Editing Endosymbiont (section)

===== Secondary =====
[[File:HEMI Aphididae Aphidius attacking pea aphid.png|thumb|right|Pea aphids are commonly infested by parasitic wasps. Their secondary endosymbionts attack the infesting parasitoid wasp larvae promoting the survival of both the aphid host and its endosymbionts.]]

The pea aphid (''[[Acyrthosiphon pisum]]'') contains at least three secondary endosymbionts, ''[[Hamiltonella defensa]]'', ''[[Regiella insecticola]]'', and ''[[Serratia symbiotica]]''. ''Hamiltonella defensa'' defends its aphid host from parasitoid wasps.<ref name="pmid18029301">{{cite journal |vauthors=Oliver KM, Campos J, Moran NA, Hunter MS |title=Population dynamics of defensive symbionts in aphids |journal=Proceedings. Biological Sciences |volume=275 |issue=1632 |pages=293–299 |date=February 2008 |pmid=18029301 |pmc=2593717 |doi=10.1098/rspb.2007.1192 }}</ref> This symbiosis replaces lost elements of the insect's immune response.<ref name="pmid20186266">{{cite journal |title=Genome sequence of the pea aphid Acyrthosiphon pisum |journal=PLOS Biology |volume=8 |issue=2 |pages=e1000313 |date=February 2010 |pmid=20186266 |pmc=2826372 |doi=10.1371/journal.pbio.1000313 |author1=International Aphid Genomics Consortium |doi-access=free }}</ref>

One of the best-understood defensive symbionts is the spiral bacteria ''[[Spiroplasma poulsonii]]''. ''Spiroplasma sp.'' can be reproductive manipulators, but also defensive symbionts of ''[[Drosophila]]'' flies. In ''[[Drosophila neotestacea]]'', ''S. poulsonii'' has spread across North America owing to its ability to defend its fly host against [[nematode]] parasites.<ref>{{cite journal |vauthors=Jaenike J, Unckless R, Cockburn SN, Boelio LM, Perlman SJ |title=Adaptation via symbiosis: recent spread of a Drosophila defensive symbiont |journal=Science |volume=329 |issue=5988 |pages=212–215 |date=July 2010 |pmid=20616278 |doi=10.1126/science.1188235 |s2cid=206526012 |bibcode=2010Sci...329..212J }}</ref> This defence is mediated by toxins called "[[ribosome]]-inactivating [[proteins]]" that attack the molecular machinery of invading parasites.<ref>{{cite journal |vauthors=Hamilton PT, Peng F, Boulanger MJ, Perlman SJ |title=A ribosome-inactivating protein in a Drosophila defensive symbiont |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=113 |issue=2 |pages=350–355 |date=January 2016 |pmid=26712000 |pmc=4720295 |doi=10.1073/pnas.1518648113 |doi-access=free |bibcode=2016PNAS..113..350H }}</ref><ref>{{cite journal |vauthors=Ballinger MJ, Perlman SJ |title=Generality of toxins in defensive symbiosis: Ribosome-inactivating proteins and defense against parasitic wasps in Drosophila |journal=PLOS Pathogens |volume=13 |issue=7 |pages=e1006431 |date=July 2017 |pmid=28683136 |pmc=5500355 |doi=10.1371/journal.ppat.1006431 |doi-access=free }}</ref> These toxins represent one of the first understood examples of a defensive symbiosis with a mechanistic understanding for defensive symbiosis between an insect endosymbiont and its host.<ref name="Ballinger-2017">{{cite journal |vauthors=Ballinger MJ, Perlman SJ |date=July 2017 |title=Generality of toxins in defensive symbiosis: Ribosome-inactivating proteins and defense against parasitic wasps in Drosophila |journal=PLOS Pathogens |volume=13 |issue=7 |pages=e1006431 |doi=10.1371/journal.ppat.1006431 |pmc=5500355 |pmid=28683136 |doi-access=free }}</ref>

''[[Sodalis glossinidius]]'' is a secondary endosymbiont of tsetse flies that lives inter- and intracellularly in various host tissues, including the midgut and hemolymph. Phylogenetic studies do not report a correlation between evolution of ''[[Sodalis (genus)|Sodalis]]'' and tsetse.<ref>Aksoy, S., Pourhosseini, A. & Chow, A. 1995. Mycetome endosymbionts of tsetse flies constitute a distinct lineage related to Enterobacteriaceae. Insect Mol Biol. '''4''', 15–22.</ref> Unlike ''Wigglesworthia,'' ''Sodalis'' has been cultured ''in vitro''.<ref name="pmid3662675">{{cite journal |vauthors=Welburn SC, Maudlin I, Ellis DS |title=In vitro cultivation of rickettsia-like-organisms from Glossina spp |journal=Annals of Tropical Medicine and Parasitology |volume=81 |issue=3 |pages=331–335 |date=June 1987 |pmid=3662675 |doi=10.1080/00034983.1987.11812127 }}</ref>

''[[Cardinium]]'' and many other insects have secondary endosymbionts.<ref name="pmid15189221">{{cite journal |vauthors=Zchori-Fein E, Perlman SJ |title=Distribution of the bacterial symbiont Cardinium in arthropods |journal=Molecular Ecology |volume=13 |issue=7 |pages=2009–2016 |date=July 2004 |pmid=15189221 |doi=10.1111/j.1365-294X.2004.02203.x |bibcode=2004MolEc..13.2009Z |s2cid=24361903 }}</ref><ref name="pmid12415315">{{cite journal |vauthors=Wernegreen JJ |title=Genome evolution in bacterial endosymbionts of insects |journal=Nature Reviews. Genetics |volume=3 |issue=11 |pages=850–861 |date=November 2002 |pmid=12415315 |doi=10.1038/nrg931 |s2cid=29136336 }}</ref>