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Viral Transmission Dynamics at Single-Cell Resolution Reveal Transiently Immune Subpopulations Caused by a Carrier State Association.

Cenens W, Makumi A, Govers SK, Lavigne R, Aertsen A - PLoS Genet. (2015)

Bottom Line: Monitoring the complex transmission dynamics of a bacterial virus (temperate phage P22) throughout a population of its host (Salmonella Typhimurium) at single cell resolution revealed the unexpected existence of a transiently immune subpopulation of host cells that emerged from peculiarities preceding the process of lysogenization.Upon subsequent division, the daughter cell inheriting this episome became lysogenized by an integration event yielding a prophage, while the other daughter cell became P22-free.The iterative emergence and infection of transiently resistant subpopulations suggests a new bet-hedging strategy by which viruses could manage to sustain both vertical and horizontal transmission routes throughout an infected population without compromising a stable co-existence with their host.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Food Microbiology, Department of Microbial and Molecular Systems (M²S), Faculty of Bioscience Engineering, KU Leuven, Leuven, Belgium.

ABSTRACT
Monitoring the complex transmission dynamics of a bacterial virus (temperate phage P22) throughout a population of its host (Salmonella Typhimurium) at single cell resolution revealed the unexpected existence of a transiently immune subpopulation of host cells that emerged from peculiarities preceding the process of lysogenization. More specifically, an infection event ultimately leading to a lysogen first yielded a phage carrier cell harboring a polarly tethered P22 episome. Upon subsequent division, the daughter cell inheriting this episome became lysogenized by an integration event yielding a prophage, while the other daughter cell became P22-free. However, since the phage carrier cell was shown to overproduce immunity factors that are cytoplasmically inherited by the P22-free daughter cell and further passed down to its siblings, a transiently resistant subpopulation was generated that upon dilution of these immunity factors again became susceptible to P22 infection. The iterative emergence and infection of transiently resistant subpopulations suggests a new bet-hedging strategy by which viruses could manage to sustain both vertical and horizontal transmission routes throughout an infected population without compromising a stable co-existence with their host.

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Related in: MedlinePlus

SieA or GtrABC independently account for P22 immunity in P22-free cells.An exponential phase population of LT2ΔpSLT/pALA2705 was infected with either no phage (control) or with the indicated phages (MOI = 10). After 4 hours of semi-continuous growth, cultures were plated on agar pads seeded with P22 parS and after 45 minutes the percentage of cells infected with this phage was scored. Percentages were obtained by analysis of between 508 and 646 single cells per experiment. Below each bar-plot, a representative snapshot of each respective experiment is shown in which phase contrast images (showing the cells) and GFP signal (reporting the P22 parS chromosomes) are merged.
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pgen.1005770.g005: SieA or GtrABC independently account for P22 immunity in P22-free cells.An exponential phase population of LT2ΔpSLT/pALA2705 was infected with either no phage (control) or with the indicated phages (MOI = 10). After 4 hours of semi-continuous growth, cultures were plated on agar pads seeded with P22 parS and after 45 minutes the percentage of cells infected with this phage was scored. Percentages were obtained by analysis of between 508 and 646 single cells per experiment. Below each bar-plot, a representative snapshot of each respective experiment is shown in which phase contrast images (showing the cells) and GFP signal (reporting the P22 parS chromosomes) are merged.

Mentions: To further confirm whether the cytoplasmic inheritance of these two factors indeed plays a role in the (transient) immunity of the P22-free cells, the phage carrier state was established with P22 Δint derivatives compromised in either or both gtrABC and sieA expression and the resulting immunity was assessed after four hours of growth. As expected from the expression during the phage carrier state (Fig 4) only phage carrier cells generated by a P22 derivative in which both gtrABC and sieA were deleted (i.e. P22 Δint ΔgtrABC ΔsieA) gave rise to P22-free siblings that could readily be infected with P22 parS, indicating that GtrABC and SieA factors both independently confer the observed immunity by preventing entry of the P22 chromosome in P22-free cells (Fig 5). Notably, the latter further underscores that gtrABC expression is invariably activated during the phage carrier state irrespective of the phase variability of the gtrABC promoter.


Viral Transmission Dynamics at Single-Cell Resolution Reveal Transiently Immune Subpopulations Caused by a Carrier State Association.

Cenens W, Makumi A, Govers SK, Lavigne R, Aertsen A - PLoS Genet. (2015)

SieA or GtrABC independently account for P22 immunity in P22-free cells.An exponential phase population of LT2ΔpSLT/pALA2705 was infected with either no phage (control) or with the indicated phages (MOI = 10). After 4 hours of semi-continuous growth, cultures were plated on agar pads seeded with P22 parS and after 45 minutes the percentage of cells infected with this phage was scored. Percentages were obtained by analysis of between 508 and 646 single cells per experiment. Below each bar-plot, a representative snapshot of each respective experiment is shown in which phase contrast images (showing the cells) and GFP signal (reporting the P22 parS chromosomes) are merged.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4697819&req=5

pgen.1005770.g005: SieA or GtrABC independently account for P22 immunity in P22-free cells.An exponential phase population of LT2ΔpSLT/pALA2705 was infected with either no phage (control) or with the indicated phages (MOI = 10). After 4 hours of semi-continuous growth, cultures were plated on agar pads seeded with P22 parS and after 45 minutes the percentage of cells infected with this phage was scored. Percentages were obtained by analysis of between 508 and 646 single cells per experiment. Below each bar-plot, a representative snapshot of each respective experiment is shown in which phase contrast images (showing the cells) and GFP signal (reporting the P22 parS chromosomes) are merged.
Mentions: To further confirm whether the cytoplasmic inheritance of these two factors indeed plays a role in the (transient) immunity of the P22-free cells, the phage carrier state was established with P22 Δint derivatives compromised in either or both gtrABC and sieA expression and the resulting immunity was assessed after four hours of growth. As expected from the expression during the phage carrier state (Fig 4) only phage carrier cells generated by a P22 derivative in which both gtrABC and sieA were deleted (i.e. P22 Δint ΔgtrABC ΔsieA) gave rise to P22-free siblings that could readily be infected with P22 parS, indicating that GtrABC and SieA factors both independently confer the observed immunity by preventing entry of the P22 chromosome in P22-free cells (Fig 5). Notably, the latter further underscores that gtrABC expression is invariably activated during the phage carrier state irrespective of the phase variability of the gtrABC promoter.

Bottom Line: Monitoring the complex transmission dynamics of a bacterial virus (temperate phage P22) throughout a population of its host (Salmonella Typhimurium) at single cell resolution revealed the unexpected existence of a transiently immune subpopulation of host cells that emerged from peculiarities preceding the process of lysogenization.Upon subsequent division, the daughter cell inheriting this episome became lysogenized by an integration event yielding a prophage, while the other daughter cell became P22-free.The iterative emergence and infection of transiently resistant subpopulations suggests a new bet-hedging strategy by which viruses could manage to sustain both vertical and horizontal transmission routes throughout an infected population without compromising a stable co-existence with their host.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Food Microbiology, Department of Microbial and Molecular Systems (M²S), Faculty of Bioscience Engineering, KU Leuven, Leuven, Belgium.

ABSTRACT
Monitoring the complex transmission dynamics of a bacterial virus (temperate phage P22) throughout a population of its host (Salmonella Typhimurium) at single cell resolution revealed the unexpected existence of a transiently immune subpopulation of host cells that emerged from peculiarities preceding the process of lysogenization. More specifically, an infection event ultimately leading to a lysogen first yielded a phage carrier cell harboring a polarly tethered P22 episome. Upon subsequent division, the daughter cell inheriting this episome became lysogenized by an integration event yielding a prophage, while the other daughter cell became P22-free. However, since the phage carrier cell was shown to overproduce immunity factors that are cytoplasmically inherited by the P22-free daughter cell and further passed down to its siblings, a transiently resistant subpopulation was generated that upon dilution of these immunity factors again became susceptible to P22 infection. The iterative emergence and infection of transiently resistant subpopulations suggests a new bet-hedging strategy by which viruses could manage to sustain both vertical and horizontal transmission routes throughout an infected population without compromising a stable co-existence with their host.

Show MeSH
Related in: MedlinePlus