Final answer:
Commensal refers to an organism that benefits from another without affecting it. A symbiont lives in close association with another organism, either as a mutualist or a parasite. A pathobiont is a commensal organism that can cause disease under certain conditions.
Step-by-step explanation:
A commensal is an organism that benefits from another organism without affecting it, which is often seen in a symbiotic relationship where one organism benefits and the other is neither helped nor harmed. An example of commensalism is a remora fish attaching to a shark, where it gets free transportation and food scraps without affecting the shark.
A symbiont is an organism that lives in close association with another organism in a mutualistic or parasitic relationship. In mutualism, both organisms benefit, like bees and flowers, whereas in parasitism, one organism benefits at the expense of the other, such as tapeworms in humans.
A pathobiont refers to a commensal organism that can cause disease under certain conditions, such as when a host's immune system is compromised or when the organism is in a part of the body where it's not normally found. This term is particularly used in the context of microbiota that can switch from being harmless to pathogenic.