Project description:Relentless mining operations have destroyed our environment significantly. Soil inhabiting microbes play a significant role in ecological restoration of these areas. Microbial weathering processes like chemical dissolution of rocks significantly promotes the soil properties and enhances the rock to soil ratio respectively. Earlier studies have reported that bacteria exhibit efficient rock-dissolution abilities by releasing organic acids and other chemical elements from the silicate rocks. However, rock-dissolving mechanisms of the bacterium remain to be unclear till date. Thus, we have performed rock-dissolution experiments followed by genome and transcriptome sequencing of novel Pseudomonas sp.NLX-4 strain to explore the efficiency of microbe-mediated habitat restoration and its molecular mechanisms underlying this biological process. Results obtained from initial rock dissolution experiments revealed that Pseudomonas sp. NLX-4 strain efficiently accelerates the dissolution of silicate rocks by secreting amino acids, exopolysaccharides, and organic acids with elevated concentrations of potassium, silicon and aluminium elements. The rock dissolution experiments of NLX-4 strain exhibited an initial increase in particle diameter variation values between 0-15 days and decline after 15 days-time respectively. The 6,771,445-base pair NLX-4 genome exhibited 63.21 GC percentage respectively with a total of 6041 protein coding genes. Genome wide annotations of NLX-4 strain exhibits 5045-COG, 3996-GO, 5342-InterPro, 4386-KEGG proteins respectively Transcriptome analysis of NLX-4 cultured with/without silicate rocks resulted in 539 (288-up and 251-down) differentially expressed genes (DEGs). Fifteen DEGs encoding for siderophore transport, EPS and amino acids synthesis, organic acids metabolism, and bacterial resistance to adverse environmental conditions were highly up-regulated by cultured with silicate rocks. This study has not only provided a new strategy for the ecological restoration of rock mining areas, but also enriched the applicable bacterial and genetic resources.

Project description:Background: Frankia sp. strains are actinobacteria that form N2-fixing root nodules on angiosperms. Several reference genome sequences are available enabling transcriptome studies in Frankia sp. Genomes from Frankia sp. strains differ markedly in size, a consequence proposed to be associated with a high number of indigenous transposases, more than 200 of which are found in Frankia sp. strain CcI3 used in this study. Because Frankia exhibits a high degree of cell heterogeneity as a consequence of its mycelial growth pattern, its transcriptome is likely to be quite sensitive to culture age. This study focuses on the behavior of the Frankia sp. strain CcI3 transcriptome as a function of nitrogen source and culture age. Results: To study global transcription in Frankia sp. CcI3 grown under different conditions, complete transcriptomes were determined using high throughput RNA deep sequencing. Samples varied by time (five days vs. three days) and by culture conditions (NH4+ added vs. N2 fixing). Assembly of millions of reads revealed more diversity of gene expression between five-day and three-day old cultures than between three day old cultures differing in nitrogen sources. Heat map analysis organized genes into groups that were expressed or repressed under the various conditions compared to median expression values. Twenty-one SNPs common to all three transcriptome samples were detected indicating culture heterogeneity in this slow-growing organism. Significantly higher expression of transposase ORFs was found in the five-day and N2-fixing cultures, suggesting that N starvation and culture aging provide conditions for on-going genome modification. Transposases have previously been proposed to participate in the creating the large number of gene duplication or deletion in host strains. Subsequent RT-qPCR experiments confirmed predicted elevated transposase expression levels indicated by the mRNA-seq data. Conclusions: The overall pattern of gene expression in aging cultures of CcI3 suggests significant cell heterogeneity even during normal growth on ammonia. The detection of abundant transcription of nif (nitrogen fixation) genes likely reflects the presence of anaerobic, N-depleted microsites in the growing mycelium of the culture, and the presence of significantly elevated transposase transcription during starvation indicates the continuing evolution of the Frankia sp. strain CcI3 genome, even in culture, especially under stressed conditions. These studies also sound a cautionary note when comparing the transcriptomes of Frankia grown in root nodules, where cell heterogeneity would be expected to be quite high.

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Pseudomonas sp. X4 strain:X4

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