Journal: mBio

Article Title: Quorum Sensing and Metabolic State of the Host Control Lysogeny-Lysis Switch of Bacteriophage T1

doi: 10.1128/mBio.01884-19

Figure Lengend Snippet: E. coli ATCC 14155 carries an AI-2- and sugar-inducible prophage. (A) Optical densities of E. coli ATCC 14155 cultures (each dot represents individual culture) grown alone or in a 1:1 mixture with E. coli W3110 or W3110 Δ luxS bacteria or with 10 μl E. coli W3110 wild-type bacteria or Δ luxS cell-free supernatants. (B) Transmission electron microscopy (TEM) of phage particles found in E. coli ATCC 15144 lysates. Scale bar, 200 nm. Note that the different levels of brightness in the four quadrants of the image represent an artifact of the TEM imaging system. (C) Prophage induction in E. coli ATCC 14155 by AI-2 and sugar influx. Single dots represent individual cultures. glu, glucose; 2-DG, 2-deoxy- d -glucose. Means of results of a minimum of 12 independent replicates are shown; error bars represent standard deviations. P values were calculated using the Mann-Whitney test (*** * , P < 0.0001; ** * , P < 0.0005; *, P < 0.05; ns, not significant).

Article Snippet: In contrast, increasing the initial ATCC 15144 inoculum size did not result in significant changes in extracellular AI-2 levels in growing cultures , most likely due to the balance of AI-2 production and uptake , and thus did not lead to increased phage release.

Techniques: Transmission Assay, Electron Microscopy, Imaging, MANN-WHITNEY

Journal: mBio

Article Title: Quorum Sensing and Metabolic State of the Host Control Lysogeny-Lysis Switch of Bacteriophage T1

doi: 10.1128/mBio.01884-19

Figure Lengend Snippet: T1 phage-encoded transcription regulator Pir (Orf23) controls AI-2- and sugar-dependent prophage induction. (A) Pir is a functional transcription regulator. Activities of hol , dam , pir , and recE promoters controlling gfp expression (measured by flow cytometry and expressed in arbitrary units [AU]) in the absence ( pir − ) or presence ( pir + ) of plasmid-harbored pir were measured in E. coli W3110 by flow cytometry. (B) pir and hol were upregulated during AI-2- and glucose-mediated prophage induction. Activities of pir and hol promoters were measured at the onset of visible cell lysis by flow cytometry. (C) Activities of pir and hol promoters in a phage-free background strain, BL21(DE3), were measured by flow cytometry 2 h after addition of 30 μM DPD/AI-2 or 0.2% glucose. (D) Effect of CRISPRi-mediated inhibition of pir expression on lysis of E. coli ATCC 15144. Single dots represent optical densities of individual E. coli cultures (CRISPRi − aTc − ) carrying a CRISPRi system without (CRISPRi + aTc − ) or with (CRISPRi + aTc + ) induction of dCas9 protein expression, measured 2 h after addition of 10 μl E. coli W3110 cell-free supernatant. aTc, anhydrotetracycline. (E) hol promoter activity measured by flow cytometry in the setup described in the panel D legend. Single dots represent hol promoter activities in individual cultures. Means of results from a minimum of three independent replicates are shown; error bars represent standard deviations. P values were calculated using the Mann-Whitney test (*** * , P < 0.0001; ** * , P < 0.0005; * * , P < 0.005; ns, not significant).

Article Snippet: In contrast, increasing the initial ATCC 15144 inoculum size did not result in significant changes in extracellular AI-2 levels in growing cultures , most likely due to the balance of AI-2 production and uptake , and thus did not lead to increased phage release.

Techniques: Functional Assay, Expressing, Flow Cytometry, Plasmid Preparation, Lysis, Inhibition, Activity Assay, MANN-WHITNEY