A. Panneerselvam

Antimicrobial potentiality of a halophilic strain of Streptomyces sp. VPTSA18 isolated from the saltpan environment of Vedaranyam, India

A total of 68 morphologically different actinomycetes were isolated from the saltpan soils of Vedaranyam, Tamilnadu, India and tested for their antimicrobial activity by the cross-streak method. Among the strains tested, VPTSA18 showed strong antimicrobial activity. The culture filtrate was extracted with different solvents and tested against 11 bacterial and two fungal pathogens using the well-diffusion method. Of the solvent extracts assessed, the ethyl acetate extract showed high antimicrobial activity against all of the pathogens tested. Based on morphological, physiological, biochemical, cultural, chemo–taxonomical and molecular characteristics (16S rDNA sequencing), this strain was identified as Streptomyces sp. VPTSA18.

Extracellular biosynthesis, characterisation and in-vitro antibacterial potential of silver nanoparticles using Agaricus bisporus

Microbial silver nanoparticles have been known to have bactericidal effects but the antimicrobial mechanism has not been clearly revealed. The use of microorganisms in the synthesis of nanoparticles emerges as an ecofriendly and exciting approach. Here we report on the extracellular synthesis method for the preparation of silver nanoparticles in water using the extract of Agaricus bisporus, a naturally occurring edible mushroom, as reducing and protecting agents. The silver nanoparticles were characterised by ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy (FTIR) and X-Ray diffraction (XRD) analysis. The synthesised silver nanoparticles showed antibacterial activity against the multi-drug resistant Gram positive and Gram negative bacterial pathogens.

Preclinical evaluation and molecular docking of 4-phenyl-1-Napthyl phenyl acetamide (4P1NPA) from Streptomyces sp. DPTB16 as a potent antifungal compound

The incidence of fungal disease has increased dramatically over the past decades, mainly due to the emergence and transmission of antifungal resistance within the fungal pathogens. The present study investigates the use of novel antifungal compound 4-Phenyl-1-Napthyl Phenyl Acetamide (4P1NPA), isolated from marine Streptomyces sp. DPTB16 as a potent antifungal drug. The preclinical studies and molecular docking for 4P1NPA against Cytochrome P450 51 (CYP 51) were performed using in silico pharmacology and docking tools. The finding reveals the drug likeliness of 4P1NPA and satisfactory interaction of 4P1NPA with CYP 51. These results collectively evidence the use of 4P1NPA as a drug to treat fungal infections. On the whole, we highlight the findings of this research will be helpful to design 4P1NPA as novel antifungal drug to defend the emerging antifungal resistance.

Herbicidal agents from actinomycetes against selected crop plants and weeds

About 64 total actinomycetes were isolated from various coastal soils. Sixteen actinomycete isolates were screened for herbicidal principles. Out of these, five potent isolates were selected for characterisation and identification. Based on their morphological, biochemical and physiological characteristics, the actinomycete isolates were identified as Glyomyces, Saccharomonospra and Streptomyces sp. The Streptomycetes isolates were tested for herbicidal principles by germination inhibition assay. About 10 crop seeds were tested for herbicidal activity with Streptomycetes isolates. The crop seeds did not show growth inhibition. Four weed seeds were tested for herbicidal activity with Streptomyces isolates. Streptomyces inhibits the growth of Echinochilora crusgalli, but it could not inhibit the growth of Echinochilora colonum, Parthenium sp., or Ageratum conizoites. The present study concludes that Streptomyces isolates will be a bioherbicide against E. crusgalli. Further study is required to confirm the activity of Streptomyces isolates against E. crusgalli under field conditions.

Allelopathic effect of actinobacterial isolates against selected weeds

The taxonomic characteristics of weeds such as morphology of shoot, leaves, flowers, stem, fruits and seeds were recorded as Gynandropsis pentaphylla, DC, Amarantus spinosus Linn, Cyperus rotundus, Amarantus viridis Linn, Cassia occidentalis, Linn and Echinochilora orygicola. Totally 20 actinobacteria isolates were screened for herbicidal activity against the weed. Among the 20 isolates, only four actinobacterial isolates KA1-3, KA1-4, KA1-7 and KA23A showed significant herbicidal activity against C. rotundus. The herbicidal effect of actinobacterial culture filtrates on germination and seedling growth of C. rotundus was tested. The shoot and root growth of C. rotundus was severely affected when compared to control. The potent actinobacterial isolates KA1-4 and KA1-7 were characterised based on their morphological and molecular phylogenetic property and were identified as Streptomyces sp. The present study concludes that actinobacterial isolates will be used as bioherbicide against C. rotundus. Further studies are required to confirm the activity of actinobacterial isolates against C. rotundus under field conditions.

Optimization of sporicidal activity and environmental Bacillus endospores decontamination by biogenic silver nanoparticle.

AIM The intent of this study is to decontaminate Bacillus endospores and to determine the D-values using silver nanoparticles (AgNPs) synthesized from Streptomyces sp. cell filtrate. MATERIALS & METHODS AgNPs synthesis was performed extracellularly followed by characterization using spectrophotometer, High Resolution Transmission Electron Microscope and x-ray diffraction pattern analysis. Subsequently, the optimized conditions for the decontamination and D-value estimation of Bacillus endospores were determined using the response surface methodology. The environmental spore decontamination study was performed in mice model. RESULTS AgNPs were visibly and spectroscopically identified which were spherical with the size range of less than 20 nm. The synthesized AgNPs destroyed 1log10 CFU Bacillus endospores at around 20 min. The adherence of AgNPs to the surface of spore coat, pit formation and its complete structural loss was detected under field emission scanning electron microscopy. All the mice exposed to AgNP-treated spores showed no sign of pathological lesions. CONCLUSION The results of our study strongly suggest that the application of AgNPs as a sporicidal agent could be a new approach in consistently eliminating the hazardous Bacillus spores.

Applications of Actinobacterial Fungicides in Agriculture and Medicine

Actinobacteria are found in virtually every natural substrate, such as soils and compost, freshwater basins, foodstuffs and the atmosphere. Deep seas, however, do not offer a favorable habitat. These organisms live and multiply most abundantly in various depths of soil and compost, in cold and in tropical regions. Alkaline and neutral soils are more favorable habitats than acid soils and neutral peats are more favorable than acid peats.

Biosynthesis and Antimicrobial Potential of Metal Nanoparticles

One of the major developments in nanotechnology is the production, manipulation, and use of materials ranging in size from less than a micrometer to that of individual atoms in biology. Though nanomaterials may be synthesized by various physical and chemical methods, synthesis is now possible with the use of biological systems. Nanoparticles synthesized using biological resources have excellent antimicrobial activity. In this review, we critically assess the role of biological entities in the synthesis and antimicrobial potential of metal nanoparticles.