The arid and semi-arid regions of Rajasthan are one of the most extreme biomes of India, possessing diverse microbial communities that exhibit immense biotechnological potential for industries. Herein, we sampled study sites from arid and semi-arid regions of Thar Desert, Rajasthan, India and subjected them to chemical, physical and metagenomics analysis. The microbial diversity was studied using V3–V4 amplicon sequencing of 16S rRNA gene by Illumina MiSeq. Our metagenomic analyses revealed that the sampled sites consist mainly of Proteobacteria (19–31%) followed by unclassified bacteria (5–21%), Actinobacteria (3–25%), Planctomycetes (5–13%), Chloroflexi (2–14%), Bacteroidetes (3–12%), Firmicutes (3–7%), Acidobacteria (1–4%) and Patescibacteria (1–4%). We have found Proteobacteria in abundance which is associated with a range of activities involved in biogeochemical cycles such as carbon, nitrogen, and sulphur. Our study is perhaps the first of its kind to explore soil bacteria from arid and semi-arid regions of Rajasthan, India. We believe that the new microbial candidates found can be further explored for various industrial and biotechnological applications.
Calcium hydroxide nanoparticles (Ca(OH)2 NPs) are of great interest in the development of new products due to their antibacterial properties. Chemical precipitation process was used for synthesizing Ca(OH)2 NPs. The synthesized Ca(OH)2 NPs were characterized by using X‐ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Fourier Transmission Infrared Spectroscopy (FTIR), UV‐Visible spectroscopy, DLS (Dynamic Light Scattering) techniques. Ca(OH)2 NPs were assessed for antibacterial activity against gram‐positive bacteria (Bacillus subtilis, Staphylococcus aureus) and gram‐negative bacteria (Escherichia coli, Pseudomonas aeruginosa). The results showed reasonable bactericidal activity and flash out that the antibacterial activity of Ca(OH)2 had an important inhibitory activity against B. subtilis and P. aeruginosa which are gram‐positive and gram‐negative bacteria respectively. Reactive oxygen species (ROS) generation of Ca(OH)2 NPs were also studied and shows significant results against both gram negative and gram positive bacteria. From the analysis of the results, it was observed that Ca(OH)2 shows the best antibacterial activity against gram‐positive bacteria B. subtilis. Further, the possible mechanisms of antibacterial behaviour of Ca(OH)2 against each bacteria were suggested. These outcomes indicate that Ca(OH)2 could be utilized as a functional antibacterial material.
The bacterial strain SHJP4 was isolated from the soil samples of arid and semi-arid zones of Rajasthan. SHJP4 experimentally confirmed to be a gram positive, rod shaped, aerobic, motile and endospore forming. The optimum growth was seen at 55°C and at alkaline pH. The strain was able to adapt itself in the medium containing 5% NaCl. The DNA was isolated from the culture and checked on 1.2% agarose gel. After amplification and sequencing by 16S rRNA the strain was identified as Aeribacillus pallidus based on nucleotide homology and Phylogenetic analysis and Bayesian. The strain SHJP4 is deposited to NCBI with accession number-MK296526.
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