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1.  Genome-scale data suggest reclassifications in the Leisingera-Phaeobacter cluster including proposals for Sedimentitalea gen. nov. and Pseudophaeobacter gen. nov. 
Earlier phylogenetic analyses of the marine Rhodobacteraceae (class Alphaproteobacteria) genera Leisingera and Phaeobacter indicated that neither genus might be monophyletic. We here used phylogenetic reconstruction from genome-scale data, MALDI-TOF mass-spectrometry analysis and a re-assessment of the phenotypic data from the literature to settle this matter, aiming at a reclassification of the two genera. Neither Phaeobacter nor Leisingera formed a clade in any of the phylogenetic analyses conducted. Rather, smaller monophyletic assemblages emerged, which were phenotypically more homogeneous, too. We thus propose the reclassification of Leisingera nanhaiensis as the type species of a new genus as Sedimentitalea nanhaiensis gen. nov., comb. nov., the reclassification of Phaeobacter arcticus and Phaeobacter leonis as Pseudophaeobacter arcticus gen. nov., comb. nov. and Pseudophaeobacter leonis comb. nov., and the reclassification of Phaeobacter aquaemixtae, Phaeobacter caeruleus, and Phaeobacter daeponensis as Leisingera aquaemixtae comb. nov., Leisingera caerulea comb. nov., and Leisingera daeponensis comb. nov. The genera Phaeobacter and Leisingera are accordingly emended.
PMCID: PMC4127530  PMID: 25157246
marine microbiology; Roseobacter group; phylogenomics; supermatrix; gene content; genus boundaries
2.  Genome sequence of the Thermotoga thermarum type strain (LA3T) from an African solfataric spring 
Standards in Genomic Sciences  2014;9(3):1105-1117.
Thermotoga thermarum Windberger et al. 1989 is a member to the genomically well characterized genus Thermotoga in the phylum ‘Thermotogae’. T. thermarum is of interest for its origin from a continental solfataric spring vs. predominantly marine oil reservoirs of other members of the genus. The genome of strain LA3T also provides fresh data for the phylogenomic positioning of the (hyper-)thermophilic bacteria. T. thermarum strain LA3T is the fourth sequenced genome of a type strain from the genus Thermotoga, and the sixth in the family Thermotogaceae to be formally described in a publication. Phylogenetic analyses do not reveal significant discrepancies between the current classification of the group, 16S rRNA gene data and whole-genome sequences. Nevertheless, T. thermarum significantly differs from other Thermotoga species regarding its iron-sulfur cluster synthesis, as it contains only a minimal set of the necessary proteins. Here we describe the features of this organism, together with the complete genome sequence and annotation. The 2,039,943 bp long chromosome with its 2,015 protein-coding and 51 RNA genes is a part of the Genomic Encyclopedia of Bacteria and Archaea project.
PMCID: PMC4148951  PMID: 25197486
anaerobic; motile; thermophilic; chemoorganotrophic; solfataric spring; outer sheath-like structure; Thermotogaceae; GEBA
3.  Complete genome sequence of the Phaeobacter gallaeciensis type strain CIP 105210T (= DSM 26640T = BS107T) 
Standards in Genomic Sciences  2014;9(3):914-932.
Phaeobacter gallaeciensis CIP 105210T (= DSM 26640T = BS107T) is the type strain of the species Phaeobacter gallaeciensis. The genus Phaeobacter belongs to the marine Roseobacter group (Rhodobacteraceae, Alphaproteobacteria). Phaeobacter species are effective colonizers of marine surfaces, including frequent associations with eukaryotes. Strain BS107T was isolated from a rearing of the scallop Pecten maximus. Here we describe the features of this organism, together with the complete genome sequence, comprising eight circular replicons with a total of 4,448 genes. In addition to a high number of extrachromosomal replicons, the genome contains six genomic island and three putative prophage regions, as well as a hybrid between a plasmid and a circular phage. Phylogenomic analyses confirm previous results, which indicated that the originally reported P. gallaeciensis type-strain deposit DSM 17395 belongs to P. inhibens and that CIP 105210T (= DSM 26640T) is the sole genome-sequenced representative of P. gallaeciensis.
PMCID: PMC4148982  PMID: 25197473
Alphaproteobacteria; Roseobacter group; Plasmid wealth; Replication systems; Sister species; Phaeobacter inhibens
4.  Complete genome sequence of the halophilic bacterium Spirochaeta africana type strain (Z-7692T) from the alkaline Lake Magadi in the East African Rift 
Standards in Genomic Sciences  2013;8(2):165-176.
Spirochaeta africana Zhilina et al. 1996 is an anaerobic, aerotolerant, spiral-shaped bacterium that is motile via periplasmic flagella. The type strain of the species, Z-7692T, was isolated in 1993 or earlier from a bacterial bloom in the brine under the trona layer in a shallow lagoon of the alkaline equatorial Lake Magadi in Kenya. Here we describe the features of this organism, together with the complete genome sequence, and annotation. Considering the pending reclassification of S. caldaria to the genus Treponema, S. africana is only the second 'true' member of the genus Spirochaeta with a genome-sequenced type strain to be published. The 3,285,855 bp long genome of strain Z-7692T with its 2,817 protein-coding and 57 RNA genes is a part of the G enomic E ncyclopedia of B acteria and A rchaea project.
PMCID: PMC3746417  PMID: 23991249
anaerobic; aerotolerant; mesophilic; halophilic; spiral-shaped; motile; periplasmic flagella; Gram-negative; chemoorganotrophic; Spirochaetaceae; GEBA
5.  Genome sequence of the thermophilic fresh-water bacterium Spirochaeta caldaria type strain (H1T), reclassification of Spirochaeta caldaria, Spirochaeta stenostrepta, and Spirochaeta zuelzerae in the genus Treponema as Treponema caldaria comb. nov., Treponema stenostrepta comb. nov., and Treponema zuelzerae comb. nov., and emendation of the genus Treponema 
Standards in Genomic Sciences  2013;8(1):88-105.
Spirochaeta caldaria Pohlschroeder et al. 1995 is an obligately anaerobic, spiral-shaped bacterium that is motile via periplasmic flagella. The type strain, H1T, was isolated in 1990 from cyanobacterial mat samples collected at a freshwater hot spring in Oregon, USA, and is of interest because it enhances the degradation of cellulose when grown in co-culture with Clostridium thermocellum. Here we provide a taxonomic re-evaluation for S. caldaria based on phylogenetic analyses of 16S rRNA sequences and whole genomes, and propose the reclassification of S. caldaria and two other Spirochaeta species as members of the emended genus Treponema. Whereas genera such as Borrelia and Sphaerochaeta possess well-distinguished genomic features related to their divergent lifestyles, the physiological and functional genomic characteristics of Spirochaeta and Treponema appear to be intermixed and are of little taxonomic value. The 3,239,340 bp long genome of strain H1T with its 2,869 protein-coding and 59 RNA genes is a part of the Genomic Encyclopedia of Bacteria and Archaea project.
PMCID: PMC3739177  PMID: 23961314
obligately anaerobic; thermophilic; spiral-shaped; motile; periplasmic flagella; Gram-negative; chemoorganotrophic; Spirochaetaceae; Spirochaeta; Treponema; GEBA
6.  Complete genome sequence of the termite hindgut bacterium Spirochaeta coccoides type strain (SPN1T), reclassification in the genus Sphaerochaeta as Sphaerochaeta coccoides comb. nov. and emendations of the family Spirochaetaceae and the genus Sphaerochaeta 
Standards in Genomic Sciences  2012;6(2):194-209.
Spirochaeta coccoides Dröge et al. 2006 is a member of the genus Spirochaeta Ehrenberg 1835, one of the oldest named genera within the Bacteria. S. coccoides is an obligately anaerobic, Gram-negative, non-motile, spherical bacterium that was isolated from the hindgut contents of the termite Neotermes castaneus. The species is of interest because it may play an important role in the digestion of breakdown products from cellulose and hemicellulose in the termite gut. Here we provide a taxonomic re-evaluation for strain SPN1T, and based on physiological and genomic characteristics, we propose its reclassification as a novel species in the genus Sphaerochaeta, a recently published sister group of the Spirochaeta. The 2,227,296 bp long genome of strain SPN1T with its 1,866 protein-coding and 58 RNA genes is a part of the Genomic Encyclopedia of Bacteria and Archaea project.
PMCID: PMC3388779  PMID: 22768363
obligately anaerobic; non-motile; termite hindgut; Gram-negative; di- and oligosaccharide-degrading; mesophilic; chemoorganotrophic; Spirochaetaceae; Sphaerochaeta; GEBA
7.  Codivergence of Mycoviruses with Their Hosts 
PLoS ONE  2011;6(7):e22252.
The associations between pathogens and their hosts are complex and can result from any combination of evolutionary events such as codivergence, switching, and duplication of the pathogen. Mycoviruses are RNA viruses which infect fungi and for which natural vectors are so far unknown. Thus, lateral transfer might be improbable and codivergence their dominant mode of evolution. Accordingly, mycoviruses are a suitable target for statistical tests of virus-host codivergence, but inference of mycovirus phylogenies might be difficult because of low sequence similarity even within families.
We analyzed here the evolutionary dynamics of all mycovirus families by comparing virus and host phylogenies. Additionally, we assessed the sensitivity of the co-phylogenetic tests to the settings for inferring virus trees from their genome sequences and approximate, taxonomy-based host trees.
While sequence alignment filtering modes affected branch support, the overall results of the co-phylogenetic tests were significantly influenced only by the number of viruses sampled per family. The trees of the two largest families, Partitiviridae and Totiviridae, were significantly more similar to those of their hosts than expected by chance, and most individual host-virus links had a significant positive impact on the global fit, indicating that codivergence is the dominant mode of virus diversification. However, in this regard mycoviruses did not differ from closely related viruses sampled from non-fungus hosts. The remaining virus families were either dominated by other evolutionary modes or lacked an apparent overall pattern. As this negative result might be caused by insufficient taxon sampling, the most parsimonious hypothesis still is that host-parasite evolution is basically the same in all mycovirus families. This is the first study of mycovirus-host codivergence, and the results shed light not only on how mycovirus biology affects their co-phylogenetic relationships, but also on their presumable host range itself.
PMCID: PMC3146478  PMID: 21829452
8.  Novel Insights into the Diversity of Catabolic Metabolism from Ten Haloarchaeal Genomes 
PLoS ONE  2011;6(5):e20237.
The extremely halophilic archaea are present worldwide in saline environments and have important biotechnological applications. Ten complete genomes of haloarchaea are now available, providing an opportunity for comparative analysis.
Methodology/Principal Findings
We report here the comparative analysis of five newly sequenced haloarchaeal genomes with five previously published ones. Whole genome trees based on protein sequences provide strong support for deep relationships between the ten organisms. Using a soft clustering approach, we identified 887 protein clusters present in all halophiles. Of these core clusters, 112 are not found in any other archaea and therefore constitute the haloarchaeal signature. Four of the halophiles were isolated from water, and four were isolated from soil or sediment. Although there are few habitat-specific clusters, the soil/sediment halophiles tend to have greater capacity for polysaccharide degradation, siderophore synthesis, and cell wall modification. Halorhabdus utahensis and Haloterrigena turkmenica encode over forty glycosyl hydrolases each, and may be capable of breaking down naturally occurring complex carbohydrates. H. utahensis is specialized for growth on carbohydrates and has few amino acid degradation pathways. It uses the non-oxidative pentose phosphate pathway instead of the oxidative pathway, giving it more flexibility in the metabolism of pentoses.
These new genomes expand our understanding of haloarchaeal catabolic pathways, providing a basis for further experimental analysis, especially with regard to carbohydrate metabolism. Halophilic glycosyl hydrolases for use in biofuel production are more likely to be found in halophiles isolated from soil or sediment.
PMCID: PMC3102087  PMID: 21633497
9.  The Genome Sequence of Methanohalophilus mahii SLPT Reveals Differences in the Energy Metabolism among Members of the Methanosarcinaceae Inhabiting Freshwater and Saline Environments 
Archaea  2010;2010:690737.
Methanohalophilus mahii is the type species of the genus Methanohalophilus, which currently comprises three distinct species with validly published names. Mhp. mahii represents moderately halophilic methanogenic archaea with a strictly methylotrophic metabolism. The type strain SLPT was isolated from hypersaline sediments collected from the southern arm of Great Salt Lake, Utah. Here we describe the features of this organism, together with the complete genome sequence and annotation. The 2,012,424 bp genome is a single replicon with 2032 protein-coding and 63 RNA genes and part of the Genomic Encyclopedia of Bacteria and Archaea project. A comparison of the reconstructed energy metabolism in the halophilic species Mhp. mahii with other representatives of the Methanosarcinaceae reveals some interesting differences to freshwater species.
PMCID: PMC3017947  PMID: 21234345

Results 1-9 (9)