Related Experiment Video
Updated: Jul 3, 2026
10:01
Quantification of Intracellular Growth Inside Macrophages is a Fast and Reliable Method for Assessing the Virulence of Leishmania Parasites
Published on: March 16, 2018
Low migration decreases interference competition among parasites and increases virulence
F Vigneux1, F Bashey, M Sicard
1Department of Biology, Indiana University, Bloomington, IN 47405, USA.
Journal of Evolutionary Biology
|July 19, 2008
Summary
Parasite competition influences host virulence. Lower parasite migration increased host mortality, while higher migration led to bacterial self-inhibition, demonstrating the impact of within-host parasite interactions on disease severity.
Area of Science:
- Evolutionary biology
- Microbial ecology
- Parasitology
Background:
- Parasite competition within a host can impact virulence.
- Bacteriocins, toxins produced by bacteria, are a mechanism for within-host competition.
- Relatedness among parasites can influence within-host conflict and virulence.
Purpose of the Study:
- To investigate how parasite population structure affects virulence.
- To examine the role of within-host competition and cooperation in parasite evolution.
- To understand the impact of migration rates on parasite interactions and host mortality.
Main Methods:
- Evolving insect-parasitic nematodes (Steinernema carpocapsae) and their symbiotic bacteria (Xenorhabdus nematophila) for 20 passages.
- Implementing two migration treatments: low and high.
- Assessing host mortality rates and bacterial growth inhibition in different treatments.
Main Results:
- Host mortality rates were significantly higher in the low-migration treatment compared to the high-migration treatment.
- Bacteria isolated from the same host inhibited each other's growth exclusively in the high-migration treatment.
- These findings suggest a link between parasite population structure and virulence.
Conclusions:
- Population structure and within-host interactions among parasites are critical factors in determining virulence.
- Reduced migration can lead to increased host exploitation and higher mortality.
- High migration can promote parasite cooperation or reduce competition, potentially lowering virulence.
Related Concept Videos
01:22Microbial Interactions: Parasitism
Parasitism is a form of microbial interaction in which parasitic microbes exploit a host organism for nutrients and shelter, often at the host's expense. Unlike mutualistic relationships, where both organisms benefit, parasitism benefits only the parasite and harms the host.Classification of ParasitesMicrobial parasites are broadly classified based on their location relative to the host.Ectoparasites remain on the host’s surface, such as the skin or outer tissues, drawing nutrients...
01:29Malaria
Malaria pathogenesis in humans reflects a delicate interplay between parasite biology and host response. Clinical illness reflects a host’s immune response to the parasite’s asexual replication cycle, which is often asymptomatic in individuals with partial immunity. From the parasite's perspective, transmission between mosquito and human with minimal host pathology is evolutionarily advantageous. Among the six Plasmodium species infecting humans, P. falciparum and P. vivax dominate in global...
01:21Frequency-dependent Selection
When the fitness of a trait is influenced by how common it is (i.e., its frequency) relative to different traits within a population, this is referred to as frequency-dependent selection. Frequency-dependent selection may occur between species or within a single species. This type of selection can either be positive—with more common phenotypes having higher fitness—or negative, with rarer phenotypes conferring increased fitness.Positive Frequency-Dependent SelectionIn positive...
02:34Competition
When organisms require the same limited resources within an environment, they may have to compete for them. Competition is a net-negative interaction. Even if two competing individuals or populations do not interact directly, the overall fitness of both competitors is lowered as a result of not having full access to the limited resource.Intraspecific competition, which occurs between individuals of the same species, serves as a natural mechanism for regulating population size. Too much...
01:26Microbial Interactions: Cooperation
Microbial cooperation involves beneficial interactions in which different species work together for individual or mutual advantage. These interactions can profoundly influence ecological dynamics and evolutionary processes, and they are essential to many pathogenic and symbiotic relationships.Nematode–Bacteria CooperationA striking example is the relationship between the Gram-negative bacterium Xenorhabdus nematophila and the parasitic nematode Steinernema carpocapsae. Juvenile nematodes...
01:26Microbial Interactions: Competition
Microbial competition is an ecological interaction in which microorganisms vie for limited resources within shared environments. These resources may include nutrients, space, or light, depending on the system. The intensity and outcome of competition are influenced by the environmental context, such as nutrient availability, spatial constraints, and the diversity of microbial species present. These competitive interactions significantly influence the structure, function, and resilience of...