the.com/symbiont
A roommate so committed to the lease it became part of you.
means An organism that lives in close, lasting partnership with another, for better or worse.
from From Greek symbioun, to live together, coined by botanist Anton de Bary in 1879 to name life sharing life.
Inside jobYour mitochondria were once free-living bacterial symbionts.
Not all friendlySymbiosis includes parasites, not just helpful tenants.
Glowing exampleBobtail squid hire bacteria to fake the moonlight.