Functionally coherent transcriptional responses of Jatropha curcas and Pseudomonas fragi for rhizosphere mediated degradation of pyrene.

Pyrene is an extremely hazardous, carcinogenic polycyclic aromatic hydrocarbon (PAH). The plant-microbe interaction between Pseudomonas fragi DBC and Jatropha curcas was employed for biodegradation of pyrene and their transcriptional responses were compared. The genome of P. fragi DBC had genes for PAH degrading enzymes i.e. dioxygenases and dehydrogenases, along with root colonization (trpD, trpG, trpE and trpF), chemotaxis (flhF and flgD), stress adaptation (gshA, nuoHBEKNMG), and detoxification (algU and yfc). The transcriptional expression of catA and yfc that respectively code for catabolic enzyme (catechol-1, 2-dioxygnase) and glutathione-s-transferase for detoxification functions were quantitatively measured by qPCR. The catA was expressed in presence of artificial root exudate with or without pyrene, and glucose confirming the non-selective approach of bacteria, as desired. Pyrene induced 100-fold increase of yfc expression than catA, while there was no expression of yfc in absence of pyrene. The transcriptome of plant roots, in presence of pyrene, with or without P. fragi DBC inoculation was analysed. The P. fragi DBC could upregulate the genes for plant growth, induced the systemic acquired resistance and also ameliorated the stress response in Jatropha roots.

Host specific endophytic microbiome diversity and associated functions in three varieties of scented black rice are dependent on growth stage.

The compositional and functional role of the endophytic bacterial community, associated with black scented rice, in correlation with its antioxidant property has been elucidated. Community dissimilarity analysis confirmed the overlapping of community in shoot and root tissues at the young stage, but not in mature plants. Proteobacteria was the most abundant phylum, in which Agrobacterium, Pleomorphomonas, Bradyrhizobium, Novasphingobium, Caulobacter were the most abundant genera, followed by Cyanobacteria and Planctomycetes in all three different varieties of the black rice. The antioxidant activity of mature plants was found to be higher in comparison to young plants. Intrinsically, the relative abundance of Pleomorphomonas and Streptomyces was positively correlated with total phenol content, while Gemmata, unclassified Pirellulaceae, unclassified Stramenopiles positively correlated with total flavonoid content and negatively correlated with Free radical scavenging activity. Accordingly, functional metagenome analysis of the endophytic microbiome revealed that naringenin -3-dioxygenase and anthocyanidin 3-O-glucosyltransferase for phenylpropanoid (flavonoid and anthocyanin) synthesis were abundant in the endophytic microbiome of mature plants. Specific enrichment of the antioxidant producing genes in the mature plant endophytic microbiome was assigned to some bacteria such as Streptomyces, Pantoea which might have contributed to the common pathway of flavonoid synthesis. The genomes of endophytic isolates Kluyvera sp.PO2S7, Bacillus subtilis AMR1 and Enterobacter sp. SES19 were sequenced and annotated, and were found to have genes for phenylpropanoid synthesis in their genomes.

Shape dependent physical mutilation and lethal effects of silver nanoparticles on bacteria.

In this report, spherical silver nanoparticle (AgNP-sp) and rod-shaped silver nanoparticle (AgNR) were prepared by chemical reduction method and their antibacterial activity against various Gram-positive and Gram-negative bacteria had been evaluated for their efficiency. Minimal inhibitory concentration (MIC) tests were conducted to study the antibacterial properties, and substantiated with killing kinetics of silver nanoparticles (AgNPs). The study revealed that both AgNP-sp and AgNRs are good antibacterial candidates. Bacterial sensitivity to nanoparticles (NPs) was found to vary depending on microbial species. Disc diffusion studies revealed the greater effectiveness of AgNP-sp and AgNR against Klebsiella pneumoniae AWD5 at the doses of 249 and 392 µg. The dose dependent activities of prepared NPs were also observed on the batch studies of disc diffusion and MIC with various strains. The optical and morphological structures of NPs were analyzed by UV-visible, XRD, FE-SEM and TEM. Further, FESEM of bacterial culture treated with AgNPs confirmed antibacterial activity of NPs by showing rupture of bacterial cell wall. Also, the genome of test organism was found to have CusCFBA and CusRS operons. The killing kinetics confirmed that the death rate of K. pneumoniae was higher against AgNP-sp as compared to AgNR.