Chlamydial symbionts in the enigmatic Xenoturbella (Deuterostomia)

Israelsson, Olle

doi:10.1016/j.jip.2007.05.002

Cited by 29 publications

(30 citation statements)

References 34 publications

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“…S2B in the supplemental material). The chlamydial endosymbionts reported by Israelsson (17) were not detected in these general clone libraries. Therefore, a Chlamydiales-specific PCR was employed which finally retrieved a 16S rRNA gene fragment identical to that of the chlamydial endosymbiont.…”

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confidence: 76%

“…2A). The same library also contained the 16S and 23S rRNA gene sequences of the chlamydial endosymbionts (17). The chlamydial endosymbionts were originally described in samples collected already in 1998, and the detection of at least three different bacterial morphotypes by TEM in these specimens (17) suggests that also the gammaproteobacterial endosymbionts have been consistently associated with Xenoturbella.…”

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confidence: 99%

“…The same library also contained the 16S and 23S rRNA gene sequences of the chlamydial endosymbionts (17). The chlamydial endosymbionts were originally described in samples collected already in 1998, and the detection of at least three different bacterial morphotypes by TEM in these specimens (17) suggests that also the gammaproteobacterial endosymbionts have been consistently associated with Xenoturbella. We realize that the number of specimens analyzed is still small, which is mainly due to the difficulty of finding the animal; however, the consistent detection of both endosymbionts in six or seven independent samples from different years or months that were analyzed in different laboratories is, in our view, a strong indication of a specific and stable symbiotic association between Xenoturbella and the two bacterial types.…”

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Two Types of Endosymbiotic Bacteria in the Enigmatic Marine Worm Xenoturbella bocki

Kjeldsen

Obst

Nakano

et al. 2010

Appl Environ Microbiol

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Two types of endosymbiotic bacteria were identified in the gastrodermis of the marine invertebrate Xenoturbella bocki (Xenoturbellida, Bilateria). While previously described Chlamydia-like endosymbionts were rare, Gammaproteobacteria distantly related to other endosymbionts and pathogens were abundant. The endosymbionts should be considered when interpreting the poorly understood ecology and evolution of Xenoturbella.Xenoturbella bocki is a benthic marine worm first described in 1949 and only found at a few geographical locations at apparently low population densities. It has a very simple body plan ( Fig. 1A) with a blind gut (cul-de-sac) and lacks coelomic cavities, a brain, and reproductive and excretory organs (35). Xenoturbella was originally classified as a flatworm, but molecular analyses have placed it within its own animal phylum, with various affiliations (reviewed in reference 34). The most recent phylogenetic analyses using mitochondrial genome and phylogenomic data indicate a position either within Deuterostomia (5) or at the base of Bilateria (14). Thus, the evolutionary history of Xenoturbella remains elusive and it is unclear whether its simple body plan represents a plesiomorphic character or, alternatively, is the result of secondary loss (34). In addition, the ecology of Xenoturbella is not well understood, leaving, e.g., its food source unresolved (4, 18).Symbiotic bacteria are found in a remarkable number of diverse marine invertebrates (11), where they affect both the ecology and the evolution of their hosts. The first indications of intracellular endosymbionts in Xenoturbella were published by Israelsson (17) and confirmed by electron microscopy of a Xenoturbella spermatid cluster (Fig. 1B); however, our first molecular analyses identified the putative endosymbionts as Gammaproteobacteria, whereas Israelsson (17) had reported a group of endosymbiotic Chlamydiae. The objectives of this study were therefore (i) to identify the putative endosymbionts by 16S rRNA gene analysis, (ii) to localize them inside the host by fluorescence in situ hybridization (FISH), and (iii) to specifically test for the prevalence of the gammaproteobacterial endosymbionts in Xenoturbella.Sample collection and preparation. Seven specimens of X. bocki were collected at two different sites on six different dates in 2005 (GPS position: 58°16ЈN, 11°26ЈE) and 2006 (GPS position: 58°17ЈN, 11°31ЈE) by dredging and sieving of surface sediment at a 100-m water depth in the Gullmar Fjord, Sweden (4). Whole animals were fixed in 4% (wt/vol) paraformaldehyde in sterile seawater and stored in 70% ethanol. Two spermatid clusters (i.e., aggregations of male gametes at the stage of maturation just before becoming fully mature spermatozoa) could be dissected from two whole animals and were preserved in 98% ethanol; since these dissected animals could not be utilized, a total of five whole animals and two spermatid clusters were available for further analysis. The identity of the X. bocki specimens and spermatid cluster was confirmed...

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Two Types of Endosymbiotic Bacteria in the Enigmatic Marine Worm Xenoturbella bocki

Kjeldsen

Obst

Nakano

et al. 2010

Appl Environ Microbiol

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“…Additionally, seven DNA sequences recovered in environmental samples were recently described as putative members of the Simkaniaceae family based on their 16S rRNA and 23S rRNA encoding genes sequences. The first sequence (EF177461) was recovered in gastrodermal cells of Xenoturbella, a primitive marine worm (Israelsson, 2007). Three other sequences (FJ976094, FJ976095 and AF448723.3) were identified in environmental water samples and grouped as the cvE9 cluster (cvE38, cvE41 and cvE9) (Corsaro & Venditti, 2009;Corsaro et al, 2002).…”

Section: Microbiology Simkaniaceae Diversitymentioning

confidence: 99%

“…Fritschea were discovered in arthropods (Everett et al, 2005) and Syngnamydia in fish (Fehr et al, 2013;Nylund et al, 2015). Additionally, various Simkania-related DNA sequences were amplified from marine environments (Israelsson, 2007;Santelli et al, 2008;Sauvadet et al, 2011) and in one case in vegetal cells (Sagaram et al, 2009). This wide host range is quite impressive and contrasts with the narrow host range of Chlamydia trachomatis (human-specific) and Chlamydia felis (cat-specific).…”

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confidence: 99%

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

Vouga

Baud

Greub

2016

Critical Reviews in Microbiology

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Simkania negevensis is a Chlamydia-related bacterium discovered in 1993 and represents the founding member of the Simkaniaceae family within the Chlamydiales order. As other Chlamydiales, it is an obligate intracellular bacterium characterized by a biphasic developmental cycle. Its similarities with the pathogenic Chlamydia trachomatis and Chlamydia pneumoniae make it an interesting bacterium. So far, little is known about its biology, but S. negevensis harbors various microbiological characteristics of interest, including a strong association of the Simkania-containing vacuole with the ER and the presence of an intron in the 23S rRNA encoding gene. Evidence of human exposition has been reported worldwide. However, there is a lack of robust clinical studies evaluating its implication in human diseases; current data suggest an association with pneumonia and bronchiolitis making S. negevensis a potential emerging pathogen. Owing to its fastidious growth requirements, the clinical relevance of S. negevensis is probably underestimated. In this review, we summarize the current knowledge on S. negevensis and explore future research challenges. ARTICLE HISTORY

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Simkaniaceae

Horn¹

2015

Bergey's Manual of Systematics of Archaea and Bacteria

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Chlamydial symbionts in the enigmatic Xenoturbella (Deuterostomia)

Cited by 29 publications

References 34 publications

Two Types of Endosymbiotic Bacteria in the Enigmatic Marine Worm Xenoturbella bocki

Two Types of Endosymbiotic Bacteria in the Enigmatic Marine Worm Xenoturbella bocki

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

Simkaniaceae

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