Isolation and sequencing of three RB49-like bacteriophages infecting O antigen-producing E. coli strains

E. coli strains 4s, F5 and F17, whose O antigens are structurally characterized and shown to effectively shield the cell surface from bacteriophage attack, were used as the hosts to isolate novel RB49-like bacteriophages. Three novel phage isolates were obtained, and their genomes were sequenced and annotated. Despite high overall identity levels of these genomic sequences, the variants of large distal tail fiber subunit, orthologous to the bacteriophage T2 long tail receptor recognition protein gp38, were unique for each phage, suggesting their role in host range determination. The annotated genomes are available via NCBI Genbank, acc. numbers MZ504876-MZ504878.

PHIDA: A High Throughput Turbidimetric Data Analytic Tool to Compare Host Range Profiles of Bacteriophages Isolated Using Different Enrichment Methods

Bacteriophages are viruses that infect bacteria and are present in niches where bacteria thrive. In recent years, the suggested application areas of lytic bacteriophage have been expanded to include therapy, biocontrol, detection, sanitation, and remediation. However, phage application is constrained by the phage’s host range—the range of bacterial hosts sensitive to the phage and the degree of infection. Even though phage isolation and enrichment techniques are straightforward protocols, the correlation between the enrichment technique and host range profile has not been evaluated. Agar-based methods such as spotting assay and efficiency of plaquing (EOP) are the most used methods to determine the phage host range. These methods, aside from being labor intensive, can lead to subjective and incomplete results as they rely on qualitative observations of the lysis/plaques, do not reflect the lytic activity in liquid culture, and can overestimate the host range. In this study, phages against three bacterial genera were isolated using three different enrichment methods. Host range profiles of the isolated phages were quantitatively determined using a high throughput turbidimetric protocol and the data were analyzed with an accessible analytic tool “PHIDA”. Using this tool, the host ranges of 9 Listeria, 14 Salmonella, and 20 Pseudomonas phages isolated with different enrichment methods were quantitatively compared. A high variability in the host range index (HRi) ranging from 0.86–0.63, 0.07–0.24, and 0.00–0.67 for Listeria, Salmonella, and Pseudomonas phages, respectively, was observed. Overall, no direct correlation was found between the phage host range breadth and the enrichment method in any of the three target bacterial genera. The high throughput method and analytics tool developed in this study can be easily adapted to any phage study and can provide a consensus for phage host range determination.

ASSESSMENT OF THE THREAT OF COLLISION OF AN UNMANNED VEHICLE WITH OTHER VEHICLES BY LASER LOCATION INFORMATION

The problems of using two-beam Laser Locators (LL) on Unmanned Vehicles (UV) are analyzed. The article discusses the solution to the problem of automatic assessment of the possibility of collision of a UV with other traffic participants based on information generated by the LL. LL performs controlled scanning of the road surface at a given distance from the vehicle. To generate the error signal in the tilt angle control loop, a special filtering of the correction sequence is applied. Such filtering eliminates numerous outliers and forms a sample of correction values that do not lead to abrupt changes in the road sensing range. The modeling of the system is performed, the adequacy of which is due to the results of the conducted field experiments with a real LL. It is shown that the threat of collision arises if the vehicle speed is in a certain (dangerous) interval, the boundaries of which are functions of the following arguments: – the angle between the tangents to the trajectories of the UV and the vehicle during the LL measurements “angle-angle-range”; – distances between the UV and the vehicle at the same time interval. Tasks solved: – estimates of the angle and distances between the UV and the vehicle based on the current LL measurements “angle-angle-range”; – determination of the boundaries of the dangerous range of vehicle speeds at known UV speeds and dimensions of the UV and vehicle; – estimation of the vehicle speed according to LL measurements “angle-angle-range”. Simulation methods were used to determine the accuracy of estimates of the boundaries of the vehicle speeds dangerous range, which made it possible to create an algorithm for warning about a possible collision.

Genomic and functional characterization of five novel Salmonella-targeting bacteriophages

Background The host-unrestricted, non-typhoidal Salmonella enterica serovar Enteritidis (S. Enteritidis) and the serovar Typhimurium (S. Typhimurium) are major causative agents of food-borne gastroenteritis, and the host-restricted Salmonella enterica serovar Gallinarum (S. Gallinarum) is responsible for fowl typhoid. Increasing drug resistance in Salmonella contributes to the reduction of effective therapeutic and/or preventive options. Bacteriophages appear to be promising antibacterial tools, able to combat infectious diseases caused by a wide range of Salmonella strains belonging to both host-unrestricted and host-restricted Salmonella serovars. Methods In this study, five novel lytic Salmonella phages, named UPWr_S1-5, were isolated and characterized, including host range determination by plaque formation, morphology visualization with transmission electron microscopy, and establishment of physiological parameters. Moreover, phage genomes were sequenced, annotated and analyzed, and their genomes were compared with reference Salmonella phages by use of average nucleotide identity, phylogeny, dot plot, single nucleotide variation and protein function analysis. Results It was found that UPWr_S1-5 phages belong to the genus Jerseyvirus within the Siphoviridae family. All UPWr_S phages were found to efficiently infect various Salmonella serovars. Host range determination revealed differences in host infection profiles and exhibited ability to infect Salmonella enterica serovars such as Enteritidis, Gallinarum, Senftenberg, Stanley and Chester. The lytic life cycle of UPWr_S phages was confirmed using the mitomycin C test assay. Genomic analysis revealed that genomes of UPWr_S phages are composed of 51 core and 19 accessory genes, with 33 of all predicted genes having assigned functions. UPWr_S genome organization comparison revealed 3 kinds of genomes and mosaic structure. UPWr_S phages showed very high sequence similarity to each other, with more than 95% average nucleotide identity. Conclusions Five novel UPWr_S1-5 bacteriophages were isolated and characterized. They exhibit host lysis range within 5 different serovars and are efficient in lysis of both host-unrestricted and host-restricted Salmonella serovars. Therefore, because of their ability to infect various Salmonella serovars and lytic life cycle, UPWr_S1-5 phages can be considered as useful tools in biological control of salmonellosis.

Method for increasing noise immunity of radar "friend or foe" identification systems under the action of intentional correlated interference

The paper analyzes the principles of construction and structure of "friend or foe" identification systems. It is revealed, that the party, interested in the existing system, has the ability of unauthorized use of this information resource for long-range determination of air objects coordinates, on the one hand, and distortion of information of this information resource, on the other hand, which leads to unpredictable consequences. It is shown, that the most vulnerable place in the "friend or foe" identification systems is the aircraft transponder, which significantly affects noise stability and noise immunity of the identification systems of air objects. The paper proposes a method of hereditary transition to noise-immune "friend or foe" identification systems based on synchronous networks of identification systems, which allows expanding significantly the methods of servicing requests and methods of constructing systems. This method of constructing identification systems eliminates the existing problem of dispersed identification systems, as well as the problem of temporal matching of signals coming from primary and secondary radar systems. The proposed method of hereditary transition to noise-immune "friend or foe" identification systems makes it possible to exclude the possibility of unauthorized access to identification information resources by an interested party, significantly increases the noise immunity of the identification system as a whole.