Induction and migration of cryptic/defective Salmonella enterica prophages as a consequence of infection with lytic phages is an additional factor in stability of a coevolutionary vector

The influence of infection of natural isolates of Salmonella enterica with lytic (nonlysogenic) phages on the expression of resident cryptic or defective prophages in host bacteria was studied. The induction of defective/cryptic phages after infection with nonlysogenic phages and packaging of bacterial chromosomal fragments in capsids of defective phages is demonstrated. This may lead to migration and wide distribution of both the genomes of defective phages per se and various fragments of the bacterial chromosome (including pathogenic islands) in new bacterial strains with concomitant change of their properties, the acquired new features of pathogenicity among them.This work was supported by EC PhageVet-P (contract no. FOOD-CT-2005-007224) and by the Russian Foundation for Basic Research (grant no. 08-04-00162-a). We gratefully acknowledge the support of organizations presenting the grants.info:eu-repo/semantics/publishedVersio

Regulating of wear properties through microstructure engineering in novel cost-effective Fe30Ni25Cr25Mo10Al10 high-entropy alloy processed by cyclic closed-die forging

This study presents a novel cost-effective Fe30Ni25Cr25Mo10Al10 high-entropy alloy with a dual-phase microstructure that was processed using cyclic closed-die forging (CCDF) at room temperature for a maximum of six passes. The as-homogenized alloy exhibited [CrMoFe]-rich dendrites with dual-size morphology dispersed in an almost uniform face-centered cubic (FCC) matrix. It was found that as the number of CCDF passes increased, leading to a more homogenous nanograin, there was an accumulation of dislocations, fragmentation of [CrMoFe]-rich dendrites, and enhanced distribution within the matrix. These conditions were conducive to the creation of a nanostructured Fe30Ni25Cr25Mo10Al10 alloy with superior mechanical properties. Texture analysis indicated that the prominent texture components for the Fe30Ni25Cr25Mo10Al10 alloy after six passes were Rotated Cube {001}, S {123}, and Dillamore {4 4 11}. After the sixth CCDF pass, the Fe30Ni25Cr25Mo10Al10 alloy exhibited the highest microhardness (∼ 974 HV) and the lowest wear rate (∼ (0.8 ± 0.1) × 10–5 mm3.N−1.m−1). Additionally, it was proposed that the development of the Rotated Cube {001} texture component contributed positively to enhancing wear resistance in the cost-effective high-entropy alloys. Considering the obtained results, it is reasonable to propose that CCDF processing is significant potential for the advancement of cost-effective nanostructured high-entropy alloys for industrial applications.The study was supported by the Russian Science Foundation, project No. 24–29–00740, https://rscf.ru/en/project/24–29-00740/

The T7-Related Pseudomonas putida Phage ϕ15 Displays Virion-Associated Biofilm Degradation Properties

Formation of a protected biofilm environment is recognized as one of the major causes of the increasing antibiotic resistance development and emphasizes the need to develop alternative antibacterial strategies, like phage therapy. This study investigates the in vitro degradation of single-species Pseudomonas putida biofilms, PpG1 and RD5PR2, by the novel phage ϕ15, a ‘T7-like virus’ with a virion-associated exopolysaccharide (EPS) depolymerase. Phage ϕ15 forms plaques surrounded by growing opaque halo zones, indicative for EPS degradation, on seven out of 53 P. putida strains. The absence of haloes on infection resistant strains suggests that the EPS probably act as a primary bacterial receptor for phage infection. Independent of bacterial strain or biofilm age, a time and dose dependent response of ϕ15-mediated biofilm degradation was observed with generally a maximum biofilm degradation 8 h after addition of the higher phage doses (104 and 106 pfu) and resistance development after 24 h. Biofilm age, an in vivo very variable parameter, reduced markedly phage-mediated degradation of PpG1 biofilms, while degradation of RD5PR2 biofilms and ϕ15 amplification were unaffected. Killing of the planktonic culture occurred in parallel with but was always more pronounced than biofilm degradation, accentuating the need for evaluating phages for therapeutic purposes in biofilm conditions. EPS degrading activity of recombinantly expressed viral tail spike was confirmed by capsule staining. These data suggests that the addition of high initial titers of specifically selected phages with a proper EPS depolymerase are crucial criteria in the development of phage therapy

Complete genome sequence of the giant pseudomonas phage lu11

The complete genome sequence of the giant Pseudomonas phage Lu11 was determined, comparing 454 and Sanger sequencing. The double-stranded DNA (dsDNA) genome is 280,538 bp long and encodes 391 open reading frames (ORFs) and no tRNAs. The closest relative is Ralstonia phage ϕRSL1, encoding 40 similar proteins. As such, Lu11 can be considered phylogenetically unique within the Myoviridae and indicates the diversity of the giant phages within this family.status: publishe

Ambivalent bacteriophages of different species active on Escherichia coli K12 and Salmonella sps. strains

A study was made of several bacteriophages (including phages U2 and LB related to T-even phages of Escherichia coli) that grow both on E. coli K12 and on some Salmonella strains. Such phages were termed ambivalent. T-even ambivalent phages (U2 and LB) are rare and have a limited number of hosts among Salmonella strains. U2 and LB are similar to canonical E. coli-specific T-even phages in morphological type and size of the phage particle and in reaction with specific anti-T4 serum. Phages U2 and LB have identical sets of structural proteins, some of which are similar in size to structural proteins of phages T2 and T4. DNA restriction patterns of phages U2 and LB differ from each other and from those of T2 and T4. Still, DNAs of all four phages have considerable homology. Unexpectedly, phages U2 and LB grown on Salmonella bungori were unstable during centrifugation in a CsCl gradient. Ambivalent bacteriophages were found in species other than T-even phages and were similar in morphotype to lambdoid and other E. coli phages. One of the ambivalent phages was highly similar to well-known Felix01, which is specific for Salmonella. Ambivalent phages can be used to develop a new set for phage typing in Salmonella. An obvious advantage is that ambivalent phages can be reproduced in the E. coli K12 laboratory strain, which does not produce active temperate phages. Consequently, the resulting typing phage preparation is devoid of an admixture of temperate phages, which are common in Salmonella. The presence of temperate phages in phage-typing preparations may cause false-positive results in identifying specific Salmonella strains isolated from the environment or salmonellosis patients. Ambivalent phages are potentially useful for phage therapy and prevention of salmonellosis in humans and animals