Pseudomonas isolates obtained from the rhizosphere of chickpea (Cicer arietinum L.) and green gram (Vigna radiata) were found to produce significant amount of indole acetic acid (IAA) when grown in a LB medium broth supplemented with L-tryptophan. Seed bacterization of chickpea cultivar C235 with different Pseudomonas isolates showed stunting effect on the development of root and shoot at 5 and 10 days of seedling growth except the strains MPS79 and MPS90 that showed stimulation of root growth, and strains MPS104 and MRS13 that showed shoot growth stimulation at 10 days. Exogenous treatment of seeds with IAA at 0.5 and 1.0 μM concentration caused similar stunting effects on root and shoot growth compared to untreated control both at 5 and 10 days of observation, whereas higher concentration of IAA (10.0 μM) inhibited the growth of seedlings. Coinoculation of chickpea with IAA-producing Pseudomonas strains increased nodule number and nodule biomass by Mesorhizobium sp. Cicer strain Ca181. The plant dry weights of coinoculated treatments showed 1.10 to 1.28 times increase in comparison to Mesorhizobium-inoculated plants alone and 3.62 to 4.50 times over uninoculated controls at 100 days of plant growth. The results indicated the potential usefulness of allelopathic rhizosphere bacteria and growth-mediating IAA in enhancement of nodulation and stimulation of plant growth in chickpea.

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Emergence of resistant microbes to conventional antibiotics and increased emphasis on health-care costs has raised the concern for the development of new effective antimicrobial reagents. Silver nanoparticles being an excellent broad-spectrum antibacterial agent could be considered as a suitable alternative for existing antibiotic. This study demonstrates the extra-cellular synthesis of stable silver nanoparticles using supernatant of Lysinibacillus varians. The synthesized silver nanoparticles were characterized by using UV–visible spectrum analysis, X-ray diffraction, Transmission electron microscopy (TEM) and FT-IR analysis. The synthesized silver nanoparticles showed a peak around 420 nm. TEM analysis revealed that the size of silver nanoparticles was in the range of 10–20 nm. Silver nanoparticles carry a charge of −39.86 mV, which confirmed the stability of silver nanoparticles. The biologically synthesized silver nanoparticles showed antimicrobial activity against Gram-positive, Gram-negative bacteria and fungi. Therefore, the current study reveals an efficient and eco-friendly synthesis of silver nanoparticles by L. varians with potent antimicrobial activity.

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