Complete genome sequence of Planctomyces brasiliensis type strain (DSM 5305(T)), phylogenomic analysis and reclassification of Planctomycetes including the descriptions of Gimesia gen. nov., Planctopirus gen. nov. and Rubinisphaera gen. nov. and emended descriptions of the order Planctomycetales and the family Planctomycetaceae

Stratiformator vulcanicus gen. nov., sp. nov., a marine member of the family Planctomycetaceae isolated from a red biofilm in the Tyrrhenian Sea close to the volcanic island Panarea

A novel planctomycetal strain, designated Pan189T, was isolated from biofilm material sampled close to Panarea Island in the Tyrrhenian Sea. Cells of strain Pan189T are round grain rice-shaped, form pink colonies and display typical planctomycetal characteristics including asymmetric cell division through polar budding and presence of crateriform structures. Cells bear a stalk opposite to the division pole and fimbriae cover the cell surface. Strain Pan189T has a mesophilic (optimum at 24 °C) and neutrophilic (optimum at pH 7.5) growth profile, is aerobic and heterotrophic. Under laboratory-scale cultivation conditions, it reached a generation time of 102 h (µmax = 0.0068 h-1), which places the strain among the slowest growing members of the phylum Planctomycetota characterized so far. The genome size of the strain is with 5.23 Mb at the lower limit among the family Planctomycetaceae (5.1-8.9 Mb). Phylogenetically, the strain represents a novel genus and species in the family Planctomycetaceae, order Planctomycetales, class Planctomycetia. We propose the name Stratiformator vulcanicus gen. nov., sp. nov. for the novel taxon, that is represented by the type strain Pan189T (= DSM 101711 T = CECT 30699 T).

Dissipation kinetics of chlorpyrifos and 3,5,6 trichloro-2-pyridinol under vegetation of different aromatic grasses: Linkage with enzyme kinetics and microbial community of soil

The dissipation of chlorpyrifos (CP) and its hydrolytic metabolite 3,5,6-trichloro-2-pyridinol (TCP) in the soil is crucial for safe agriculture. However, there is still lacking relevant information about its dissipation under different vegetation for remediation purposes. In the present study, evaluation of dissipation of CP and TCP in non-planted and planted soil with different cultivars of three types of aromatic grass viz Cymbopogon martinii (Roxb. Wats), Cymbopogon flexuosus, and Chrysopogon zizaniodes (L.) Nash was examined in light of soil enzyme kinetics, microbial communities, and root exudation. Results revealed that the dissipation of CP was well-fitted into a single first-order exponential model (SFO). A significant reduction in the half-life (DT₅₀) of CP was observed in planted soil (30-63 days) than in non-planted soil (95 days). The presence of TCP in all soil samples was observed. The three types of the inhibitory effect of CP i.e. linear mixed inhibition (increase in enzyme-substrate affinity (Km) and decrease in enzyme pool (Vmax), un-competitive inhibition (decrease in Km and Vmax), and simple competitive inhibition were observed on soil enzymes involved in mineralization of carbon, nitrogen, phosphorus, and sulfur. The improvement in the enzyme pool (Vmax) was observed in planted soil. Streptomyces, Clostridium, Kaistobacter, Planctomyces, and Bacillus were the dominant genera in CP stress soil. CP contamination in soil demonstrated a reduction of richness in microbial diversity and enhancement of functional gene family related to cellular process, metabolism, genetic, and environmental information processing. Among all the cultivars, C. flexuosus cultivars demonstrated a higher dissipation rate of CP along with more root exudation.

Metagenomics and metatranscriptomics reveal broadly distributed, active, novel methanotrophs in the Gulf of Mexico hypoxic zone and in the marine water column

The northern Gulf of Mexico (nGOM) hypoxic zone is a shallow water environment where methane, a potent greenhouse gas, fluxes from sediments to bottom water and remains trapped due to summertime stratification. When the water column is destratified, an active planktonic methanotrophic community could mitigate the efflux of methane, which accumulates to high concentrations, to the atmosphere. To investigate the possibility of such a biofilter in the nGOM hypoxic zone we performed metagenome assembly, and metagenomic and metatranscriptomic read mapping. Methane monooxygenase (pmoA) was an abundant transcript, yet few canonical methanotrophs have been reported in this environment, suggesting a role for non-canonical methanotrophs. To determine the identity of these methanotrophs, we reconstructed six novel metagenome-assembled genomes (MAGs) in the Planctomycetota, Verrucomicrobiota and one putative Latescibacterota, each with at least one pmoA gene copy. Based on ribosomal protein phylogeny, closely related microbes (mostly from Tara Oceans) and isolate genomes were selected and co-analyzed with the nGOM MAGs. Gene annotation and read mapping suggested that there is a large, diverse and unrecognized community of active aerobic methanotrophs in the nGOM hypoxic zone and in the global ocean that could mitigate methane flux to the atmosphere.

Rubinisphaera margarita sp. nov., a novel planctomycete isolated from marine sediments collected in the Portuguese north coast

The phylum Planctomycetota is constituted by bacteria with unique features that are well adapted to a vast range of habitats. Here, we describe a novel planctomycete isolated from marine sediments collected on a beach in Matosinhos (Portugal) using an iChip-based culturing technique. Strain ICM_H10T forms beige-coloured colonies in modified M14 medium and its cells are spherical to ovoid in shape, stalked, rosette-forming and showing motility in a phase of the life cycle. Transmission electron microscopy observations showed a typical planctomycetal cell plan and cell division by budding. This strain requires salt for growth and grows in the range of 2.0–5.0 % (w/v) NaCl, from 20 to 37 °C, within a pH of 6.0–9.0 and is able to use diverse nitrogen and carbon sources. It is heterotrophic, aerobic and capable of microaerobic growth. This strain has a genome size of approximately 6.0 Mb and a G+C content of 58.1 mol%. A 16S rRNA gene-based phylogenetic analysis supports the association of strain ICM_H10T to the phylum Planctomycetota and the family Planctomycetaceae , as it shares only 96.8 and 96.4% similarity to its closest relatives Rubinisphaera italica Pan54T and Rubinisphaera brasiliensis IFAM 1448T, respectively. Other phylogenetic markers also support the separation of this strain into a novel species. Morphological, physiological and genomic comparisons between strain ICM_H10T and its closest relatives strongly suggest that ICM_H10T represents a new species of the genus Rubinisphaera , for which we propose the name Rubinisphaera margarita sp. nov., with ICM_H10T (=CECT 30326T=LMG 32234T) as type strain.

Alienimonas californiensis gen. nov. sp. nov., a novel Planctomycete isolated from the kelp forest in Monterey Bay

Planctomycetes are environmentally and biotechnologically important bacteria and are often found in association with nutrient-rich (marine) surfaces. To allow a more comprehensive understanding of planctomycetal lifestyle and physiology we aimed at expanding the collection of axenic cultures with new isolates. Here, we describe the isolation and genomic and physiological characterisation of strain CA12T obtained from giant bladder kelp (Macrocystis pyrifera) in Monterey Bay, California, USA. 16S rRNA gene sequence and whole genome-based phylogenetic analysis showed that strain CA12T clusters within the family Planctomycetaceae and that it has a high 16S rRNA sequence similarity (82.3%) to Planctomicrobium piriforme DSM 26348T. The genome of strain CA12T has a length of 5,475,215 bp and a G+C content of 70.1%. The highest growth rates were observed at 27 °C and pH 7.5. Using different microscopic methods, we could show that CA12T is able to divide by consecutive polar budding, without completing a characteristic planctomycetal lifestyle switch. Based on our data, we suggest that the isolated strain represents a novel species within a novel genus. We thus propose the name Alienimonas gen. nov. with Alienimonas californiensis sp. nov. as type species of the novel genus and CA12T as type strain of the novel species.

Additions to the genus Gimesia: description of Gimesia alba sp. nov., Gimesia algae sp. nov., Gimesia aquarii sp. nov., Gimesia aquatilis sp. nov., Gimesia fumaroli sp. nov. and Gimesia panareensis sp. nov., isolated from aquatic habitats of the Northern Hemisphere

Thirteen novel planctomycetal strains were isolated from five different aquatic sampling locations. These comprise the hydrothermal vent system close to Panarea Island (Italy), a biofilm on the surface of kelp at Monterey Bay (CA, USA), sediment and algae on Mallorca Island (Spain) and Helgoland Island (Germany), as well as a seawater aquarium in Braunschweig, Germany. All strains were shown to belong to the genus Gimesia. Their genomes cover a size range from 7.22 to 8.29 Mb and have a G+C content between 45.1 and 53.7%. All strains are mesophilic (Topt 26-33 °C) with generation times between 12 and 32 h. Analysis of fatty acids yielded palmitic acid (16:0) and a fatty acid with the equivalent chain length of 15.817 as major compounds. While five of the novel strains belong to the already described species Gimesia maris and Gimesia chilikensis, the other strains belong to novel species, for which we propose the names Gimesia alba (type strain Pan241wT = DSM 100744T = LMG 31345T = CECT 9841T = VKM B-3430T), Gimesia algae (type strain Pan161T = CECT 30192T = STH00943T = LMG 29130T), Gimesia aquarii (type strain V144T = DSM 101710T = VKM B-3433T), Gimesia fumaroli (type strain Enr17T = DSM 100710T = VKM B-3429T) and Gimesia panareensis (type strain Enr10T = DSM 100416T = LMG 29082T). STH numbers refer to the Jena Microbial Resource Collection (JMRC).

Maioricimonas rarisocia gen. nov., sp. nov., a novel planctomycete isolated from marine sediments close to Mallorca Island

Planctomycetes are ubiquitous bacteria with environmental and biotechnological relevance. Axenic cultures of planctomycetal strains are the basis to analyse their unusual biology and largely uncharacterised metabolism in more detail. Here, we describe strain Mal4T isolated from marine sediments close to Palma de Mallorca, Spain. Strain Mal4T displays common planctomycetal features, such as division by polar budding and the presence of fimbriae and crateriform structures on the cell surface. Cell growth was observed at ranges of 10-39 °C (optimum at 31 °C) and pH 6.5-9.0 (optimum at 7.5). The novel strain shows as pear-shaped cells of 2.0 ± 0.2 × 1.4 ± 0.1 µm and is one of the rare examples of orange colony-forming Planctomycetes. Its genome has a size of 7.7 Mb with a G+C content of 63.4%. Phylogenetically, we conclude that strain Mal4T (= DSM 100296T = LMG 29133T) is the type strain representing the type species of a novel genus, for which we propose the name Maioricimonas rarisocia gen. nov., sp. nov.

Rubinisphaera italica sp. nov. isolated from a hydrothermal area in the Tyrrhenian Sea close to the volcanic island Panarea

Planctomycetes is a fascinating phylum of mostly aquatic bacteria, not only due to the environmental importance in global carbon and nitrogen cycles, but also because of a unique cell biology. Their lifestyle and metabolic capabilities are not well explored, which motivated us to study the role of Planctomycetes in biofilms on marine biotic surfaces. Here, we describe the novel strain Pan54T which was isolated from algae in a hydrothermal area close to the volcanic island Panarea in the Tyrrhenian Sea, north of Sicily in Italy. The strain grew best at pH 9.0 and 26 °C and showed typical characteristics of planctomycetal bacteria, e.g. division by polar budding, formation of aggregates and presence of stalks and crateriform structures. Phylogenetically, the strain belongs to the genus Rubinisphaera. Our analysis suggests that Pan54T represents a novel species of this genus, for which we propose the name Rubinisphaera italica sp. nov. We suggest Pan54T (= DSM 29369 = LMG 29789) as the type strain of the novel species.

Three Planctomycetes isolated from biotic surfaces in the Mediterranean Sea and the Pacific Ocean constitute the novel species Symmachiella dynata gen. nov., sp. nov. and Symmachiella macrocystis sp. nov

Planctomycetes is a phylum of environmentally important bacteria, which also receive significant attention due to their fascinating cell biology. Access to axenic Planctomycete cultures is crucial to study cell biological features within this phylum in further detail. In this study, we characterise three novel strains, Mal52T, Pan258 and CA54T, which were isolated close to the coasts of the islands Mallorca (Spain) and Panarea (Italy), and from Monterey Bay, CA, USA. The three isolates show optimal growth at temperatures between 22 and 24 °C and at pH 7.5, divide by polar budding, lack pigmentation and form strong aggregates in liquid culture. Analysis of five phylogenetic markers suggests that the strains constitute two novel species within a novel genus in the family Planctomycetaceae. The strains Mal52T (DSM 101177T = VKM B-3432T) and Pan258 were assigned to the species Symmachiella dynata gen nov., sp. nov., while strain CA54T (DSM 104301T = VKM B-3450T) forms a separate species of the same genus, for which we propose the name Symmachiella macrocystis sp. nov.

Planctomycetes as Host-Associated Bacteria: A Perspective That Holds Promise for Their Future Isolations, by Mimicking Their Native Environmental Niches in Clinical Microbiology Laboratories

Traditionally recognized as environmental bacteria, Planctomycetes have just been linked recently to human pathology as opportunistic pathogens, arousing a great interest for clinical microbiologists. However, the lack of appropriate culture media limits our future investigations as no Planctomycetes have ever been isolated from patients' specimens despite several attempts. Several Planctomycetes have no cultivable members and are only recognized by 16S rRNA gene sequence detection and analysis. The cultured representatives are slow-growing fastidious bacteria and mostly difficult to culture on synthetic media. Accordingly, the provision of environmental and nutritional conditions like those existing in the natural habitat where yet uncultured/refractory bacteria can be detected might be an option for their potential isolation. Hence, we systematically reviewed the various natural habitats of Planctomycetes, to review their nutritional requirements, the physicochemical characteristics of their natural ecological niches, current methods of cultivation of the Planctomycetes and gaps, from a perspective of collecting data in order to optimize conditions and the protocols of cultivation of these fastidious bacteria. Planctomycetes are widespread in freshwater, seawater, and terrestrial environments, essentially associated to particles or organisms like macroalgae, marine sponges, and lichens, depending on the species and metabolizable polysaccharides by their sulfatases. Most Planctomycetes grow in nutrient-poor oligotrophic environments with pH ranging from 3.4 to 11, but a few strains can also grow in quite nutrient rich media like M600/M14. Also, a seasonality variation of abundance is observed, and bloom occurs in summer-early autumn, correlating with the strong growth of algae in the marine environments. Most Planctomycetes are mesophilic, but with a few Planctomycetes being thermophilic (50°C to 60°C). Commonly added nutrients are N-acetyl-glucosamine, yeast-extracts, peptone, and some oligo and macro-elements. A biphasic host-associated extract (macroalgae, sponge extract) conjugated with a diluted basal medium should provide favorable results for the success of isolation in pure culture.

Gimesia benthica sp. nov., a planctomycete isolated from a deep-sea water sample of the Northwest Indian Ocean

A Gram-stain-negative, stalked, oval-shaped and budding bacterial strain, designated E7^T, was isolated from a deep-sea water sample collected from the Northwest Indian Ocean. The novel strain was strictly aerobic, and catalase- and oxidase-positive. It grew at 6-40 °C (optimum 30 °C) and pH 5.5-8.0 (optimum pH 7.0-7.5). The strain required 0.5-9.0 % (w/v) NaCl (optimum 3.0-5.0 %) for growth. Aesculin, starch, pectin and Tween 20 were hydrolysed. Based on 16S rRNA gene sequence analysis, strain E7^T showed the highest similarity with Gimesia maris DSM 8797^T (97.5 %). The average nucleotide identity and in silico DNA-DNA hybridization values between strain E7^T and G. maris DSM 8797^T were 78.0 and 19.3 %, respectively. The predominant cellular fatty acids of strain E7^T were C_16 : 0 and summed feature 3 (comprising C_16 : 1ω7c and/or C_16 : 1ω6c). The major respiratory quinone was menaquinone-6 (MK-6) and the major polar lipids were phosphatidylethanolamine (PE), phosphatidylmonomethylethanolamine (PMME), phosphatidyldimethylethanolamine (PDME), phosphatidylcholine (PC) and diphosphatidylglycerol (DPG). The genomic DNA G+C content of strain E7^T was 52.8 mol%. On the basis of phylogenetic inference and phenotypic characteristics, it is proposed that strain E7^T represents a novel species of the genus Gimesia, for which the name Gimesia benthica sp. nov. is proposed. The type strain is E7^T (=CGMCC 1.16119^T=KCTC 72737^T).

S, Uppada J, Ch. S, Ch.V. R. Gimesia chilikensis sp. nov., a haloalkali-tolerant planctomycete isolated from Chilika lagoon and emended description of the genus Gimesia

A Gram-stain-negative, aerobic, non-motile, salt- and alkali-tolerant, pear to oval shaped, rosette-forming, white coloured, bacterium, designated as strain JC646T, was isolated from a sediment sample collected from Chilika lagoon, India. Strain JC646T reproduced through budding, grew well at up to pH 9.0 and tolerated up to 7 % NaCl. Strain JC 646T utilized α-d-glucose, fumarate, lactose, sucrose, fructose, d-galactose, mannose, maltose and d-xylose as carbon sources. Peptone, l-isoleucine, l-serine, l-lysine, l-glutamic acid, l-aspartic acid, dl-threonine and l-glycine were used by the strain as nitrogen sources for growth. The respiratory quinone was MK6. Major fatty acids were C16 : 1 ω7c/C16 : 1 ω6c and C16 : 0. The polar lipids of strain JC646T comprised phosphatidyl-dimethylethanolamine, phosphatidylcholine, diphosphatidylglycerol, an unidentified amino lipid and two unidentified lipids. Strain JC646T had highest (97.3 %) 16S rRNA gene sequence identity to the only species of the genus Gimesia , Gimesia maris DSM 8797T. The genome of strain JC646T was 7.64 Mbp with a DNA G+C content of 53.2 mol%. For the resolution of the phylogenetic congruence of the novel strain, the phylogeny was also reconstructed with the sequences of 92 housekeeping genes. Based on phylogenetic analyses, digital DNA–DNA hybridization (19.0 %), genome average nucleotide identity (74.5 %) and average amino acid identity/percentageof conserved proteins (77 %) results, chemotaxonomic characteristics, and differential physiological properties, strain JC646T is recognized as representing a new species of the genus Gimesia , for which we propose the name Gimesia chilikensis sp. nov. The type strain is JC646T (=KCTC 72175T=NBRC 113881T).

Limnoglobus roseus gen. nov., sp. nov., a novel freshwater planctomycete with a giant genome from the family Gemmataceae

The family Gemmataceae accommodates aerobic, chemoorganotrophic planctomycetes, which inhabit various freshwater ecosystems, wetlands and soils. Here, we describe a novel member of this family, strain PX52T, which was isolated from a boreal eutrophic lake in Northern Russia. This isolate formed pink-pigmented colonies and was represented by spherical cells that occurred singly, in pairs or aggregates and multiplied by budding. Daughter cells were highly motile. PX52T was an obligate aerobic chemoorganotroph, which utilized various sugars and some heteropolysaccharides. Growth occurred at pH 5.0-7.5 (optimum pH 6.5) and at temperatures between 10 and 30 °C (optimum 20-25 °C). The major fatty acids were C18 : 1ɷ7c, C18 : 0 and βOH-C16:0; the major intact polar lipid was trimethylornithine, and the quinone was MK-6. The complete genome of PX52T was 9.38 Mb in size and contained nearly 8000 potential protein-coding genes. Among those were genes encoding a wide repertoire of carbohydrate-active enzymes (CAZymes) including 33 glycoside hydrolases (GH) and 87 glycosyltransferases (GT) affiliated with 17 and 12 CAZy families, respectively. DNA G+C content was 65.6 mol%. PX52T displayed only 86.0-89.8 % 16S rRNA gene sequence similarity to taxonomically described Gemmataceae planctomycetes and differed from them by a number of phenotypic characteristics and by fatty acid composition. We, therefore, propose to classify it as representing a novel genus and species, Limnoglobus roseus gen. nov., sp. nov. The type strain is strain PX52T (=KCTC 72397T=VKM B-3275T).

Pink- and orange-pigmented Planctomycetes produce saproxanthin-type carotenoids including a rare C45 carotenoid

Planctomycetes are ubiquitous and environmentally important Gram-negative aquatic bacteria with key roles in global carbon and nitrogen cycles. Many planctomycetal species have a pink or orange colour and have been suggested to produce carotenoids. Potential applications as food colorants or anti-oxidants have been proposed. Hitherto, the planctomycetal metabolism is largely unexplored and the strain pigmentation has not been explored. For a holistic view of the complex planctomycetal physiology, we analysed carotenoid profiles of the pink-pigmented strain Rhodopirellula rubra LF2^T and of the orange strain Rubinisphaera brasiliensis Gr7. During LC-MS/MS analysis of culture extracts, we could identify three saproxanthin-type carotenoids including a rare C₄₅ carotenoid. These compounds, saproxanthin, dehydroflexixanthin and 2'-isopentenyldehydrosaproxanthin, derive from the common carotenoid precursor lycopene and are characterized by related end groups, namely a 3-hydroxylated β-carotene-like cyclohexene ring as one end group and simple hydration on the other end of the molecule. Based on the observed molecule structure we present putative pathways for their biosynthesis. Results support Planctomycetes as a promising, yet mostly untapped source of carotenoids.

Effects of water recirculation rate on the microbial community and water quality in relation to the growth and survival of white shrimp (Litopenaeus vannamei)

Background

Microbial community and its management are crucial to the stabilization of culture environment for recirculating aquaculture system (RAS). Although several studies have been carried out for the microbial community of RAS, few studies were on the RAS for shrimp. Water recirculation ratio is an important factor for the microbial community and the management of RAS. Therefore, low (LC), medium (MC) and high (HC) recirculation ratio systems were set to explore the microbial community constitution of RAS for Litopenaeus vannamei and study the effect of water recirculation rate on it.

Results

The bacterial community of bioreactor was mainly dominated by Proteobacteria (41.6–70.7%), followed with Planctomycetes (12.5–31.0%), Bacteroidetes (10.5–26.0%), Actinobacteria (1.1–4.8%) and Verrucomicrobia (1.4–6.8%) phylum. The most dominant family of bioreactor was Rhodobacteraceae or Planctomycetaceae. The bacterial community of culture water was simpler than bioreactor and dominated by Proteobacteria (61.8–96.4%). The dominant bacterial groups of bioreactor and culture water are also different among the three water recirculation rates, and the proportions of dominant groups showed a trend with the variety of water recirculation rate. Water quality indexes including ammonia and nitrite decreased with the increasing of water recirculation rate. According to the growth performance of L. vannamei, shrimp had better performance of growth rate and final weight in MC and HC, however, shrimp had higher survival and yield in LC. Shrimp survival and yield had an inverse correlation with water recirculation rate.

Conclusions

The results demonstrate the microbial community of RAS for shrimp, highlight the importance of further studies on the function of bacterial taxa, and promote the understanding of the effects of water recirculation rate on the microbiota. The findings suggest that water recirculation rate has important impacts on the microbial community, water quality and shrimp growth. Increasing the water recirculation rate could improve the water quality and promote the growth of shrimp. However, the survival rate and yield of L. vannamei are higher under low water recirculation rate. Recirculation rate is an effective method to manage RAS, and its impact on RAS needs further study, especially in the application of low level of water recirculation.

Genome-based classification of micromonosporae with a focus on their biotechnological and ecological potential

There is a need to clarify relationships within the actinobacterial genus Micromonospora, the type genus of the family Micromonosporaceae, given its biotechnological and ecological importance. Here, draft genomes of 40 Micromonospora type strains and two non-type strains are made available through the Genomic Encyclopedia of Bacteria and Archaea project and used to generate a phylogenomic tree which showed they could be assigned to well supported phyletic lines that were not evident in corresponding trees based on single and concatenated sequences of conserved genes. DNA G+C ratios derived from genome sequences showed that corresponding data from species descriptions were imprecise. Emended descriptions include precise base composition data and approximate genome sizes of the type strains. antiSMASH analyses of the draft genomes show that micromonosporae have a previously unrealised potential to synthesize novel specialized metabolites. Close to one thousand biosynthetic gene clusters were detected, including NRPS, PKS, terpenes and siderophores clusters that were discontinuously distributed thereby opening up the prospect of prioritising gifted strains for natural product discovery. The distribution of key stress related genes provide an insight into how micromonosporae adapt to key environmental variables. Genes associated with plant interactions highlight the potential use of micromonosporae in agriculture and biotechnology.

Sustained Bauxite Residue Rehabilitation with Gypsum and Organic Matter 16 years after Initial Treatment

Bauxite residue is a high volume byproduct of alumina manufacture which is commonly disposed of in purpose-built bauxite residue disposal areas (BRDAs). Natural waters interacting with bauxite residue are characteristically highly alkaline, and have elevated concentrations of Na, Al, and other trace metals. Rehabilitation of BRDAs is therefore often costly and resource/infrastructure intensive. Data is presented from three neighboring plots of bauxite residue that was deposited 20 years ago. One plot was amended 16 years ago with process sand, organic matter, gypsum, and seeded (fully treated), another plot was amended 16 years ago with process sand, organic matter, and seeded (partially treated), and a third plot was left untreated. These surface treatments lower alkalinity and salinity, and thus produce a substrate more suitable for biological colonisation from seeding. The reduction of pH leads to much lower Al, V, and As mobility in the actively treated residue and the beneficial effects of treatment extend passively 20-30 cm below the depth of the original amendment. These positive rehabilitation effects are maintained after 2 decades due to the presence of an active and resilient biological community. This treatment may provide a lower cost solution to BRDA end of use closure plans and orphaned BRDA rehabilitation.

Draft genome sequences of Bradyrhizobium shewense sp. nov. ERR11T and Bradyrhizobium yuanmingense CCBAU 10071T

The type strain of the prospective 10.1601/nm.30737 sp. nov. ERR11^T, was isolated from a nodule of the leguminous tree Erythrina brucei native to Ethiopia. The type strain 10.1601/nm.1463 10.1601/strainfinder?urlappend=%3Fid%3DCCBAU+10071 ^T, was isolated from the nodules of Lespedeza cuneata in Beijing, China. The genomes of ERR11^T and 10.1601/strainfinder?urlappend=%3Fid%3DCCBAU+10071 ^T were sequenced by DOE-JGI and deposited at the DOE-JGI genome portal as well as at the European Nucleotide Archive. The genome of ERR11^T is 9,163,226 bp in length and has 102 scaffolds, containing 8548 protein-coding and 86 RNA genes. The 10.1601/strainfinder?urlappend=%3Fid%3DCCBAU+10071 ^T genome is arranged in 108 scaffolds and consists of 8,201,522 bp long and 7776 protein-coding and 85 RNA genes. Both genomes contain symbiotic genes, which are homologous to the genes found in the complete genome sequence of 10.1601/nm.24498 10.1601/strainfinder?urlappend=%3Fid%3DUSDA+110 ^T. The genes encoding for nodulation and nitrogen fixation in ERR11^T showed high sequence similarity with homologous genes found in the draft genome of peanut-nodulating 10.1601/nm.27386 10.1601/strainfinder?urlappend=%3Fid%3DLMG+26795 ^T. The nodulation genes nolYA-nodD2D1YABCSUIJ-nolO-nodZ of ERR11^T and 10.1601/strainfinder?urlappend=%3Fid%3DCCBAU+10071 ^T are organized in a similar way to the homologous genes identified in the genomes of 10.1601/strainfinder?urlappend=%3Fid%3DUSDA+110 ^T, 10.1601/nm.25806 10.1601/strainfinder?urlappend=%3Fid%3DUSDA+4 and 10.1601/nm.1462 10.1601/strainfinder?urlappend=%3Fid%3DCCBAU+05525. The genomes harbor hupSLCFHK and hypBFDE genes that code the expression of hydrogenase, an enzyme that helps rhizobia to uptake hydrogen released by the N₂-fixation process and genes encoding denitrification functions napEDABC and norCBQD for nitrate and nitric oxide reduction, respectively. The genome of ERR11^T also contains nosRZDFYLX genes encoding nitrous oxide reductase. Based on multilocus sequence analysis of housekeeping genes, the novel species, which contains eight strains formed a unique group close to the 10.1601/nm.25806 branch. Genome Average Nucleotide Identity (ANI) calculated between the genome sequences of ERR11^T and closely related sequences revealed that strains belonging to 10.1601/nm.25806 branch (10.1601/strainfinder?urlappend=%3Fid%3DUSDA+4 and 10.1601/strainfinder?urlappend=%3Fid%3DCCBAU+15615), were the closest strains to the strain ERR11^T with 95.2% ANI. Type strain ERR11^T showed the highest DDH predicted value with 10.1601/strainfinder?urlappend=%3Fid%3DCCBAU+15615 (58.5%), followed by 10.1601/strainfinder?urlappend=%3Fid%3DUSDA+4 (53.1%). Nevertheless, the ANI and DDH values obtained between ERR11^T and 10.1601/strainfinder?urlappend=%3Fid%3DCCBAU+15615 or 10.1601/strainfinder?urlappend=%3Fid%3DUSDA+4 were below the cutoff values (ANI ≥ 96.5%; DDH ≥ 70%) for strains belonging to the same species, suggesting that ERR11^T is a new species. Therefore, based on the phylogenetic analysis, ANI and DDH values, we formally propose the creation of 10.1601/nm.30737 sp. nov. with strain ERR11^T (10.1601/strainfinder?urlappend=%3Fid%3DHAMBI+3532 ^T=10.1601/strainfinder?urlappend=%3Fid%3DLMG+30162 ^T) as the type strain.

Tuwongella immobilis gen. nov., sp. nov., a novel non-motile bacterium within the phylum Planctomycetes

A gram-negative, budding, catalase negative, oxidase positive and non-motile bacterium (MBLW1^T) with a complex endomembrane system has been isolated from a freshwater lake in southeast Queensland, Australia. Phylogeny based on 16S rRNA gene sequence analysis places the strain within the family Planctomycetaceae, related to Zavarzinella formosa (93.3 %), Telmatocola sphagniphila (93.3 %) and Gemmata obscuriglobus (91.9 %). Phenotypic and chemotaxonomic analysis demonstrates considerable differences to the type strains of the related genera. MBLW1^T displays modest salt tolerance and grows optimally at pH values of 7.5–8.0 and at temperatures of 32–36 °C. Transmission electron microscopy analysis demonstrates the presence of a complex endomembrane system, however, without the typically condensed nucleoid structure found in related genera. The major fatty acids are 16 : 1 ω5c, 16 : 0 and 18 : 0. Based on discriminatory results from 16S rRNA gene sequence analysis, phenotypic, biochemical and chemotaxonomic analysis, MBLW1^T should be considered as a new genus and species, for which the name Tuwongella immobilis gen. nov., sp. nov. is proposed. The type strain is MBLW1^T (=CCUG 69661^T=DSM 105045^T).

Tundrisphaera lichenicola gen. nov., sp. nov., a psychrotolerant representative of the family Isosphaeraceae from lichen-dominated tundra soils

Two strains of aerobic, budding, pink-pigmented bacteria, P12T and P515, were isolated from a lichen-dominated peatland and a forested tundra soil of north-western Siberia, respectively. Cells of these isolates were represented by non-motile spheres that occurred singly or were arranged in short chains and aggregates. While growing on solid media, cells of strains P12T and P515 attached to the surface by means of holdfast-like appendages. These isolates were mildly acidophilic (optimum growth at pH 5.5-6.0), psychrotolerant bacteria, which displayed tolerance of low temperatures (4-15 °C), grew optimally at 15-22 °C and did not grow at temperatures above 28 °C. The preferred growth substrates were sugars and some heteropolysaccharides. The major fatty acids were C18 : 1ω9c, C16 : 0 and C14 : 0. Trimethylornithine lipid was the major polar lipid. The only quinone was MK-6, and the G+C content of the DNA was 61.2-62.2 mol%. Strains P12T and P515 possessed identical 16S rRNA gene sequences, which affiliated them with the family Isosphaeraceae, order Planctomycetales, and these displayed the highest similarity (93-94 %) to 16S rRNA gene sequences from members of the genus Singulisphaera. However, the signature fatty acid of species of the genus Singulisphaera, i.e. C18 : 2ω6c,12c, was absent in cells of strains P12T and P515. They also differed from members of the genus Singulisphaera by substrate utilization pattern and a number of physiological characteristics. Based on these data, the novel isolates should be considered as representing a novel genus and species of planctomycetes, for which the name Tundrisphaera lichenicola gen. nov., sp. nov, is proposed. The type strain is P12T (=LMG 29571T=VKM B-3044T).

Fimbriiglobus ruber gen. nov., sp. nov., a Gemmata-like planctomycete from Sphagnum peat bog and the proposal of Gemmataceae fam. nov

An aerobic, budding, dark pink to red-pigmented bacterium was isolated from an acidic boreal Sphagnum peat bog and designated strain SP5T. Cells of this strain were non-motile spheres that were uniformly covered with crateriform pits and fimbria, and tended to form aggregates during growth in liquid media. Strain SP5T was capable of growth between pH 4.0 and pH 6.8 (optimum at pH 5.5-6.0) and at temperatures between 10 and 30 °C (optimum at 20-25 °C). The preferred growth substrates were sugars and some heteropolysaccharides. The major fatty acids were C20 : 1ω9c, C16 : 1ω9c and C16 : 0, and the major polar lipid was trimethylornithine. Cells contained also significant amounts of bound (ω-1)OH-C30 : 1 fatty acid. The quinone was menaquinone-6, and the G+C content of the DNA was 60.7 mol%. Strain SP5T was a member of the order Planctomycetales and belonged to the phylogenetic lineage defined by the genus Gemmata. It displayed 88 and 89 % 16S rRNA gene sequence similarity to Gemmata obscuriglobusUQM 2246T and 'Gemmata massiliana' IIL30, 89 % to Zavarzinella formosa A10T and 86 % to Telmatocola sphagniphila SP2T. However, strain SP5T differed from members of these genera by cell morphology, substrate utilization pattern and fatty acid composition. Based on these data, the novel isolate should be considered as representing a novel species of a new genus of planctomycetes, for which the name Fimbriiglobus ruber gen. nov., sp. nov, is proposed. The type strain is SP5T (=LMG 29572T=VKM B-3045T). We also suggest the establishment of a novel family, Gemmataceaefam. nov., which includes the phylogenetically related genera Gemmata, Zavarzinella, Telmatocola and Fimbriiglobus.

Comparative Genomics of Four Isosphaeraceae Planctomycetes: A Common Pool of Plasmids and Glycoside Hydrolase Genes Shared by Paludisphaera borealis PX4T, Isosphaera pallida IS1BT, Singulisphaera acidiphila DSM 18658T, and Strain SH-PL62

The family Isosphaeraceae accommodates stalk-free planctomycetes with spherical cells, which can be assembled in short chains, long filaments, or aggregates. These bacteria inhabit a wide variety of terrestrial environments, among those the recently described Paludisphaera borealis PX4T that was isolated from acidic boreal wetlands. Here, we analyzed its finished genome in comparison to those of three other members of the Isosphaeraceae: Isosphaera pallida IS1BT, Singulisphaera acidiphila DSM 18658T, and the uncharacterized planctomycete strain SH-PL62. The complete genome of P. borealis PX4T consists of a 7.5 Mb chromosome and two plasmids, 112 and 43 kb in size. Annotation of the genome sequence revealed 5802 potential protein-coding genes of which 2775 could be functionally assigned. The genes encoding metabolic pathways common for chemo-organotrophic bacteria, such as glycolysis, citrate cycle, pentose-phosphate pathway, and oxidative phosphorylation were identified. Several genes involved in the synthesis of peptidoglycan as well as N-methylated ornithine lipids were present in the genome of P. borealis PX4T. A total of 26 giant genes with a size >5 kb were detected. The genome encodes a wide repertoire of carbohydrate-active enzymes (CAZymes) including 44 glycoside hydrolases (GH) and 83 glycosyltransferases (GT) affiliated with 21 and 13 CAZy families, respectively. The most-represented families are GH5, GH13, GH57, GT2, GT4, and GT83. The experimentally determined carbohydrate utilization pattern agrees well with the genome-predicted capabilities. The CAZyme repertoire in P. borealis PX4T is highly similar to that in the uncharacterized planctomycete SH-PL62 and S. acidiphila DSM 18658T, but different to that in the thermophile I. pallida IS1BT. The latter strain has a strongly reduced CAZyme content. In P. borealis PX4T, many of its CAZyme genes are organized in clusters. Contrary to most other members of the order Planctomycetales, all four analyzed Isosphaeraceae planctomycetes have plasmids in numbers varying from one to four. The plasmids from P. borealis PX4T display synteny to plasmids from other family members, providing evidence for their common evolutionary origin.

Combined iron and sulfate reduction biostimulation as a novel approach to enhance BTEX and PAH source-zone biodegradation in biodiesel blend-contaminated groundwater

The use of biodiesel as a transportation fuel and its growing mandatory blending percentage in diesel increase the likelihood of contaminating groundwater with diesel/biodiesel blends. A 100L-field experiment with B20 (20% biodiesel and 80% diesel, v/v) was conducted to assess the potential for the combined biostimulation of iron and sulfate reducing bacteria to enhance BTEX and PAH biodegradation in a diesel/biodiesel blend-contaminated groundwater. A B20 field experiment under monitored natural attenuation (MNA) was used as a baseline control. Ammonium acetate and a low-cost and sustainable product recovered from acid mine drainage treatment were used to stimulate iron and sulfate-reducing conditions. As a result, benzene and naphthalene concentrations (maximum concentrations were 28.1μgL^-1 and 10.0μgL^-1, respectively) remained lower than the MNA experiment (maximum concentrations were 974.7μgL^-1 and 121.3μgL^-1, respectively) over the whole experiment. Geochemical changes were chronologically consistent with the temporal change of the predominance of Geobacter and GOUTA19 which might be the key players responsible for the rapid attenuation of benzene and naphthalene. To the best of our knowledge, this is the first field experiment to demonstrate the potential for the combined iron and sulfate biostimulation to enhance B20 source-zone biodegradation.

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 NH11^T, 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 NH11^T shares only 80% sequence identity with the closest relative of both genera, Rhodopirellula and Pirellula. Thus, strain NH11^T is unique in terms of origin and phylogeny. While the pear to ovoid shaped cells of strain NH11^T 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 NH11^T was unusually enlarged and differed from previously known planctomycetes. The complete genome of strain NH11^T, 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 NH11^T. 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 NH11^T from other cultivated Planctomycetes of the same phylogenetic cluster. Thus, based on our findings, we propose to classify strain NH11^T as Fuerstia marisgermanicae gen. nov., sp. nov., with the type strain NH11^T, within the phylum Planctomycetes.

Genome-Based Taxonomic Classification of Bacteroidetes

The bacterial phylum Bacteroidetes, characterized by a distinct gliding motility, occurs in a broad variety of ecosystems, habitats, life styles, and physiologies. Accordingly, taxonomic classification of the phylum, based on a limited number of features, proved difficult and controversial in the past, for example, when decisions were based on unresolved phylogenetic trees of the 16S rRNA gene sequence. Here we use a large collection of type-strain genomes from Bacteroidetes and closely related phyla for assessing their taxonomy based on the principles of phylogenetic classification and trees inferred from genome-scale data. No significant conflict between 16S rRNA gene and whole-genome phylogenetic analysis is found, whereas many but not all of the involved taxa are supported as monophyletic groups, particularly in the genome-scale trees. Phenotypic and phylogenomic features support the separation of Balneolaceae as new phylum Balneolaeota from Rhodothermaeota and of Saprospiraceae as new class Saprospiria from Chitinophagia. Epilithonimonas is nested within the older genus Chryseobacterium and without significant phenotypic differences; thus merging the two genera is proposed. Similarly, Vitellibacter is proposed to be included in Aequorivita. Flexibacter is confirmed as being heterogeneous and dissected, yielding six distinct genera. Hallella seregens is a later heterotypic synonym of Prevotella dentalis. Compared to values directly calculated from genome sequences, the G+C content mentioned in many species descriptions is too imprecise; moreover, corrected G+C content values have a significantly better fit to the phylogeny. Corresponding emendations of species descriptions are provided where necessary. Whereas most observed conflict with the current classification of Bacteroidetes is already visible in 16S rRNA gene trees, as expected whole-genome phylogenies are much better resolved.

Methylophaga and Hyphomicrobium can be used as target genera in monitoring saline water methanol-utilizing denitrification

Which bacterial taxonomic groups can be used in monitoring saline water methanol-utilizing denitrification and whether nitrate is transformed into N2 in the process are unclear. Therefore, methylotrophic bacterial communities of two efficiently functioning (nitrate/nitrite reduction was 63–96 %) tropical and cool seawater reactors at a public aquarium were investigated with clone library analysis and 454 pyrosequencing of the 16S rRNA genes. Transformation of nitrate into N2 was confirmed using 15N labeling in incubation of carrier material from the tropical reactor. Combining the data with previous study results, Methylophaga and Hyphomicrobium were determined to be suitable target genera for monitoring the function of saline water methanol-fed denitrification systems. However, monitoring was not possible at the single species level. Interestingly, potential nitrate-reducing methylotrophs within Filomicrobium and closely related Fil I and Fil II clusters were detected in the reactors suggesting that they also contributed to methylotrophic denitrification in the saline environment.

Comparative genomics of biotechnologically important yeasts

Ascomycete yeasts are metabolically diverse, with great potential for biotechnology. Here, we report the comparative genome analysis of 29 taxonomically and biotechnologically important yeasts, including 16 newly sequenced. We identify a genetic code change, CUG-Ala, in Pachysolen tannophilus in the clade sister to the known CUG-Ser clade. Our well-resolved yeast phylogeny shows that some traits, such as methylotrophy, are restricted to single clades, whereas others, such as l-rhamnose utilization, have patchy phylogenetic distributions. Gene clusters, with variable organization and distribution, encode many pathways of interest. Genomics can predict some biochemical traits precisely, but the genomic basis of others, such as xylose utilization, remains unresolved. Our data also provide insight into early evolution of ascomycetes. We document the loss of H3K9me2/3 heterochromatin, the origin of ascomycete mating-type switching, and panascomycete synteny at the MAT locus. These data and analyses will facilitate the engineering of efficient biosynthetic and degradative pathways and gateways for genomic manipulation.

Comparison of the compatible solute pool of two slightly halophilic planctomycetes species, Gimesia maris and Rubinisphaera brasiliensis

Gimesia maris and Rubinisphaera brasiliensis are slightly halophilic representatives of the deep-branching phylum Planctomycetes. For osmoadaptation both species accumulated α-glutamate, sucrose, ectoine and hydroxyectoine. A major role was found for ectoine, hydroxyectoine as well as sucrose under hyper-osmotic shock conditions. Nevertheless, the levels of sucrose were up-regulated by the increased salinity levels and also by low nitrogen availability. Additionally, G. maris accumulated glucosylglycerate (GG) as major solute specifically under low nitrogen levels, which prompted us to analyse the transcript abundance of two homologues genes known for the biosynthesis of GG, namely glucosyl-3-phosphoglycerate synthase (GpgS) and glucosyl-3-phosphoglycerate phosphatase (GpgP). By qPCR using a suitable reference gene selected in this study, the transcript abundance of the biosynthetic genes was quantified in G. maris cells under hyper-osmotic shock or under low nitrogen conditions. The gpgS gene was induced under nitrogen-limiting conditions suggesting that GG synthesis is regulated primarily at the transcription level. Moreover, the expression of a gene coding for a putative sucrose-phosphorylase (Spase) located upstream the gpgS and gpgP genes was up-regulated, predicting a metabolic role of Spase probably related to GG synthesis.

Global and Targeted Lipid Analysis of Gemmata obscuriglobus Reveals the Presence of Lipopolysaccharide, a Signature of the Classical Gram-Negative Outer Membrane

Planctomycete bacteria possess many unusual cellular properties, contributing to a cell plan long considered to be unique among the bacteria. However, data from recent studies are more consistent with a modified Gram-negative cell plan. A key feature of the Gram-negative plan is the presence of an outer membrane (OM), for which lipopolysaccharide (LPS) is a signature molecule. Despite genomic evidence for an OM in planctomycetes, no biochemical verification has been reported. We attempted to detect and characterize LPS in the planctomycete Gemmata obscuriglobus. We obtained direct evidence for LPS and lipid A using electrophoresis and differential staining. Gas chromatography-mass spectrometry (GC-MS) compositional analysis of LPS extracts identified eight different 3-hydroxy fatty acids (3-HOFAs), 2-keto 3-deoxy-d-manno-octulosonic acid (Kdo), glucosamine, and hexose and heptose sugars, a chemical profile unique to Gram-negative LPS. Combined with molecular/structural information collected from matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) MS analysis of putative intact lipid A, these data led us to propose a heterogeneous hexa-acylated lipid A structure (multiple-lipid A species). We also confirmed previous reports of G. obscuriglobus whole-cell fatty acid (FA) and sterol compositions and detected a novel polyunsaturated FA (PUFA). Our confirmation of LPS, and by implication an OM, in G. obscuriglobus raises the possibility that other planctomycetes possess an OM. The pursuit of this question, together with studies of the structural connections between planctomycete LPS and peptidoglycans, will shed more light on what appears to be a planctomycete variation on the Gram-negative cell plan.

IMPORTANCE

Bacterial species are classified as Gram positive or negative based on their cell envelope structure. For 25 years, the envelope of planctomycete bacteria has been considered a unique exception, as it lacks peptidoglycan and an outer membrane (OM). However, the very recent detection of peptidoglycan in planctomycete species has provided evidence for a more conventional cell wall and raised questions about other elements of the cell envelope. Here, we report direct evidence of lipopolysaccharide in the planctomycete G. obscuriglobus, suggesting the presence of an OM and supporting the proposal that the planctomycete cell envelope is an extension of the canonical Gram-negative plan. This interpretation features a convoluted cytoplasmic membrane and expanded periplasmic space, the functions of which provide an intriguing avenue for future investigation.

Paludisphaera borealis gen. nov., sp. nov., a hydrolytic planctomycete from northern wetlands, and proposal of Isosphaeraceae fam. nov

Two isolates of aerobic, budding, pink-pigmented bacteria, designated strains PX4^T and PT1, were isolated from a boreal Sphagnum peat bog and a forested tundra wetland. Cells of these strains were non-motile spheres that occurred singly or in short chains. Novel isolates were capable of growth at pH values between 3.5 and 6.5 (optimum at pH 5.0-5.5) and at temperatures between 6 and 30 °C (optimum at 15-25 °C). Most sugars and a number of polysaccharides including pectin, xylan, lichenin and Phytagel were used as growth substrates. The major fatty acids were C_16 : 0, C_18 : 1ω9 and C_18 : 0; the major polar lipids were phosphocholine and trimethylornithine. The quinone was menaquinone-6, and the G+C content of the DNA was 66 mol%. Strains PX4^T and PT1 were members of the order Planctomycetales and displayed 93-94 % 16S rRNA gene sequence similarity to Aquisphaera giovannonii, 91-92 % to species of the genus Singulisphaera and 90-91 % to Isosphaera pallida. The two novel strains, however, differed from members of these genera by cell morphology, substrate utilization pattern and a number of physiological characteristics. Based on these data, the novel isolates should be considered as representing a novel genus and species of planctomycetes, for which the name Paludisphaera borealis gen. nov., sp. nov., is proposed. The type strain is PX4^T ( = DSM 28747^T = VKM B-2904^T). We also suggest the establishment of a novel family, Isosphaeraceae fam. nov., to accommodate stalk-free planctomycetes with spherical cells, which can be assembled in short chains, long filaments or shapeless aggregates. This family includes the genera Isosphaera, Aquisphaera, Singulisphaera and Paludisphaera.

A taxonomic framework for emerging groups of ecologically important marine gammaproteobacteria based on the reconstruction of evolutionary relationships using genome-scale data

In recent years a large number of isolates were obtained from saline environments that are phylogenetically related to distinct clades of oligotrophic marine gammaproteobacteria, which were originally identified in seawater samples using cultivation independent methods and are characterized by high seasonal abundances in coastal environments. To date a sound taxonomic framework for the classification of these ecologically important isolates and related species in accordance with their evolutionary relationships is missing. In this study we demonstrate that a reliable allocation of members of the oligotrophic marine gammaproteobacteria (OMG) group and related species to higher taxonomic ranks is possible by phylogenetic analyses of whole proteomes but also of the RNA polymerase beta subunit, whereas phylogenetic reconstructions based on 16S rRNA genes alone resulted in unstable tree topologies with only insignificant bootstrap support. The identified clades could be correlated with distinct phenotypic traits illustrating an adaptation to common environmental factors in their evolutionary history. Genome wide gene-content analyses revealed the existence of two distinct ecological guilds within the analyzed lineage of marine gammaproteobacteria which can be distinguished by their trophic strategies. Based on our results a novel order within the class Gammaproteobacteria is proposed, which is designated Cellvibrionales ord. nov. and comprises the five novel families Cellvibrionaceae fam. nov., Halieaceae fam. nov., Microbulbiferaceae fam. nov., Porticoccaceae fam. nov., and Spongiibacteraceae fam. nov.