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
ABSTRACT
Cardinium
bacteria, members of the phylum
Cytophaga
-
Flavobacterium
-
Bacteroides
(CFB), are intracellular bacteria in arthropods that are capable of inducing reproductive abnormalities in their hosts, which include parasitic wasps, mites, and spiders. A high frequency of
Cardinium
infection was detected in planthoppers (27 out of 57 species were infected). A high frequency of
Cardinium
infection was also found in spider mites (9 out of 22 species were infected). Frequencies of double infection by
Cardinium
and
Wolbachia
bacteria (
Alphaproteobacteria
capable of manipulating reproduction of their hosts) were disproportionately high in planthoppers but not in spider mites. A new group of bacteria, phylogenetically closely related to but distinct from previously described
Cardinium
bacteria (based on 16S rRNA and
gyrB
genes) was found in 4 out of 25 species of
Culicoides
biting midges. These bacteria possessed a microfilament-like structure that is a morphological feature previously found in
Cardinium
and
Paenicardinium
. The bacteria close to the genus
Cardinium
consist of at least three groups, A, B, and C. Group A is present in various species of arthropods and was previously referred to as “
Candidatus
Cardinium hertigii,” group B is present in plant parasitic nematodes and was previously referred to as “
Candidatus
Paenicardinium endonii,” and group C is present in
Culicoides
biting midges. On the basis of morphological and molecular data, we propose that the nomenclature of these three groups be integrated into a single species, “
Candidatus
Cardinium hertigii.”