Cellular component - Host

  • Definition
    The host is any organism in which another organism, or symbiont, spends part or all of its life cycle. Most animals and plants live symbiotically with microorganisms. The larger organism is called the host and smaller organism the symbiont. When the interactions between the symbiont and the host benefits both partners, the symbiotic interaction is called mutualism. When there is a negative effect on one of the partners, it is called a parasitic symbiosis and if there is no beneficial or negative effect it is a commensal symbiosis. These clear-cut definitions are not always easy to apply in nature. Take the bacterium Pseudomonas aeruginosa for example. This bacterium can be found on the skin of humans and not cause disease, perhaps we would call it a commensial, but if the person has a severe burn P. aeruginosa can cause an infection and becomes a pathogen (a medicinal term for parasitism). This type of organism is called an opportunistic pathogen. Whether an association is a mutualist, commensal or parasitic depends on the relative "strengths" of the partners and the balance of power can change over time.
  • Category
    Cellular component
  • Content
    Host

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