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Item Antibacterial, anti-biofilm and anti-virulence activity of biosynthesized silver nanoparticles against drug-resistant Staphylococcus aureus(Springer, 2025-10) Jha, Prabhat NathAntibiotic resistance in bacteria has become a major concern for the effective treatment of infections; therefore, alternatives to antibiotics are being extensively researched to combat drug-resistant microbes. In this study, silver nanoparticles (AgNPs) were biosynthesized using aqueous extracts of papaya leaves (Carica papaya), cannabis leaves (Cannabis sativa), and cardamom (Elettaria cardamomum) and characterized by field-emission scanning electron microscopy (FE-SEM) and UV-visible spectrophotometry. Biosynthesized AgNPs were evaluated for their antibacterial, anti-biofilm, and anti-virulence potential by phenotypic and genotypic methods. AgNPs biosynthesized by all three extracts had spherical morphology and sizes in the nanoscale, average diameter ranging from 46.05 to 94.12 nm. Antibacterial susceptibility testing of S. aureus field isolates under study revealed 48% (24/50) and 38% (19/50) to be resistant to methicillin and amoxycillin-clavulanic acid, respectively. Antibacterial activity of biosynthesized AgNPs against S. aureus strains was determined by the well diffusion method. AgNPs were found to be effective on 90.90% (50/55) S. aureus strains with a zone of inhibition varying from 10 to 21 mm. The AgNPs were also found to be effective on other important bacterial pathogens (viz. Bacillus cereus ATCC 10876, Pseudomonas aeruginosa ATCC 27853, Salmonella Enteritidis ATCC 13070, Escherichia coli ATCC 43888, and Listeria monocytogenes MTCC 657) screened in the study with a ZOI of 15–18 mm. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of AgNPs against S. aureus ranged between 0.015625-0.125 mg/mL and 0.015625-0.25 mg/mL, respectively. In the time kill assay, AgNPs were able to kill S. aureus rapidly within 0.5–1.0 h. In the haemolytic assay, 4–9% haemolysis was observed at concentrations ranging from 0.015625 to 0.25 mg/mL of AgNPs. Biofilm-forming ability of all strains of S. aureus (n = 55) determined by crystal violet assay revealed that 87.27% (48/55) were biofilm formers, while 12.73% (7/55) were non-biofilm formers. Out of 48 biofilm-forming strains, 81.25% (39/48) were strong biofilm producers, 10.41% (5/48) were moderate biofilm producers, and 8.33% (4/48) were weak biofilm producers. Anti-biofilm effect of AgNPs was found at sub-MIC (0.03125 mg/mL), phenotypically. Exopolysaccharide production was found to be reduced by 53.38% indicating the anti-virulence potential of AgNPs at sub-MIC. Relative expression analysis revealed that AgNPs downregulated the expression of biofilm-related genes, namely icaC, icaD, and spa, by 14.2, 10.6, and 8.7-fold, respectively, compared to the control at 3 h of incubation. Other biofilm-related and virulence genes, including icaA, icaB, icaR, agr, ebps, fnb-B, sar-A, and katA, were also found to be downregulated by 7.4, 7.5, 6.2, 5, 4.2, 7.3, 4, and 3.6-fold, respectively, at 3 h. All the target genes were also found to be downregulated at 24 h post-treatment with AgNPs, except icaD, icaR, and agr, which were slightly upregulated. In the present study, AgNPs were successfully biosynthesized and found to possess broad-spectrum antibacterial activity, reduce biofilm formation, and EPS production.Item Metabolomic profiling of biphenyl-induced stress response of Brucella anthropi MAPB-9(Springer Nature, 2025-04) Jha, Prabhat Nath; Paul, Atish TulshiramThe exposure of bacteria to toxic compounds such as polychlorinated biphenyl (PCB) and biphenyl induces an adaptive response at different levels of cell morphology, biochemistry, and physiology. PCB and biphenyl are highly toxic compounds commercially used in the industry. In our previous study, Brucella anthropi MAPB-9 efficiently degraded PCB-77 and biphenyl at a high concentration. In this study, we used metabolomic analyses to understand the metabolic processes occurring in MAPB-9 during exposure to biphenyl. A combination of analytical techniques such as GC-MS/MS and HR-MS study confirmed the complete biphenyl degradation pathway. The intermediate metabolic products identified were cis-2, 3-dihydro-2, 3-dihydroxy biphenyl, 2,3-dihydroxy biphenyl, and 4-dihydroxy-2-oxo-valerate. Further, benzoic acid and 2,3-dihydroxy benzoic acid metabolites identified in the extract revealed the interconnection of biphenyl and benzoic degradation pathways. In addition, the variations in the functioning of the major biochemical pathways in the cells were revealed through changes in the profile of metabolites belonging to glyoxylate, tricarboxylic acid (TCA) cycle, and fatty acid pathways. The exposure to biphenyl inhibited metabolic activity leading to changes in the morphology and metabolism. Despite many adverse changes, the MAPB-9 was able to adapt and grow in the toxic environment undergoing upper and lower biphenyl degradation pathways.Item Secretory molecules from secretion systems fine-tune the host-beneficial bacteria (PGPRs) interaction(Frontiers, 2024-02) Jha, Prabhat NathNumerous bacterial species associate with plants through commensal, mutualistic, or parasitic association, affecting host physiology and health. The mechanism for such association is intricate and involves the secretion of multiple biochemical substances through dedicated protein systems called secretion systems SS. Eleven SS pathways deliver protein factors and enzymes in their immediate environment or host cells, as well as in competing microbial cells in a contact-dependent or independent fashion. These SS are instrumental in competition, initiation of infection, colonization, and establishment of association (positive or negative) with host organisms. The role of SS in infection and pathogenesis has been demonstrated for several phytopathogens, including Agrobacterium, Xanthomonas, Ralstonia, and Pseudomonas. Since there is overlap in mechanisms of establishing association with host plants, several studies have investigated the role of SSs in the interaction of plant and beneficial bacteria, including symbiotic rhizobia and plant growth bacteria (PGPB). Therefore, the present review updates the role of different SSs required for the colonization of beneficial bacteria such as rhizobia, Burkholderia, Pseudomonas, Herbaspirillum, etc., on or inside plants, which can lead to a long-term association. Most SS like T3SS, T4SS, T5SS, and T6SS are required for the antagonistic activity needed to prevent competing microbes, including phytopathogens, ameliorate biotic stress in plants, and produce substances for successful colonization. Others are required for chemotaxis, adherence, niche formation, and suppression of immune response to establish mutualistic association with host plants.Item Valorization of spent mushroom substrate (sms) as a sustainable approach to remediation of xenobiotic compounds in groundwater - a comprehensive review(Elsevier, 2024-08) Jha, Prabhat NathIn the present era of the industrial revolution, chemical-based agriculture practices, and urbanization, the environment has severe repercussions from various xenobiotics and has become a pitfall worldwide. Xenobiotic compounds such as heavy metals, dyes, polycyclic aromatic hydrocarbons (PAHs), oil spills, pharmaceuticals' active compounds (PhACs), and agrochemicals show detrimental effects on the environment through long-term persistence causing biomagnification, pollution, etc. In the last few decades, researchers have dedicated themselves to developing different physical and chemical remediation methods, although facing several drawbacks and challenges and searching for eco-friendly alternatives like bioremediation. Conventionally bioremediation utilizes biological agents such as plants, microbes, fungi, etc. To reduce environmental pollutants' effects. Although conventional bioremediation has certain limitations, SMS (spent mushroom substrate) has recently drawn great attention worldwide because of its low cost, environment-friendly nature, easy availability, and higher remediation efficiency. Scientists have used waste mushroom SMS for bioremediation purposes for various xenobiotic compounds. Therefore, the present review's foremost aim is to encompass the role of mushroom SMS in the remediation of xenobiotic compounds, techniques for studying the adsorbent properties of SMS, factors affecting the adsorption process, and the probable mechanism involved in its remediation process. This study has noteworthy findings implying that eco-friendly multi-purpose SMS has great efficacy against environmental contaminants, and its removal efficiency gets increased with combinatorial approaches like SMS amendments (biochar, etc), phytoremediation, rhizoremediation, and nanoremediation. Various mechanisms, including ion exchange, free radical reactions, enzymatic processes, microbe-mediated remediation, permeation, and chelation, may play a role in SMS-mediated groundwater and environmental contaminant remediation.Item Pyridinium-based schiff-base fluorescent chemosensor for sequential detection of al3+ ions and tnp: applications in cell imaging and latent fingerprint visualization(Wiley, 2024-12) Jha, Prabhat Nath; Khungar, BhartiA fluorescent pyridinium-based chemosensor (E)-1-(2-(3-hydroxy-4-((pyridin-2-ylimino) methyl) phenoxy) ethyl) pyridin-1-ium bromide (BzPySB) was synthesized and characterized using various spectroscopic techniques. The chemosensing potential of BzPySB was explored using UV-vis and fluorescence spectroscopy in the aqueous medium. The turn-on fluorescence behavior was observed for BzPySB in the presence of Al3+, while other metal ions were non-responsive. The B−H and Job′s plot confirmed the 1 : 1 stoichiometric ratio of the BzPySB and Al3+. The in situ generated complex BzPySB-Al3+ offered selectivity toward TNP via fluorescence turn-off phenomena with high Ksv and LOD values. The “off-on-off” sensing mechanism was elucidated through 1H NMR, mass spectrometry, and DFT calculations. The probe also detected Al3+ in plant and MCF-7 cells, highlighting its potential in biological systems. Moreover, BzPySB exhibited solid-state luminescent properties credited to weak π-π interaction, leading to its successful application in the visualization of latent fingerprints.Item Endophytic Bacteria Pseudomonas aeruginosa PM389 Subsists Host’s (Triticum aestivum) Immune Response for Gaining Entry Inside the Host(JPAM, 2021) Jha, Prabhat NathThe present study was designed to compare the defense response of the host plant towards endophytic bacteria Pseudomonas aeruginosa PM389 and pathogenic bacteria Erwinia carotovora and to correlate the level of defense enzymes vis-a-vis bacterial colonization in the host. Wheat seedlings were treated with 107-108 cells ml-1 endophytic and pathogenic bacteria in the separate experimental set-up, and the level of plant defense enzyme was measured at various time intervals. Comparatively reduced level of most defense enzymes was produced in endophytic bacteria treated plants. While the endophytic bacterial population was almost constant after 24 HAI (hour after inoculation), the population of pathogenic bacteria kept fluctuating during the study period from 24 HAI. Unlike pathogenic bacteria, we observed attenuated defense response in challenged host plants towards endophytic bacteria, which helps endophytes establish inside plant. This study would be useful for understanding the mechanism of colonization and strategies of endophytes to fight against the host defense response.Item Comparative analysis of defence responses Triticum aestivum L in response to the endophytic Pseudomonas aeruginosa PM389 and the non-host microbial pathogens Erwinia carotovora and Fusarium monaliforme(World Researcher Association, 2022) Jha, Prabhat NathIn the present study, Pseudomonas aeruginosa PM389 has been studied for comparing the defense responses in wheat plant against non-host pathogens Fusarium monaliforme and Erwinia caratovora. The comparative studies of defense enzymes produced on pretreatment of plants in the presence and absence of PM389 were also studied. Apart from it, disease incidence as well as plant growth promotion under in vitro and pot condition was recorded in the presence or absence of PM389 on challenging wheat plant with the non-host pathogen. Induction in all defense enzymes was observed on pretreatment of the plant with PM389 before pathogenic challenge with non-host. It was suggested that PM389 can generate induced systemic resistance in plants against pathogens. A less pathogenic population was recorded in the presence of PM389 than in its absence. In addition, it also showed plant growth promotion in the wheat under in vitro and pot studies. It was observed that PM389 was more effective against fungal pathogen than bacterial pathogen in both plant growth promotions as well as in decreasing disease incidence. Thus, PM389 can serve as a potential candidate as biofertilizer and biocontrol agent for non-host pathogens as well as having chances of cross-infection among various crops.Item Transposon mutagenesis of ACC deamination gene alters the proteomic analysis of wheat plant under non-saline and saline stress(Springer, 2022-01) Jha, Prabhat NathThe development of high-throughput techniques with evolving bioinformatics tools has elucidated the adaptation mechanism of plant to certain environmental stress like salinity. The characterization of proteins is critical for plant stress responses and it provides the comprehensive information about the cellular and biochemical pathway involved in various stress mitigation. In the present work, we provide the information about the alteration in wheat proteomic profile in response to plant growth-promoting rhizobacterial (PGPR)-inoculation under abiotic stress like salinity. PGPR facilitate the plant growth and enhance their induced systemic tolerance (ISR) under various stress conditions. The present study was aimed to generate the AcdS− mutant of Enterobacter cloacae SBP-8 which differs in its ability to breakdown the stress ethylene precursor ‘ACC’ (1-aminocyclopropane-1-carboxylic acid). The proteomic profile of wheat (Triticum aestivum L.) plant was investigated under non-saline and high salinity stress (200 mM NaCl) following wild type and its mutant inculcation. A total of four treatments were taken to monitor the differential expression of proteins in the wheat seedlings exposed to high salt stress for 15 days. The major changes concerned the proteins involved in metabolism, ion-transport, photosynthesis, defense and stress responses. The observed changes at the proteomic level in each treatment can be related to effects of salt and bacterial inoculation. The identified proteins were further classified into cellular, biological and molecular function. Bacterial inoculation significantly enhanced the expression of Thioredoxin and Ninja family proteins in addition to Heat shock proteins (Hsp70, Hsp 90), which play a major role in defense against abiotic stress. Taken together, the observed results suggest that bacterial inoculation alleviated the salinity-induced damages by improving the metabolism, photosynthesis and defense-related proteins.Item ACC deaminase producing rhizobacterium Enterobacter cloacae ZNP-4 enhance abiotic stress tolerance in wheat plant(PLOS Biology, 2022-05) Jha, Prabhat NathPlant growth promoting rhizobacterium (PGPR) designated as ZNP-4, isolated from the rhizosphere of Ziziphus nummularia, was identified as Enterobacter cloacae following 16S rRNA sequence analysis. The isolated strain exhibited various plant growth promoting (PGP) traits. The 1-aminocyclopropane-1-carboxylic acid deaminase (ACCD) activity was evaluated under diverse physiological conditions that could be useful for minimizing the abiotic stress-induced inhibitory effects on wheat plants. The strain showed resistance to salt (NaCl) and metal (ZnSO4) stress. The effect of E. cloacae ZNP-4 on the augmentation of plant growth was studied under salinity stress of 150 mM (T1 treatment) & 200 mM (T2 treatment) NaCl. The inoculation of strain ZNP-4 significantly improved the various growth parameters of wheat plant such as shoot length (41%), root length (31%), fresh weight (28%), dry weight (29%), photosynthetic pigments chlorophyll a (62%) and chlorophyll b (34%). Additionally, the strain was found to be efficient for minimizing the imposed Zn stress in terms of improving plant growth, biomass and photosynthetic pigments in pots containing different levels of metal stress of 150 mg kg-1 (treatment T1) and 250 mg kg-1 (treatment T2). Isolate ZNP-4 also improved the proline content and decreased malondialdehyde (MDA) level under both salinity and metal stress, therefore maintaining the membrane integrity. Furthermore, bacterial inoculation increased the activities of antioxidative enzymes such as superoxide dismutase (SOD), catalase (CAT), and peroxidase (POX). The positive effects of PGPR occurred concurrently with the decrease in abiotic stress-induced reactive oxygen species (ROS) molecules such as hydrogen peroxide (H2O2) and superoxide (O2-) contents. Overall, the observed results indicate that use of bacteria with such beneficial traits could be used as bio-fertilizers for many crops growing under stress conditions.Item Exploring Functional Diversity and Community Structure of Diazotrophic Endophytic Bacteria Associated with Pennisetum glaucum Growing under Field in a Semi-Arid Region(MDPI, 2022-06) Jha, Prabhat NathDiazotrophic endophytic bacteria (DEB) are the key drivers of nitrogen fixation in rainfed soil ecosystems and, hence, can influence the growth and yield of crop plants. Therefore, the present work investigated the structure and composition of the DEB community at different growth stages of field-grown pearl millet plants, employing the cultivation-dependent method. Diazotrophy of the bacterial isolates was confirmed by acetylene reduction assay and amplification of the nifH gene. ERIC-PCR-based DNA fingerprinting, followed by 16S rRNA gene analysis of isolates recovered at different time intervals, demonstrated the highest bacterial diversity during early (up to 28 DAS (Days after sowing)) and late (63 DAS onwards) stages, as compared to the vegetative growth stage (28–56 DAS). Among all species, Pseudomonas aeruginosa was the most dominant endophyte. Assuming modulation of the immune response as one of the tactics for successful colonization of P. aeruginosa PM389, we studied the expression of the profile of defense genes of wheat, used as a host plant, in response to P. aeruginosa inoculation. Most of the pathogenesis-related PR genes were induced initially (at 6 h after infection (HAI)), followed by their downregulation at 12 HAI. The trend of bacterial colonization was quantified by qPCR of 16S rRNAs. The results obtained in the present study indicated an attenuated defense response in host plants towards endophytic bacteria, which is an important feature that helps endophytes establish themselves inside the endosphere of roots.