Cardinium
{{Short description|Genus of bacteria}}
{{Taxobox
| name = "Candidatus Cardinium"
| domain = Bacteria
| phylum = Bacteroidota
| classis = Sphingobacteriia
| ordo = Sphingobacteriales
| familia = incertae sedis
| genus = "Candidatus Cardinium"
| binomial = "Candidatus Cardinium hertigii"
| binomial_authority = Zchori-Fein et al. 2004
| species = "Ca. C. hertigii"
}}
File:Phylogeny of several reproductive parasites, including Cardinium and Wolbachia.jpg based on various sequencing data. It includes two Wolbachia genes and Cardinium 16S rRNA sequence data, along with a reference P-endosymbiont and Arsenophonus. ]]
"Candidatus Cardinium" is a genus of Gram-negative parasitic bacteria that reside within cells of some arthropods and nematodes.{{cite journal | vauthors = Nakamura Y, Kawai S, Yukuhiro F, Ito S, Gotoh T, Kisimoto R, Yanase T, Matsumoto Y, Kageyama D, Noda H | display-authors = 6 | title = Prevalence of Cardinium bacteria in planthoppers and spider mites and taxonomic revision of "Candidatus Cardinium hertigii" based on detection of a new Cardinium group from biting midges | journal = Applied and Environmental Microbiology | volume = 75 | issue = 21 | pages = 6757–63 | date = November 2009 | pmid = 19734338 | pmc = 2772453 | doi = 10.1128/AEM.01583-09 | bibcode = 2009ApEnM..75.6757N }} Although they have not yet been isolated in pure culture (hence the designation Candidatus), they are known to negatively influence reproduction in their hosts in order to further their own proliferation. This leads to their classification as a reproductive parasite. One of the only other examples of this type of parasitism is the genus Wolbachia, which also infects arthropods.{{cite journal | vauthors = Dorigatti I, McCormack C, Nedjati-Gilani G, Ferguson NM | title = Using Wolbachia for Dengue Control: Insights from Modelling | journal = Trends in Parasitology | volume = 34 | issue = 2 | pages = 102–113 | date = February 2018 | pmid = 29183717 | pmc = 5807169 | doi = 10.1016/j.pt.2017.11.002 }} These two genera can also co-infect the same animal, as in some nematodes.{{cite journal | vauthors = Brown AM, Wasala SK, Howe DK, Peetz AB, Zasada IA, Denver DR | title = Cardinium Dual Endosymbiosis in a Plant-Parasitic Nematode | journal = Frontiers in Microbiology | volume = 9 | pages = 2482 | date = 2018-10-16 | pmid = 30459726 | pmc = 6232779 | doi = 10.3389/fmicb.2018.02482 | doi-access = free }} "Candidatus Cardinium" bacteria use many of the same methods to interfere with host reproduction as Wolbachia, including inducing cytoplasmic incompatibility and distorting the sex ratio in the host population to favor females. The mechanisms by which "Candidatus Cardinium" induces these conditions in hosts are thought to be different from the mechanisms used by Wolbachia.{{cite journal | vauthors = Doremus MR, Kelly SE, Hunter MS | title = Exposure to opposing temperature extremes causes comparable effects on Cardinium density but contrasting effects on Cardinium-induced cytoplasmic incompatibility | journal = PLOS Pathogens | volume = 15 | issue = 8 | pages = e1008022 | date = August 2019 | pmid = 31425566 | pmc = 6715252 | doi = 10.1371/journal.ppat.1008022 | editor-first = Elizabeth Ann | editor-last = McGraw | doi-access = free }} "Candidatus Cardinium" bacteria are maternally inherited; infections are maintained through generations through the egg cells (termed vertical transmission).{{cite journal | vauthors = Konecka E, Olszanowski Z | title = A new Cardinium group of bacteria found in Achipteria coleoptrata (Acari: Oribatida) | journal = Molecular Phylogenetics and Evolution | volume = 131 | pages = 64–71 | date = February 2019 | pmid = 30391314 | doi = 10.1016/j.ympev.2018.10.043 }} It is estimated that 6–10% of all arthropods are infected with "Candidatus Cardinium" bacteria.
"Candidatus Cardinium" were first discovered in 1996 in the cells of deer ticks, although attempts to culture them independently of host cells were unsuccessful.{{cite journal | vauthors = Kurtti TJ, Munderloh UG, Andreadis TG, Magnarelli LA, Mather TN | title = Tick cell culture isolation of an intracellular prokaryote from the tick Ixodes scapularis | journal = Journal of Invertebrate Pathology | volume = 67 | issue = 3 | pages = 318–21 | date = May 1996 | pmid = 8812616 | doi = 10.1006/jipa.1996.0050 }}