Related Experiment Video
Updated: Apr 15, 2026
07:11
Digital PCR-based Competitive Index for High-throughput Analysis of Fitness in Salmonella
Published on: May 13, 2019
10.2K
Adaptive virulence evolution: the good old fitness-based approach
Samuel Alizon1, Yannis Michalakis1
1Laboratoire MIVEGEC (UMR CNRS 5290, IRD 224, UM), 911 Avenue Agropolis, BP 64501, 34394 Montpellier Cedex 5, France.
Trends in Ecology & Evolution
|April 4, 2015
Summary
Virulence in infectious diseases is often maintained due to adaptive benefits for parasites, as suggested by the transmission-virulence trade-off hypothesis. This study critiques the hypothesis
Area of Science:
- Evolutionary biology
- Parasitology
- Disease ecology
Background:
- Infectious diseases are expected to evolve towards avirulence over time.
- However, many pathogens maintain virulence, often linked to parasite adaptive advantages.
- The transmission-virulence trade-off hypothesis attempts to explain this phenomenon.
Purpose of the Study:
- To critically evaluate the limitations of the transmission-virulence trade-off hypothesis.
- To propose a fitness-based approach to directly assess the adaptive nature of virulence.
- To address challenges in defining virulence, identifying multiple trade-offs, and empirical testing.
Main Methods:
- Critique of the transmission-virulence trade-off hypothesis.
- Adoption of a fitness-based approach for parasite evolution studies.
- Direct assessment of the relationship between virulence and parasite fitness across the life cycle.
Main Results:
- Identified three key limitations of the transmission-virulence trade-off hypothesis: definition of virulence, potential for multiple trade-offs, and empirical testability.
- Demonstrated that a fitness-based approach can overcome these limitations.
- Provided a framework for directly determining if virulence is an adaptive trait.
Conclusions:
- The transmission-virulence trade-off hypothesis has significant limitations.
- A fitness-based approach offers a more direct and robust method for studying virulence evolution.
- Directly assessing parasite fitness is crucial for understanding the adaptive significance of virulence.
Related Concept Videos
01:16Transduction
2.9K
Among the three main modes of HGT—transformation, conjugation, and transduction—transduction is unique in that it is mediated by bacteriophages, or bacterial viruses.Transduction occurs in two ways. Generalized transduction occurs during the lytic cycle of a bacteriophage infection. In this process, bacteriophages infect bacterial cells, replicate within them, and ultimately cause cell lysis, releasing newly assembled virions. Occasionally, random fragments of the bacterial genome...
2.9K
01:24Evolution of New Traits in Microbes
167
Microorganisms evolve rapidly due to their large population sizes and short generation times, often exhibiting measurable changes within days under laboratory conditions. Natural selection acts on standing genetic variation, enabling the retention and amplification of beneficial traits that confer fitness advantages in changing environments.Adaptive Pigment Regulation in RhodobacterIn Rhodobacter, a genus of purple non-sulfur bacteria, light-harvesting pigments such as bacteriochlorophyll and...
167
00:36Viral Mutations
41.0K
A mutation is a change in the sequence of bases of DNA or RNA in a genome. Some mutations occur during replication of the genome due to errors made by the polymerase enzymes that replicate DNA or RNA. Unlike DNA polymerase, RNA polymerase is prone to errors because it is not capable of “proofreading” its work. Viruses with RNA-based genomes, like HIV, therefore accrue mutations faster than viruses with DNA-based genomes. Because mutation and recombination provide the raw material...
41.0K
01:28Regulation of Bacterial Virulence
57
Pathogenic bacteria employ a range of regulatory mechanisms to modulate the expression of virulence genes in response to environmental and host-derived signals. These mechanisms ensure that virulence factors are expressed only under favorable conditions, thereby optimizing infection and survival strategies.Mechanisms of Virulence RegulationKey regulatory strategies include:Two-Component Systems: These consist of a membrane-bound sensor kinase and a cytoplasmic response regulator. Environmental...
57
01:26Evolutionary Processes in Microbes
167
Microbial evolution occurs rapidly due to short generation times and a variety of genetic processes, including horizontal gene transfer, mutation, recombination, and genetic drift. These mechanisms collectively enable microbes to adapt swiftly to changing environments.Horizontal gene transfer (HGT) allows genes to move between different species and occurs through three main mechanisms: conjugation, transformation, and transduction. Conjugation involves direct cell-to-cell contact for DNA...
167
01:09Mutation, Gene Flow, and Genetic Drift
66.4K
In a population that is not at Hardy-Weinberg equilibrium, the frequency of alleles changes over time. Therefore, any deviations from the five conditions of Hardy-Weinberg equilibrium can alter the genetic variation of a given population. Conditions that change the genetic variability of a population include mutations, natural selection, non-random mating, gene flow, and genetic drift (small population size).
66.4K