Einnischung und Mikrodiversität planktonischer Bakterienpopulationen

The water column of marine and limnic habitats might appear as a homogeneous space without visible constraints. However, free-living bacteria struggle for survival and adapted to various ecological niches within this seemingly homogeneous habitat. To understand the processes of niche formation and bacterial speciation, two different systems were investigated: i) a microdiverse cluster of dominant freshwater Sphingomonadaceae (phylotype G1A) and ii) a uniform marine population of green sulfur bacteria (Chlorobium BS-1). The microdiversity of the G1A-cluster was identified by nucleotide differences within a non-coding region (ITS1), that is located between the 16S rRNA gene and 23S rRNA gene, whereas the 16S rRNA gene sequence was identical for all members of the phylotype. In contrast, all members of the Chlorobium BS-1 population exhibited identical 16S rRNA and ITS1 sequences. The main objective of this study was to determine the factors that caused the microdiversity among the limnic phylotype G1A and the homogeny of the marine Chlorobium BS-1 population.Die Wassersäulen mariner und limnischer Habitate können wie ein homogener Raum ohne sichtbare Grenzen wirken. Allerdings kämpfen freilebende Bakterien um das Überleben in diesem homogen erscheinenden Habitat und adaptierten sich an verschiedene ökologische Nischen. Um die Prozesse der Nischenbildung und der bakteriellen Artbildung zu verstehen, wurden zwei unterschiedliche Systeme untersucht: i) eine mikrodiverse Gruppe limnischer Sphingomonadaceae (Phylotyp G1A) und ii) eine homogene marine Population grüner Schwefelbakterien (Chlorobium BS-1). Die Mikrodiversität des G1A Phylotypen wurde anhand von Nukleotidunterschieden innerhalb eines nicht-codierenden Bereiches (ITS1), der sich zwischen dem 16S rRNA und 23S rRNA Gen befindet, identifiziert. Die Sequenz des 16S rRNA Gens ist hingegen bei allen Individuen des Phylotyps identisch. Im Gegensatz dazu, besitzen alle Individuen der Chlorobium BS-1 Population identische 16S rRNA Gensequenzen und identische ITS1 Sequenzen. Das Hauptziel dieser Studie lag darin die Faktoren zu erfassen, die zur Mikrodiversität des limnischen Phylotypen G1A und zur Homogenität der marinen Chlorobium BS-1 Population führten

Description of Polystyrenella longa gen. nov., sp. nov., isolated from polystyrene particles incubated in the Baltic Sea

Planctomycetes occur in almost all aquatic ecosystems on earth. They have a remarkable cell biology, and members of the orders Planctomycetales and Pirellulales feature cell division by polar budding, perform a lifestyle switch from sessile to motile cells and have an enlarged periplasmic space. Here, we characterise a novel planctomycetal strain, Pla110$^{τ}$, isolated from the surface of polystyrene particles incubated in the Baltic Sea. After phylogenetic analysis, the strain could be placed in the family Planctomycetaceae. Strain Pla110$^{τ}$ performs cell division by budding, has crateriform structures and grows in aggregates or rosettes. The strain is a chemoheterotroph, grows under mesophilic and neutrophilic conditions, and exhibited a doubling time of 21 h. Based on our phylogenetic and morphological characterisation, strain Pla110$^{τ}$ (DSM 103387$^{τ}$ = LMG 29693$^{τ}$) is concluded to represent a novel species belonging to a novel genus, for which we propose the name Polystyrenella longa gen. nov., sp. nov

Tautonia plasticadhaerens sp. nov., a novel species in the family Isosphaeraceae isolated from an alga in a hydrothermal area of the Eolian Archipelago

A novel planctomycetal strain, designated ElP$^{T}$, was isolated from an alga in the shallow hydrothermal vent system close to Panarea Island in the Tyrrhenian Sea. Cells of strain ElP$^{T}$ are spherical, form pink colonies and display typical planctomycetal characteristics including division by budding and presence of crateriform structures. Strain ElP$^{T}$ has a mesophilic (optimum at 30 °C) and neutrophilic (optimum at pH 7.5) growth profile, is aerobic and heterotrophic. It reaches a generation time of 29 h (μ$_{max}$ = 0.024 h$^{-1}$). The strain has a genome size of 9.40 Mb with a G + C content of 71.1% and harbours five plasmids, the highest number observed in the phylumPlanctomycetes thus far. Phylogenetically, the strain represents a novel species of the recently described genus Tautonia in the family Isosphaeraceae. A characteristic feature of the strain is ist tendency to attach strongly to a range of plastic surfaces. We thus propose the name Tautonia plasticadhaerens sp. nov. for the novel species, represented by the type strain ElP$^{T}$ (DSM 101012$^{T}$ = LMG 29141$^{T}$)

Mucisphaera calidilacus gen. nov., sp. nov., a novel planctomycete of the class Phycisphaerae isolated in the shallow sea hydrothermal system of the Lipari Islands

For extending the current collection of axenic cultures of planctomycetes, we describe in this study the isolation and characterisation of strain Pan265(T) obtained from a red biofilm in the hydrothermal vent system close to the Lipari Islands in the Tyrrhenian Sea, north of Sicily, Italy. The strain forms light pink colonies on solid medium and grows as a viscous colloid in liquid culture, likely as the result of formation of a dense extracellular matrix observed during electron microscopy. Cells of the novel isolate are spherical, motile and divide by binary fission. Strain Pan265(T) is mesophilic (temperature optimum 30–33 °C), neutrophilic (pH optimum 7.0–8.0), aerobic and heterotrophic. The strain has a genome size of 3.49 Mb and a DNA G + C content of 63.9%. Phylogenetically, the strain belongs to the family Phycisphaeraceae, order Phycisphaerales, class Phycisphaerae. Our polyphasic analysis supports the delineation of strain Pan265(T) from the known genera in this family. Therefore, we conclude to assign strain Pan265(T) to a novel species within a novel genus, for which we propose the name Mucisphaera calidilacus gen. nov., sp. nov. The novel species is the type species of the novel genus and is represented by strain Pan265(T) (= DSM 100697(T) = CECT 30425(T)) as type strain

Calycomorphotria hydatis gen. nov., sp. nov., a novel species in the family Planctomycetaceae with conspicuous subcellular structures

A novel strain belonging to the family Planctomycetaceae, designated V22$^{T}$, was isolated from sediment of a seawater fish tank in Braunschweig, Germany. The isolate forms pink colonies on solid medium and displays common characteristics of planctomycetal strains, such as division by budding, formation of rosettes, a condensed nucleoid and presence of crateriform structures and fimbriae. Unusual invaginations of the cytoplasmic membrane and filamentous putative cytoskeletal elements were observed in thin sections analysed by transmission electron microscopy. Strain V22$^{T}$ is an aerobic heterotroph showing optimal growth at 30 °C and pH 8.5. During laboratory cultivations, strain V22$^{T}$ reached generation times of 10 h (maximal growth rate of 0.069 h$^{-1}$). Its genome has a size of 5.2 Mb and a G + C content of 54.9%. Phylogenetically, the strain represents a novel genus and species in the family Planctomycetaceae, order Planctomycetales, class Planctomycetia. We propose the name Calycomorphotria hydatis gen. nov., sp. nov. for the novel taxon, represented by the type strain V22$^{T}$ (DSM 29767$^{T}$ = LMG 29080$^{T}$)

Rosistilla oblonga gen. nov., sp. nov. and Rosistilla carotiformis sp. nov., isolated from biotic or abiotic surfaces in Northern Germany, Mallorca, Spain and California, USA

Planctomycetes are ubiquitous bacteria with fascinating cell biological features. Strains available as axenic cultures in most cases have been isolated from aquatic environments and serve as a basis to study planctomycetal cell biology and interactions in further detail. As a contribution to the current collection of axenic cultures, here we characterise three closely related strains, Poly24$^{T}$, CA51$^{T}$ and Mal33, which were isolated from the Baltic Sea, the Pacific Ocean and the Mediterranean Sea, respectively. The strains display cell biological features typical for related Planctomycetes, such as division by polar budding, presence of crateriform structures and formation of rosettes. Optimal growth was observed at temperatures of 30–33 °C and at pH 7.5, which led to maximal growth rates of 0.065–0.079 h$^{-1}$, corresponding to generation times of 9–11 h. The genomes of the novel isolates have a size of 7.3–7.5 Mb and a G + C content of 57.7–58.2%. Phylogenetic analyses place the strains in the family Pirellulaceae and suggest that Roseimaritima ulvae and Roseimaritima sediminicola are the current closest relatives. Analysis of five different phylogenetic markers, however, supports the delineation of the strains from members of the genus Roseimaritima and other characterised genera in the family. Supported by morphological and physiological differences, we conclude that the strains belong to the novel genus Rosistilla gen. nov. and constitute two novel species, for which we propose the names Rosistilla carotiformis sp. nov. and Rosistilla oblonga sp. nov. (the type species). The two novel species are represented by the type strains Poly24$^{T}$ (= DSM 102938$^{T}$ = VKM B-3434$^{T}$ = LMG 31347$^{T}$ = CECT 9848$^{T}$) and CA51$^{T}$ (= DSM 104080$^{T}$ = LMG 29702$^{T}$), respectively

The Microbiome of Posidonia oceanica Seagrass Leaves Can Be Dominated by Planctomycetes

Seagrass meadows are ubiquitous, fragile and endangered marine habitats, which serve as fish breeding grounds, stabilize ocean floor substrates, retain nutrients and serve as important carbon sinks, counteracting climate change. In the Mediterranean Sea, seagrass meadows are mostly formed by the slow-growing endemic plant Posidonia oceanica (Neptune grass), which is endangered by global warming and recreational motorboating. Despite its importance, surprisingly little is known about the leaf surface microbiome of P. oceanica. Using amplicon sequencing, we here show that species belonging to the phylum Planctomycetes can dominate the biofilms of young and aged P. oceanica leaves. Application of selective cultivation techniques allowed for the isolation of two novel planctomycetal strains belonging to two yet uncharacterized genera