Whole genome analysis, thermal and UV-tolerance of Lactococcus phage BIM BV-114 isolated from cheese brine.

Lactococcus phages that belong to the genus Ceduovirus are among the three most frequently isolated phage groups infecting Lactococcus lactis starter strains in dairy plants. In this study, we characterized virulent Lactococcus phage BIM BV-114 isolated from industrial cheese brine in Belarus and identified as Ceduovirus. The bacteriophage demonstrated a relatively short lytic cycle (latent period of 23 ± 5 min, lysis time of 90 ± 5 min), high thermal stability (inactivation after 7 min at 95 °C in skimmed milk) and tolerance to UV radiation (inactivation time - 15 min), indicating adaptation for better persistence in dairy facilities. The genome of the phage BIM BV-114 (21 499 bp; 37 putative open reading frames) has a similar organization to that of other Ceduovirus phages. RLf1_00140 and RLf_00050 gene products, found in the early genes region, may be involved in the sensitivity of phage to the lactococcal abortive infection mechanisms AbiV and AbiQ, respectively. Furthermore, nucleotide deletion, observed in the middle region of the gene encoding putative tape measure protein (RLf1_00300), is possibly responsible for increased thermal tolerance of phage BIM BV-114. Together, these findings will contribute to a better knowledge of virulent Lactococcus phages and the development of effective methods of their control for dairy technologies.

Sterically hindered phenolic derivatives: effect on the production of Pseudomonas aeruginosa virulence factors, high-throughput virtual screening and ADME properties prediction.

Inhibition of quorum sensing is considered to be an effective strategy of control and treatment of a wide range of acute and persistent infections. Pseudomonas aeruginosa is an opportunistic bacterium with a high adaptation potential that contributes to healthcare-associated infections. In the present study, the effects of the synthesized hybrid structures bearing sterically hindered phenolic and heterocyclic moieties in a single scaffold on the production of virulence factors by P. aeruginosa were determined. It has been shown that the obtained compounds significantly reduce both pyocyanin and alginate production and stimulate the biosynthesis of siderophores in vitro, which may be attributed to their iron-chelating properties. The results of docking-based inverse high-throughput virtual screening indicate that transcription regulator LasR and Cu-transporter OPRC could be potential molecular targets for these compounds. Investigation of the impact small molecules exert on the molecular mechanisms of the production of bacterial virulence factors may pave the way for the design and development of novel antibacterial agents.

Roseateles amylovorans sp. nov., isolated from freshwater.

A Gram-stain-negative, rod-shaped, amylolytic bacterial strain, designated as bsSlp3-1T, was isolated from the Slepian water system, a freshwater reservoir. Strain bsSlp3-1T was found to be aerobic, oxidase-positive and catalase-negative, grew at 5-37 °C (optimum, 28 °C), pH 5.0-9.5 (optimum, pH 7.0) and low NaCl concentration (up to 1.0 %). Comparative analysis of 16S rRNA gene sequence similarity revealed that strain bsSlp3-1T clustered with Roseateles species and is closely related to Roseateles depolymerans KCTC 42856T (98.7 %) and Roseateles terrae CCUG 52222T (98.6 %). Whole-genome comparisons using average nucleotide identity and digital DNA-DNA hybridization values suggested that strain bsSlp3-1T represents a novel species within the genus Roseateles and is most closely related to Roseateles aquatilis CCUG 48205T (81.2 and 25.6 %, respectively). The genome of strain bsSlp3-1T consisted of a single circular chromosome with size 6 289 366 bp and DNA G+C content of 66.8 mol%. The predominant cellular fatty acids of bsSlp3-1T were cis-9-hexadecanoic and hexadecenoic acids. According to the data obtained in this work, strain bsSlp3-1T represents a novel Roseateles species for which the name Roseateles amylovorans sp. nov. is proposed. The type strain is bsSlp3-1T (=BIM B-1768T=NBIMCC 9098T=VKM B-3671T).

Alginate coated biogenic silver nanoparticles for the treatment of Pseudomonas infections in rainbow trout.

Pseudomonas species are among the main pathogens causing rainbow trout infections. The present study provides a simple, green, sustainable, and rapid technique to synthesize of biogenic alginate-capped silver nanoparticles (Alg-Ag NPs) suitable for the treatment of Pseudomonas infections. It has been shown that the mechanism (aggregative or autocatalytic) of Alg-Ag NPs formation depended on Alg concentration and the heating approach used. The rate constants and activation energy were calculated. Alg-Ag NPs were characterized by UV-Vis, FTIR, XRD, TEM, AFM, XPS, and DLS. The optimal conditions for the fabrication of spherically-shaped (17-19 nm) and negatively-charged (zeta-potential <-50 mV) Alg-Ag NPs, which are stable during 9 months, included hot-plate assisted synthesis at 100 °C in diluted (1 mg/mL) Alg solutions. In vitro studies showed that Alg-Ag NPs exhibited prominent antimicrobial activity against collection Pseudomonas strains (inhibition zones ranged from 9.0 ± 1.0 to 19.0 ± 1.0 mm), with no significant loss of antibacterial efficacy after 9 months of storage. AFM analysis confirmed that the antibacterial effect of Alg-Ag NPs dealt with the direct nanomechanical disrupting of bacterial cells. The ability of Alg-Ag NPs to inhibit the growth of virulent P.aeruginosa, P.fluorescens and P. putida strains isolated from infected rainbow trout was evaluated. All tested strains were susceptible to Alg(10)-Ag NPs, while Alg(1)-Ag NPs demonstrated a limited strain-specific antibacterial effect. The obtained data displayed the prospects for the application of biogenic Alg-Ag NPs to create novel delivery systems for combating Pseudomonas infections in rainbow trout.

Isolation and characterization of fast-growing green snow bacteria from coastal East Antarctica.

Snow microorganisms play a significant role in climate change and affecting the snow melting rate in the Arctic and Antarctic regions. While research on algae inhabiting green and red snow has been performed extensively, bacteria dwelling in this biotope have been studied to a much lesser extent. In this study, we performed 16S rRNA gene amplicon sequencing of two green snow samples collected from the coastal area of the eastern part of Antarctica and conducted genotypic and phenotypic profiling of 45 fast-growing bacteria isolated from these samples. 16S rRNA gene amplicon sequencing of two green snow samples showed that bacteria inhabiting these samples are mostly represented by families Burkholderiaceae (46.31%), Flavobacteriaceae (22.98%), and Pseudomonadaceae (17.66%). Identification of 45 fast-growing bacteria isolated from green snow was performed using 16S rRNA gene sequencing. We demonstrated that they belong to the phyla Actinobacteria and Proteobacteria, and are represented by the genera Arthrobacter, Cryobacterium, Leifsonia, Salinibacterium, Paeniglutamicibacter, Rhodococcus, Polaromonas, Pseudomonas, and Psychrobacter. Nearly all bacterial isolates exhibited various growth temperatures from 4°C to 25°C, and some isolates were characterized by a high level of enzymatic activity. Phenotyping using Fourier transform infrared (FTIR) spectroscopy revealed a possible accumulation of intracellular polymer polyhydroxyalkanoates (PHA) or lipids in some isolates. The bacteria showed different lipids/PHA and protein profiles. It was shown that lipid/PHA and protein spectral regions are the most discriminative for differentiating the isolates.