Potential role of viral metagenomics as a surveillance tool for the early detection of emerging novel pathogens.

Since the early times, human beings have always been faced with deadly microbial infections, both bacterial and viral. Pathogens such as viruses are always evolving owing to the processes of antigenic shift and drift. Such viral evolution results in the emergence of new types and serovars that prove deadly for humans-like influenza pandemics, severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS). The pandemic of novel coronavirus SARS-CoV-2 is the recent example. It has resulted in a great loss of human lives and a serious burden on economy across the globe. To counter such situations, a system should exist for the early detection of emerging viral pathogens. This will help prevent possible outbreaks and save human lives. Most of such deadly novel viruses and viral outbreaks are known to be originated from animal hosts. Regular monitoring of potential hot spots of such emerging microbes, such as zoos and animal markets, through metagenomics could help assess the presence of new viruses and pathogens. In this review, we focus on the potential of viral metagenomics and propose a surveillance system based on it for the early detection and hence prevention of such emerging viral infections.

Mutation in pvcABCD operon of Pseudomonas aeruginosa modulates MexEF-OprN efflux system and hence resistance to chloramphenicol and ciprofloxacin.

Pseudomonas aeruginosa harbors pvcABCD operon that is responsible for the synthesis of paerucumarin. Here we report the involvement of pvcABCD operon in chloramphenicol and ciprofloxacin resistance. P. aeruginosa mutant defective in pvcB (PW4832) was more sensitive to chloramphenicol and ciprofloxacin in comparison with its parent strain (MPAO1). A mutation in pvcA gene in MPAO1 (PW4830) did not alter the sensitivity to either antibiotic. As chloramphenicol and ciprofloxacin are substrates of MexEF-OprN efflux pump, so we decided to investigate the modulation of MexEF-OprN and its transcriptional regulator MexT in PW4832, PW4830 and MPAO1 strains. We isolated and sequenced mexT gene from MPAO1, PW4830 and PW4832. The nucleotide sequence of mexT gene in all three strains was identical. Expression levels of mexEF-oprN, mexT and mexS genes were checked via quantitative real-time RT-PCR. All these genes showed significant repression in mRNA levels in PW4832 as compared to MPAO1. These results indicate that chloramphenicol and ciprofloxacin sensitivity in PW4832 is due to transcriptional repression of mexT and mexEF-oprN genes. Exogenous addition of paerucumarin resumed the expression of mexT and mexEF-oprN genes as well as resistance against chloramphenicol and ciprofloxacin in PW4832 strain. This is a novel finding linking pvcB gene of P. aeruginosa with chloramphenicol and ciprofloxacin resistance and MexEF-OprN pump modulation which needs to be further explored.

Anoxic growth optimization for metal respiration and photobiological hydrogen production by arsenic-resistant Rhodopseudomonas and Rhodobacter species.

The current research focuses on anaerobic respiration of arsenic and other toxic metals by purple nonsulfur bacteria (PNSB). Among the optimization assays performed were carbon utilization, cross metal resistance, and metal respiration, along with a comparison of each assay in photoheterotrophic and chemoheterotrophic growth. The bacteria were identified by the classification of 16S ribosomal RNA gene sequences. Rhodobacter sp. PI3 proved to be more versatile in carbon source utilization (acetate, lactate, citrate, and oxalate), whereas Rhodopseudomonas palustris PI5 proved to be more versatile in metal resistance (arsenate, arsenite, cobalt, lead, selenium, and nickel). Both the strains were found to be positive for photofermentative hydrogen production along with arsenic respiration. This study reveals that anaerobic conditions are more appropriate for better efficiency of PNSB. Our study demonstrates that R. palustris PI5 and Rhodobacter sp. PI3 can be promising candidates for the biohydrogen production along with metal detoxification using heavy metal-polluted effluents as a substrate.

Advances In Research On Genome Editing Crispr-Cas9 Technology.

BACKGROUND: The current era of genome engineering has been revolutionized by the evolution of a bacterial adaptive immune system, CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) into a radical technology that is making an expeditious progress in its mechanism, function and applicability.. METHODS: A systematic literature review study was carried out with the help of all available information and online resources.. RESULTS: In this review, we intend to elucidate different aspects of CRISPR in the light of current advancements. Utilizing a nonspecific Cas9 nuclease and a sequence specific programmable CRISPR RNA (crRNA), this system cleaves the target DNA with high precision. With a vast potential for profound implications, CRISPR has emerged as a mainstream method for plausible genomic manipulations in a range of organisms owing to its simplicity, accuracy and speed. A modified form of CRISPR system, known as CRISPR/Cpf1 that employs a smaller and simpler endonuclease (Cpf1) than Cas9, can be used to overcome certain limitations of CRISPR/Cas9 system. Despite clear-cut innovative biological applications, this technology is challenged by off-target effects and associated risks, thus safe and controlled implementation is needed to enable this emerging technique assist both biological research and translational applications. CONCLUSIONS: CRISPR/Cas9 systems will undoubtedly revolutionize the study and treatment of both immunologic and allergic diseases. Concerned authorities should formulate and authorize such laws and regulations that permit the safe and ethical use of this emerging technology for basic research and clinical purposes.

Isonitrile-functionalized tyrosine modulates swarming motility and quorum sensing in Pseudomonas aeruginosa.

Paerucumarin synthesized by pvc operon pvcABCD is an iron binding molecule which modulates biofilm formation in Pseudomonas aeruginosa but its direct function in bacterial pathogenesis needs further investigation. pvcA synthesizes isonitrile functionalized tyrosine (IFT) which is converted to mature paerucumarin by the proteins encoded by pvcB, pvcC and pvcD genes. Interruption of pvcB in MPAO1 resulted in accumulation of IFT as it cannot be converted to mature molecule. The MPAO1 pvcB mutant (PW4832) showed enhanced swarming motility, while complementation with plasmid pLL2 carrying pvcB reduced swarming motility. Enhanced levels of rhlA expression and rhamnolipid production were observed in PW4832 compared to the parent strain. Overexpression of ptxR, the positive regulator of pvcABCD, in PW4832 caused accumulation of more IFT and further elevated the level of rhlA expression. Expression of the quorum sensing system transcriptional activators lasR and rhlR, as well as the synthase genes lasI and rhlI, was enhanced in PW4832 compared to MPAO1, as was PQS accumulation. Exogenously added IFT, but not paerucumarin, enhanced the production of rhamnolipids in P. aeruginosa. These results suggest that IFT enhances swarming motility in P. aeruginosa either directly by enhancing rhamnolipid production or indirectly through modulation of the quorum sensing systems. This is the first report assigning an independent function to IFT in P. aeruginosa.