Editing Pathogen transmission (section)

===Horizontal transmission===

Some beneficial symbionts are acquired [[Horizontal transmission|horizontally]], from the environment or unrelated individuals. This requires that host and symbiont have some method of recognizing each other or each other's products or services. Often, horizontally acquired symbionts are relevant to [[secondary metabolism|secondary]] rather than primary metabolism, for example for use in defense against pathogens,<ref>{{cite journal | vauthors = Kaltenpoth M, Engl T |title=Defensive microbial symbionts in Hymenoptera |journal=Functional Ecology |date=2013 |volume=28 |issue=2 |doi=10.1111/1365-2435.12089 |pages=315–327|hdl=11858/00-001M-0000-000E-B76B-E |hdl-access=free }}</ref> but some primary nutritional symbionts are also horizontally (environmentally) acquired.<ref>{{cite journal | vauthors = Nussbaumer AD, Fisher CR, Bright M | title = Horizontal endosymbiont transmission in hydrothermal vent tubeworms | journal = Nature | volume = 441 | issue = 7091 | pages = 345–348 | date = May 2006 | pmid = 16710420 | doi = 10.1038/nature04793 | s2cid = 18356960 | bibcode = 2006Natur.441..345N }}</ref> Additional examples of horizontally transmitted beneficial symbionts include  [[Bobtail squid#light organ|bioluminescent bacteria associated with bobtail squid]] and [[Rhizobia|nitrogen-fixing bacteria in plants]].{{cn|date=February 2023}}