Endosymbiosis in statu nascendi: close phylogenetic relationship between obligately endosymbiotic and obligately free‐living <i>Polynucleobacter</i> strains (<i>Betaproteobacteria</i>)

Vannini, Claudia; Pöckl, Matthias; Petroni, Giulio; Wu, Qinglong L.; Lang, Elke; Stackebrandt, Erko; Schrallhammer, Martina; Richardson, Paul M.; Hahn, Martin W.

doi:10.1111/j.1462-2920.2006.01144.x

Cited by 63 publications

(82 citation statements)

References 56 publications

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“…It is more difficult to understand why the symbiont is essential for Euplotes survival (12,15). Many obligate symbionts of eukaryotes described as mutualists serve as a source of essential molecules (7,25).…”

Section: Resultsmentioning

confidence: 99%

“…The metabolic profile provides a clear explanation for the inability to grow symbiotic P. necessarius strains outside their hosts (15). The symbiont relies on the ciliate at least for carbon sources, organic nitrogen and sulfur, and other essential molecules, including many cofactors.…”

Section: Resultsmentioning

confidence: 99%

“…In the few cases in which P. necessarius is not present, a different and rarer bacterium apparently supplies the same function (12,14). No attempt to grow symbiotic P. necessarius outside their hosts has yet been successful (15), strongly suggesting that the relationship is obligate for both partners, in contrast to most other known prokaryote/ ciliate symbioses (6).…”

mentioning

confidence: 84%

“…They are smaller and do not show the most prominent morphological feature of the symbiotic form: the presence of multiple nucleoids, each containing one copy of the genome (10,11). It is clear that free-living and endosymbiotic P. necessarius are not different life stages of the same organism (15). Nevertheless, these strikingly different bacteria, occupying separate ecological niches, exhibit >99% 16S rRNA gene sequence identity, and phylogenetic analyses fail to separate them into two distinct groups (15).…”

mentioning

confidence: 99%

“…Nevertheless, these strikingly different bacteria, occupying separate ecological niches, exhibit >99% 16S rRNA gene sequence identity, and phylogenetic analyses fail to separate them into two distinct groups (15). Rather, several lines of evidence point to multiple, recent origins of symbiotic strains from the free-living bacterial pool (14,15).…”

mentioning

confidence: 99%

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Polynucleobacter necessarius , a model for genome reduction in both free-living and symbiotic bacteria

Boscaro

Felletti

Vannini

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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We present the complete genomic sequence of the essential symbiont Polynucleobacter necessarius (Betaproteobacteria), which is a valuable case study for several reasons. First, it is hosted by a ciliated protist, Euplotes; bacterial symbionts of ciliates are still poorly known because of a lack of extensive molecular data. Second, the single species P. necessarius contains both symbiotic and free-living strains, allowing for a comparison between closely related organisms with different ecologies. Third, free-living P. necessarius strains are exceptional by themselves because of their small genome size, reduced metabolic flexibility, and high worldwide abundance in freshwater systems. We provide a comparative analysis of P. necessarius metabolism and explore the peculiar features of a genome reduction that occurred on an already streamlined genome. We compare this unusual system with current hypotheses for genome erosion in symbionts and free-living bacteria, propose modifications to the presently accepted model, and discuss the potential consequences of translesion DNA polymerase loss.symbiosis | nonsynonymous mutation rates | Burkholderiales | protozoa | genome streamlining

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 84%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Polynucleobacter necessarius , a model for genome reduction in both free-living and symbiotic bacteria

Boscaro

Felletti

Vannini

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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P olynucleobacter

Hahn

Hoetzinger

2019

Bergey's Manual of Systematics of Archaea and Bacteria

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Po.ly.nu.cle.o.bac'ter. Gr. adj. polys, many, numerous; L. masc. n. nucleus, a little nut, kernel; N.L. masc. n. bacter, a rod; N.L. masc. n. polynucleobacter, the rod (bacterium) with many nucleoids. Proteobacteria / Betaproteobacteria / Burkholderiales / Burkholderiaceae / Polynucleobacter The genus Polynucleobacter harbors bacteria with distinct lifestyles, dwelling either as free‐living organisms contributing to bacterioplankton in the water columns of freshwater systems or as obligate endosymbionts in the cytoplasm of ciliates ( Euplotes ). Obligate endosymbionts represent derived evolutionary stages of the primary free‐living strains. Polynucleobacter bacteria are cosmopolitan and ubiquitous in freshwater systems, which means, they dwell in freshwater systems worldwide and are omnipresent at least in lakes and ponds but frequently also dwell in running waters. Planktonic Polynucleobacter are abundant in many lakes and ponds, especially in acidic waters. Investigations on a broad variety of systems reported relative abundances of Polynucleobacter bacteria in the range of <1% up to 60% of bacterioplankton. The strains are usually characterized by small genomes of 1.5–2.5 Mb with medium G + C contents of 40–50 mol%. Cultivated strains require complex media and grow as aerobic chemoorganoheterotrophs; however, some strains contain genes putatively encoding anoxygenic photosynthesis or proteorhodopsins. Free‐living strains form small circular convex colonies with shiny surface on agar plates, and usually lack pigmentation. The majority of strains are characterized by small cell sizes and appear as curved or straight rods. Currently (August 2018), the genus contains 16 described species including one endosymbiotic taxon. DNA G + C content of P. necessarius 47.7 mol% (melting point profile) and 44.9 mol% (buoyant density). Type species : Polynucleobacter necessarius Heckmann and Schmidt 1987, 457 VP .

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Diversity of Endosymbiotic Bacteria inParamecium

Görtz

Fokin

2009

Microbiology Monographs

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Endosymbiosis in statu nascendi: close phylogenetic relationship between obligately endosymbiotic and obligately free‐living Polynucleobacter strains (Betaproteobacteria)

Cited by 63 publications

References 56 publications

Polynucleobacter necessarius , a model for genome reduction in both free-living and symbiotic bacteria

Polynucleobacter necessarius , a model for genome reduction in both free-living and symbiotic bacteria

P olynucleobacter

Diversity of Endosymbiotic Bacteria inParamecium

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