Editing Endosymbiont (section)

=== Horizontal ===
Horizontal symbiont transfer ([[horizontal transmission]]) is a process where a host acquires a facultative symbiont from the environment or another host.<ref name="Bright-2010" /> The Rhizobia-Legume symbiosis (bacteria-plant endosymbiosis) is a prime example of this modality.<ref name="Gage-2004" /> The Rhizobia-legume symbiotic relationship is important for processes such as the formation of root nodules. It starts with flavonoids released by the legume host, which causes the rhizobia species (endosymbiont) to activate its ''Nod'' genes.<ref name="Gage-2004">{{Cite journal |last=Gage |first=Daniel J. |date=June 2004 |title=Infection and Invasion of Roots by Symbiotic, Nitrogen-Fixing Rhizobia during Nodulation of Temperate Legumes |journal=Microbiology and Molecular Biology Reviews |language=en |volume=68 |issue=2 |pages=280–300 |doi=10.1128/MMBR.68.2.280-300.2004 |issn=1092-2172 |pmc=419923 |pmid=15187185}}</ref> These ''Nod'' genes generate [[Lipopolysaccharide|lipooligosaccharide]] signals that the legume detects, leading to root nodule formation.<ref name="pmid109930772">{{cite journal |vauthors=Shigenobu S, Watanabe H, Hattori M, Sakaki Y, Ishikawa H |date=September 2000 |title=Genome sequence of the endocellular bacterial symbiont of aphids Buchnera sp. APS |journal=Nature |volume=407 |issue=6800 |pages=81–86 |bibcode=2000Natur.407...81S |doi=10.1038/35024074 |pmid=10993077 |doi-access=free}}</ref> This process bleeds into other processes such as nitrogen fixation in plants.<ref name="Gage-2004" /> The evolutionary advantage of such an interaction allows genetic exchange between both organisms involved to increase the propensity for novel functions as seen in the plant-bacterium interaction ([[holobiont]] formation).<ref>{{Cite journal |last1=Chrostek |first1=Ewa |last2=Pelz-Stelinski |first2=Kirsten |last3=Hurst |first3=Gregory D. D. |last4=Hughes |first4=Grant L. |date=2017 |title=Horizontal Transmission of Intracellular Insect Symbionts via Plants |journal=Frontiers in Microbiology |volume=8 |page=2237 |doi=10.3389/fmicb.2017.02237 |issn=1664-302X |pmc=5712413 |pmid=29234308 |doi-access=free }}</ref>