Project description:The choice between cell death (lysis) and viral dormancy (lysogeny) following bacteriophage infection serves as a founding paradigm for the emergence of cellular heterogeneity in a genetically uniform population. The determination of host fate arises through the stochastic transcription from multiple viral genomes present within each cell, but this activity remains hidden from empirical interrogation, which typically stops at the whole-cell level. Here we use parallel sequential fluorescence in situ hybridization (par-seqFISH), followed by spatial clustering of phage-encoded transcripts within each cell, to profile the transcriptional activity of individual phages during synchronized infection of Escherichia coli (E. coli) by bacteriophage lambda. At the whole-cell level, transcription kinetics capture the developmental choice between lysis and lysogeny, and further demonstrate that viral replication is required for the emergence of diverging fate decisions. Zooming in to the single-phage level illuminates an individuality of viral activity during infection. We find that, while cells pursuing lysogeny display consensus activity of all in-habiting phages, lytic cells may contain phages that exhibit lysogenic activity. These findings support an earlier suggestion that consensus among coinfecting phages is required for cell dormancy. More broadly, our results highlight the need to identify how whole-cell behavior emerges from the activity of physically distinct copies of the same genetic circuit.
Project description:Bacteriophage P1 along with λ and T4 phages are among the best described bacterial viruses in molecular biology. For years, P1 features as well as its life cycle have been studied and its complete genome was published. Undeciphered phenomenon of improved P1vir lytic development in the absence of DksA protein in cell engaged us to more holistic experimental approach. Bacterial wild type and dksA strains were cultured to OD600 = 0.2. Next, P1vir was added, samples were withdrawn at 0, 10 and 30 minutes after P1vir infection. Total RNA was isolated and checked for quality using the Bioanalyzer 2100. The sequencing run was conducted on the Illumina NovaSeq6000 platform. 30 million pair-end reads per samples were assessed with 101 pb read length. Reference P1 phage genome sequence and annotations were downloaded from GenBank. We have discovered many changes in virus transcriptome. For instance: downregulation of phage genes encoding the main repressor of lysogeny C1 or proteins triggering cell lysis (e.g., lysozyme, holin) and upregulation of genes encoding antiholins in dksA mutant. This results support our gentle lysis hypothesis – less efficient lysis, combined with minor improvements of phage development which may lead to higher phage yield in DksA-devoid cells. We have observed upregulated expression of phage genes responsible for virion-parts production in the dksA mutant. Interestingly, expression of lysogeny-related c8 gene is upregulated in the dksA mutant. We speculate that P1vir developing in the dksA host is at the brink of lysogeny but is unable to established it and eventually enters the lytic pathway. We also found some interesting events in host cells upon infection. P1vir is taking control of the cellular protein, sugar and lipid metabolism in both, the wild type and dksA mutant hosts. However, in dksA mutant several genes involved in sulfur metabolism were uniquely upregulated. It remains unclear if this associates with obtaining new energy sources or with global reprograming via H2S signaling functions. Generally, the hosts are reacting by activating SOS response or upregulating the heat shock proteins. But we also found downregulation of proteolysis which was unique for the dksA strain. We believe that this extensive and comprehensive study not only finds reasonable explanations for the improved P1vir development in dksA strain, but also makes a great contribution to the field of P1 phage biology. Funding: This research was funded by the National Science Center, Poland (grant PRELUDIUM 2013/09/N/NZ2/01899 to G.M.C.)
2021-04-30 | GSE173614 | GEO
Project description:Communication between viruses guides lysis-lysogeny decisions
Project description:Virulent bacteriophages (or phages) are viruses that specifically infect and lyse a bacterial host. When multiple phages co-infect a bacterial host, the extent of lysis, dynamics of bacteria-phage and phage-phage interactions are expected to vary. The objective of this study is to identify the factors influencing the interaction of two virulent phages with different Pseudomonas aeruginosa growth states (planktonic, an infected epithelial cell line, and biofilm) by measuring the bacterial time-kill and individual phage replication kinetics. A single administration of phages effectively reduced P. aeruginosa viability in planktonic conditions and infected human lung cell cultures, but phage-resistant variants subsequently emerged. In static biofilms, the phage combination displayed initial inhibition of biofilm dispersal, but sustained control was achieved only by combining phages and meropenem antibiotic. In contrast, adherent biofilms showed tolerance to phage and/or meropenem, suggesting a spatiotemporal variation in the phage-bacterial interaction. The kinetics of adsorption of each phage to P. aeruginosa during single- or co-administration were comparable. However, the phage with the shorter lysis time depleted bacterial resources early and selected a specific nucleotide polymorphism that conferred a competitive disadvantage and cross-resistance to the second phage. The extent and strength of this phage-phage competition and genetic loci conferring phage resistance, are, however, P. aeruginosa genotype dependent. Nevertheless, adding phages sequentially resulted in their unimpeded replication with no significant increase in bacterial host lysis. These results highlight the interrelatedness of phage-phage competition, phage resistance and specific bacterial growth state (planktonic/biofilm) in shaping the interplay among P. aeruginosa and virulent phages.