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Nature Communications, 12 (1), ISSN:2041-1723

The toxicological impact of TiO2 nanoparticles on the environment and human health has been extensively studied in the last few decades, but the mechanistic details were unknown. In this study, we evaluated the impact of industrially prepared TiO2 nanoparticles on the biological system using zebrafish embryo as an in vivo model. The industrial synthesis of TiO2 nanoparticles was mimicked on the lab scale using the high energy ball milling (HEBM) method by milling bulk TiO2 particles for 5 h, 10 h, and 15 h in an ambient environment. The physiochemical properties were characterized by standard methods like field emission scanning electron microscopy (FESEM), dynamic light scattering (DLS), X-ray diffraction (XRD) and UV-Visible spectroscopy. In vivo cytotoxicity was assessed on zebrafish embryos by the evaluation of their mortality rate and hatching rate. Experimental and computational analysis of reactive oxygen species (ROS) induction, apoptosis, and neutral lipid alteration was done to study the effects on the cellular level of zebrafish larvae. The analysis depicted the change in size and surface charge of TiO2 nanoparticles with respect to the increase in milling time. In silico investigations revealed the significant role of ROS quenching and altered neutral lipid accumulation functionalised by the molecular interaction of respective metabolic proteins in the cytotoxicity of TiO2 nanoparticles with zebrafish embryos. The results reveal the hidden effect of industrially synthesized TiO2 nanoparticle exposure on the alteration of lipid accumulation and ROS in developing zebrafish embryos. Moreover, the assessment provided a detailed mechanistic analysis of in vivo cytotoxicity at the molecular level.

Membrane biofouling limits its lifetime and application. Our objective is to optimize surface modification and subsequent silver nanoparticle impregnation on polyethersulfone (PES) membrane for biofouling prevention. For this, silver nanoparticles were selectively impregnated on the PES membrane, via carbonyl group attachment on membrane surface by acrylic acid grafting. Based on mechanical property and silver loading, three different membranes (AA-Ag-PES-25, AA-Ag-PES-62 and AA-Ag-PES-185 with acrylic acid grafting of 25, 62 and 185 μg cm−2, respectively, and having resultant silver loading of 4.4, 9.06 and 16.94 wt%, respectively) were screened for further testing. Performance of the AA-Ag-PES-62 membrane was best, with least reduction of permeate flux at steady state (12.69%), signifying biofouling prevention, compared to only PES membrane (62.2% permeate flux reduction); the latter due to attached live E. coli cells, in absence of silver nanoparticles. For AA-Ag-PES-25 with a lower silver loading, bacterial cell killing was slower, with resultant permeate flux-drop at steady state (19.7%) being more than the optimum AA-Ag-PES-62 membrane. In contrast, for the higher silver loaded AA-Ag-PES-185, silver nanoparticles formed a surface layer, which resulted in partial pore-blockage with higher permeate flux reduction (27.28%). Regarding long-term performance, for AA-Ag-PES-62, there was neither flux-drop nor bacterial growth till 48 h, whereas, due to low silver content in AA-Ag-PES-25, bacteria re-grew after 24 h, which reflected into permeate flux-drop. AA-Ag-PES-62 membrane provides optimum performance in terms of E. coli killing and anti-biofouling effect, maintaining silver concentration in permeate (29.8 ppb), well within the permissible 100 ppb limit.

Salmonella Typhimurium is an enteric pathogen that has evolved masterful strategies to enable survival under stress conditions both within and outside a host. The acid tolerance response (ATR) is one such mechanism that enhances the viability of acid adapted bacteria to lethal pH levels. While numerous studies exist on the protein coding components of this response, there is very little data on the roles of small RNAs (sRNAs). These non-coding RNA molecules have recently been shown to play roles as regulators of bacterial stress response and virulence pathways. They function through complementary base pairing interactions with target mRNAs and affect their translation and/or stability. There are also a few that directly bind to proteins by mimicking their respective targets. Here, we identify several sRNAs expressed during the ATR of S. Typhimurium and characterize one highly induced candidate, RyeC. Further, we identify ptsI as a trans-encoded target that is directly regulated by this sRNA. From a functional perspective, over-expression of RyeC in Salmonella produced a general attenuation of several in vitro phenotypes including acid survival, motility, adhesion and invasion of epithelial cell lines as well as replication within macrophages. Together, this study highlights the diverse roles played by sRNAs in acid tolerance and virulence of S. Typhimurium.

The work is based on augmentation of active sites of calcium alginate bead by immobilizing bromelain to remove lead(II) from simulated solution. The optimum immobilization condition as specified by response surface methodology is as follows: initial concentration of sodium alginate, bromelain, and calcium chloride are 20, 21.09, and 20 g/L, respectively, at pH 7 and 35°C and the sample, thus prepared, is termed as alginate immobilized bromelain (AIB). Maximum 99.5% lead(II) has been removed when 30 mL lead(II) solution having initial concentration of 0.0048 mmol L−1 has been treated with 5 g of AIB at pH 7 and 35°C. 77.9% lead(II) has been recovered when 1 g of spent adsorbent is stirred in 100 mL of solution having pH 2 for 30 min. The removal of lead(II) using AIB and, thereby, simultaneous inhibition of enzyme have been modeled both statistically and empirically.

The enterobacterial pathogen Salmonella has long served as a model for bacterial pathogenesis, stress response, gene expression and regulation with extensive investigation involving protein function. With the advent of high-throughput sequencing technologies and their applications in genomics and transcriptomics, a wealth of data particularly with respect to small RNAs (sRNAs) is being generated. These molecules serve as regulators of major stress response and virulence networks in diverse species including Salmonella enterica subsp. enterica serovar Typhimurium (S. Typhimurium) and have received a lot of focus in the last decade. sRNAs are major post-transcriptional regulators that either repress or activate their targets, the former comprising the bulk of known interactions. In this review, we update and summarize validated sRNA-target regulatory information in S. Typhimurium. It covers the largest group of sRNAs in this pathogen, namely trans-encoded antisense RNAs which have received a lot of focus over the past decade. Additionally, we explore the role of Hfq as a global RNA-binding protein and highlight current techniques developed to identify sRNA targets.