‘Candidatus Rhabdochlamydia porcellionis’, an intracellular bacterium from the hepatopancreas of the terrestrial isopod Porcellio scaber (Crustacea: Isopoda)

Abstract

Intracellular bacteria were observed in the hepatopancreas of the terrestrial isopod Porcellio scaber. Comparative 16S rRNA gene sequence analysis and electron microscopic observations were used to determine the taxonomic position of these intracellular bacteria. Phylogenetic analysis and a complex developmental cycle affiliate these bacteria to the order Chlamydiales, within which they form a distinctive lineage, close to the family Simkaniaceae. They share <92 % 16S rRNA gene sequence similarity with their closest relative and <88 % similarity with other members of the order Chlamydiales. A specific signature oligonucleotide sequence was identified and used as a probe, enabling the identification of intracellular bacteria in infected hepatopancreatic tissue. According to the distinctive morphology of their elementary bodies, which are rod-shaped rather than spherical and contain translucent oblong structures, their genomic properties and their crustacean host, the name ‘Candidatus Rhabdochlamydia porcellionis' is proposed for intracellular bacteria in the hepatopancreas of P. scaber.

Simkania negevensis, an insight into the biology and clinical importance of a novel member of the Chlamydiales order

“…Three evolutionary clusters appear to exist: (i) the Chlamydiaceae/Clavichlamydiaceae cluster, which harbors the smallest genomes and seems to have branched the earliest, (ii) the Parachlamydiaceae/ Waddliaceae/Criblamydiaceae cluster and (iii) the Simkaniaceae/Rhabdochlamydiaceae cluster (Lagkouvardos et al, 2014). Indeed, Simkaniaceae share an 86-87% homology in the 16S rRNA encoding gene sequence with Rhabdochlamydiaceae (Kostanjsek et al, 2004) and only 82% homology with Chlamydiaceae (Kahane et al, 1995). Comparative analysis of the full genome sequences showed more than 400 conserved core genes preserved in all Chlamydiales members (Bertelli et al, 2010;Collingro et al, 2011;Pillonel et al, 2015).…”

Pathogenic Potential of Novel Chlamydiae and Diagnostic Approaches to Infections Due to These Obligate Intracellular Bacteria

“…Universal/eubacterial primer sets have been used to amplify and sequence the 16S rRNA genes of uncharacterized chlamydia-like organisms first documented by morphological analyses and then described as Parachlamydiaceae (5,36), as Waddlia chondrophila (85), and as Rhabdochlamydia porcellionis (64). These primer sets have in some instances also allowed identification of new chlamydial phylotypes from whole DNA extracts of environmental samples.…”

“…These include Fritschea bemisiae and Fritschea eriococci (family Simkaniaceae), which infect homopteran insects (28,92), and Rhabdochlamydia porcellionis (64) and Rhabdochlamydia crassificans (19), which infect the woodlouse Porcellio scaber (Crustacea: Isopoda) and the cockroach Blatta orientalis (Insecta: Blattodea), respectively. The presence of chlamydiae in arthropods is interesting, since arthropods were not previously considered to play a role in the epidemiology of chlamydial infections, with the only exception being flies as a vector of the agent of trachoma (25,26).…”

“CandidatusBacilloplasma,” a Novel Lineage ofMollicutesAssociated with the Hindgut Wall of the Terrestrial IsopodPorcellio scaber(Crustacea: Isopoda)

“…These bacteria are morphologically distinct and differ from other bacteria observed in the P. scaber digestive system (references 15,25,39, and 40; summarized in ref- erence 26).…”