The complete genome sequence of Thermoproteus tenax: a physiologically versatile member of the Crenarchaeota.

Here, we report on the complete genome sequence of the hyperthermophilic Crenarchaeum Thermoproteus tenax (strain Kra1, DSM 2078(T)) a type strain of the crenarchaeotal order Thermoproteales. Its circular 1.84-megabase genome harbors no extrachromosomal elements and 2,051 open reading frames are identified, covering 90.6% of the complete sequence, which represents a high coding density. Derived from the gene content, T. tenax is a representative member of the Crenarchaeota. The organism is strictly anaerobic and sulfur-dependent with optimal growth at 86°C and pH 5.6. One particular feature is the great metabolic versatility, which is not accompanied by a distinct increase of genome size or information density as compared to other Crenarchaeota. T. tenax is able to grow chemolithoautotrophically (CO2/H2) as well as chemoorganoheterotrophically in presence of various organic substrates. All pathways for synthesizing the 20 proteinogenic amino acids are present. In addition, two presumably complete gene sets for NADH:quinone oxidoreductase (complex I) were identified in the genome and there is evidence that either NADH or reduced ferredoxin might serve as electron donor. Beside the typical archaeal A0A1-ATP synthase, a membrane-bound pyrophosphatase is found, which might contribute to energy conservation. Surprisingly, all genes required for dissimilatory sulfate reduction are present, which is confirmed by growth experiments. Mentionable is furthermore, the presence of two proteins (ParA family ATPase, actin-like protein) that might be involved in cell division in Thermoproteales, where the ESCRT system is absent, and of genes involved in genetic competence (DprA, ComF) that is so far unique within Archaea.

Kroppenstedtia eburnea gen. nov., sp. nov., a thermoactinomycete isolated by environmental screening, and emended description of the family Thermoactinomycetaceae Matsuo et al. 2006 emend. Yassin et al. 2009.

A Gram-positive, spore-forming, aerobic, filamentous bacterium, strain JFMB-ATE(T), was isolated in 2008 during environmental screening of a plastic surface in grade C in a contract manufacturing organization in southern Germany. The isolate grew at temperatures of 25-50 °C and at pH 5.0-8.5, forming ivory-coloured colonies with sparse white aerial mycelia. Chemotaxonomic and molecular characteristics of the isolate matched those described for members of the family Thermoactinomycetaceae, except that the cell-wall peptidoglycan contained LL-diaminopimelic acid, while all previously described members of this family display this diagnostic diamino acid in meso-conformation. The DNA G+C content of the novel strain was 54.6 mol%, the main polar lipids were diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylglycerol, and the major menaquinone was MK-7. The major fatty acids had saturated C14-C16 branched chains. No diagnostic sugars were detected. Based on the chemotaxonomic results and 16S rRNA gene sequence analysis, the isolate is proposed to represent a novel genus and species, Kroppenstedtia eburnea gen. nov. sp. nov. The type strain is JFMB-ATE(T) ( = DSM 45196(T)  = NRRL B-24804(T)  = CCUG 59226(T)).

Design principles for chlorophyll-binding sites in helical proteins.

The cyclic tetrapyrroles, viz. chlorophylls (Chl), their bacterial analogs bacteriochlorophylls, and hemes are ubiquitous cofactors of biological catalysis that are involved in a multitude of reactions. One systematic approach for understanding how Nature achieves functional diversity with only this handful of cofactors is by designing de novo simple and robust protein scaffolds with heme and/or (bacterio)chlorophyll [(B)Chls]-binding sites. This strategy is currently mostly implemented for heme-binding proteins. To gain more insight into the factors that determine heme-/(B)Chl-binding selectivity, we explored the geometric parameters of (B)Chl-binding sites in a nonredundant subset of natural (B)Chl protein structures. Comparing our analysis to the study of a nonredundant database of heme-binding helical histidines by Negron et al. (Proteins 2009;74:400-416), we found a preference for the m-rotamer in (B)Chl-binding helical histidines, in contrast to the preferred t-rotamer in heme-binding helical histidines. This may be used for the design of specific heme- or (B)Chl-binding sites in water-soluble helical bundles, because the rotamer type defines the positioning of the bound cofactor with respect to the helix interface and thus the protein-binding site. Consensus sequences for (B)Chl binding were identified by combining a computational and database-derived approach and shown to be significantly different from the consensus sequences recommended by Negron et al. (Proteins 2009;74:400-416) for heme-binding helical proteins. The insights gained in this work on helix- (B)Chls-binding pockets provide useful guidelines for the construction of reasonable (B)Chl-binding protein templates that can be optimized by computational tools.

Digital DNA-DNA hybridization for microbial species delineation by means of genome-to-genome sequence comparison.

The pragmatic species concept for Bacteria and Archaea is ultimately based on DNA-DNA hybridization (DDH). While enabling the taxonomist, in principle, to obtain an estimate of the overall similarity between the genomes of two strains, this technique is tedious and error-prone and cannot be used to incrementally build up a comparative database. Recent technological progress in the area of genome sequencing calls for bioinformatics methods to replace the wet-lab DDH by in-silico genome-to-genome comparison. Here we investigate state-of-the-art methods for inferring whole-genome distances in their ability to mimic DDH. Algorithms to efficiently determine high-scoring segment pairs or maximally unique matches perform well as a basis of inferring intergenomic distances. The examined distance functions, which are able to cope with heavily reduced genomes and repetitive sequence regions, outperform previously described ones regarding the correlation with and error ratios in emulating DDH. Simulation of incompletely sequenced genomes indicates that some distance formulas are very robust against missing fractions of genomic information. Digitally derived genome-to-genome distances show a better correlation with 16S rRNA gene sequence distances than DDH values. The future perspectives of genome-informed taxonomy are discussed, and the investigated methods are made available as a web service for genome-based species delineation.

Complete genome sequence of Archaeoglobus profundus type strain (AV18).

Archaeoglobus profundus (Burggraf et al. 1990) is a hyperthermophilic archaeon in the euryarchaeal class Archaeoglobi, which is currently represented by the single family Archaeoglobaceae, containing six validly named species and two strains ascribed to the genus 'Geoglobus' which is taxonomically challenged as the corresponding type species has no validly published name. All members were isolated from marine hydrothermal habitats and are obligate anaerobes. Here we describe the features of the organism, together with the complete genome sequence and annotation. This is the second completed genome sequence of a member of the class Archaeoglobi. The 1,563,423 bp genome with its 1,858 protein-coding and 52 RNA genes is a part of the Genomic Encyclopedia of Bacteria and Archaea project.

Nocardiopsis sinuspersici sp. nov., isolated from sandy rhizospheric soil.

A polyphasic taxonomic study of a halotolerant bacterium, isolated from sandy rhizospheric soil in Sarbandar, Persian Gulf, Iran, revealed that strain HM6(T) represents a novel species within the genus Nocardiopsis. Results of the 16S rRNA gene sequence comparison revealed that strain HM6(T) clustered with strains of the genus Nocardiopsis, showing the highest degree of 16S rRNA gene sequence similarity to Nocardiopsis quinghaiensis (99.2 %), Nocardiopsis aegyptia (98.5 %) and Nocardiopsis halotolerans (98.3 %). However, DNA-DNA hybridization studies with these type strains revealed less than 39.6 % similarity. Rather than genotypic differences, there are some phenotypic discrepancies between strain HM6(T) and closely related species of the genus Nocardiopsis. Main morphological and chemotaxonomical features of strain HM6(T) include: (i) growth characteristics, i.e. the formation of a scant light-yellow to white aerial mycelium and the typical zig-zag form of the hyphae, which fragment during ageing into smooth rod-shaped spores; (ii) the presence of meso-diaminopimelic acid and glucose plus ribose in whole-cell hydrolysates; (iii) the presence of diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine and phosphatidylinositol, together with three unknown Nocardiopsis-specific phospholipids (close to diphosphatidylglycerol in position) in polar lipid extracts; (iv) the presence of the major menaquinones MK-10(H0), MK-10(H2) and MK-9(H0) in the non-polar fraction; (v) the presence of iso/anteiso-branched plus 10-methyl-branched fatty acids, showing the diagnostic combination for species of the genus Nocardiopsis of iso-16 : 0 (31.1 %), anteiso-17 : 0 (19.2 %), 10-methyl-17 : 0 (5.8 %) and tuberculostearic acid (8.8 %); and (vi) the absence of mycolic acids. Analysis of the 16S rRNA gene sequence revealed that strain HM6(T) represents a distinct taxon within the genus Nocardiopsis. Based upon genotypic and phenotypic differences from other members of the genus, a novel species, Nocardiopsis sinuspersici sp. nov., is proposed. The type strain is HM6(T) (=UTMC 00102(T) =DSM 45277(T) =CCUG 57624(T)).

The complete genome sequence of the algal symbiont Dinoroseobacter shibae: a hitchhiker's guide to life in the sea.

Dinoroseobacter shibae DFL12(T), a member of the globally important marine Roseobacter clade, comprises symbionts of cosmopolitan marine microalgae, including toxic dinoflagellates. Its annotated 4 417 868 bp genome sequence revealed a possible advantage of this symbiosis for the algal host. D. shibae DFL12(T) is able to synthesize the vitamins B(1) and B(12) for which its host is auxotrophic. Two pathways for the de novo synthesis of vitamin B(12) are present, one requiring oxygen and the other an oxygen-independent pathway. The de novo synthesis of vitamin B(12) was confirmed to be functional, and D. shibae DFL12(T) was shown to provide the growth-limiting vitamins B(1) and B(12) to its dinoflagellate host. The Roseobacter clade has been considered to comprise obligate aerobic bacteria. However, D. shibae DFL12(T) is able to grow anaerobically using the alternative electron acceptors nitrate and dimethylsulfoxide; it has the arginine deiminase survival fermentation pathway and a complex oxygen-dependent Fnr (fumarate and nitrate reduction) regulon. Many of these traits are shared with other members of the Roseobacter clade. D. shibae DFL12(T) has five plasmids, showing examples for vertical recruitment of chromosomal genes (thiC) and horizontal gene transfer (cox genes, gene cluster of 47 kb) possibly by conjugation (vir gene cluster). The long-range (80%) synteny between two sister plasmids provides insights into the emergence of novel plasmids. D. shibae DFL12(T) shows the most complex viral defense system of all Rhodobacterales sequenced to date.

"Hot standards" for the thermoacidophilic archaeon Sulfolobus solfataricus.

Within the archaea, the thermoacidophilic crenarchaeote Sulfolobus solfataricus has become an important model organism for physiology and biochemistry, comparative and functional genomics, as well as, more recently also for systems biology approaches. Within the Sulfolobus Systems Biology ("SulfoSYS")-project the effect of changing growth temperatures on a metabolic network is investigated at the systems level by integrating genomic, transcriptomic, proteomic, metabolomic and enzymatic information for production of a silicon cell-model. The network under investigation is the central carbohydrate metabolism. The generation of high-quality quantitative data, which is critical for the investigation of biological systems and the successful integration of the different datasets, derived for example from high-throughput approaches (e.g., transcriptome or proteome analyses), requires the application and compliance of uniform standard protocols, e.g., for growth and handling of the organism as well as the "-omics" approaches. Here, we report on the establishment and implementation of standard operating procedures for the different wet-lab and in silico techniques that are applied within the SulfoSYS-project and that we believe can be useful for future projects on Sulfolobus or (hyper)thermophiles in general. Beside established techniques, it includes new methodologies like strain surveillance, the improved identification of membrane proteins and the application of crenarchaeal metabolomics.

Streptomyces iranensis sp. nov., isolated from soil.

A novel streptomycete, designated strain HM 35(T), was isolated from soil in Isfahan city, Iran. Strain HM 35(T) produced a branched substrate mycelium and aerial hyphae that developed into short, compact, spiral spore chains with grey rugose spores at the tips of the aerial hyphae. On some media, these spirals coalesced into dark masses of spores with age. Whole-cell hydrolysates of strain HM 35(T) contained LL-diaminopimelic acid, glucose and ribose. Phospholipids detected were phosphatidylglycerol, phosphatidylinositol, phosphatidylethanolamine, phosphatidylinositol mannosides, hydroxy-phosphatidylethanolamine, lyso-phosphatidylethanolamine and hydroxy-lyso-phosphatidylethanolamine. MK-9(H(4)), MK-9(H(6)) and MK-9(H(8)) were the predominant menaquinones. The major fatty acids were iso- and anteiso-branched components. The chemotaxonomic characteristics of the novel isolate matched those described for members of the genus Streptomyces. Based on 16S rRNA gene sequence analysis, strain HM 35(T) showed highest similarity to Streptomyces rapamycinicus NRRL 5491(T) (99.2 %), Streptomyces violaceusniger DSM 40563(T) (99.1 %), Streptomyces javensis DSM 41764(T) (99.1 %) and Streptomyces yogyakartensis DSM 41766(T) (99.1 %). The novel strain formed a distinct monophyletic line within the 16S rRNA gene sequence tree. The level of DNA-DNA relatedness between strain HM 35(T) and the type strain of S. rapamycinicus was 72.7 %. Strain HM 35(T) showed the typical morphology found among members of the S. violaceusniger/Streptomyces hygroscopicus group but could be clearly differentiated from closely related species based on other phenotypic markers. Phenotypic and genotypic data thus indicate that strain HM 35(T) represents a novel species of the genus Streptomyces, for which the name Streptomyces iranensis is proposed. The type strain is HM 35(T) (=DSM 41954(T)=CCUG 57623(T)).