scholarly journals Repeated outbreaks drive the evolution of bacteriophage communication

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Hilje M Doekes ◽  
Glenn A Mulder ◽  
Rutger Hermsen
Keyword(s):  
Mathematical Model ◽  
Evolutionary Dynamics ◽  
Communication Strategy ◽  
Lytic Cycle ◽  
Host Cells ◽  
Bet Hedging ◽  
Hedging Strategy ◽  
Susceptible Host ◽  
Selection Of ◽  
Molecule Communication

Recently, a small-molecule communication mechanism was discovered in a range of Bacillus-infecting bacteriophages, which these temperate phages use to inform their lysis-lysogeny decision. We present a mathematical model of the ecological and evolutionary dynamics of such viral communication, and show that a communication strategy in which phages use the lytic cycle early in an outbreak (when susceptible host cells are abundant) but switch to the lysogenic cycle later (when susceptible cells become scarce) is favoured over a bet-hedging strategy in which cells are lysogenised with constant probability. However, such phage communication can evolve only if phage-bacteria populations are regularly perturbed away from their equilibrium state, so that acute outbreaks of phage infections in pools of susceptible cells continue to occur. Our model then predicts the selection of phages that switch infection strategy when half of the available susceptible cells have been infected.

scholarly journals How repeated outbreaks drive the evolution of bacteriophage communication: Insights from a mathematical model

2020 ◽  
Author(s):  
Hilje M. Doekes ◽  
Glenn A. Mulder ◽  
Rutger Hermsen
Keyword(s):  
Mathematical Model ◽  
Host Cell ◽  
Evolutionary Dynamics ◽  
Communication Strategy ◽  
Lytic Cycle ◽  
Host Cells ◽  
Hedging Strategy ◽  
Susceptible Host ◽  
Signalling Molecules ◽  
Selection Of

AbstractCommunication based on small signalling molecules is widespread among bacteria. Recently, such communication was also described in bacteriophages. Upon infection of a host cell, temperate phages of the Bacillus subtilis-infecting SPbeta group induce the secretion of a phage-encoded signalling peptide, which is used to inform the lysis-lysogeny decision in subsequent infections: the phages produce new virions and lyse their host cell when the signal concentration is low, but favour a latent infection strategy, lysogenising the host cell, when the signal concentration is high. Here, we present a mathematical model to study the ecological and evolutionary dynamics of such viral communication. We show that a communication strategy in which phages use the lytic cycle early in an outbreak (when susceptible host cells are abundant) but switch to the lysogenic cycle later (when susceptible cells become scarce) is favoured over a bet-hedging strategy in which cells are lysogenised with constant probability. However, such phage communication can evolve only if phage-bacteria populations are regularly perturbed away from their equilibrium state, so that acute outbreaks of phage infections in pools of susceptible cells continue to occur. Our model then predicts the selection of phages that switch infection strategy when half of the available susceptible cells have been infected.

scholarly journals Synthesizing within-host and population-level selective pressures on viral populations: the impact of adaptive immunity on viral immune escape

2010 ◽  
Vol 7 (50) ◽  
pp. 1311-1318 ◽  
Author(s):  
Igor Volkov ◽  
Kim M. Pepin ◽  
James O. Lloyd-Smith ◽  
Jayanth R. Banavar ◽  
Bryan T. Grenfell
Keyword(s):  
Evolutionary Dynamics ◽  
Immune Escape ◽  
Adaptive Immune Response ◽  
Population Level ◽  
Analytical Framework ◽  
Host Population ◽  
Host Immunity ◽  
Host Cells ◽  
Susceptible Host ◽  
The Impact

The evolution of viruses to escape prevailing host immunity involves selection at multiple integrative scales, from within-host viral and immune kinetics to the host population level. In order to understand how viral immune escape occurs, we develop an analytical framework that links the dynamical nature of immunity and viral variation across these scales. Our epidemiological model incorporates within-host viral evolutionary dynamics for a virus that causes acute infections (e.g. influenza and norovirus) with changes in host immunity in response to genetic changes in the virus population. We use a deterministic description of the within-host replication dynamics of the virus, the pool of susceptible host cells and the host adaptive immune response. We find that viral immune escape is most effective at intermediate values of immune strength. At very low levels of immunity, selection is too weak to drive immune escape in recovered hosts, while very high levels of immunity impose such strong selection that viral subpopulations go extinct before acquiring enough genetic diversity to escape host immunity. This result echoes the predictions of simpler models, but our formulation allows us to dissect the combination of within-host and transmission-level processes that drive immune escape.

scholarly journals Individual reversible plasticity as a genotype‐level bet‐hedging strategy

2021 ◽  
Author(s):  
Thomas R. Haaland ◽  
Jonathan Wright ◽  
Irja I. Ratikainen
Keyword(s):  
Bet Hedging ◽  
Hedging Strategy

scholarly journals Evolutionary Genetics of Mycobacterium tuberculosis and HIV-1: “The Tortoise and the Hare”

2021 ◽  
Vol 9 (1) ◽  
pp. 147
Author(s):  
Ana Santos-Pereira ◽  
Carlos Magalhães ◽  
Pedro M. M. Araújo ◽  
Nuno S. Osório
Keyword(s):  
Genetic Diversity ◽  
Drug Resistance ◽  
Mycobacterium Tuberculosis ◽  
Evolutionary Dynamics ◽  
Evolutionary Genetics ◽  
Host Cells ◽  
Whole Genome Sequencing Data ◽  
Host Immune System ◽  
Viral Mutant ◽  
Hiv 1

The already enormous burden caused by Mycobacterium tuberculosis and Human Immunodeficiency Virus type 1 (HIV-1) alone is aggravated by co-infection. Despite obvious differences in the rate of evolution comparing these two human pathogens, genetic diversity plays an important role in the success of both. The extreme evolutionary dynamics of HIV-1 is in the basis of a robust capacity to evade immune responses, to generate drug-resistance and to diversify the population-level reservoir of M group viral subtypes. Compared to HIV-1 and other retroviruses, M. tuberculosis generates minute levels of genetic diversity within the host. However, emerging whole-genome sequencing data show that the M. tuberculosis complex contains at least nine human-adapted phylogenetic lineages. This level of genetic diversity results in differences in M. tuberculosis interactions with the host immune system, virulence and drug resistance propensity. In co-infected individuals, HIV-1 and M. tuberculosis are likely to co-colonize host cells. However, the evolutionary impact of the interaction between the host, the slowly evolving M. tuberculosis bacteria and the HIV-1 viral “mutant cloud” is poorly understood. These evolutionary dynamics, at the cellular niche of monocytes/macrophages, are also discussed and proposed as a relevant future research topic in the context of single-cell sequencing.

Etude ultrastructurale des relations hôte–parasite au cours de l'infection des pommes par le Phytophthora cactorum

1981 ◽  
Vol 59 (2) ◽  
pp. 251-263 ◽  
Author(s):  
X. Mourichon ◽  
G. Sallé
Keyword(s):  
Cell Walls ◽  
Susceptible Variety ◽  
Host Cells ◽  
Phytophthora Cactorum ◽  
Electron Microscopic ◽  
Susceptible Host ◽  
Golden Delicious ◽  
Extrahaustorial Matrix ◽  
Apple Fruits

An electron microscopic study was performed on haustoria of Phytophthora cactorum (L. et C.) Schroeter developed in tissues of two cultivars of apple fruits: a susceptible variety ('Golden delicious') and a resistant one ('Belle de Boskoop'). Ultrastructure of intercellular hyphae and some aspects of their penetration between contiguous host cells were described. A light dissolution of the host cell walls was observed. Ontogenic investigations indicated that in the susceptible host, the wall of the fungal haustoria was covered with a dense-stained extrahaustorial matrix. Its origin and its polysaccharide nature were demonstrated. On the other hand, the resistant host developed, immediately after the inoculation, a papilla which gave rise, later on, to a sheath enclosing adult haustoria. The role of these callosic structures in the phenomenon of resistance was discussed.

scholarly journals Exposure of ichnovirus particles to digitonin leads to enhanced infectivity and induces fusion from without in an in vitro model system

2007 ◽  
Vol 88 (11) ◽  
pp. 2977-2984 ◽  
Author(s):  
Don Stoltz ◽  
Renée Lapointe ◽  
Andrea Makkay ◽  
Michel Cusson
Keyword(s):  
Outer Membrane ◽  
In Vitro Model ◽  
Model System ◽  
Host Cells ◽  
Fusion Event ◽  
Susceptible Host ◽  
In Vitro Model System ◽  
Vitro Model

Unlike most viruses, the mature ichnovirus particle possesses two unit membrane envelopes. Following loss of the outer membrane in vivo, nucleocapsids are believed to gain entry into the cytosol via a membrane fusion event involving the inner membrane and the plasma membrane of susceptible host cells; accordingly, experimentally induced damage to the outer membrane might be expected to increase infectivity. Here, in an attempt to develop an in vitro model system for studying ichnovirus infection, we show that digitonin-induced disruption of the virion outer membrane not only increases infectivity, but also uncovers an activity not previously associated with any polydnavirus: fusion from without.

DIFFERENTIAL EQUATIONS FOR TRAIN STARTING WITH ELASTIC CONNECTIONS

2021 ◽  
Vol 2 ◽  
pp. 18-26
Author(s):  
I.P. POPOV
Keyword(s):  
Mathematical Model ◽  
Differential Equations ◽  
Friction Force ◽  
Static Friction ◽  
Longitudinal Vibrations ◽  
Maximum Tension ◽  
Inert Mass ◽  
The Moment ◽  
Elastic Couplings ◽  
Selection Of

The starting mode for the train is the most difficult. An effective method of pulling is the selection of coupling clearances. In this case, the cars are set in motion sequentially and the inert mass, as well as the static friction force immediately at the moment of starting, are minimal. This method has two significant drawbacks - a small fixed value of the gaps in the couplings and the shock nature of the impulse transfer. These disadvantages can be avoided by using elastically deformable couplings. The aim of this work is to construct a mathematical model of "easy" starting of a train with elastic couplings. The softening of the train start-off mode is essentially due to the replacement of the simultaneous start-off of the sections with alternate ones. To exclude longitudinal vibrations of the composition, after reaching the maximum tension of the coupling, the possibility of its harmonic compression should be mechanically blocked.

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