| polynucleobacter necessarius, an obligate bacterial endosymbiont of the hypotrichous ciliate euplotes aediculatus, is a member of the beta-subclass of proteobacteria. | an almost full length 16s rrna gene of the obligate bacterial endosymbiont polynucleobacter necessarius was amplified using the polymerase chain reaction in combination with site-specific primers. the amplified dna was directly sequenced and compared with other bacterial 16s rrna sequences. p. necessarius belongs to the beta-subclass of proteobacteria and shows the closest relationship to alcaligenes eutrophus, burkholderia solanacearum, and b. pickettii. in proteobacteria and shows the closest ... | 1996 | 8595875 |
| isolation of strains belonging to the cosmopolitan polynucleobacter necessarius cluster from freshwater habitats located in three climatic zones. | more than 40 bacterial strains belonging to the cosmopolitan polynucleobacter necessarius cluster (betaproteobacteria) were isolated from a broad spectrum of freshwater habitats located in three climatic zones. sequences affiliated with the freshwater p. necessarius cluster are among the most frequently detected in studies on bacterial diversity in freshwater ecosystems. despite this frequent detection with culture-independent techniques and the cosmopolitan occurrence of members affiliated with ... | 2003 | 12957910 |
| members of a readily enriched beta-proteobacterial clade are common in surface waters of a humic lake. | humic lakes are systems often characterized by irregular high input of dissolved organic carbon (doc) from the catchment. we hypothesized that specific bacterial groups which rapidly respond to changes in doc availability might form large populations in such habitats. seasonal changes of microbial community composition were studied in two compartments of an artificially divided bog lake with contrasting doc inputs. these changes were compared to community shifts induced during short-term enrichm ... | 2003 | 14602613 |
| bacterial diversity of metagenomic and pcr libraries from the delaware river. | to determine whether metagenomic libraries sample adequately the dominant bacteria in aquatic environments, we examined the phylogenetic make-up of a large insert metagenomic library constructed with bacterial dna from the delaware river, a polymerase chain reaction (pcr) library of 16s rrna genes, and community structure determined by fluorescence in situ hybridization (fish). the composition of the libraries and community structure determined by fish differed for the major bacterial groups in ... | 2005 | 16309387 |
| polynucleobacter cosmopolitanus sp. nov., free-living planktonic bacteria inhabiting freshwater lakes and rivers. | five heterotrophic, aerobic, catalase- and oxidase-positive, non-motile strains were characterized from freshwater habitats located in austria, france, uganda, p. r. china and new zealand. the strains shared 16s rrna gene similarities of >/=99.3 %. the novel strains grew on nsy medium over a temperature range of 10-35 degrees c (two strains also grew at 5 degrees c and one strain grew at 38 degrees c) and a nacl tolerance range of 0.0-0.3 % (four strains grew up to 0.5 % nacl). the predominant f ... | 2010 | 19648339 |
| ubiquity of polynucleobacter necessarius ssp. asymbioticus in lentic freshwater habitats of a heterogeneous 2000 km area. | we present a survey on the distribution and habitat range of polynucleobacter necessarius ssp. asymbioticus (pnecc), a numerically and functionally important taxon in the plankton of freshwater systems. we systematically sampled stagnant freshwater habitats in a heterogeneous 2000 km(2) area, together with ecologically different habitats outside this area. in total, 137 lakes, ponds and puddles were investigated, which represent an enormous diversity of habitats differing, e.g. in depth (< 10 cm ... | 2010 | 20041938 |
| polynucleobacter rarus sp. nov., a free-living planktonic bacterium isolated from an acidic lake. | the heterotrophic, aerobic, facultatively anaerobic under denitrifying conditions, catalase- and oxidase-positive, non-motile strain mt-cbb6a5(t), which was isolated from an acidic lake located in wisconsin (usa), was characterized. the strain grew on nsy medium over a temperature range of 15-30 °c and a nacl range of 0.0-0.3 % (w/v). the predominant fatty acids were c(16 : 0), c(18 : 1)ω7c, 11-methyl c(18 : 1)ω7c, feature 3 (including c(16 : 1)ω7c), and feature 2 (including c(14 : 0) 3-oh). the ... | 2011 | 20435748 |
| singlet oxygen, a neglected but important environmental factor: short-term and long-term effects on bacterioplankton composition in a humic lake. | photolysis of dissolved organic matter (dom) leads to contrasting effects on bacterioplankton dynamics, i.e. stimulation and inhibition of bacterial activity. in particular, the role of short-lived reactive oxygen species (ros), e.g. singlet oxygen (¹o₂), in altering microbial activity and species composition has scarcely been investigated. therefore, we have artificially increased the natural rate of ¹o₂ formation in short-term (∼4 h) in situ and long-term (72 h) laboratory incubations of surfa ... | 2010 | 20636377 |
| temporal patterns in glycolate-utilizing bacterial community composition correlate with phytoplankton population dynamics in humic lakes. | previous observations of correlated community dynamics between phytoplankton and bacteria in lakes indicate that phytoplankton populations may influence bacterial community structure. to investigate the possibility that bacterial use of phytoplankton exudates contributes to observed patterns of community change, we characterized the diversity and dynamics of heterotrophic bacterioplankton with genetic potential to use glycolate, a photorespiration-specific exudate, in five lakes over a 15-week p ... | 2010 | 20652236 |
| ubiquity of polynucleobacter necessarius subspecies asymbioticus results from ecological diversification. | the subspecies polynucleobacter necessarius asymbioticus (> 99% 16s rrna similarity) has a cosmopolitan distribution and a ubiquitous occurrence in lentic freshwater habitats. we tested if the observed ubiquity of these free-living planktonic freshwater bacteria results from a euryoecious (generalist) adaptation of p. n. asymbioticus strains, or from ecological diversification within the subspecies. we developed a reverse line blot hybridization assay enabling the cultivation-independent detecti ... | 2011 | 21208356 |
| alga-derived substrates select for distinct betaproteobacterial lineages and contribute to niche separation in limnohabitans strains. | we examined the proportions of major betaproteobacteria subgroups within bacterial communities in diverse nonaxenic, monospecific cultures of algae or cyanobacteria: four species of cryptophyta (genera cryptomonas and rhodomonas), four species of chlorophyta (genera pediastrum, staurastrum, and chlamydomonas), and two species of cyanobacteria (genera dolichospermum and aphanizomenon). in the cryptophyta cultures, betaproteobacteria represented 48 to 71% of total bacteria, the genus limnohabitans ... | 2011 | 21873481 |
| the passive yet successful way of planktonic life: genomic and experimental analysis of the ecology of a free-living polynucleobacter population. | the bacterial taxon polynucleobacter necessarius subspecies asymbioticus represents a group of planktonic freshwater bacteria with cosmopolitan and ubiquitous distribution in standing freshwater habitats. these bacteria comprise <1% to 70% (on average about 20%) of total bacterioplankton cells in various freshwater habitats. the ubiquity of this taxon was recently explained by intra-taxon ecological diversification, i.e. specialization of lineages to specific environmental conditions; however, d ... | 2012 | 22448227 |
| contrasting effects of singlet oxygen and hydrogen peroxide on bacterial community composition in a humic lake. | light excitation of humic matter generates reactive oxygen species (ros) in surface waters of aquatic ecosystems. abundant ros generated in humic matter rich lakes include singlet oxygen ((1)o2) and hydrogen peroxide (h2o2). because these ros differ in half-life time and toxicity, we compared their effects on microbial activity ((14)c-leucine incorporation) and bacterial community composition (bcc) in surface waters of humic lake grosse fuchskuhle (north-eastern germany). for this purpose, exper ... | 2014 | 24667441 |
| a house for two--double bacterial infection in euplotes woodruffi sq1 (ciliophora, euplotia) sampled in southeastern brazil. | several ciliated protists form symbiotic associations with a diversity of microorganisms, leading to drastic impact on their ecology and evolution. in this work, two euplotes spp. sampled in rio de janeiro, brazil, were identified based on morphological and molecular features as euplotes woodruffi strain sq1 and e. encysticus strain sq2 and investigated for the presence of endosymbionts. while e. woodruffi sq1 stably hosts two bacterial populations, namely polynucleobacter necessarius (betaprote ... | 2016 | 26381539 |
| global phylogeography of pelagic polynucleobacter bacteria: restricted geographic distribution of subgroups, isolation by distance and influence of climate. | the free-living planktonic freshwater bacterium polynucleobacter necessarius subspecies asymbioticus (> 99% 16s rrna similarity) represents a taxon with a cosmopolitan distribution and apparently ubiquitous occurrence in lentic freshwater habitats. we tested for intra-taxon biogeographic patterns by combining cultivation-independent and cultivation methods. a culture collection of 204 strains isolated from globally distributed freshwater habitats (arctic to antarctica) was investigated for phylo ... | 2015 | 24920455 |
| polynucleobacter necessarius, a model for genome reduction in both free-living and symbiotic bacteria. | 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 ... | 2013 | 24167248 |
| freshwater bacterial lifestyles inferred from comparative genomics. | while micro-organisms actively mediate and participate in freshwater ecosystem services, we know little about freshwater microbial genetic diversity. genome sequences are available for many bacteria from the human microbiome and the ocean (over 800 and 200, respectively), but only two freshwater genomes are currently available: the streamlined genomes of polynucleobacter necessarius ssp. asymbioticus and the actinobacterium aci-b1. here, we sequenced and analysed draft genomes of eight phylogent ... | 2014 | 23889754 |
| betaproteobacterial symbionts of the ciliate euplotes: origin and tangled evolutionary path of an obligate microbial association. | the polynucleobacter-euplotes association is an obligatory symbiotic system between a monophyletic group of ciliate species belonging to the genus euplotes and bacteria of the species polynucleobacter necessarius (betaproteobacteria). both organisms are unable to survive independently. several studies revealed the existence of free-living populations of polynucleobacter bacteria which are phylogenetically closely related to the endosymbiotic ones, but never share associations with euplotes in th ... | 2012 | 22533449 |
| contrasting trends in distribution of four major planktonic betaproteobacterial groups along a ph gradient of epilimnia of 72 freshwater habitats. | the distribution and abundance of betaproteobacteria and three of its genera - limnohabitans (r-bt065 lineage), polynucleobacter (including subclusters polynucleobacter necessarius and polynucleobacter acidiphobus/polynucleobacter difficilis), and methylophilus - across the epilimnia of 72 limnologically diverse freshwater habitats were investigated using fluorescence in situ hybridization. moreover, seasonal development of betaproteobacteria subgroups along the longitudinal axis of a reservoir ... | 2012 | 22452571 |