The genusLimnohabitans(Comamonadaceae,Betaproteobacteria) is a common and a highly active component of freshwater bacterioplanktonic communities. To date, the genus has been considered to contain only heterotrophic species. In this study, we detected the photosynthesis genespufLMandbchYin 28 of 46 strains from threeLimnohabitanslineages. ThepufMsequences obtained are very closely related to environmentalpufMsequences detected in various freshwater habitats, indicating the ubiquity and potential importance of photoheterotrophicLimnohabitansin nature. Additionally, we sequenced and analyzed the genomes of 5 potentially photoheterotrophicLimnohabitansstrains, to gain further insights into their phototrophic capacity. The structure of the photosynthesis gene cluster turned out to be highly conserved within the genusLimnohabitansand also among all potentially photosyntheticBetaproteobacteriastrains. The expression of photosynthetic complexes was detected in a culture ofLimnohabitans planktonicusII-D5Tusing spectroscopic and pigment analyses. This was further verified by a novel combination of infrared microscopy and fluorescentin situhybridization.IMPORTANCEThe data presented document that the capacity to perform anoxygenic photosynthesis is common among the members of the genusLimnohabitans, indicating that they may have a novel role in freshwater habitats.
Bacteria of the genus Limnohabitans, more precisely the R-BT lineage, have a prominent role in freshwater bacterioplankton communities due to their high rates of substrate uptake and growth, growth on algal-derived substrates and high mortality rates from bacterivory. Moreover, due to their generally larger mean cell volume, compared to typical bacterioplankton cells, they contribute over-proportionally to total bacterioplankton biomass. Here we present genetic, morphological and ecophysiological properties of 35 bacterial strains affiliated with the Limnohabitans genus newly isolated from 11 non-acidic European freshwater habitats. The low genetic diversity indicated by the previous studies using the ribosomal SSU gene highly contrasted with the surprisingly rich morphologies and different patterns in substrate utilization of isolated strains. Therefore, the intergenic spacer between 16S and 23S rRNA genes was successfully tested as a fine-scale marker to delineate individual lineages and even genotypes. For further studies, we propose the division of the Limnohabitans genus into five lineages (provisionally named as LimA, LimB, LimC, LimD and LimE) and also additional sublineages within the most diversified lineage LimC. Such a delineation is supported by the morphology of isolated strains which predetermine large differences in their ecology.
- MeSH
- Betaproteobacteria klasifikace genetika růst a vývoj metabolismus MeSH
- biomasa MeSH
- ekosystém * MeSH
- fylogeneze MeSH
- genetická variace * MeSH
- molekulární sekvence - údaje MeSH
- RNA ribozomální 16S genetika MeSH
- sladká voda mikrobiologie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Two bacterial strains, II-B4(T) and II-D5(T), isolated from the meso-eutrophic freshwater Římov reservoir (Czech Republic), were characterized phenotypically, phylogenetically and chemotaxonomically. Both strains were chemo-organotrophic, facultatively anaerobic, non-motile rods, with identical DNA G+C contents of 59.9 mol%. Their major polar lipids were diphosphatidylglycerol, phosphatidylglycerol and phosphatidylethanolamine and their major fatty acids were C(16 : 1)ω7c/C(16 : 1)ω6c, C(16 : 0), C(18 : 1)ω7c/C(18 : 1)ω6c and C(12 : 0). Both strains contained Q-8 as the only respiratory quinone component. The 16S rRNA gene sequences of the two strains possessed 99.1 % similarity; however, the level of DNA-DNA reassociation was only 26.7 %. The strains can also be discriminated from each other by several chemotaxonomic and biochemical traits. Phylogenetic analysis of the 16S rRNA gene sequences revealed the affiliation of both strains with the genus Limnohabitans within the family Comamonadaceae. The two investigated strains represent the first isolated members of a narrow phylogenetic cluster (the so-called R-BT065 cluster) formed by a large number of environmental sequences and abundant populations detected in the pelagic zones of various freshwater habitats. We propose to place the two strains in separate novel species within the genus Limnohabitans, Limnohabitans planktonicus sp. nov., with the type strain II-D5(T) (=DSM 21594(T) =CIP 109844(T)), and Limnohabitans parvus sp. nov., with the type strain II-B4(T) (=DSM 21592(T) =CIP 109845(T)). The description of the genus Limnohabitans is emended accordingly.
- MeSH
- Comamonadaceae klasifikace genetika izolace a purifikace MeSH
- DNA bakterií genetika MeSH
- fenotyp MeSH
- fosfolipidy krev MeSH
- fylogeneze * MeSH
- mastné kyseliny chemie MeSH
- molekulární sekvence - údaje MeSH
- RNA ribozomální 16S genetika MeSH
- sekvenční analýza DNA MeSH
- sladká voda mikrobiologie MeSH
- techniky typizace bakterií MeSH
- ubichinon chemie MeSH
- zastoupení bazí MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Geografické názvy
- Česká republika MeSH
