Criblamydia sequanensis
Domain: Bacteria
Phylum: Chlamydiae
Class: Chlamydia
Order: Chlamydiales
Family: Chlamydiaceace
Genus: Criblamydia
Species: C. sequanensis
Criblamydia sequanensis is a nonmotile, star-shaped, obligately intracellular bacterium that grows within host-derived vacuoles. C. sequanensis grows in high numbers in amoebae, and exhibits a developmental cycle consistent with other Chlamydia species[1][2]. C. sequanensis belongs to the class Chlamydia and was the first species to be identified in the Criblamydia genus. C. sequanensis was recovered from a water sample from the river Seine in France and co-cultivated with the amoeba Acanthamoeba castellanii ATCC 30010[2].
Discovery
C. sequanensis was isolated from a sample of water from the Seine river, near the entry of the Morsang-sur-Seine drinking water plant. Environmental samples from this location were generally shown to display bacterial overgrowth with amoebal lysis or encystment, therefore the samples underwent a pan-Chlamydiales specific polymerase chain reaction (PCR) for screening each well of amoebal co‐culture[2]. Of the eight water samples that were screened, two were found to be positive for Chlamydiales specific primers. These samples were cultured along with Acanthamoeba castellanii for a period of 6 to 14 days. Following this subculturing of these two samples took place with A. castellanii and ampicillin and vancomycin, which led to the recovery of two strains of chlaymdia-like bacteria[2]. One of the two would go on to be proposed as a new species of Chlamydiales, named Criblamydia sequanensis. Criblamydia was derived from the abbreviation CRIB which stands for the Center for Research on Intracellular Bacteria. Sequanisis comes from the Latin name for the Seine River.
Morphology
C. sequanensis is 0.5-1µm in diameter[1]. Transmission electron microscopy showed the organism to have a star-shaped body, a trait unique in comparison to most other clamydiae[2].
Developmental Cycle
C. sequanensis have a developmental cycle consistent with other Chlamydiae, which includes two major morphological and physiological stages, the replicating reticulate body and the non-replicating infectious elementary body[3]. C. sequanensis alternate between elementary and reticulate bodies during their developmental cycle. An elementary body, is an infectious extracellular body, which enters mucosal cells and differentiates into reticulate bodies. Reticulate bodies Reticulate bodies are non-infectious extracellular bodies, which are eventually re-differentiated back to elementary bodies as the cycle continues in this fashion[4]. C. sequanensis development, the reticule body divides by binary fission. The elementary bodies are star shaped with seven branches[2].
Energy Metabolism
Bacteria of the family Chlamydiaceace encode for the enzymes phosphoglycerate kinase and pyruvate kinase which facilitate the metabolism of glucose-6-phsphate to pyruvate through glycolysis. This allows for these bacteria to generate ATP. Chlamydiacae therefore depend on the import of glucose form the host cell cytosol[3]; for C. sequanensis this host cell is an amoeba such as Acanthamoeba castellanii, which C. sequanensis was co-cultured with[2]. C. sequananesis relies on the host cell cytosol as its main source of carbon.
Chlamyidacae are able to produce ATP through oxidative phosphorylation using the respiratory chain that includes the enzymes which consists of a Na+-translocating NADH dehydrogenase, succinate dehydrogenase, cytochrome bd oxidase, and a V-type ATPase[3].
Genome and Phylogeny
The genome of C. sequanensis was first sequenced in 2014 and has a total number of 2,969,604 bases, with a guanine-cytosine (G-C) content of 38.2 %. The chromosome is one of the largest within the chlamydiales order, and contains 2476 genes in total, with 2416 of these genes being protein encoding[5]. The function of the protein coding genes is predicted in 66% percent of these genes.
Sequencing of the 16s rRNA encoding gene showed the closest similarity with Parachlamydiaceae (88.5–89.8%), followed by Waddliaceae (87.1-88.3%), Chlamydiaceae (86.2–87.2%), Simkaniaceae (84.7–85.6%) and Rhabdochlamydiaceae (84.9–85.2%), showing closest similarity within the Chlaymdiales order. Furthering sequencing of the 23s rRNA sequence again showed the closest similarity to Chlamydiales, with the highest being Waddliaceae (84.8–87.4%), followed by Parachlamydiaceae (82.2–85.2%), Simkaniaceae (80.0–83.1%) and Chlamydiaceae (77.6–80.4%)[2].
Additionally, C. sequanensis possesses a circular plasmid, made up of 89, 525 base pairs, with a G-C conetent of 40.8%. This megaplasmid encodes 92 proteins. 48% of these proteins are conserved with an unknown function. Interestingly the proteins appear to be from various different origins. A BLAST search indicated the highest similarity to Chlamydiales and Proteobacteria (each 25%). Other notable similarities included a 7% similarity to Bacteriodetes and a 5% similarity to Firmicutes. Further, 7% of the proteins were found to be of phagic origin[5]. This sequenced plasmid will allow for researchers to further investigate the genetic background of C. sequanensis, as well as the evolution of chlamydial plasmids.
Arsenite Resistance
The Bertelli et al. studied indicated a 25% similarity of the C. sequanisis plasmid with Proteobacteria. Within the 25% of genes that hit in this BLAST search, was a gene in proteobacteria that is an operon for arsenite resistance. This gene is not found in any other sequenced Chlamydiales, but interestingly is often found in environmental bacteria[5]. It is likely that this detoxification property is linked to the bacterium’s natural environment within the Seine River.
Pathogenic Role
Although much is still unknown about the pathogenic role of C. Sequanensis, a 2009 study gave some insight into the bacterium’s pathogenesis. The study sampled the blood of 482 men, 101 of which screened positive for Criblamydia. Analysis of those that screened positive showed a suggestion of a possible association between the presence C. sequnensis and asthma[6]. Additionally, the study hypothesizes that human infection may occur from exposure to infected water due to C. sequanensis’s discovery from the Seine River. Further, a correlation was shown between exposure to dog and farm animals and the presence of C. Sequanensis, indicating zoonogtical transmission may be possible[6]. Although these correlations are not strongly proven, they do highlight areas of investigation for C. sequanensis and provide a future direction for research.
References
- ↑ 1.0 1.1 Whitman. Bergeys manual of systematics of Archaea and Bacteria. John Wiley & Sons, Inc.; 2015.
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 Thomas V, Casson N, Greub G. Criblamydia sequanensis, a new intracellular Chlamydiales isolated from Seine river water using amoebal co-culture. Environmental Microbiology. 2006;8(12):2125–35.
- ↑ 3.0 3.1 3.2 Omsland A, Sixt BS, Horn M, Hackstadt T. Chlamydial metabolism revisited: interspecies metabolic variability and developmental stage-specific physiologic activities. FEMS Microbiology Reviews. 2014;38(4):779–801.
- ↑ Elwell C, Mirrashidi K, Engel J. Chlamydia cell biology and pathogenesis. Nature Reviews Microbiology. 2016;14(6):385–400.
- ↑ 5.0 5.1 5.2 Bertelli C, Goesmann A, Greub G. Criblamydia sequanensis Harbors a Megaplasmid Encoding Arsenite Resistance. Genome Announcements. 2014;2(5).
- ↑ 6.0 6.1 Baud D, Kebbi C, Külling J-P, Greub G. Seroprevalence of different Chlamydia-like organisms in an asymptomatic population. Clinical Microbiology and Infection. 2009;15:213–5.