The metastable associations of bacteriophages and Erwinia amylovora.

Bacteriophages are often considered as possible agents of biological control of unwanted bacterial populations in medicine, agriculture and food industry. Although the virulent phages can efficiently kill the infected host cells but at the population level phage attack not always leads to the host population collapse but may result in establishment of a more or less stable co-existence. The mechanism of the long-term stabilization of the mixed phage-host cultures is poorly understood. Here we describe bacteriophages VyarbaL and Hena2, the members of the Molineuxvirinae and the Ounavirinae subfamilies, respectively, that are able to form the pseudolysogenic associations (PA) with their host Erwinia amylovora 1/79Sm on solid media. These PAs were stable through multiple passages. The phenomenon of the PA formation between a bacterial culture and bacteriophages decreases the effectiveness of bacteriophage-mediated biological control agents based on lytic bacteriophages.

Two novel Erwinia amylovora bacteriophages, Loshitsa2 and Micant, isolated in Belarus.

The complete genomes of the new Erwinia amylovora bacteriophages Loshitsa2 and Micant are 43,092 bp and 43,028 bp long, respectively, encode 51 putative proteins, and have two tRNA genes. Comparative analysis with representatives of the class Caudoviricetes suggests that bacteriophages Loshitsa2 and Micant are related to LIMElight bacteriophage belonging to the family Autographiviridae and could be proposed to be members of a novel subfamily.

The CssRS two-component system of Bacillus subtilis contributes to teicoplanin and polymyxin B response.

CssRS is a two-component system that plays a pivotal role in mediating the secretion stress response in Bacillus subtilis. This system upregulates the synthesis of membrane-bound HtrA family proteases that cope with misfolded proteins that accumulate within the cell envelope as a result of overexpression or heat shock. Recent studies have shown the induction of CssRS-regulated genes in response to cell envelope stress. We investigated the induction of the CssRS-regulated htrA promoter in the presence of different cell wall- and membrane-active substances and observed induction of the CssRS-controlled genes by glycopeptides (vancomycin and teicoplanin), polymyxins B and E, certain ß-lactams, and detergents. Teicoplanin was shown to elicit remarkably stronger induction than vancomycin and polymyxin B. Teicoplanin and polymyxin B induced the spxO gene expression in a CssRS-dependent fashion, resulting in increased activity of Spx, a master regulator of disulfide stress in Bacillus subtilis. The CssRS signaling pathway and Spx activity were demonstrated to be involved in Bacillus subtilis resistance to teicoplanin and polymyxin B.

Bismuth(III) Complexes with Schiff Bases: Synthesis, Characterization, Interaction with Biomolecules, Antioxidant and Antimicrobial Activity.

AIMS AND BACKGROUND: In contrast to antibiotics, metal complexes can realize more than one mechanism of biocidal action to fight multidrug-resistant bacterial strains (due essentially to the metal ions), involving targets like functional groups in the walls of microbial cells and various enzymes. Among the potential antimicrobials are Bi(III) complexes with diphenols. OBJECTIVE: The present work aimed at synthesizing and investigating novel Bi(III) complexes with Schiff bases as potential antimicrobial and antioxidant agents. METHODS: Bi(III) complexes were characterized by means of elemental analysis, FT-IR, UV-Vis, 1H NMR spectroscopy, XRD, cyclic voltammetry and conductivity measurements as well as biological methods. RESULTS: The complexes are characterized by the formula Bi(L)2Cl and pyramidal geometry of their coordination cores BiO2N2Cl, wherein the Bi(III) cation is coordinated by hydroxyl and azomethine moieties. The ligands coordinate in their monoanionic forms. The complexes are more lipophilic and more bioactive against the bacteria tested than the ligands. Both the ligands and their complexes exhibited the capability for the Fe(III)-Cyt c reduction and displayed comparable reducing rates. All the compounds are characterized by the DPPH and ABTS radical scavenging activity, and they are more active reductants than Trolox in the CUPRAC assay too. The peculiarities of the interaction of the complexes with BSA suggest that Cys-34 of BSA is not a major binding site for these complexes. According to molecular docking studies, the complexes bind to BSA via non-covalent interactions. CONCLUSION: Bi(III) complexation with Schiff bases plays an important role in their antimicrobial and antioxidant activities as well as in their interaction with BSA.

Isolation and characterization of Hena1 - a novel Erwinia amylovora bacteriophage.

Fire blight, caused by plant pathogenic bacterium Erwinia amylovora, is one of the most important diseases of Rosaceae plants. Due to the lack of effective control measures, fire blight infections pose a recurrent threat on agricultural production worldwide. Recently, bacterial viruses, or bacteriophages, have been proposed as environmentally friendly natural antimicrobial agents for fire blight control. Here, we isolated a novel bacteriophage Hena1 with activity against E. amylovora. Further analysis revealed that Hena1 is a narrow-host-range lytic phage belonging to Myoviridae family. Its genome consists of a linear 148,842 bp dsDNA (48.42% GC content) encoding 240 ORFs and 23 tRNA genes. Based on virion structure and genomic composition, Hena1 was classified as a new species of bacteriophage subfamily Vequintavirinae. The comprehensive analysis of Hena1 genome may provide further insights into evolution of bacteriophages infecting plant pathogenic bacteria.

Characterization of a new ViI-like Erwinia amylovora bacteriophage phiEa2809.

Erwinia amylovora is a Gram-negative plant pathogenic bacteria causing fire blight disease in many Rosaceae species. A novel E. amylovora bacteriophage, phiEa2809, was isolated from symptomless apple leaf sample collected in Belarus. This phage was also able to infect Pantoea agglomerans strains. The genome of phiEa2809 is a double-stranded linear DNA 162,160 bp in length, including 145 ORFs and one tRNA gene. The phiEa2809 genomic sequence is similar to the genomes of the Serratia plymutica phage MAM1, Shigella phage AG-3, Dickeya phage vB DsoM LIMEstone1 and Salmonella phage ViI and lacks similarity to described E. amylovora phage genomes. Based on virion morphology (an icosahedral head, long contractile tail) and genome structure, phiEa2809 was classified as a member of Myoviridae, ViI-like bacteriophages group. PhiEa2809 is the firstly characterized ViI-like bacteriophage able to lyse E. amylovora.