The study of stress conditions on growth and proteome of Raoultella planticola: a new emerging pathogen.

All bacteria can survive and adapt to different stresses, such as fluctuations in temperature, pH oxidative, and osmotic pressure occurring in their surrounding environments. This study aims to evaluate the effects of a variety of stress conditions on the growth, and proteome of Raoultella planticola PTCC 1598. R. planticola cells were exposed to different values of temperatures, sodium chloride, pH, and hydrogen peroxide stresses. Among the stress conditions, oxidative stress, upon exposure to hydrogen peroxide (H2O2) at 4000 ppm concentration was selected for proteomics analysis in detail. Approximately, 1400 spots were identified in two-dimensional gel electrophoresis (2-DE). Among the identified spots, 85 spots were repeatable using 2D-Platinum software and eye confirmation and, nine protein spots were differentially expressed. Among nine proteins, six proteins identified successfully with an MASCOT score greater than 40 (p < 0.05) were 2,3-dihydroxybenzoate-2,3-dehydrogenase (oxidoreductase family), hypothetical protein G787-04832, periplasmic D-galactose-binding protein, uridine phosphorylase (glycosyltransferases), a single peptide match to cysteine-binding periplasmic protein, and NADP(H) nitroreductase. All identified proteins showed decreased level expression. Based on the obtained results, we concluded that hydrogen peroxide as an antiseptic compound could affect cell growth and proteomics of R. planticola. Therefore, we recommend using an antiseptic solution containing H2O2 to prevent the spread of R. planticola as a new emerging pathogen.

Antimicrobial activity of bacteriocin produced by a new Latilactobacillus curvatus sp.LAB-3H isolated from traditional yogurt.

In recent years, the use of bacteriocin-producing Lactobacillus species has received much attention in different areas, including using as probiotics, food preservation, and as broad antimicrobial spectrum activity. In this study, a bacteriocin-producing Lactobacillus strain was isolated from traditional yogurt. The isolate was identified by morphological, biochemical, 16S rRNA analyses, and designated as Latilactobacillus curvatus LAB-3H. The primary antimicrobial activity of the isolate was evaluated on Micrococcus luteus PTCC 1408 by the agar gel diffusion method. The growth of L. curvatus LAB-3H in MRS broth at 37 °C and its antimicrobial activity against Lactobacillus casei ATCC 39,392 was evaluated. In batch culture analysis, bacteriocin production starts at the early exponential growth phase and continues to the middle of the stationary phase about (660 AU/ml) at 28 h and pH 3.8. Bacteriocin produced by L. curvatus LAB-3H showed antibacterial activity against some selected foodborne pathogens, including Listeria monocytogenes PTCC1294, Bacillus cereus PTCC1857, Staphylococcus aureus PTCC1917, and Escherichia coli PTCC1276. For purification of bacteriocin, ammonium sulfate precipitation and cation exchange chromatography methods were used. The maximum antimicrobial activity observed was about 3985.15 AU/mg of protein, which was a 249.22-fold increase, and 5.21% yield compared with that in the cell-free supernatant. The molecular weight of bacteriocin was approximately 55 kDa by SDS-PAGE. The obtained results in this study demonstrate that bacteriocin from L. curvatus LAB-3H is a potential candidate for controlling microbial contaminations and can be used in different sectors, such as food industries.

Nanoporous iron oxide nanoparticle: hydrothermal fabrication, human serum albumin interaction and potential antibacterial effects.

Nanoporous iron oxide (Fe3O4) nanoparticles (NIONPs) have been widely used as promising agents in biomedical applications. Herein, the NIONPs were synthesized by one-step hydrothermal method and well-characterized by FESEM and TEM investigations. Afterwards, their interaction with human serum albumin (HSA) was studied using a wide range of biophysical approaches, including intrinsic and extrinsic fluorescence, far and near UV-CD, and UV-Vis spectroscopic methods as well as molecular docking investigation. Furthermore, the antibacterial effect of NIONPs was examined on the standard strains of the following pathogenic bacteria, Staphylococcus aureus (ATCC 25923), Klebsiella penumoniae (ATCC 33883), Enterococcus faecalis (ATCC 29212) and Pseudomonas aeruginosa (ATCC 27853). The results showed the feasible fabrication of spherical-shaped NIONPs with an average diameter of around 100 nm. Intrinsic fluorescence spectroscopy data depicted that NIONPs formed a complex with HSA by a KSV value of 0.092 (µg/ml)-1. Extrinsic fluorescence, near UV-CD and UV-vis spectroscopic methods revealed that NIONPs induced some changes on the quaternary structure of HSA, whereas Tm measurement and far UV-CD spectroscopy showed some slight changes on the secondary structure of HSA even in the presence of high concentration of NIONPs. Molecular docking study disclosed that Fe3O4 nanoclusters with varying morphologies and dimensions could interact with different residues on the surface of HSA molecules. In addition, antibacterial assays exhibited a significant inhibition on both Gram-positive and Gram-negative pathogenic bacteria. In conclusion, these NPs can be used as promising antibacterial agents.Communicated by Ramaswamy H. Sarma.