Crystal structure of a MarR family protein from the psychrophilic bacterium Paenisporosarcina sp. TG-14 in complex with a lipid-like molecule

MarR family proteins regulate the transcription of multiple antibiotic-resistance genes and are widely found in bacteria and archaea. Recently, a new MarR family gene was identified by genome analysis of the psychrophilic bacterium Paenisporosarcina sp. TG-14, which was isolated from sediment-laden basal ice in Antarctica. In this study, the crystal structure of the MarR protein from Paenisporosarcina sp. TG-14 (PaMarR) was determined at 1.6 Å resolution. In the crystal structure, a novel lipid-type compound (palmitic acid) was found in a deep cavity, which was assumed to be an effector-binding site. Comparative structural analysis of homologous MarR family proteins from a mesophile and a hyperthermophile showed that the DNA-binding domain of PaMarR exhibited relatively high mobility, with a disordered region between the β1 and β2 strands. In addition, structural comparison with other homologous complex structures suggests that this structure constitutes a conformer transformed by palmitic acid. Biochemical analysis also demonstrated that PaMarR binds to cognate DNA, where PaMarR is known to recognize two putative binding sites depending on its molar concentration, indicating that PaMarR binds to its cognate DNA in a stoichiometric manner. The present study provides structural information on the cold-adaptive MarR protein with an aliphatic compound as its putative effector, extending the scope of MarR family protein research.

Cloning, Expression, Characterization, and Antioxidant Protection of Glutaredoxin3 From Psychrophilic Bacterium Psychrobacter sp. ANT206

Glutaredoxins (Grxs) are proteins that catalyze the glutathione (GSH)-dependent reduction of protein disulfides. In this study, a Grx-related gene (264 bp), encoding a Ps-Grx3, was cloned from Psychrobacter sp. ANT206. Sequence analysis indicated the presence of the active site motif CPYC in this protein. Homology modeling showed that Ps-Grx3 had fewer hydrogen bonds and salt bridges, as well as a lower Arg/(Arg + Lys) ratio than its mesophilic homologs, indicative of an improved catalytic ability at low temperatures. Site-directed mutagenesis demonstrated that the Cys13, Pro14, and Cys16 sites were essential for the catalytic activity of Ps-Grx3, while circular dichroism (CD) spectroscopy confirmed that point mutations in these amino acid residues led to the loss or reduction of enzyme activity. Furthermore, analysis of the biochemical properties of Ps-Grx3 showed that the optimum temperature of this enzyme was 25 °C. Importantly, Ps-Grx3 was more sensitive to tBHP and CHP than to H2O2, and retained approximately 40% activity even when the H2O2 concentration was increased to 1 mm Regarding substrate specificity, Ps-Grx3 had a higher affinity for HED, L-cystine, and DHA than for S-sulfocysteine and BSA. We also investigated the DNA-protective ability of Ps-Grx3 using the pUC19 plasmid, and found that Ps-Grx3 could protect supercoiled DNA from oxidation-induced damage at 15°C for 1.5 h. This study provides new insights into the structure and catalytic activity of a cold-adapted Grx3.

Screening of essential oils activity against a gram negative psychrophilic bacterium isolated from aquatic environment (Water & Biofilm)

Among the applications of medicinal plants, it is their use as antimicrobial agents. The objective of this study was to investigate the effect of some essential oils against an etiological pathogen Flavobacterium spp. responsible for several lost in rainbow trout, (Oncorhynchus mykiss) hatcheries, the strains used in this study were isolated from rearing tanks water and biofilm, identified as Flavobacterium spp. based on phenotypic, biochemical and enzymatic characterizations. A collection of eight essential oils were extracted, analyzed and tested for an inhibitory activity against the isolated strains, the effect on this bacterium has been demonstrated by the aromatogram method based on a screening of bacterial growth in a solid medium culture with disks containing essential oils. Our study’s results show that the chemical composition of the extracted essential oils play a crucial role in their antibacterial activity, which varies from 6 mm up to 34 mm as maximal inhibitory diameter.

Production and characterization of psychrophilic α-amylase from a psychrophilic bacterium, Shewanella sp. ISTPL2

A psychrophilic and halophilic bacterial isolate, Shewanella sp. ISTPL2, procured from the pristine Pangong Lake, Ladakh, Jammu and Kashmir, India, was used for the production and characterization of the psychrophilic and alkalophilic α-amylase enzyme. The α-amylase is a critical enzyme that catalyses the hydrolysis of α-1,4-glycosidic bonds of starch molecules and is predominately utilized in biotechnological applications. The highest enzyme activity of partially purified extracellular α-amylase was 10,064.20 U/mL after 12 h of incubation in a shake flask at pH 6.9 and 10 °C. Moreover, the maximum intracellular α-amylase enzyme activity (259.62 U/mL) was also observed at 6 h of incubation. The extracellular α-amylase was refined to the homogeneity with the specific enzyme activity of 36,690.47 U/mg protein corresponding to 6.87-fold purification. The optimized pH and temperature for the α-amylase were found to be pH 8 and 4 °C, respectively, suggesting its stability at alkaline conditions and low or higher temperatures. The amylase activity was highly activated by Cu2+, Fe2+ and Ca2+, while inhibited by Cd2+, Co2+ and Na2+. As per our knowledge, the current study reports the highest activity of a psychrophilic α-amylase enzyme providing prominent biotechnological potential.

The Beneficial Effect of Eco-Friendly Green Nanoparticles Using Garcinia mangostana Peel Extract against Pathogenicity of Listeria monocytogenes in Female BALB/c Mice

Listeria monocytogenes is a psychrophilic bacterium, which causes widespread zoonosis in the natural environment, and mainly affects goat, sheep, and cattle herds. Recently, we predicted that it can be transmitted through food. It causes listeriosis, a severe infectious disease, which occurs with food contaminated with the pathogenic bacterium. Anti-inflammatory factors are important to treat the dangers of chronic inflammation associated with chronic diseases. Natural foodstuffs have made and are continuing to make vital contributions to the search for new antilisterial agents. The use of natural products in association with silver nanoparticles has drawn attention because of its easy, nonpathogenic, eco-friendly, and economical protocol. Hence, we aimed to biosynthesize silver nanoparticles (Ag-NPs) using Garcinia mangostana peel extract, which was found to be a good source for the synthesis of silver nanoparticles, their formation being confirmed by color change and stability in solution, and investigated the antilisterial activity of these nanoparticles in a murine model of L. monocytogenes infection. A total of 28 mice were divided into four groups—healthy control, infected, infected mice treated with green Ag-NPs biosynthesized with G. mangostana (5 mg/mL), and infected mice pretreated with Ag-NPs. From our results, oral treatment with Ag-NPs biosynthesized with G. mangostana peel extract resulted in a significant reduction in malondialdehyde (MDA), enhanced antioxidant enzyme activities, and increased the levels of the antiapoptotic protein, compared with the untreated mice. These results indicate that G. mangostana may provide therapeutic value against L. monocytogenes-induced oxidative stress and histopathological alterations, and that these effects may be related to antiapoptotic and antioxidant activities.