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![Neighbour-joining tree based on almost complete 16S rRNA gene sequences reconstructing the phylogenetic position of Polynucleobacter difficilis sp. nov. strain AM-8B5 T . Bootstrap percentages [1000 (NJ, MP) or 100 iterations (ML)] obtained by NJ/MP/ML methods are shown at nodes. Bar, 0.01 substitutions per nucleotide position.](profile/Martin-Hahn-2/publication/50867824/figure/fig1/AS:460281756295168@1486751130071/Neighbour-joining-tree-based-on-almost-complete-16S-rRNA-gene-sequences-reconstructing.png)
Neighbour-joining tree based on almost complete 16S rRNA gene sequences reconstructing the phylogenetic position of Polynucleobacter difficilis sp. nov. strain AM-8B5 T . Bootstrap percentages [1000 (NJ, MP) or 100 iterations (ML)] obtained by NJ/MP/ML methods are shown at nodes. Bar, 0.01 substitutions per nucleotide position.
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Strain AM-8B5(T), isolated from Lake Sevan in Armenia, was characterized phenotypically, chemotaxonomically and phylogenetically. This chemo-organoheterotrophic, aerobic, facultatively anaerobic, catalase- and oxidase-positive, non-motile strain grew on NSY medium at NaCl concentrations of 0.0-0.2 % (w/v) and at 4-30 °C. Whole-cell fatty acids were...
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Context 1
... inference by NJ, MP and ML methods consistently resulted in clustering of the almost complete 16S rRNA gene sequence of strain AM-8B5 T within the genus Polynucleobacter (Fig. 1). All three methods indicated Table 2. Whole-cell fatty acid compositions of Polynucleobacter difficilis strain AM-8B5 T and related strains Taxa: 1, strain AM-8B5 T ; 2, P. acidiphobus MWH-PoolGreenA3 T (Hahn et al., 2011a); 3, P. rarus MT-CBb6A5 T (Hahn et al., 2011b); 4, P. cosmopolitanus MWH-MoIso2 T ( Hahn et al., 2010); 5, five P. ...
Context 2
... all three analyses of 16S rRNA sequences indicated that P. necessarius represents the closest relative of the subcluster (PnecB) represented by P. acidiphobus and AM-8B5 T . In contrast, trees constructed by the ML method differed from trees calculated by the other two methods regarding the branching order of P. cosmopolitanus and P. rarus (Fig. ...
Context 3
... from the phylogenetic analysis and chemotaxo- nomic investigations demonstrated the affiliation of strain AM-8B5 T with the genus Polynucleobacter (Tables 1 and 2, Fig. 1) but also revealed pronounced differences between this strain and strains affiliated with the four previously described Polynucleobacter species. DNA-DNA reassocia- tion data indicated that the isolate does not belong to the previously described species P. necessarius, P. cosmopolita- nus and P. acidiphobus and the 16S rRNA gene ...
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... A cultivation-independent investigation based on massive parallel sequencing of amplicons of a protein-encoding marker gene providing a much higher taxonomic resolution than 16S rRNA gene sequences suggested, that in European freshwater habitats dwell at least 600 species-like Polynucleobacter taxa [19]. This, as well as a previous investigation [20], indicated that in tropical climates, as well as on the southern hemisphere, dwell [1][2][3][4][5][6][7][8][9][10][11][12][13][14] and of the previously described species (numbers [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31]. The colour code indicates the current annual mean temperatures at terrestrial locations predicted by the WorldClim model (version 1.3, with a resolution of 2.5 min) [58]. ...
... The strains representing the 14 new Polynucleobacter species, as well as the type strains of all 16 free-living Polynucleobacter species described previously [18,[24][25][26][27][28][29][30][31][32][33][34], were obtained from the water column of freshwater habitats. The geographic origin of the 14 new strains and the 17 previously described species is shown in Fig. 1. ...
... The analysis of the whole-cell fatty acid composition (Table S2) was carried out as described previously [31]. The cell masses were cultivated on Reasoner's 2A (R2A) [36] agar slants which were filled up with 1.5 ml liquid R2A medium at 28 °C. ...
Fourteen strains, all isolated from the surface of freshwater habitats, were genomically, phylogenetically and phenotypically characterized. The strains were obtained from geographically and climatically broadly scattered sites. This included two lakes in Antarctica, one arctic pond located on the Svalbard archipelago (Norway), a tropical habitat located in Uganda, some lakes in Southern Europe (Spain and France), lakes, ponds and a puddle in Central Europe (Austria, Czech Republic and Germany), and lakes in Northern Europe (Finland). Most of the investigated strains were characterized by rather small cell sizes and rather slow growth on media such as nutrient broth–soyotone–yeast extract (NSY) medium. Phylogenomic analyses indicated that all fourteen strains are affiliated with the genus Polynucleobacter ( Burkholderiaceae , Pseudomonadota ). Thirteen of the strains were found to be affiliated with subcluster PnecC of the genus. All these strains were characterized by genome sizes in the range of 1.7–2.3 Mbp and G+C values of 44.9–46.5 mol%. Furthermore, all PnecC-affiliated strains shared 16S rRNA gene sequence similarities >99 %. Only one strain characterized by a larger genome size of 2.9 Mbp and a lower G+C value of 41.0 mol% was found to be affiliated with subcluster PnecA. Whole genome sequence comparisons revealed that all 14 strains shared among each other, as well as with the type strains of the previously described 17 Polynucleobacter species, whole-genome average nucleotide identities values <95 %. This suggested that the 14 investigated strains represent 14 different new species. We propose the establishment of 14 new Polynucleobacter species represented by the following type strains: UB-Domo-W1 T (=DSM 103491 T =CIP 111598 T =JCM 32562 T ), VK13 T (=DSM 103488 T =JCM 32564 T ), LimPoW16 T (=DSM 24085 T =CIP 111098 T ), UK-Long2-W17 T (=DSM 103489 T =CIP 111328 T =JCM 32563 T ), UK-Pondora-W15 T (=DSM 103423 T =JCM 32939 T ), MWH-Mekk-B1 T (=DSM 106779 T =JCM 32556 T ), MWH-Mekk-C3 T (=DSM 103415 T =JCM 32557 T ), Ross1-W9 T (=DSM 103416 T =JCM 32561 T ), MWH-Hall10 T (=DSM 107042 T =JCM 32938 T ), AP-Basta-1000A-D1 T (=DSM 107039 T =JCM 32933 T ), AP-Melu-1000-A1 T (=DSM 107036 T =JCM 32935 T ), es-MAR-2 T (=DSM 103424 T =JCM 32554 T ), AP-Mumm-500A-B3 T (=DSM 107037 T =JCM 32936 T ), MWH-UH21B T (=DSM 23884 T =LMG 29707 T ).
... Moreover, ultramicrobacteria that have a large specific surface area and thus possibly an advantage in substrate acquisition are believed to have a highly passive but successful lifestyle in highly dynamic and eutrophic freshwater environments (Boenigk et al., 2004). In our study, the relative abundance of taxa of the typical freshwater ultramicrobacteria, including Polynucleobacter (Gammaproteobacteria, Wu and Hahn, 2006;Hahn et al., 2012), the hgcI clade (Actinobacteria, Tarao et al., 2009), as well as picocyanobacteria Cyanobium (Jezberová and Komárková, 2007), clearly increased in some of the eutrophic reservoirs (Fig. S7). ...
Understanding microbial metacommunity assemblies and the underlying methanisms are fundamental objectives of aquatic ecology. However, little is known about how eutrophication, the primary water quality issue of aquatic ecosystems, regulates bacterioplankton metacommunity assemblies at a regional scale in reservoirs. In this study, we applied a metacommunity framework to study bacterioplankton communities in 210 samples collected from 42 tropical coastal reservoirs in the wet summer season. We found that the spatial pattern of bacterioplankton community composition (BCC) at a regional scale was shaped mainly by species sorting. The reservoir trophic state index (TSI) was the key determinant of bacterioplankton metacommunity assemblies. BCC turnover increased significantly with the TSI differences between sites (∆TSI) when ∆TSI was < 20, but remained at a level of about 80% when ∆TSI was > 20. Compared to oligo-mesotrophic and mesotrophic reservoirs, increased heterogeneity of co-occurrence bacterioplankton networks and bacterioplankton β-diversity were observed across eutrophic reservoirs. We propose that larger variation in phytoplankton community assemblies may play directly or indirectly deterministic processes in controlling the bacterioplankton metacommunity assemblies and became the potential mechanisms behind the observed higher BCC heterogeneity across the eutrophic reservoirs. Our research contributes to a broader understanding of the ecological effects of eutrophication on reservoir ecosystems and provides clues to the management of the tropical coastal reservoirs.
... Some of these candidates were meanwhile described as new taxa (e.g. Hahn et al. 2010Hahn et al. , 2012aJezbera et al. 2009). The lower ratio of taxa discovered per isolated strain (0.2 for the Filtration-Acclimatization Method versus 0.7 for the standard plating methods) probably resulted from the Filtration-Acclimatization Method entailing too strong of a selection step, i.e. filtration through 0.2 mm filters. ...
Isolation and cultivation of microorganisms enables in combination with cultivation-independent methods comprehensive research on ecology and function of microbes. The availability of cultures provides opportunities for ecophysiological experiments, enables high-quality genome research and represents a mandatory prerequisite for the description of new taxa of prokaryotes. Unfortunately, access to microorganism by cultivation methods is still quite limited, and the majority of the microbial diversity remains uncultured so far. This chapter discusses the potential reasons for this lack in cultivability and reviews advances in cultivation methods for prokaryotes. Detailed analysis of the media and methods used by taxonomists for isolation of bacterial strains used for description of >1000 new species revealed that the description of new taxa in the ranks of species and genera is currently not methodically limited. On the other hand, isolation of strains enabling the description of taxa representing higher ranks is obviously strongly limited by the currently applied methods. Consequently, different cultivation strategies are required according to the scientific goals of the respective research. While taxonomists interested in the description of new species affiliated with any genus or family can isolate new strains suitable for this task by using standard cultivation methods and media, ecologists interested in cultivation of model organisms appearing in natural systems with high cell numbers, as well as taxonomists interested in isolation of strains representing new higher ranking taxa like orders, classes and phyla, should rather use high-throughput non-standard methods in combination with optimized screening protocols.
... By contrast, the type strain of Polynucleobacter rarus, the only described species representing subcluster PnecA, is characterized by a G + C value of 40.3 mol% [reversed-phase HPLC (Hahn et al., 2011b)] or rather 39.9 mol% [genome sequence (Pitt et al., 2018)]. (Hahn et al., 2011a(Hahn et al., , 2012aPitt et al., 2018). Fatty acid profiles have been determined for the type strains of all free-living Polynucleobacter species (Table 3). ...
... Fatty acid profiles have been determined for the type strains of all free-living Polynucleobacter species (Table 3). In all strains, the unsaturated fatty acid C 16:1 ω7c contributed with 32-47% the largest fraction of the total fatty acids content of the cells (Hahn et al., 2012aPitt et al., 2018). The second largest fraction was contributed either by the saturated compound C 16:0 or by the unsaturated compound C 18:1 ω7c. ...
... By contrast, a large number of Polynucleobacter strains obtained from tropical habitats did not grow at 4 ∘ C (Hahn et al., 2015). For the 15 tested type strains, the maximum temperature enabling growth was in the range of 28-38 ∘ C (Table 1) (Hahn et al., 2012aPitt et al., 2018 The phylogenetic position of the genus Polynucleobacter was reconstructed using 16S rRNA gene sequences of type material representing the type species of the genus (Springer et al., 1996) and free-living strains ). These analyses suggest that the genus belongs to the family Burkholderiaceae, with Cupriavidus and Ralstonia being the closest related genera. ...
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, 457VP.
... A huge number of novel bacteria belonging to various classes and families have been reported from freshwater lake ecosystem worldwide e.g. Ferribacterium limneticum, CdA-1 Coeur d'Alene Lake, 54 Hymenobacter aquatilis, HMF3095 T Artificial lake, 55 Sphingobium fontiphilum, Chen16-4 T Chengcing Lake, 56 Limnobacter thiooxidans, CS-K1 Chiemsee Lake, 57 Desulfovibrio idahonensis, CY1 T Coeur d'Alene, 58 Thiobaca trueperi, Eutrophic lake, 59 Listeria marthii, FSL S4-120 T Finger Lakes 60 Sphingomonas hengshuiensis, WHSC-8 T Hengshui Lake, 61 Kinneretia asaccharophila, KIN192 T Kinneret Lake, 62 Algoriphagus aquatilis A8-7 T Longhu Lake, 63 Limnohabitans curvus, MWH-C5 T Mondsee Lake, 64 Cloacibacterium rupense, R2A-16 T Rupa Lake, 65 Undibacterium seohonense, SHS5-24 T Seoho lake, 66 Polynucleobacter difficilis, AM-8B5 T Sevan Lake, 67 Flavobacterium chuncheonense Soyang Lake, 68 Flavobacterium soyangense, IMCC26223 T Soyang Lake, 69 Flavobacterium luteum IMCC26026 T, Soyang Lake, 68 Mucilaginibacter soyangensis, HME6664 T Soyang Lake, 70 Flavobacterium lacicola, IMCC25901 T Soyang lake, 71 Flavobacterium saliperosum, S13 T, Taihu Lake, 72 Roseomonas lacus TH-G33 T Taihu Lake, 73 Rhodoluna lacicola, MWH-Ta8 T Taihu Lake, 74 Nocardioides taihuensis, X17 T Taihu Lake, 75 Lysobacter oligotrophicus, 107-E2 T Tanago Ike, 76 and Nocardioides ungokensis, UKS-03 T Ungok Lake. 77 ...
... Ten free-living and one endosymbiotic species are currently described. The other four Polynucleobacter subclusters currently contain five described free-living species [16][17][18][19][20]. ...
... The analysis of the whole-cell fatty acid composition (Table 5) was carried out as described previously [19]. The cell masses were cultivated on R2A [41] agar slants which were filled up with 1.5 ml liquid R2A medium at 28°C. ...
Six Polynucleobacter (Burkholderiaceae, Betaproteobacteria) strains isolated from different freshwater lakes located across Europe were taxonomically investigated. Phylogenetic analyses based on 16S rRNA gene sequences assigns all six strains to the cryptic species complex PnecC within the genus Polynucleobacter. Analyses of partial glutamine synthetase (glnA) genes suggests that all six strains belong to the species-like taxon designated F15 in previous papers. Comparative genome analyses reveal that the six strains form a genomically coherent group characterized by whole-genome average nucleotide identity (gANI) values of >98 % but separated by gANI values of <88 % from the type strains and representatives of the 16 previously described Polynucleobacter species. In phylogenetic analyses based on nucleotide sequences of 319 orthologous genes, the six strains represent a monophyletic cluster that is clearly separated from all other described species. Genome sizes of the six strains range from 1.61 to 1.83 Mbp, which is smaller than genome sizes of the majority of type strains representing previously described Polynucleobacter species. By contrast, the G+C content of the DNA of the strains is well in the range of 44.8-46.6 mol% previously found for other type strains of species affiliated with the subgroup PnecC. Variation among the six strains representing the new species is evident in a number of traits. These include gene content differences, for instance regarding a gene cluster encoding anoxygenic photosynthesis, as well as phenotypic traits. We propose to name the new species represented by the six strains Polynucleobacter paneuropaeus sp. nov. and designate strain MG-25-Pas1-D2T (=DSM 103454T =CIP 111323T) as the type strain.
... The analysis of the whole-cell fatty acid composition (Table 4) was carried out as described previously [31]. The cell masses were cultivated on Reasoner's 2A (R2A) [32] agar slants which were filled up with 1.5 ml liquid R2A medium. ...
Strains MWH-EgelM1-30-B4T and MWH-Feld-100T were isolated from the water columns of two freshwater systems. Both strains represent delicate bacteria not easy to work with in laboratory experiments. Phylogenetic analyses of the 16S rRNA genes suggested that both strains were affiliated with the genus Polynucleobacter. Both strains share 16S rRNA gene sequence similarities of >99 % with eight free-living Polynucleobacter type strains, all affiliated with the cryptic species complex PnecC. The full-length 16S rRNA gene sequences of the two strains differ only in two and three positions, respectively, from the sequence of the closest related Polynucleobacter type strain. Genome sequencing of both strains revealed relatively small genome sizes of 2.0 Mbp and G+C contents of 45 mol%. Phylogenetic analyses based on nucleotide sequences of 319 shared protein-encoding genes consistently placed the two strains in taxon PnecC but did not suggest an affiliation with one of the previously described species. Pairwise analyses of whole genome average nucleotide identities (gANI) with representatives of all previously described Polynucleobacter species resulted in both cases throughout in values <80 %. Pairwise comparison of the genomes of the two new strains resulted in gANI values of 83.3 %. All gANI analyses clearly suggested that strains MWH-EgelM1-30-B4T and MWH-Feld-100T represent two novel Polynucleobacter species. We propose for these novel species the names Polynucleobacter hirudinilacicola sp. nov. and Polynucleobacter campilacus sp. nov. and strains MWH-EgelM1-30-B4T (=DSM 23911T=LMG 30144T) and MWH-Feld-100T (=DSM 24007T=LMG 29705T) as the type strains, respectively.
... Utilization of various substrates was investigated in the same way as for previously described Polynucleobacter species [13][14][15][16][17]. Briefly, growth enabled by utilization of a specific substrate was determined by comparison of the optical density (OD) at 575 nm following growth in one tenthstrength NSY broth (0.3 g l À1 ) with and without 0.5 g l À1 test substrate. ...
... The analysis of the whole-cell fatty acid composition ( Table 2) was carried out as described previously [14] except that the cell masses were cultivated on R2A agar slants which were filled up with 1.5 ml liquid R2A medium. The slants were incubated at 28 C and inspected for growth daily. ...
... The genomes of type strains P. rarus MT-CBb6A5 T [16], P. difficilis AM-8B5 T [14], and P. acidiphobus MWH-Pool-GreenA3 T [17] were sequenced as described previously for the Silvanigrella aquatica type strain [20]. For each strain, two libraries were reconstructed. ...
Strain AP-Melu-1000-B4 was isolated from a lake located in the mountains of the Mediterranean island of Corsica (France). Phenotypic, chemotaxonomic and genomic traits were investigated. Phylogenetic analyses based on 16S rRNA gene sequencing referred the strain to the cryptic species complex PnecC within the genus Polynucleobacter. The strain encoded genes for biosynthesis of proteorhodopsin and retinal. When pelleted by centrifugation the strain showed an intense rose colouring. Major fatty acids were C16 : 1ω7c, C16 : 0, C18 : 1ω7c and summed feature 2 (C16 : 1 isoI and C14 : 0-3OH). The sequence of the 16S rRNA gene contained an indel which was not present in any previously described Polynucleobacter species. Genome sequencing revealed a genome size of 1.89 Mbp and a G+C content of 46.6 mol%. In order to resolve the phylogenetic position of the new strain within subcluster PnecC, its phylogeny was reconstructed from sequences of 319 shared genes. To represent all currently described Polynucleobacter species by whole genome sequences, three type strains were additionally sequenced. Our phylogenetic analysis revealed that strain AP-Melu-100-B4 occupied a basal position compared with previously described PnecC strains. Pairwise determined whole genome average nucleotide identity (gANI) values suggested that strain AP-Melu-1000-B4 represents a new species, for which we propose the name Polynucleobacter meluiroseus sp. nov. with the type strain AP-Melu-1000-B4T (=DSM 103591T=CIP 111329T).
... Comparative genome analyses of a planktonic [8,9] and an endosymbiotic strain [10] revealed that the endosymbiotic strain represents an evolutionary derivative form undergoing reductive genome evolution. Isolation of free-living strains from various freshwater systems [11] enabled the description of ten new Polynucleobacter species recently [12][13][14][15][16][17][18]. The majority of these species are affiliated with subcluster PnecC [11], which represents a large cryptic species complex characterized by 16S rRNA gene sequence similarity values ≥ 99% [16,19]. ...
... Utilization of various substrates was investigated in the same way as for previously described Polynucleobacter species [12][13][14][15][16][17][18]. Briefly, growth enabled by utilization of a specific substrate was determined by comparison of optical densities (OD) at 575 nm established in liquid one tenth-strength NSY medium (0.3 g l -1 ) with and without 0.5 g l -1 test substrate, respectively. ...
... Incubation times were, from left to right column, 8, 4, 6 and 5 days. Data for more distantly related Polynucleobacter species can be found elsewhere [12][13][14][15][16][17]. Table 5 Loci used for the multilocus sequence analysis presented in Fig. 2. The table lists the loci of two strains, the not genome sequenced endosymbiont P. ...
The bacterial strain MWH-K35W1(T) was isolated from a permanently anoxic water layer of a meromictic lake located in the Austrian Salzkammergut area. The basically chemo-organoheterotrophic strain was isolated and maintained under aerobic conditions. Phylogenetic analyses of the 16S rRNA gene and the glutamine synthetase gene (glnA) of the strain suggested an affiliation to the genus Polynucleobacter and the cryptic species complex PnecC. Strain MWH-K35W1(T) shares with the type strains of the six free-living species of the genus Polynucleobacter affiliated with this species complex 16S rRNA gene sequence similarities of 99.6-99.9 %, while the type material of the obligate endosymbiont Polynucleobacternecessarius, which is also affiliated with this species complex, shares a gene sequence similarity of 99.1 %. Genome sequencing resulted in a genome size of 2.14 Mbp and a DNA G+C content of 45.98 mol%. Major fatty acids were C16 : 1ω7c, C18 : 1ω7c and C16 : 0. This strain is the first strain of the genus Polynucleobacter found to encode a proteorhodopsin-like protein but, in contrast to some other strains affiliated to this genus, it does not encode a putative anoxygenic photosynthesis system. Multilocus sequence analysis based on partial sequences of eight housekeeping genes, as well as average nucleotide identity (ANI) analyses, did not suggest that strain MWH-K35W1(T) belongs to a previously described species. We propose the name Polynucleobacter aenigmaticus for a novel species with strain MWH-K35W1(T) (=DSM 24006(T)=LMG 29706(T)) as the type strain.
... Utilization of various substrates was investigated in the same way as for previously described Polynucleobacter species [11][12][13][14][15]. Briefly, growth enabled by utilization of a specific substrate was determined by comparison of OD at 575 nm established in liquid one-tenth-strength NSY medium (0.3 g l À1 ) with and without 0.5 g l À1 test substrate, respectively. ...
... The analysis of the whole-cell fatty acid composition ( Table 2) was carried out as described previously [12]. Biomass was harvested from cultures on R2A agar plates, which were inoculated with a 1 ml cell suspension, incubated while keeping the agar surface moist and inspected daily for growth, starting the third day after inoculation. ...
... Strain MWH-Weng1-1 T can be discriminated from the type strains of Polynucleobacter species not affiliated with subcluster PnecC by its chemotaxonomic traits. As for other species affiliated with subcluster PnecC, strain MWH-Weng1-1 T can be discriminated from the type strains of P. rarus [14], P. acidiphobus [15] and P. difficilis [12] based on the G+C content of their DNA [6]. Discrimination of strain MWH-Weng1-1 T from P. cosmopolitanus is possible by the absence of the fatty acid C 12 : 0 3-OH [13], which has so far only been found in Polynucleobacter strains affiliated with the species P. cosmopolitanus. ...
Strain MWH-Weng1-1T, isolated from an acidic freshwater habitat located in the Wenger Moor, Austria, was characterized by investigating its phenotypic, chemotaxonomic and genomic traits. Phylogenetic analyses based on 16S rRNA gene sequencing placed the strain in the cryptic species complex PnecC within the genus Polynucleobacter. The strain had a genome of 2.04 Mbp with a G+C content of 45.6 mol%. The major fatty acids of the strain were C16 : 1ω7c, C16 : 0 and C18 : 1ω7c. In order to resolve the systematic position of the strain within the species complex PnecC, concatenated partial sequences of eight housekeeping genes were used for phylogenetic analyses. The obtained trees did not place strain MWH-Weng1-1T close to any of the six previously described species within this cryptic species complex. Pairwise whole genome average nucleotide identity comparisons with genome sequences of strains representing the six previously described species of the subcluster resulted throughout in values <78 %, which clearly suggested that strain MWH-Weng1-1T (DSM 24018T=CIP 111099T) represents a novel species. We propose the name Polynucleobacter sphagniphilus sp. nov. and strain MWH-Weng1-1T as the type strain for this new species.
