Explore the vast range of titles available.

The virus–host interaction requires a complex interplay between the phage strategy of reprogramming the host machinery to produce and release progeny virions, and the host defense against infection. Using RNA sequencing, we investigated the phage–host interaction to resolve the phenomenon of improved lytic development of P1vir phage in a DksA-deficient E. coli host. Expression of the ant1 and kilA P1vir genes in the wild-type host was the highest among all and most probably leads to phage virulence. Interestingly, in a DksA-deficient host, P1vir genes encoding lysozyme and holin are downregulated, while antiholins are upregulated. Gene expression of RepA, a protein necessary for replication initiating at the phage oriR region, is increased in the dksA mutant; this is also true for phage genes responsible for viral morphogenesis and architecture. Still, it seems that P1vir is taking control of the bacterial protein, sugar, and lipid metabolism in both, the wild type and dksA− hosts. Generally, bacterial hosts are reacting by activating their SOS response or upregulating the heat shock proteins. However, only DksA-deficient cells upregulate their sulfur metabolism and downregulate proteolysis upon P1vir infection. We conclude that P1vir development is enhanced in the dksA mutant due to several improvements, including replication and virion assembly, as well as a less efficient lysis.

Vibrio cholerae represents a constant threat to public health, causing widespread infections, especially in developing countries with a significant number of fatalities and serious complications every year. The standard treatment by oral rehydration does not eliminate the source of infection, while increasing antibiotic resistance among pathogenic V. cholerae strains makes the therapy difficult. Thus, we assessed the antibacterial potential of plant-derived phytoncides, isothiocyanates (ITC), against V. cholerae O365 strain. Sulforaphane (SFN) and 2-phenethyl isothiocyanate (PEITC) ability to inhibit bacterial growth was assessed. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values indicate that these compounds possess antibacterial activity and are also effective against cells growing in a biofilm. Tested ITC caused accumulation of stringent response alarmone, ppGpp, which indicates induction of the global stress response. It was accompanied by bacterial cytoplasm shrinkage, the inhibition of the DNA, and RNA synthesis as well as downregulation of the expression of virulence factors. Most importantly, ITC reduced the toxicity of V. cholerae in the in vitro assays (against Vero and HeLa cells) and in vivo, using Galleria mellonella larvae as an infection model. In conclusion, our data indicate that ITCs might be considered promising antibacterial agents in V. cholerae infections.

Enterohemorrhagic Escherichia coli (EHEC) is a common pathotype of E. coli that causes numerous outbreaks of foodborne illnesses. EHEC is a zoonotic pathogen that is transmitted from animals to humans. Ruminants, particularly cattle, are considered important reservoirs for virulent EHEC strains. Humans can become infected with EHEC through the consumption of contaminated food and water or through direct contact with infected animals or humans. E. coli O157:H7 is one of the most commonly reported causes of foodborne illnesses in developed countries. The formation of attaching and effacing (A/E) lesions on the intestinal epithelium, combined with Shiga toxin production, is a hallmark of EHEC infection and can lead to lethal hemolytic–uremic syndrome (HUS). For the phage-dependent regulation of Shiga toxin production, antibiotic treatment is contraindicated, as it may exacerbate toxin production, limiting therapeutic options to supportive care. In response to this challenge and the growing threat of antibiotic resistance, phytochemicals have emerged as promising antivirulence agents. These plant-derived compounds target bacterial virulence mechanisms without promoting resistance. Therefore, the aim of this study is to summarize the recent knowledge on the use of phytochemicals targeting EHEC. We focused on the molecular basis of their action, targeting the principal virulence determinants of EHEC.

Bacteriophage-based applications have a renaissance today, increasingly marking their use in industry, medicine, food processing, biotechnology, and more. However, phages are considered resistant to various harsh environmental conditions; besides, they are characterized by high intra-group variability. Phage-related contaminations may therefore pose new challenges in the future due to the wider use of phages in industry and health care. Therefore, in this review, we summarize the current knowledge of bacteriophage disinfection methods, as well as highlight new technologies and approaches. We discuss the need for systematic solutions to improve bacteriophage control, taking into account their structural and environmental diversity.

Isothiocyanates (ITCs) derived from cruciferous plants reveal antibacterial activity, although detailed mechanism is not fully elucidated. Recently it has been reported that ITCs induce the stringent response in Escherichia coli strains. The aim of this work was to determine whether two isothiocyanates, sulforaphane (SFN) and phenethyl isothiocyanate (PEITC), similarly as in E . coli induce stringent response in Bacillus subtilis , model Gram(+) bacterium, and test their potency against a panel of clinical isolates belonging to Gram(+) or Gram(−) groups. Minimal inhibitory concentrations were determined as well as effect of ITCs on membranes integrity, synthesis of DNA, RNA and stringent response alarmones was assessed. SFN and PEITC are effective against B . subtilis and bacterial isolates, namely E . coli , K . pneumonia , S . aureus , S . epidermidis and E . faecalis . Interestingly, in B . subtilis and E . faecalis the inhibition of growth and nucleic acids synthesis is independent of ppGpp accumulation. In bacteria, which do not induce the stringent response in the presence of ITCs, membrane integrity disruption is observed. Thus, ITCs are effective against different pathogenic bacteria and act by at least two mechanisms depending on bacteria species.

Production of Shiga toxins by enterohemorrhagic Escherichia coli (EHEC) which is responsible for the pathogenicity of these strains, is strictly correlated with induction of lambdoid bacteriophages present in the host’s genome, replication of phage DNA and expression of stx genes. Antibiotic treatment of EHEC infection may lead to induction of prophage into a lytic development, thus increasing the risk of severe complications. This, together with the spread of multi-drug resistance, increases the need for novel antimicrobial agents. We report here that isothiocyanates (ITC), plant secondary metabolites, such as sulforaphane (SFN), allyl isothiocyanate (AITC), benzyl isothiocynanate (BITC), phenyl isothiocyanate (PITC) and isopropyl isothiocyanate (IPRITC), inhibit bacterial growth and lytic development of stx -harboring prophages. The mechanism underlying the antimicrobial effect of ITCs involves the induction of global bacterial stress regulatory system, the stringent response. Its alarmone, guanosine penta/tetraphosphate ((p)ppGpp) affects major cellular processes, including nucleic acids synthesis, which leads to the efficient inhibition of both, prophage induction and toxin synthesis, abolishing in this way EHEC virulence for human and simian cells. Thus, ITCs could be considered as potential therapeutic agents in EHEC infections.

Urinary tract infections are one of the most frequent bacterial diseases worldwide. UPECs are the most prominent group of bacterial strains among pathogens responsible for prompting such infections. As a group, these extra-intestinal infection-causing bacteria have developed specific features that allow them to sustain and develop in their inhabited niche of the urinary tract. In this study, we examined 118 UPEC isolates to determine their genetic background and antibiotic resistance. Moreover, we investigated correlations of these characteristics with the ability to form biofilm and to induce a general stress response. We showed that this strain collection expressed unique UPEC attributes, with the highest representation of FimH, SitA, Aer, and Sfa factors (100%, 92.5%, 75%, and 70%, respectively). According to CRA (Congo red agar) analysis, the strains particularly predisposed to biofilm formation represented 32.5% of the isolates. Those biofilm forming strains presented a significant ability to accumulate multi-resistance traits. Most notably, these strains presented a puzzling metabolic phenotype—they showed elevated basal levels of (p)ppGpp in the planktonic phase and simultaneously exhibited a shorter generation time when compared to non-biofilm-forming strains. Moreover, our virulence analysis showed these phenotypes to be crucial for the development of severe infections in the Galleria mellonella model.

The aim of the existence of every organism is to survive and replicate its genetic material. The pathogen, after infection of the host, has to overcome the host’s defensive barrier. For this, bacterial pathogens use virulence-related factors, such as cell and tissue invasion, adhesion to the surface and toxin production. Numerous pathogenic microorganisms combine their virulence pathways with general mechanisms that allow their adaptation to changing environmental conditions. For this purpose, many bacteria use the global mechanisms of reaction to a stress condition, the stringent response. Here we discuss how the components of stringent response influence the virulence of pathogenic bacteria.1. Introduction. 2. Metabolism of (p)ppGpp. 2.1. Regulatory targets of (p)ppGpp. 3. Virulence and adaptation to adverse environmental conditions. 4. The role of stringent response in the virulence of Gram-negative bacteria 4.1. Escherichia coli EHEC. 4.2. Escherichia coli UPEC. 4.3. Shigella flexneri. 4.4. Vibrio cholerae. 4.5. Salmonella enterica. 4.6. Pseudomonas aeruginosa. 4.7. Francisella tularensis. 4.8. Bordetella pertussis. 5. The role of stringent response in the virulence of Gram-positive bacteria. 5.1. Enterococcus faecalis. 5.2. Bacillus anthracis. 5.3. Staphylococcus aureus. 5.4. Streptococcus pyogenes. 5.5. Listeria monocytogenes. 6. The effect of the stringent response on the virulence of Mycobacterium tuberculosis. 7. Summary

Cruciferous vegetables, widely present in daily diets, are a rich source of organosulfur compounds with proven health benefits, especially chemopreventive or antioxidative effects. Isothiocyanate derivatives (ITCs) exhibit a broad spectrum of biological and pharmacological activity and recently, their antibacterial properties have been of particular importance. Here, we have focused on the anti-shigellosis activity of sulforaphane (SFN) and phenethyl ITC (PEITC). The genus Shigella causes gastroenteritis in humans, which constitutes a threat to public health. Production of a potent Stx toxin by S. dysenteriae type 1 results not only in more severe symptoms but also in serious sequela, including the hemolytic uremic syndrome. Here, we present evidence that two aliphatic and aromatic ITCs derivatives, SFN and PEITC, have an effective antibacterial potency against S. dysenteriae, also negatively regulating the stx gene expression. The molecular mechanism of this effect involves induction of the global stress-induced stringent response. ITCs also inhibit bacterial virulence against the Vero and HeLa cells. We present evidence for the therapeutic effect of sulforaphane and phenethyl ITC against a S. dysenteriae infection in the Galleria mellonella larvae model. Thus, our results indicate that isothiocyanates can be effectively used to combat dangerous bacterial infections.

Transcriptional repression is a mechanism which enables effective gene expression switch off. The activity of most of type II toxin-antitoxin (TA) cassettes is controlled in this way. These cassettes undergo negative autoregulation by the TA protein complex which binds to the promoter/operator sequence and blocks transcription initiation of the TA operon. Precise and tight control of this process is vital to avoid uncontrolled expression of the toxin component. Here, we employed a series of in vivo and in vitro experiments to establish the molecular basis for previously observed differences in transcriptional activity and repression levels of the pyy and pat promoters which control expression of two homologous TA systems, YefM-YoeB and Axe-Txe, respectively. Transcriptional fusions of promoters with a lux reporter, together with in vitro transcription, EMSA and footprinting assays revealed that: (1) the different sequence composition of the −35 promoter element is responsible for substantial divergence in strengths of the promoters; (2) variations in repression result from the TA repressor complex acting at different steps in the transcription initiation process; (3) transcription from an additional promoter upstream of pat also contributes to the observed inefficient repression of axe-txe module. This study provides evidence that even closely related TA cassettes with high sequence similarity in the promoter/operator region may employ diverse mechanisms for transcriptional regulation of their genes.