silver nanoparticles for food packaging purpose.

The study reports a one-step preparation of polyvinyl alcohol/boiled rice starch blend film fabricated with in situ generated silver nanoparticles (PVA/BRS/sAgNPs) formed in the presence of sunlight irradiation. The bionanocomposite appeared to have dark brown color with a characteristic surface plasmon resonance peak at 439 nm. Further characterization has confirmed the presence of physical interactions among the components PVA, BRS and sAgNPs. Compared to the control PVA, the nanocomposites showed improved mechanical and optical properties with decreased water sensitivity. Presence of boiled rice starch and sAgNPs were also found to influence the light transmittance of composite film. Moreover, PVA/BRS/sAgNPs film was found to have superior barrier property against environmental microorganisms. Biodegradation of the composite films was studied by indoor soil burial test and was assessed by visual appearance, weight loss and FTIR analysis. Interestingly, both the PVA/BRS and PVA/BRS/sAgNPs films proved to be biodegradable and hence have promising application as cost effective food packaging material with the latter having marked antimicrobial property.

Biogenic Gold Nanoparticle Supplementation to Plant Beneficial Pseudomonas monteilii was Found to Enhance its Plant Probiotic Effect.

Rhizosphere provides unique space for intensive chemical conversation between plant and microorganisms. The common rhizobacterial mechanisms which have been demonstrated to promote plant growth include production of phytohormones, nitrogen fixation, synthesis of 1-aminocyclopropane-1-carboxylate deaminase (ACC deaminase) and phosphate solubilization. The microbially produced phytohormone indole-3-acetic acid (IAA) is considered to have significant role in interaction between plant and bacteria. Hence any substance with modulatory effect on rhizobacterial IAA production can expect to have its impact on plant-microbe interaction. With the advent of nanotechnology, nanoparticles are being used for diverse applications. However, applications of nanotechnology in agriculture have not been studied in detail. In the study, rhizospheric Pseudomonas monteilii was selected to investigate the concentration-dependent effect of biogenic gold nanoparticles (AuNPs) on its IAA production. For this, AuNPs synthesized by Bacillus subtilis SJ15 were characterized by UV-Vis spectroscopy, FT-IR, TEM and EDS. The results showed AuNPs to have spherical, hexagonal and triangular shapes with a size range of 12-32 nm and absorption peak at 545 nm. Further, various concentrations of AuNPs were used to identify its impact on IAA production by P. monteilii. From this, enhanced production of IAA by P. monteilii was found to take place in the presence of 50 µg/mL AuNPs. When Vigna unguiculata seedlings were grown in presence of 50 µg/mL of AuNPs, increased growth was observed. The results of the study thus showed the ability of AuNPs to augment the IAA-producing potential of P. monteilii.