The gender gap in names of prokaryotes honouring persons.

The aim of this study is to analyse prokaryotic names which honour persons, eponyms, from a gender perspective. Data were retrieved from the List of Prokaryotic names with Standing in Nomenclature. Excluding new combinations, the etymologies of 23 315 unique names at the rank of genus, species and subspecies were analysed. A total of 2018 (8.7 %) names honour persons (eponyms), for which the development of the female share over time was further investigated. Women started to be honoured very recently (1947) compared to men (1823). Moreover, only 14.8 % of all prokaryotic eponyms refer to females. This ratio has hardly improved since 1947, although the number of women whose contributions to microbiology could have been recognized has increased over time. In contrast, about 50 % of prokaryotic names derived from mythological characters refer to females. To reduce this gender gap, we encourage authors proposing new taxon names to honour female scientists who can serve as role models for new generations.

Ongoing diversification of the global fish pathogen Piscirickettsia salmonis through genetic isolation and transposition bursts.

The management of bacterial pathogens remains a key challenge of aquaculture. The marine gammaproteobacterium Piscirickettsia salmonis is the etiological agent of piscirickettsiosis and causes multi-systemic infections in different salmon species, resulting in considerable mortality and substantial commercial losses. Here, we elucidate its global diversity, evolution, and selection during human interventions. Our comprehensive analysis of 73 closed, high quality genome sequences covered strains from major outbreaks and was supplemented by an analysis of all P. salmonis 16S rRNA gene sequences and metagenomic reads available in public databases. Genome comparison showed that Piscirickettsia comprises at least three distinct, genetically isolated species of which two showed evidence for continuing speciation. However, at least twice the number of species exist in marine fish or seawater. A hallmark of Piscirickettsia diversification is the unprecedented amount and diversity of transposases which are particularly active in subgroups undergoing rapid speciation and are key to the acquisition of novel genes and to pseudogenization. Several group-specific genes are involved in surface antigen synthesis and may explain the differences in virulence between strains. However, the frequent failure of antibiotic treatment of piscirickettsiosis outbreaks cannot be explained by horizontal acquisition of resistance genes which so far occurred only very rarely. Besides revealing a dynamic diversification of an important pathogen, our study also provides the data for improving its surveillance, predicting the emergence of novel lineages, and adapting aquaculture management, and thereby contributes towards the sustainability of salmon farming.

New Microviridae isolated from Sulfitobacter reveals two cosmopolitan subfamilies of single-stranded DNA phages infecting marine and terrestrial Alphaproteobacteria.

The Microviridae family represents one of the major clades of single-stranded DNA (ssDNA) phages. Their cultivated members are lytic and infect Proteobacteria, Bacteroidetes, and Chlamydiae. Prophages have been predicted in the genomes from Bacteroidales, Hyphomicrobiales, and Enterobacteriaceae and cluster within the 'Alpavirinae', 'Amoyvirinae', and Gokushovirinae. We have isolated 'Ascunsovirus oldenburgi' ICBM5, a novel phage distantly related to known Microviridae. It infects Sulfitobacter dubius SH24-1b and uses both a lytic and a carrier-state life strategy. Using ICBM5 proteins as a query, we uncovered in publicly available resources sixty-five new Microviridae prophages and episomes in bacterial genomes and retrieved forty-seven environmental viral genomes (EVGs) from various viromes. Genome clustering based on protein content and phylogenetic analysis showed that ICBM5, together with Rhizobium phages, new prophages, episomes, and EVGs cluster within two new phylogenetic clades, here tentatively assigned the rank of subfamily and named 'Tainavirinae' and 'Occultatumvirinae'. They both infect Rhodobacterales. Occultatumviruses also infect Hyphomicrobiales, including nitrogen-fixing endosymbionts from cosmopolitan legumes. A biogeographical assessment showed that tainaviruses and occultatumviruses are spread worldwide, in terrestrial and marine environments. The new phage isolated here sheds light onto new and diverse branches of the Microviridae tree, suggesting that much of the ssDNA phage diversity remains in the dark.

Beyond the ABCs-Discovery of Three New Plasmid Types in Rhodobacterales (RepQ, RepY, RepW).

Copiotrophic marine bacteria of the Roseobacter group (Rhodobacterales, Alphaproteobacteria) are characterized by a multipartite genome organization. We sequenced the genomes of Sulfitobacter indolifex DSM 14862T and four related plasmid-rich isolates in order to investigate the composition, distribution, and evolution of their extrachromosomal replicons (ECRs). A combination of long-read PacBio and short-read Illumina sequencing was required to establish complete closed genomes that comprised up to twelve ECRs. The ECRs were differentiated in stably evolving chromids and genuine plasmids. Among the chromids, a diagnostic RepABC-8 replicon was detected in four Sulfitobacter species that likely reflects an evolutionary innovation that originated in their common ancestor. Classification of the ECRs showed that the most abundant plasmid system is RepABC, followed by RepA, DnaA-like, and RepB. However, the strains also contained three novel plasmid types that were designated RepQ, RepY, and RepW. We confirmed the functionality of their replicases, investigated the genetic inventory of the mostly cryptic plasmids, and retraced their evolutionary origin. Remarkably, the RepY plasmid of S. pontiacus DSM 110277 is the first high copy-number plasmid discovered in Rhodobacterales.

Fatal affairs - conjugational transfer of a dinoflagellate-killing plasmid between marine Rhodobacterales.

The roseobacter group of marine bacteria is characterized by a mosaic distribution of ecologically important phenotypes. These are often encoded on mobile extrachromosomal replicons. So far, conjugation had only been experimentally proven between the two model organisms Phaeobacter inhibens and Dinoroseobacter shibae. Here, we show that two large natural RepABC-type plasmids from D. shibae can be transferred into representatives of all known major Rhodobacterales lineages. Complete genome sequencing of the newly established Phaeobacter inhibens transconjugants confirmed their genomic integrity. The conjugated plasmids were stably maintained as single copy number replicons in the genuine as well as the new host. Co-cultivation of Phaeobacter inhibens and the transconjugants with the dinoflagellate Prorocentrum minimum demonstrated that Phaeobacter inhibens is a probiotic strain that improves the yield and stability of the dinoflagellate culture. The transconjugant carrying the 191 kb plasmid, but not the 126 kb sister plasmid, killed the dinoflagellate in co-culture.

High Potential for Secondary Metabolite Production of Paracoccus marcusii CP157, Isolated From the Crustacean Cancer pagurus.

Secondary metabolites are key components in microbial ecology by mediating interactions between bacteria and their environment, neighboring species or host organisms. Bioactivities can be beneficial for both interaction partners or provide a competitive advantage only for the producer. Colonizers of confined habitats such as biofilms are known as prolific producers of a great number of bioactive secondary metabolites and are a potential source for novel compounds. We investigated the strain Paracoccus marcusii CP157, which originates from the biofilm on the carapace of a shell disease-affected Cancer pagurus specimen, for its potential to produce bioactive secondary metabolites. Its closed genome contains 22 extrachromosomal elements and several gene clusters potentially involved in biosynthesis of bioactive polyketides, bacteriocins, and non-ribosomal peptides. Culture extracts of CP157 showed antagonistic activities against bacteria from different phyla, but also against microalgae and crustacean larvae. Different HPLC-fractions of CP157 culture extracts had antibacterial properties, indicating that several bioactive compounds are produced by CP157. The bioactive extract contains several small, antibacterial compounds that partially withstand elevated temperatures, extreme pH values and exposure to proteolytic enzymes, providing high stability toward environmental conditions in the natural habitat of CP157. Further, screening of 17 Paracoccus spp. revealed that antimicrobial activity, hemolysis and production of N-acyl homoserine lactones are common features within the genus. Taking into account the large habitat diversity and phylogenetic distance of the tested strains, we hypothesize that bioactive secondary metabolites play a central role in the ecology of Paracoccus spp. in their natural environments.

RepC_soli: a novel promiscuous plasmid type of Rhodobacteraceae mediates horizontal transfer of antibiotic resistances in the ocean.

Alphaproteobacteria are typically characterized by a multipartite genome organization with a chromosome, stable chromids and accessory plasmids. Extrachromosomal elements determine the lifestyle of roseobacters and their horizontal transfer was previously correlated with rapid adaptations to novel ecological niches. We characterized the distribution and biology of a novel Rhodobacteraceae-specific plasmid type that was designated RepC_soli according to its diagnostic solitary replicase. This low copy number replicon exhibits an exceptional stability, which is likely ensured by non-canonical separate parA and parB partitioning genes. RepC_soli plasmids occur frequently in the surface-associated marine genus Phaeobacter and comparative genome analyses revealed the emergence of four compatibility groups. The universal presence of conserved type IV secretion systems in RepC_soli plasmids is indicative of their recurrent mobilization, a prediction that was experimentally validated by conjugation of the 57 kb Phaeobacter inhibens P72 plasmid (pP72_e) over genus borders. RepC_soli plasmids harbour a diverse collection of beneficial genes including transporters for heavy metal detoxification, prokaryotic defence systems and a conspicuous abundance of antibiotic resistance genes. The pP72_e-encoded efflux pump FloR conferred an about 50-fold increase of resistance against chloramphenicol. Its specific occurrence in Phaeobacter likely reflects a genetic footprint of (former) antimicrobial use in marine aquaculture.

Global Response of Phaeobacter inhibens DSM 17395 to Deletion of Its 262-kb Chromid Encoding Antibiotic Synthesis.

The marine alphaproteobacterium Phaeobacter inhibens DSM 17395, a member of the Roseobacter group, was recently shown to markedly enhance growth upon deletion of its 262-kb chromid encoding biosynthesis of tropodithietic acid (TDA). To scrutinize the metabolic/regulatory adaptations that underlie enhanced growth of the Δ262 mutant, its transcriptome and proteome compared to the wild type were investigated in process-controlled bioreactors with Casamino Acids as growth substrate. Genome resequencing revealed only few additional genetic changes (a heterogenic insertion, prophage activation, and several point mutations) between wild type and Δ262 mutant, albeit with no conceivable effect on the studied growth physiology. The abundances of the vast majority of transcripts and proteins involved in the catabolic network for complete substrate oxidation to CO2 were found to be unchanged, suggesting that the enhanced amino acid utilization of the Δ262 mutant did not require elevated synthesis of most enzymes of the catabolic network. Similarly, constituents of genetic information processing and cellular processes remained mostly unchanged. In contrast, 426 genes displayed differential expression, of which 410 were localized on the 3.2-Mb chromosome, 5 on the 65-kb chromid, and 11 on the 78-kb chromid. Notably, the branched-chain amino transferase IlvE acting on rapidly utilized Val, Ile, and Leu was upregulated. Moreover, the transportome was reconfigured, as evidenced from increased abundances of transcripts and proteins of several uptake systems for amino acids and inorganic nutrients (e.g., phosphate). Some components of the respiratory chain were also upregulated, which correlates with the higher respiration rates of the Δ262 mutant. Furthermore, chromosomally encoded transcripts and proteins that are peripherally related to TDA biosynthesis (e.g., the serine acyl transferase CysE) were strongly downregulated in the Δ262 mutant. Taken together, these observations reflect adaptations to enhanced growth as well as the functional interconnectivity of the replicons of P. inhibens DSM 17395.

Genomic, metabolic and phenotypic variability shapes ecological differentiation and intraspecies interactions of Alteromonas macleodii.

Ecological differentiation between strains of bacterial species is shaped by genomic and metabolic variability. However, connecting genotypes to ecological niches remains a major challenge. Here, we linked bacterial geno- and phenotypes by contextualizing pangenomic, exometabolomic and physiological evidence in twelve strains of the marine bacterium Alteromonas macleodii, illuminating adaptive strategies of carbon metabolism, microbial interactions, cellular communication and iron acquisition. In A. macleodii strain MIT1002, secretion of amino acids and the unique capacity for phenol degradation may promote associations with Prochlorococcus cyanobacteria. Strain 83-1 and three novel Pacific isolates, featuring clonal genomes despite originating from distant locations, have profound abilities for algal polysaccharide utilization but without detrimental implications for Ecklonia macroalgae. Degradation of toluene and xylene, mediated via a plasmid syntenic to terrestrial Pseudomonas, was unique to strain EZ55. Benzoate degradation by strain EC673 related to a chromosomal gene cluster shared with the plasmid of A. mediterranea EC615, underlining that mobile genetic elements drive adaptations. Furthermore, we revealed strain-specific production of siderophores and homoserine lactones, with implications for nutrient acquisition and cellular communication. Phenotypic variability corresponded to different competitiveness in co-culture and geographic distribution, indicating linkages between intraspecific diversity, microbial interactions and biogeography. The finding of "ecological microdiversity" helps understanding the widespread occurrence of A. macleodii and contributes to the interpretation of bacterial niche specialization, population ecology and biogeochemical roles.

Corrigendum: Fuerstia marisgermanicae gen. nov., sp. nov., an Unusual Member of the Phylum Planctomycetes From the German Wadden Sea.

[This corrects the article DOI: 10.3389/fmicb.2016.02079.].

Adaptations of Alteromonas sp. 76-1 to Polysaccharide Degradation: A CAZyme Plasmid for Ulvan Degradation and Two Alginolytic Systems.

Studying the physiology and genomics of cultured hydrolytic bacteria is a valuable approach to decipher the biogeochemical cycling of marine polysaccharides, major nutrients derived from phytoplankton and macroalgae. We herein describe the profound potential of Alteromonas sp. 76-1, isolated from alginate-enriched seawater at the Patagonian continental shelf, to degrade the algal polysaccharides alginate and ulvan. Phylogenetic analyses indicated that strain 76-1 might represent a novel species, distinguished from its closest relative (Alteromonas naphthalenivorans) by adaptations to their contrasting habitats (productive open ocean vs. coastal sediments). Ecological distinction of 76-1 was particularly manifested in the abundance of carbohydrate-active enzymes (CAZymes), consistent with its isolation from alginate-enriched seawater and elevated abundance of a related OTU in the original microcosm. Strain 76-1 encodes multiple alginate lyases from families PL6, PL7, PL17, and PL18 largely contained in two polysaccharide utilization loci (PUL), which may facilitate the utilization of different alginate structures in nature. Notably, ulvan degradation relates to a 126 Kb plasmid dedicated to polysaccharide utilization, encoding several PL24 and PL25 ulvan lyases and monomer-processing genes. This extensive and versatile CAZyme repertoire allowed substantial growth on polysaccharides, showing comparable doubling times with alginate (2 h) and ulvan (3 h) in relation to glucose (3 h). The finding of homologous ulvanolytic systems in distantly related Alteromonas spp. suggests CAZyme plasmids as effective vehicles for PUL transfer that mediate niche gain. Overall, the demonstrated CAZyme repertoire substantiates the role of Alteromonas in marine polysaccharide degradation and how PUL exchange influences the ecophysiology of this ubiquitous marine taxon.

Biphasic cellular adaptations and ecological implications of Alteromonas macleodii degrading a mixture of algal polysaccharides.

Algal polysaccharides are an important bacterial nutrient source and central component of marine food webs. However, cellular and ecological aspects concerning the bacterial degradation of polysaccharide mixtures, as presumably abundant in natural habitats, are poorly understood. Here, we contextualize marine polysaccharide mixtures and their bacterial utilization in several ways using the model bacterium Alteromonas macleodii 83-1, which can degrade multiple algal polysaccharides and contributes to polysaccharide degradation in the oceans. Transcriptomic, proteomic and exometabolomic profiling revealed cellular adaptations of A. macleodii 83-1 when degrading a mix of laminarin, alginate and pectin. Strain 83-1 exhibited substrate prioritization driven by catabolite repression, with initial laminarin utilization followed by simultaneous alginate/pectin utilization. This biphasic phenotype coincided with pronounced shifts in gene expression, protein abundance and metabolite secretion, mainly involving CAZymes/polysaccharide utilization loci but also other functional traits. Distinct temporal changes in exometabolome composition, including the alginate/pectin-specific secretion of pyrroloquinoline quinone, suggest that substrate-dependent adaptations influence chemical interactions within the community. The ecological relevance of cellular adaptations was underlined by molecular evidence that common marine macroalgae, in particular Saccharina and Fucus, release mixtures of alginate and pectin-like rhamnogalacturonan. Moreover, CAZyme microdiversity and the genomic predisposition towards polysaccharide mixtures among Alteromonas spp. suggest polysaccharide-related traits as an ecophysiological factor, potentially relating to distinct 'carbohydrate utilization types' with different ecological strategies. Considering the substantial primary productivity of algae on global scales, these insights contribute to the understanding of bacteria-algae interactions and the remineralization of chemically diverse polysaccharide pools, a key step in marine carbon cycling.

Tritonibacter horizontis gen. nov., sp. nov., a member of the Rhodobacteraceae, isolated from the Deepwater Horizon oil spill.

A heterotrophic, Gram-stain-negative, aerobic, sodium-requiring and motile bacterium was isolated from oil-contaminated surface water of the Gulf of Mexico during the Deepwater Horizon oil spill. Strain O3.65T showed highest 16S rRNA gene sequence similarity to Phaeobacter gallaeciensis BS107T and Phaeobacter inhibens T5T, both with 98.3 %, respectively. Based on complete genome analysis, highest similarity was observed to species of the genus Ruegeria. Strain O3.65T exhibited a broad salinity, temperature and pH range of 0.5-10 % NaCl, 4-45 °C and 5.5-9.0, respectively. The DNA G+C content of strain O3.65T was 61.5 mol%. The major respiratory lipoquinone was ubiquinone-10 (Q-10), the most dominant fatty acids (>1 %) comprised 18 : 1ω7c and 18 : 1ω7c 11-methyl, 10 : 0 3OH, 12 : 1 3OH, 14 : 1 3OH/3-oxo-14 : 0, 16 : 0, 16 : 0 2OH, 18 : 1 2OH and 12 : 1. The polar lipid pattern indicated presence of phosphatidylcholine, phosphatidylglycerol, an unidentified aminolipid, two unidentified phospholipids and seven unidentified lipids. On Difco marine broth agar, strain O3.65T formed smooth, shiny white to beige and convex colonies with regular edges. Phylogenetic, phylogenomic and phenotypic differences revealed that strain O3.65T represents a new species of a novel genus within the family Rhodobacteraceae, for which we propose the name Tritonibacter horizontis gen. nov., sp. nov. The type strain of the type species is O3.65T (=DSM 101689T=LMG 29740T).

Trajectories and Drivers of Genome Evolution in Surface-Associated Marine Phaeobacter.

The extent of genome divergence and the evolutionary events leading to speciation of marine bacteria have mostly been studied for (locally) abundant, free-living groups. The genus Phaeobacter is found on different marine surfaces, seems to occupy geographically disjunct habitats, and is involved in different biotic interactions, and was therefore targeted in the present study. The analysis of the chromosomes of 32 closely related but geographically spread Phaeobacter strains revealed an exceptionally large, highly syntenic core genome. The flexible gene pool is constantly but slightly expanding across all Phaeobacter lineages. The horizontally transferred genes mostly originated from bacteria of the Roseobacter group and horizontal transfer most likely was mediated by gene transfer agents. No evidence for geographic isolation and habitat specificity of the different phylogenomic Phaeobacter clades was detected based on the sources of isolation. In contrast, the functional gene repertoire and physiological traits of different phylogenomic Phaeobacter clades were sufficiently distinct to suggest an adaptation to an associated lifestyle with algae, to additional nutrient sources, or toxic heavy metals. Our study reveals that the evolutionary trajectories of surface-associated marine bacteria can differ significantly from free-living marine bacteria or marine generalists.

Phaeobacter piscinae sp. nov., a species of the Roseobacter group and potential aquaculture probiont.

Four heterotrophic, antimicrobial, motile, marine bacterial strains, 27-4T, 8-1, M6-4.2 and S26, were isolated from aquaculture units in Spain, Denmark and Greece. All four strains produced the antibiotic compound tropodithietic acid, which is a key molecule in their antagonism against fish pathogenic bacteria. Cells of the strains were Gram-reaction-negative, rod-shaped and formed star-shaped aggregates in liquid culture and brown-coloured colonies on marine agar. The predominant cellular fatty acids were C18 : 1ω7c, C16 : 0, C11 methyl C18 : 1ω7c and C16 : 0 2-OH, and the polar lipids comprised phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, an aminolipid, a phospholipid and an unidentified lipid. The strains grew optimally at 31-33 °C. Growth was observed at a salt concentration between 0.5 and 5-6 % NaCl with an optimum at 2-3 %. The pH range for growth of the strains was from pH 6 to 8-8.5 with an optimum at pH 7. Based on 16S rRNA gene sequence analysis, the strains are affiliated with the genus Phaeobacter. The genome sequences of the strains have a DNA G+C content of 60.1 % and share an average nucleotide identity (ANI) of more than 95 %. The four strains are distinct from the type strains of the closely related species Phaeobactergallaeciensis and Phaeobacterinhibens based on an ANI of 90.5-91.7 and 89.6-90.4 %, respectively, and an in silico DNA-DNA hybridization relatedness of 43.9-46.9 and 39.8-41.9 %, respectively. On the basis of phylogenetic analyses as well as phenotypic and chemotaxonomic properties, the isolates are considered to represent a novel species, for which the name Phaeobacter piscinae sp. nov. is proposed. The type strain is 27-4T (=DSM 103509T=LMG 29708T).

Adaptation of Surface-Associated Bacteria to the Open Ocean: A Genomically Distinct Subpopulation of Phaeobacter gallaeciensis Colonizes Pacific Mesozooplankton.

The marine Roseobacter group encompasses numerous species which occupy a large variety of ecological niches. However, members of the genus Phaeobacter are specifically adapted to a surface-associated lifestyle and have so far been found nearly exclusively in disjunct, man-made environments including shellfish and fish aquacultures, as well as harbors. Therefore, the possible natural habitats, dispersal and evolution of Phaeobacter spp. have largely remained obscure. Applying a high-throughput cultivation strategy along a longitudinal Pacific transect, the present study revealed for the first time a widespread natural occurrence of Phaeobacter in the marine pelagial. These bacteria were found to be specifically associated to mesoplankton where they constitute a small but detectable proportion of the bacterial community. The 16S rRNA gene sequences of 18 isolated strains were identical to that of Phaeobacter gallaeciensis DSM26640T but sequences of internal transcribed spacer and selected genomes revealed that the strains form a distinct clade within P. gallaeciensis. The genomes of the Pacific and the aquaculture strains were highly conserved and had a fraction of the core genome of 89.6%, 80 synteny breakpoints, and differed 2.2% in their nucleotide sequences. Diversification likely occurred through neutral mutations. However, the Pacific strains exclusively contained two active Type I restriction modification systems which is commensurate with a reduced acquisition of mobile elements in the Pacific clade. The Pacific clade of P. gallaeciensis also acquired a second, homolog phosphonate transport system compared to all other P. gallaeciensis. Our data indicate that a previously unknown, distinct clade of P. gallaeciensis acquired a limited number of clade-specific genes that were relevant for its association with mesozooplankton and for colonization of the marine pelagial. The divergence of the Pacific clade most likely was driven by the adaptation to this novel ecological niche rather than by geographic isolation.

Phaeobacter porticola sp. nov., an antibiotic-producing bacterium isolated from a sea harbour.

Three heterotrophic, aerobic, brown-pigmented strains, designated P97T, P100 and P104, were isolated from a harbour in the southern North Sea. Phylogenetic analysis of 16S rRNA gene sequences revealed that the isolates are affiliated to the genus Phaeobacter. In silico DNA-DNA hybridization of the genome of strain P97T against those of existing type species indicated that P97T represents a novel species within the genus Phaeobacter, with Phaeobacter inhibens T5T as the closest described organism (29.6 % DNA-DNA relatedness) followed by P. gallaeciensis CIP 105210T (26.4 %). DNA-DNA hybridization demonstrated that the three new strains belong to the same species. The new isolates inhibited Pseudoalteromonas tunicata DSM 14096T, and were Gram-stain-negative, catalase- and oxidase-positive, chemo-organoheterotrophic and motile. Growth occurred at pH 6.5-9.5 (optimum 7.0-8.0) and at 4-30 °C (optimum 20-28 °C). The strains required NaCl for growth. The salinity range was 0.5-6.0 % (w/v) NaCl for P97T and P100, and 0.5-5.0 % for P104, lower than values described for Phaeobacter gallaeciensis and Phaeobacter inhibens. The optimum NaCl concentration for strains P97T and P104 was 2.0-4.0 %, and for P100 was 2.0-3.0 %. Fatty acids (>1 %) comprised 18 : 1ω7c, 16 : 0, 18 : 1 ω7c 11-methyl, 18 : 0, 12 :1, 18 : 2ω7c,12, 10 : 0 3-OH and 12 : 0 3-OH. Polar lipids were phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, an aminolipid, one unknown lipid and one additional unknown lipid in strain P97T. The major respiratory quinone was Q10. Based on phylogenetic and phenotypic differences, the strains represent a novel species in the genus Phaeobacter, for which the name Phaeobacter porticola sp. nov. is proposed. The type strain is P97T (=DSM 103148T=LMG 29594T).

Fuerstia marisgermanicae gen. nov., sp. nov., an Unusual Member of the Phylum Planctomycetes from the German Wadden Sea.

Members of the phylum Planctomycetes are ubiquitous bacteria that dwell in aquatic and terrestrial habitats. While planctomycetal species are important players in the global carbon and nitrogen cycle, this phylum is still undersampled and only few genome sequences are available. Here we describe strain NH11T, a novel planctomycete obtained from a crustacean shell (Wadden Sea, Germany). The phylogenetically closest related cultivated species is Gimesia maris, sharing only 87% 16S rRNA sequence identity. Previous isolation attempts have mostly yielded members of the genus Rhodopirellula from water of the German North Sea. On the other hand, only one axenic culture of the genus Pirellula was obtained from a crustacean thus far. However, the 16S rRNA gene sequence of strain NH11T shares only 80% sequence identity with the closest relative of both genera, Rhodopirellula and Pirellula. Thus, strain NH11T is unique in terms of origin and phylogeny. While the pear to ovoid shaped cells of strain NH11T are typical planctomycetal, light-, and electron microscopic observations point toward an unusual variation of cell division through budding: during the division process daughter- and mother cells are connected by an unseen thin tubular-like structure. Furthermore, the periplasmic space of strain NH11T was unusually enlarged and differed from previously known planctomycetes. The complete genome of strain NH11T, with almost 9 Mb in size, is among the largest planctomycetal genomes sequenced thus far, but harbors only 6645 protein-coding genes. The acquisition of genomic components by horizontal gene transfer is indicated by the presence of numerous putative genomic islands. Strikingly, 45 "giant genes" were found within the genome of NH11T. Subsequent analysis of all available planctomycetal genomes revealed that Planctomycetes as such are especially rich in "giant genes". Furthermore, Multilocus Sequence Analysis (MLSA) tree reconstruction support the phylogenetic distance of strain NH11T from other cultivated Planctomycetes of the same phylogenetic cluster. Thus, based on our findings, we propose to classify strain NH11T as Fuerstia marisgermanicae gen. nov., sp. nov., with the type strain NH11T, within the phylum Planctomycetes.

Draft Genome Sequence of Serratia sp. Strain DD3, Isolated from the Guts of Daphnia magna.

We report the draft genome sequence of Serratia sp. strain DD3, a gammaproteobacterium from the family Enterobacteriaceae. It was isolated from homogenized guts of Daphnia magna. The genome size is 5,274 Mb.

A dietary polyunsaturated fatty acid improves consumer performance during challenge with an opportunistic bacterial pathogen.

A dietary deficiency in polyunsaturated fatty acids (PUFAs) and/or sterols can severely constrain growth and reproduction of invertebrate consumers. Single nutrients are potentially assigned to different physiological processes, for example to support defence mechanisms; therefore, lipid requirements of healthy and pathogen-challenged consumers might differ. In an oral exposure experiment, we explored the effects of dietary PUFAs and cholesterol on growth, reproduction and survival of an aquatic key herbivore (Daphnia magna) exposed to an opportunistic pathogen (Pseudomonas sp.). We show that healthy and pathogen-challenged D. magna are strongly albeit differentially affected by the biochemical composition of their food sources. Supplementation of a C20 PUFA-deficient diet with arachidonic acid (ARA) resulted in increased survival and reproduction of pathogen-challenged D. magna. We propose that the observed benefit of consuming an ARA-rich diet during pathogen challenge is conveyed partially via ARA-derived eicosanoids. This study is one of the first to consider the importance of dietary PUFAs in modifying fitness parameters of pathogen-challenged invertebrate hosts. Our results suggest that dietary PUFA supply should receive increased attention in host-microorganisms interactions and invertebrate disease models to better understand and predict disease dynamics in natural populations.