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Plant growth promoting rhizobacteria (PGPR) inhabit the rhizosphere region of plant and often found to be beneficial for the development and growth of plants. In this study, 17 pure isolates of bac...

Quorum sensing (QS)-mediated infections cause severe diseases in human beings. The control of infectious diseases by inhibiting QS using antipathogenic drugs is a promising approach as antibiotics are proving inefficient in treating these diseases. Marine fungal (Pestalotiopsis sydowiana PPR) extract was found to possess effective antipathogenic characteristics. The minimum inhibitory concentration (MIC) of the fungal extract against test pathogen Pseudomonas aeruginosa PAO1 was 1,000 μg/ml. Sub-MIC concentrations (250 and 500 μg/ml) of fungal extract reduced QS-regulated virulence phenotypes such as the production of pyocyanin, chitinase, protease, elastase, and staphylolytic activity in P. aeruginosa PAO1 by 84.15%, 73.15%, 67.37%, 62.37%, and 33.65%, respectively. Moreover, it also reduced the production of exopolysaccharides (74.99%), rhamnolipids (68.01%), and alginate (54.98%), and inhibited the biofilm formation of the bacteria by 90.54%. In silico analysis revealed that the metabolite of P. sydowiana PPR binds to the bacterial QS receptor proteins (LasR and RhlR) similar to their respective natural signaling molecules. Cyclo(-Leu-Pro) (CLP) and 4-Hydroxyphenylacetamide (4-HPA) were identified as potent bioactive compounds among the metabolites of P. sydowiana PPR using in silico approaches. The MIC values of CLP and 4-HPA against P. aeruginosa PAO1 were determined as 250 and 125 μg/ml, respectively. All the antivirulence assays were conducted at sub-MIC concentrations of CLP (125 μg/ml) and 4-HPA (62.5 μg/ml), which resulted in marked reduction in all the investigated virulence factors. This was further supported by gene expression studies. The findings suggest that the metabolites of P. sydowiana PPR can be employed as promising QS inhibitors that target pathogenic bacteria.

Quorum sensing (QS) is the cell density dependent communication network which coordinates the production of pathogenic determinants in majority of pathogenic bacteria. Pseudomonas aeruginosa causes hospital-acquired infections by virtue of its well-defined QS network. As the QS regulatory network in P. aeruginosa regulates the virulence determinants and antibiotic resistance, attenuating the QS system seems to be influential in developing next-generation anti-infective agents. In the current study, the QS attenuation potential of a flavonoid, mosloflavone was investigated against P. aeruginosa virulence and biofilm formation. Mosloflavone inhibited the pyocyanin production, LasB elastase and chitinase by 59.52 ± 2.74, 35.90 ± 4.34 and 61.18 ± 5.52% respectively. The QS regulated biofilm formation and development was also reduced when supplemented with sub-MIC of mosloflavone. The gene expression studies of mosloflavone using RT-PCR depicted its ability to down-regulate the expression levels of QS regulated virulence genes such as lasI (60.64%), lasR (91.70%), rhlI (57.30%), chiC (90.20%), rhlA (47.87%), rhlR (21.55%), lasB (37.80%), phzM (42.40%), toxA (61.00%), aprA (58.4%), exoS (78.01%), algD (46.60%) and pelA (50.45%). The down-regulation of QS virulence phenotypes by mosloflavone could be attributed to its binding affinity with the QS regulatory proteins, LasR and RhlR by competitively inhibiting the binding of natural autoinducers as evidenced from simulation studies. Mosloflavone also exhibited promising potential in controlling bacterial infection in Caenorhabditis elegans model system, in vivo. The anti-biofilm and anti-QS potential of mosloflavone in the current study illustrated the candidature of mosloflavone as a promising biocide.

Catheter-related bloodstream infections (CRBSIs) are one of the leading causes of high morbidity and mortality in hospitalized patients. The proper management, prevention and treatment of CRBSIs rely on the understanding of these highly resistant bacterial infections. The emergence of such a challenge to public health has resulted in the development of an alternative antimicrobial strategy called antimicrobial photodynamic therapy (aPDT). In the presence of a photosensitizer (PS), light of the appropriate wavelength, and molecular oxygen, aPDT generates reactive oxygen species (ROS) which lead to microbial cell death and cell damage. We investigated the enhanced antibacterial and antibiofilm activities of methylene blue conjugated carbon nanotubes (MBCNTs) on biofilms of E. coli and S. aureus using a laser light source at 670 nm with radiant exposure of 58.49 J cm−2. Photodynamic inactivation in test cultures showed 4.86 and 5.55 log10 reductions in E. coli and S. aureus, respectively. Biofilm inhibition assays, cell viability assays and EPS reduction assays showed higher inhibition in S. aureus than in E. coli, suggesting that pronounced ROS generation occurred due to photodynamic therapy in S. aureus. Results from a study into the mechanism of action proved that the cell membrane is the main target for photodynamic inactivation. Comparatively higher photodynamic inactivation was observed in Gram positive bacteria due to the increased production of free radicals inside these cells. From this study, we conclude that MBCNT can be used as a promising nanocomposite for the eradication of dangerous pathogens on medical devices.

The persistence of multidrug resistance among microorganisms has directed a mandate towards a hunt for the development of alternative therapeutic modalities. In this context, antimicrobial photodynamic therapy (aPDT) is sprouted as a novel strategy to mitigate biofilms and planktonic cells of pathogens. Nanoparticles (NPs) are reported with unique intrinsic and antimicrobial properties. Therefore, silver NPs (AgNPs) were investigated in this study to determine their ability to potentiate the aPDT of photosensitizer against Staphylococcus aureus and Pseudomonas aeruginosa. Biologically synthesized AgNPs were surface coated with methylene blue (MB) and studied for their aPDT against planktonic cells and biofilms of bacteria. The nano-conjugates (MB-AgNPs) were characterized for their size, shape and coated materials. MB-AgNPs showed significant phototoxicity against both forms of test bacteria and no toxicity was observed in the dark. Moreover, activity of MB-AgNPs was comparatively higher than that of the free MB, which concludes that MB-AgNPs could be an excellent alternative to combat antibiotic resistant bacteria.

Quorum sensing (QS)-mediated infections cause severe diseases in human beings. The control of infectious diseases by inhibiting QS using antipathogenic drugs is a promising approach as antibiotics are proving inefficient in treating these diseases. Marine fungal (

Pseudomonas aeruginosa is a prevalent pathogenic species reported with severe nosocomial infections. P. aeruginosa infections gain significant concern due to the greater morbidity and mortality coupled with the development of multidrug resistance phenomenon. Furthermore, they are potentially participating in the development of infections to different organs of the human and possibly evade from the host immune defence mechanism. P. aeruginosa involves in the productions several virulence factors which makes the bacterium remains as potential life-threatening pathogen. Additionally, biofilm formation behaviours of P. aeruginosa offer windows to evade different adverse environmental conditions and initiation of adaptation process according to the stress condition and deliver highly resistance strain. The current antibiotics used to combat the Pseudomonas infection are gradually losing their efficacy in controlling the bacterial infections due to the development of the resistance mechanism within the bacterial system. The different resistance mechanisms including intrinsic, acquired and adaptive resistance are supporting the P. aeruginosa for the development of high resistance against several antimicrobial agents. Recently, several alternative therapeutic options were reported such as interference in quorum sensing of P. aeruginosa, phage therapy and development of antimicrobial peptides alternative therapeutic options against antibiotics with limited incidence of resistance development. This chapter overviews the pathogenesis and drug resistance development in P. aeruginosa and also covers the recently available therapeutic alternatives to combat Pseudomonas infection.

VT Anju,1 Parasuraman Paramanantham,1 Busi Siddhardha,1 SB Sruthil Lal,2 Alok Sharan,2 Abdullah A Alyousef,3 Mohammed Arshad,3 Asad Syed41Department of Microbiology, School of Life Sciences, Pondicherry University, Puducherry 605014, India; 2Department of Physics, School of Physical, Chemical & Applied Sciences, Pondicherry University, Puducherry 605014, India; 3Microbiology Research Group, Department of Clinical Laboratory Sciences, College of Applied Medical Sciences, King Saud University, Riyadh 11433, Saudi Arabia; 4Department of Botany and Microbiology, College of Science, King Saud University, Riyadh 11451, Saudi ArabiaPurpose: Infections associated with medical devices that are caused by biofilms remain a considerable challenge for health care systems owing to their multidrug resistance patterns. Biofilms of Pseudomonas aeruginosa and Staphylococcus aureus can result in life-threatening situations which are tough to eliminate by traditional methods. Antimicrobial photodynamic inactivation (aPDT) constitutes an alternative method of killing deadly pathogens and their biofilms using reactive oxygen species (ROS). This study investigated the efficacy of enhanced in vitro aPDT of P. aeruginosa and S. aureus using malachite green conjugated to carboxyl-functionalized multi-walled carbon nanotubes (MGCNT). Both the planktonic cells and biofilms of test bacteria were demonstrated to be susceptible to the MGCNT conjugate. These MGCNT conjugates may thus be employed as a facile strategy for designing antibacterial and anti-biofilm coatings to prevent the infections associated with medical devices.Methods: Conjugation of the cationic dye malachite green to carbon nanotube was studied by UV-visible spectroscopy, high-resolution transmission electron microscopy, and Fourier transform infrared spectrometry. P. aeruginosa and S. aureus photodestruction were studied using MGCNT conjugate irradiated for 3 mins with a red laser of wavelength 660 nm and radiant exposure of 58.49 J cm−2,.Results: Upon MGCNT treatment, S. aureus and P. aeruginosa were reduced by 5.16 and 5.55 log10 , respectively. Compared to free dye, treatment with MGCNT afforded improved phototoxicity against test bacteria, concomitant with greater ROS production. The results revealed improved biofilm inhibition, exopolysaccharide inhibition, and reduced cell viability in test bacteria treated with MGCNT conjugate. P. aeruginosa and S. aureus biofilms were considerably reduced to 60.20±2.48% and 67.59±3.53%, respectively. Enhanced relative MGCNT phototoxicity in test bacteria was confirmed using confocal laser scanning microscopy.Conclusion: The findings indicated that MGCNT conjugate could be useful to eliminate the biofilms formed on medical devices by S. aureus and P. aeruginosa.Keywords: aPDT, MGCNT, Biofilms, reactive oxygen species, CLSM

In the present study, the antimicrobial and antibiofilm efficacy of toluidine blue (TB) encapsulated in mesoporous silica nanoparticles (MSN) was investigated against Pseudomonas aeruginosa and Staphylococcus aureus treated with antimicrobial photodynamic therapy (aPDT) using a red diode laser 670 nm wavelength, 97.65 J cm

Correction for 'Synthesis and antimicrobial photodynamic effect of methylene blue conjugated carbon nanotubes on E. coli and S. aureus' by Paramanantham Parasuraman et al., Photochem. Photobiol. Sci., 2019, DOI: 10.1039/c8pp00369f.

Catheter-related bloodstream infections (CRBSIs) are one of the leading causes of high morbidity and mortality in hospitalized patients. The proper management, prevention and treatment of CRBSIs rely on the understanding of these highly resistant bacterial infections. The emergence of such a challenge to public health has resulted in the development of an alternative antimicrobial strategy called antimicrobial photodynamic therapy (aPDT). In the presence of a photosensitizer (PS), light of the appropriate wavelength, and molecular oxygen, aPDT generates reactive oxygen species (ROS) which lead to microbial cell death and cell damage. We investigated the enhanced antibacterial and antibiofilm activities of methylene blue conjugated carbon nanotubes (MBCNTs) on biofilms of E. coli and S. aureus using a laser light source at 670 nm with radiant exposure of 58.49 J cm-2. Photodynamic inactivation in test cultures showed 4.86 and 5.55 log10 reductions in E. coli and S. aureus, respectively. Biofilm inhibition assays, cell viability assays and EPS reduction assays showed higher inhibition in S. aureus than in E. coli, suggesting that pronounced ROS generation occurred due to photodynamic therapy in S. aureus. Results from a study into the mechanism of action proved that the cell membrane is the main target for photodynamic inactivation. Comparatively higher photodynamic inactivation was observed in Gram positive bacteria due to the increased production of free radicals inside these cells. From this study, we conclude that MBCNT can be used as a promising nanocomposite for the eradication of dangerous pathogens on medical devices.

Plants are recognized as metaorganisms because they harbor highly complex, diversified, and distinctive microbial communities which are symbiotically associated with each other and modulate the physiological activities of each other directly or indirectly. From plant-associated microbial community studies, hundreds of microbial species are found to inhabit different plant microenvironments such as the rhizosphere, phyllosphere, and endosphere. The plant microbiome is the key determinant of plant growth and health management by modulating plant physiological processes under different environmental conditions. Over the years, the coevolution of the microbial communities along with their plant hosts made the scientific community realize the importance of understanding the mechanism of plant-microbe interactions for the benefit of human civilization as well as environmental stability. The phyllosphere represents one of the most vibrant and dynamic inhabitants of different microbiotas and governs the different physiological processes at the interface between plants, microorganisms, and the atmosphere. Insight analysis and studies on the dynamics of the plant-associated phyllospheric microbiome and their implications could set off new dimensions to the strategies of sustainable agriculture such as the development of microbial inoculants as biofertilizers for plant growth and development and improved crop yield, improved nutrient mobilization and quality management, biocontrol agents for induced systemic resistance against phytopathogens, or stress-resistance mechanisms to overcome various biotic and abiotic stress conditions. This chapter aims to provide the dynamics of the phyllospheric microbiome, its role in sustainable agriculture, and its widespread avenues.

In the recent era, nanobased technologies have resolved many complicated issues in the field of science and technology. Nevertheless they also open a new window in biomedical field focusing personalized medicine. Nanoparticles are one of the great innovations of science because they possess unique characteristics such as high specific surface area and physicochemical properties such as optical properties, magnetic properties, electronic properties, catalytic activity, and antimicrobial properties. The delivering of therapeutic drug molecules to the targeted tumor site are highly required to overcome the side effects during cancer treatment. In the past two decades various efforts were carried out to use nanomaterial based drug delivery system to facilitate site-specific cancer therapy. Theranostics is a recently released technology from the nanoworld that refers to a technique of integration of diagnostics, imaging, and therapeutic approaches into one package. Thus, theranostics diagnosing as well as imaging diseases like cancer, on the other hand it delivers therapeutic drugs at the same time with specific dosage. This chapter presents an overview of developments in nanotheranostics with different diagnostic probes and therapeutic drugs combination of targeted nanobased medicines for cancer treatment. Synthesis and applications of nanoparticles such as inorganic nanoparticles, linear and branched polymers, micelles, protein conjugates and dendrimers in theranostics was also discussed. In addition, the application of theranostics in imaging techniques like single-photon emission computed tomography, positron emission tomography, computed tomography, magnetic resonance imaging and fluorescence/optical imaging for in vivo imaging were emphasized.

Since ancient times, fungi and fungal products have gained noticeable attention for pharmaceutical applications and even for human consumption. Recent research has provided significant evidence of fungal metabolites with a wide variety of biological activities. The bioactive compounds from fungal communities are exploited by industrial sectors from the basic biomass-based food and feed application as nutraceutials to high-value pharmaceutical, cosmeceutical, ecological, and biomedical applications. Recent advances in scientific knowledge include interest in the use of natural value-added products, especially from fungi. Fungal communities provide highly diversified value-added products with complex chemical structures impossible or difficult to produce by chemical synthetic methods. Recent efforts have explored novel endophytic fungi which are added to the list of potential providers of value-added products. Functional genomics and proteomics facilitate the isolation and production of novel metabolites from fungi. Genetic engineering is an useful tool to metabolically engineer the microorganism for the production of value-added compounds. Various high-throughput screening methods are gaining importance for the rapid detection and isolation of bioactive compounds from fungi.

The plant-microbe interaction plays an important role to achieve sustainability in the ecosystem. The functional balance between soil process and plant growth directly controls ecosystem functioning and its sustainability. The interface between soil and plant roots is a chemically complex environment that facilitates a suitable atmosphere for the development of diverse microorganisms. Herein, microorganisms drive in functions of soil processing like nutrient recycling, functional stability, and sustainability of the soil ecosystem in relation to the plant growth and development. In nature, plant-microbe interactions occurs in two different aspects such as negative interaction, which leads to disease development in plant and positive interaction that mediates stimulation of plant growth. The microbial community present in the rhizosphere and phyllosphere is dynamic and controlled by different biotic and abiotic factors such as physiochemical properties of the soil, biological activities of the plants, chemical signals between the plant and microbes, and environmental factors. Nevertheless, pollutant-degrading microorganisms also play a considerable role in the soil processing by enhancing the effective bioremediation processes. Recent advancement in plant-microbe interactions underlying structural principles of microbial community and significant knowledge on ecosystem will offer directional avenues for the development of novel techniques toward the application of beneficial microorganisms in plant growth promotion, ecosystem functioning, restoration, and environmental sustainability.

The bacterial cell communication also termed as Quorum sensing (QS) system was involved in the expression of several virulence traits during Pseudomonas infection. The attenuating of this bacterial cell communication system is an attractive approach for the management of bacterial infections without the complication of resistance development. In this respect, the marine environment has gained significant attention due to its biodiversity and as a source of novel bioactive compounds. The present study aimed to screening effective QS inhibitors from marine associated fungal species for QS inhibitors. Twelve morphologically distinct fungal isolates were isolated from the wood of Avicennia marina from marine ecosystem. The anti-QS potential of fungal crude extract from was investigated in biosensor strain and test bacterium, Chromobacterium violaceum and Pseudomonas aeruginosa PAO1, respectively. Promising anti-QS activity was observed in the crude extract of one of the fungal isolate and identified by molecular characterization using internal transcribed spacer (ITS) region as Blastobotrys parvus PPR3. The anti-virulence and antibiofilm effects of ethyl acetate fractions from PPR3 against P. aeruginosa PAO1 were evaluated. The fungal metabolites responsible for the anti-QS activity of fungal crude extract was identified using gas chromatography-mass spectrometry (GC-MS). Furthermore, molecular docking studies were performed to understand the interaction of bioactive compounds with as receptors of P. aeruginosa PAO1. The crude extract of PPR3 showed reduction in different virulence traits of P. aeruginosa PAO1 such as production of pyocyanin, elastase, protease, chitinase, swimming and swarming motility, biofilm formation, exopolysaccharide production and alginate production at different sub-MIC concentrations. Interaction of bioactive metabolites with LasR and RhlR receptors of P. aeruginosa PAO1 was reported. The findings of the present study suggested that metabolites of B. parvus PPR3 interfere with QS system of P. aeruginosa PAO1 and alters the production of virulence factors.

Cardiovascular diseases (CVDs) are a severely threatening disorder and frequently cause death in industrialized countries, posing critical challenges to modern research and medicine. Molecular imaging has been heralded as the solution to many problems encountered in individuals living with CVD. The use of probes in cardiovascular molecular imaging is causing a paradigmatic shift from regular imaging techniques, to future advanced imaging technologies, which will facilitate the acquisition of vital information at the cellular and molecular level. Advanced imaging for CVDs will help early detection of disease development, allow early therapeutic intervention, and facilitate better understanding of fundamental biological processes. To promote a better understanding of cardiovascular molecular imaging, this article summarizes the current developments in the use of molecular probes, highlighting some of the recent advances in probe design, preparation, and functional modification.