Agri-nanotechnology has the potential to transform the agricultural practices. Nanoparticles of interest can be produced both by various physical and chemical methods. The biogenetic production of nanoparticles is now of high interest due to simplicity of the procedures and their versatility. Several species of bacteria and plants are able to synthesize nanoparticles or help in the process of their production. Implementation of nanoparticlebased smart delivery system and nanosensors holds the promise of controlled release of agrochemicals and site-targeted delivery of various macromolecules needed for improved plant disease resistance, effi cient nutrient utilization and improved plant defence in an environment-friendly manner. Nanoparticle-mediated plant transformation has the potential for genetic modifi cation of plant improvement.

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Despite the high specificity between Rhizobium and legumes, the presence of non-rhizobia in root nodules has been reported. The present investigation was carried out to isolate plant growth-promoting endophytic non-rhizobial bacteria from leguminous crops viz. Glycine max, Vigna radiata, Vigna unguiculata, Arachis hypogaea and Vigna mungo, and their influence on groundnut growth. Seven endophytic non-rhizobial bacteria were isolated possessing the nifH gene showing amplification of a~380-bp fragment. Analysis by 16S rDNA gene sequence similarity characterized them as Enterobacter cloacae AS1 (accession no. KF758544), Chryseobacterium indologenes AM2 (KF758545), Enterobacter cloacae ACP3 (KF758546), Klebsiella pneumoniae AG4 (KF758547), Pseudomonas aeruginosa ABG5 (KF758548), Enterobacter ludwigii ABG6 (KF758549) and Klebsiella variicola ABG7 (KF758550). Qualitative estimation of nitrogen fixation confirmed the efficiency of isolates to fix atmospheric nitrogen in a range of 11.55 to 62.10 mg N g −1 of glucose consumed. All strains were found to produce indoleacetic acid ranging from 34.86 to 119.44 μg ml −1 . The highest phosphate solubilization index was shown by K. pneumoniae AG4 (14.67). Siderophore production was observed only in P. aeruginosa ABG5, and the highest 1-aminocyclopropane-1-carboxylate deaminase activity was shown by C. indologenes AM2, E. cloacae ACP3 and P. aeruginosa ABG5. Plant growth stimulation was confirmed by seed application in groundnuts in a gnotobiotic system and in pots. The results showed that isolates had a positive effect on groundnut growth, with no negative influence. In addition, treatment with 50 % recommended dose of chemical fertilizer demonstrated a positive influence on groundnut growth, but an increase in concentration from 50 to 100 % resulted in adverse effects on populations of non-rhizobial bacteria and groundnut growth. Thus the results of this study clearly suggest that root nodules accommodate endophytic non-rhizobial bacteria, which stimulates plant growth, and that chemical fertilizers greatly affect their number and activity.

Methylotrophic bacteria which are known to utilize C1 compounds including methane. Research during past few decades increased the interest in finding out novel genera of methane degrading bacteria to efficiently utilize methane to decrease global warming effect. Moreover, evaluation of certain known plant growth promoting strains for their methane degrading potential may open up a new direction for multiple utility of such cultures. In this study, efficient methylotrophic cultures were isolated from wetland paddy fields of Gujarat. From the overall morphological, biochemical and molecular characterization studies, the isolates were identified and designated as Bacillus aerius AAU M 8; Rhizobium sp. AAU M 10; B. subtilis AAU M 14; Paenibacillus illinoisensis AAU M 17 and B. megaterium AAU M 29. Gene specific PCR analysis of the isolates, P. illinoisensis, B. aerius, Rhizobium sp. and B. subtilis showed presence of pmoA gene encoding α subunit particulate methane monooxygenase cluster. B. megaterium, P. illinoisensis, Rhizobium sp. and Methylobacterium extrorquens showed presence of mmoX gene encoding α subunit of the hydroxylase component of the soluble methane monooxygenase cluster. P. illinoisensis and Rhizobium sp. showed presence mxaF gene encoding α subunit region of methanol dehydrogenase gene cluster showing that both isolates are efficient utilizers of methane. To the best of our knowledge, this is the first time report showing presence of methane degradation enzymes and genes within the known PGPB group of organisms from wet land paddy agro-ecosystem, which is considered as one of the leading methane producer.

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