Dnyaneshwar Rathod

Endophytic actinobacteria of medicinal plants: diversity and bioactivity

Endophytes are the microorganisms that exist inside the plant tissues without having any negative impact on the host plant. Medicinal plants constitute the huge diversity of endophytic actinobacteria of economical importance. These microbes have huge potential to synthesis of numerous novel compounds that can be exploited in pharmaceutical, agricultural and other industries. It is of prime importance to focus the present research on practical utilization of this microbial group in order to find out the solutions to the problems related to health, environment and agriculture. An extensive characterization of diverse population of endophytic actinobacteria associated with medicinal plants can provide a greater insight into the plant-endophyte interactions and evolution of mutualism. In the present review, we have discussed the diversity of endophytic actinobacteria of from medicinal plants their multiple bioactivities.

Murraya koenigii-mediated synthesis of silver nanoparticles and its activity against three human pathogenic bacteria

Synthesis of silver nanoparticles (Ag NPs) by the leaf extract of Murraya koenigii (Indian curry leaf tree) is reported in this study. The colour of the leaf extract prepared by grinding turned from green to brown after treatment with AgNO3 (1 mM). The UV–visible spectroscopic analysis showed the absorbance peak at about 420 nm, which indicates the synthesis of Ag NPs. Further characterisation by Fourier transform infrared spectroscopy showed the presence of proteins as capping agents, which increase the stability of Ag NPs in the colloids. Scanning electron microscopy demonstrated the presence of spherical Ag NPs in the range of 40–80 nm. The bactericidal activity of the standard antibiotics was significantly increased in the presence of Ag NPs against pathogenic bacteria, viz., Escherichia coli-JM-103 (ATCC 39403), Staphylococcus aureus (ATCC 25923) and Pseudomonas aeruginosa (MTCC 424). Ag NPs in combination with gentamicin showed the maximum activity against E. coli (increase in fold area −4.06), foll...

A New Report on Mycosynthesis of Silver Nanoparticles by Fusarium culmorum

Plant pathogenic fungus Fusarium culmorum (MTCC-2090) assists in the mycosynthesis of silver nanoparticles. Formation of spherical silver nanoparticles was confirmed from TEM analysis and found in the range of 5-25 nm with an average diameter of 11 nm. Different temperature and pH affects the synthesis of silver nanoparticles indicating that synthesis depends significantly on temperature and pH. Formation of silver nanoparticles at room temperature and pH-7 was found to be optimum for synthesis process. The combined effects of mycosynthesized silver nanoparticles with different antibiotics like kanamycin, erythromycin, oxacillin, tetracycline, vancomy- cin and gentamycin against Klebsiella pneumoniae (MTCC-7407) and Enterobacter aerogenes (MTCC-6804) were carried out. Oxacillin showed the maximum increase in fold area as compared to other antibiotics tested against both the test organisms. Fungal proteins are re- sponsible for the synthesis of silver nanoparticles. This process is easy, eco-friendly and scalable for the large scale synthesis of silver nanoparticles. The synthesis of silver nanoparticles by F. culmorum has not been reported in the past, and thus, it is being reported for the first time.

Fungal growth promotor endophytes: a pragmatic approach towards sustainable food and agriculture

Agricultural productivity suffers a heavy loss due to plant pathogens, insect pests and various abiotic stresses. Agriculture being the world’s largest economic sector, it is the need of time to find and establish the ideal strategy for sustainable agriculture and improvement in crop growth. Endophytes are microorganisms that asymptomatically grow within the plant tissues without causing any disease to the host. Endophytic fungi live in symbiotic association with plants and play an important role in plant growth promotion, higher seed yield and plants resistant to various biotic, abiotic stresses and diseases. Many are able to produce antimicrobial compounds, plant growth hormones and various agrochemical bioactive metabolites. These mycoendophytes hold enormous potential for the development of eco-friendly and economically viable agricultural products. In this review we focused on the endophytic fungi recovered from different medicinal plants, their active principles involved in plant growth enhancement and the applications of fungal endophytes in agriculture. Moreover, we also discussed about endophytic fungi and their pragmatic approach towards sustainable food and agriculture.

Synthesis of silver nanoparticles from two acidophilic strains of Pilimelia columellifera subsp. pallida and their antibacterial activities

Biosynthesis of silver nanoparticles (AgNPs) is an eco‐friendly approach by using different biological sources; for example, plants and microorganisms such as bacteria, fungi, and actinobacteria. In this report, we present the biological synthesis of silver nanoparticles (AgNPs) by acidophilic actinomycetes SL19 and SL24 strains isolated from pine forest soil (pH < 4.0). The isolates based on 16S rRNA gene sequence were identified as Pilimelia columellifera subsp. pallida. The synthesized AgNPs were characterized by visual observations of colour change from light‐yellow to dark‐brown. The UV‐vis spectra of AgNPs were recorded at 425 and 430 nm. The AgNPs were further characterized by Nanoparticle tracking analysis (NTA), Zeta potential, Fourier transform infrared spectroscopy (FTIR) and Transmission electron microscopy (TEM). FTIR analysis revealed the presence of proteins as a capping agent. TEM analysis confirmed the formation of spherical and polydispersed NPs of 12.7 and 15.9 nm sizes. The in vitro antibacterial activity of AgNPs alone and in combination with antibiotics was evaluated against clinical bacteria viz., Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and uropathogens such as Enterobacter, S. aureus, P. aeruginosa, K. pneumoniae, and E. coli. The lowest MIC (40 μg ml−1) was demonstrated by AgNPs synthesized from SL24 against E. coli. However, the AgNPs of SL19 showed lowest MIC (70 μg ml−1) against S. aureus. The activity of antibiotic was enhanced, when tested in combination with silver nanoparticles synthesized from both actinobacterial strains.

Acidophilic actinobacteria synthesised silver nanoparticles showed remarkable activity against fungi-causing superficial mycoses in humans.

Superficial mycoses are limited to the most external part of the skin and hair and caused by Malassezia sp., Trichophyton sp. and Candida sp. We report extracellular biosynthesis of silver nanoparticles (AgNPs) by acidophilic actinobacteria (SF23, C9) and its in vitro antifungal activity against fungi‐causing superficial mycoses. The phylogenetic analysis based on the 16S rRNA gene sequence of strains SF23 and C9 showed that they are most closely related to Pilimelia columellifera subsp. pallida GU269552T. The detection of AgNPs was confirmed by visual observation of colour changes from colourless to brown, and UV–vis spectrophotometer analysis, which showed peaks at 432 and 427 nm, respectively. These AgNPs were further characterised by nanoparticle tracking analysis (NTA), Zeta potential, Fourier‐transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). The FTIR analysis exhibited the presence of proteins as capping agents. The TEM analysis revealed the formation of spherical and polydispersed nanoparticles in the size range of 4–36 nm and 8–60 nm, respectively. The biosynthesised AgNPs were screened against fungi‐causing superficial mycoses viz., Malassezia furfur, Trichophyton rubrum, Candida albicans and C. tropicalis. The highest antifungal activity of AgNPs from SF23 and C9 against T. rubrum and the least against M. furfur and C. albicans was observed as compared to other tested fungi. The biosynthesised AgNPs were found to be potential anti‐antifungal agent against fungi‐causing superficial mycoses.

Mycoendophytes as efficient synthesizers of bionanoparticles: nanoantimicrobials, mechanism, and cytotoxicity

Abstract Mycoendophytes are the fungi that occur inside the plant tissues without exerting any negative impact on the host plant. They are most frequently isolated endophytes from the leaf, stem, and root tissues of various plants. Among all fungi, the mycoendophytes as biosynthesizer of noble metal nanoparticles (NPs) are less known. However, some reports showing efficient synthesis of metal nanoparticles, mainly silver nanoparticles and its remarkable antimicrobial activity against bacterial and fungal pathogens of humans and plants. The nanoparticles synthesized from mycoendophytes present stability, polydispersity, and biocompatibility. These are non-toxic to humans and environment, can be gained in an easy and cost-effective manner, have wide applicability and could be explored as promising candidates for a variety of biomedical, pharmaceutical, and agricultural applications. Mycogenic silver nanoparticles have also demonstrated cytotoxic activity against cancer cell lines and may prove to be a promising anticancer agent. The present review focuses on the biological synthesis of metal nanoparticles from mycoendophytes and their application in medicine. In addition, different mechanisms of biosynthesis and activity of nanoparticles on microbial cells, as well as toxicity of these mycogenic metal nanoparticles, have also been discussed.

Microbial Endophytes: Progress and Challenges

Endophytes are microorganisms that reside in internal tissues of living plants without causing any negative effect. These offer remarkable potential for the exploitation of novel and eco-friendly secondary metabolites used in medicine, pharmaceutical industry, and agriculture. This chapter is focused on diversity in bioactive compounds of endophytic fungi, actinomycetes, and bacteria. Endophytes as novel source of potentially useful medicinal compounds are discussed along with the need to search for new and more effective agents from endophytes to combat disease problems.

Influence of calcium phosphate nanoparticles, Piriformospora indica and Glomus mosseae on growth of Zea mays

In this study, the arbuscular mycorrhizal fungus (G. mosseae) and endosymbiont (P. indica) colonized Zea mays were treated with calcium phosphate nanoparticles (CaPNPs) and evaluated for their plant growth promotion efficiency. It was observed that CaPNPs in combination with both G. mosseae and P. indica are more potent plant growth promoter than independent combinations of CaPNPs + G. mosseae, CaPNPs + P. indica or CaPNPs alone. The fluorimetric studies of treated plants revealed that CaPNPs alone and in combination with P. indica can enhance vitality of Zea mays by improving chlorophyll a content and performance index of treated plants. Hence, we conclude that CaPNPs exhibit synergistic growth promotion, root proliferation and vitality improvement properties along with endosymbiotic and arbuscular mycorrhizal fungi, which after further field trials can be developed as a cost-effective nanofertilizer with pronounced efficiency.

Biophysical Phenotyping as an Essential Tool for Understanding Host–Microbe Interaction

The symbiotic relationship between plant and microbes is one of the most important types of symbiosis among different living forms. Such kind of association helps both the host and the symbiont. Generally, bacteria and fungi are found in association with a variety of plants. It is believed that more than 80 % of plants from different families available on the earth surface have a symbiotic association with arbuscular mycorrhizal fungi. In this context, it is very important to understand the host–microbe interaction, which will elucidate the exact mechanisms involved in the symbiosis.