Among the various rhizospheric bacterial isolates screened from Westren Ghat regions of Kerala, a Bacillus sp. with both antagonistic activity to Pythium myriotylum and plant growth promoting properties was identified. Scanning electron microscopic analysis revealed significant ultrastructural changes of hyphae and spores of P. myriotylum upon treatment with Bacillus sp.WG4. For the structural characterization of antagonistic compound in the crude exract, GC MS analysis was carried out and this has resulted in the identification of presence of pyrrolo [1,2- a] pyrazine-1,4-dione, hexahydro-3-(phenylmethyl) as basis of antifungal activity. The in vivo antifungal activity of Bacillus strain was analysed by pre-inoculation of this to ginger rhizome. Here the presence of Bacillus strain was found to provide effective protection to ginger rhizome upon inoculation with Pythium myriotylum. Very interestingly, when the Bacillus strain was checked for its synergistic antifungal activity with commercially available biocontrol agent Trichoderma, the combination was found to have increased antifungal activity. Due to its antifungal and growth enhancement effects, the isolated strain can be of promising application as antifungal plant probiotic agent alone or in combination with other agents like Trichoderma.

Metal nanoparticle synthesis is an interesting area in nanotechnology due to their remarkable optical, magnetic, electrical, catalytic and biomedical properties, but there needs to develop clean, non-toxic and environmental friendly methods for the synthesis and assembly of nanoparticles. Biological agents in the form of microbes have emerged up as efficient candidates for nanoparticle synthesis due to their extreme versatility to synthesize diverse nanoparticles with varying size and shape. In the present study, an eco favorable method for the biosynthesis of silver nanoparticles using marine bacterial isolate has been attempted. Very interestingly, molecular identification proved it as a strain of Ochrobactrum anhtropi. In addition, the isolate was found to have the potential to form silver nanoparticles intracellularly at room temperature within 24 h. The biosynthesized silver nanoparticles were characterized by UV-Vis spectroscopy, transmission electron microscope (TEM) and scanning electron microscope (SEM). The UV-visible spectrum of the aqueous medium containing silver nanoparticles showed a peak at 450 nm corresponding to the plasmon absorbance of silver nanoparticles. The SEM and TEM micrographs revealed that the synthesized silver nanoparticles were spherical in shape with a size range from 38 nm - 85 nm. The silver nanoparticles synthesized by the isolate were also used to explore its antibacterial potential against pathogens like Salmonella Typhi, Salmonella Paratyphi, Vibrio cholerae and Staphylococcus aureus.