Anne Fiebig

Complete genome sequence of DSM 30083T, the type strain (U5/41T) of Escherichia coli, and a proposal for delineating subspecies in microbial taxonomy

Although Escherichia coli is the most widely studied bacterial model organism and often considered to be the model bacterium per se, its type strain was until now forgotten from microbial genomics. As a part of the GenomicEncyclopedia ofBacteria andArchaea project, we here describe the features of E. coli DSM 30083T together with its genome sequence and annotation as well as novel aspects of its phenotype. The 5,038,133 bp containing genome sequence includes 4,762 protein-coding genes and 175 RNA genes as well as a single plasmid. Affiliation of a set of 250 genome-sequenced E. coli strains, Shigella and outgroup strains to the type strain of E. coli was investigated using digital DNA:DNA-hybridization (dDDH) similarities and differences in genomic G+C content. As in the majority of previous studies, results show Shigella spp. embedded within E. coli and in most cases forming a single subgroup of it. Phylogenomic trees also recover the proposed E. coli phylotypes as monophyla with minor exceptions and place DSM 30083T in phylotype B2 with E. coli S88 as its closest neighbor. The widely used lab strain K-12 is not only genomically but also physiologically strongly different from the type strain. The phylotypes do not express a uniform level of character divergence as measured using dDDH, however, thus an alternative arrangement is proposed and discussed in the context of bacterial subspecies. Analyses of the genome sequences of a large number of E. coli strains and of strains from > 100 other bacterial genera indicate a value of 79-80% dDDH as the most promising threshold for delineating subspecies, which in turn suggests the presence of five subspecies within E. coli.

Non-contiguous finished genome sequence and contextual data of the filamentous soil bacterium Ktedonobacter racemifer type strain (SOSP1-21T)

Ktedonobacter racemifer corrig. Cavaletti et al. 2007 is the type species of the genus Ktedonobacter, which in turn is the type genus of the family Ktedonobacteraceae, the type family of the order Ktedonobacterales within the class Ktedonobacteria in the phylum ‘Chloroflexi’. Although K. racemifer shares some morphological features with the actinobacteria, it is of special interest because it was the first cultivated representative of a deep branching unclassified lineage of otherwise uncultivated environmental phylotypes tentatively located within the phylum ‘Chloroflexi’. The aerobic, filamentous, non-motile, spore-forming Gram-positive heterotroph was isolated from soil in Italy. The 13,661,586 bp long non-contiguous finished genome consists of ten contigs and is the first reported genome sequence from a member of the class Ktedonobacteria. With its 11,453 protein-coding and 87 RNA genes, it is the largest prokaryotic genome reported so far. It comprises a large number of over-represented COGs, particularly genes associated with transposons, causing the genetic redundancy within the genome being considerably larger than expected by chance. This work is a part of the GenomicEncyclopedia ofBacteria andArchaea project.

Genomics and Physiology of a Marine Flavobacterium Encoding a Proteorhodopsin and a Xanthorhodopsin-Like Protein

Proteorhodopsin (PR) photoheterotrophy in the marine flavobacterium Dokdonia sp. PRO95 has previously been investigated, showing no growth stimulation in the light at intermediate carbon concentrations. Here we report the genome sequence of strain PRO95 and compare it to two other PR encoding Dokdonia genomes: that of strain 4H-3-7-5 which shows the most similar genome, and that of strain MED134 which grows better in the light under oligotrophic conditions. Our genome analysis revealed that the PRO95 genome as well as the 4H-3-7-5 genome encode a protein related to xanthorhodopsins. The genomic environment and phylogenetic distribution of this gene suggest that it may have frequently been recruited by lateral gene transfer. Expression analyses by RT-PCR and direct mRNA-sequencing showed that both rhodopsins and the complete β-carotene pathway necessary for retinal production are transcribed in PRO95. Proton translocation measurements showed enhanced proton pump activity in response to light, supporting that one or both rhodopsins are functional. Genomic information and carbon source respiration data were used to develop a defined cultivation medium for PRO95, but reproducible growth always required small amounts of yeast extract. Although PRO95 contains and expresses two rhodopsin genes, light did not stimulate its growth as determined by cell numbers in a nutrient poor seawater medium that mimics its natural environment, confirming previous experiments at intermediate carbon concentrations. Starvation or stress conditions might be needed to observe the physiological effect of light induced energy acquisition.

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.

Genome sequence of the Leisingera aquimarina type strain (DSM 24565T), a member of the marine Roseobacter clade rich in extrachromosomal elements

Leisingera aquimarina Vandecandelaere et al. 2008 is a member of the genomically well characterized Roseobacter clade within the family Rhodobacteraceae. Representatives of the marine Roseobacter clade are metabolically versatile and involved in carbon fixation and biogeochemical processes. They form a physiologically heterogeneous group, found predominantly in coastal or polar waters, especially in symbiosis with algae, in microbial mats, in sediments or associated with invertebrates. Here we describe the features of L. aquimarina DSM 24565T together with the permanent-draft genome sequence and annotation. The 5,344,253 bp long genome consists of one chromosome and an unusually high number of seven extrachromosomal elements and contains 5,129 protein-coding and 89 RNA genes. It was sequenced as part of the DOE Joint Genome Institute Community Sequencing Program 2010 and of the activities of the Transregional Collaborative Research Centre 51 funded by the German Research Foundation (DFG).

Complete genome sequence of the rapeseed plant-growth promoting Serratia plymuthica strain AS9

Serratia plymuthica are plant-associated, plant beneficial species belonging to the family Enterobacteriaceae. The members of the genus Serratia are ubiquitous in nature and their life style varies from endophytic to free-living. S. plymuthica AS9 is of special interest for its ability to inhibit fungal pathogens of rapeseed and to promote plant growth. The genome of S. plymuthica AS9 comprises a 5,442,880 bp long circular chromosome that consists of 4,952 protein-coding genes, 87 tRNA genes and 7 rRNA operons. This genome is part of the project entitled “Genomics of four rapeseed plant growth promoting bacteria with antagonistic effect on plant pathogens” awarded through the 2010 DOE-JGI Community Sequencing Program (CSP2010).

Genome sequence of Phaeobacter caeruleus type strain (DSM 24564T), a surface-associated member of the marine Roseobacter clade

In 2009 Phaeobacter caeruleus was described as a novel species affiliated with the marine Roseobacter clade, which, in turn, belongs to the class Alphaproteobacteria. The genus Phaeobacter is well known for members that produce various secondary metabolites. Here we report of putative quorum sensing systems, based on the finding of six N-acyl-homoserine lactone synthetases, and show that the blue color of P. caeruleus is probably due to the production of the secondary metabolite indigoidine. Therefore, P. caeruleus might have inhibitory effects on other bacteria. In this study the genome of the type strain DSM 24564T was sequenced, annotated and characterized. The 5,344,419 bp long genome with its seven plasmids contains 5,227 protein-coding genes (3,904 with a predicted function) and 108 RNA genes.

Complete genome sequence of the marine methyl-halide oxidizing Leisingera methylohalidivorans type strain (DSM 14336T), a representative of the Roseobacter clade

Leisingera methylohalidivorans Schaefer et al. 2002 emend. Vandecandelaere et al. 2008 is the type species of the genus Leisingera. The genus belongs to the Roseobacter clade (Rhodobacteraceae, Alphaproteobacteria), a widely distributed lineage in marine environments. Leisingera and particularly L. methylohalidivorans strain MB2T is of special interest due to its methylotrophy. Here we describe the complete genome sequence and annotation of this bacterium together with previously unreported aspects of its phenotype. The 4,650,996 bp long genome with its 4,515 protein-coding and 81 RNA genes consists of three replicons, a single chromosome and two extrachromosomal elements with sizes of 221 kb and 285 kb.

Genome sequence of Phaeobacter daeponensis type strain (DSM 23529 T ), a facultatively anaerobic bacterium isolated from marine sediment, and emendation of Phaeobacter daeponensis

TF-218T is the type strain of the species Phaeobacter daeponensis Yoon et al. 2007, a facultatively anaerobic Phaeobacter species isolated from tidal flats. Here we describe the draft genome sequence and annotation of this bacterium together with previously unreported aspects of its phenotype. We analyzed the genome for genes involved in secondary metabolite production and its anaerobic lifestyle, which have also been described for its closest relative Phaeobacter caeruleus. The 4,642,596 bp long genome of strain TF-218T contains 4,310 protein-coding genes and 78 RNA genes including four rRNA operons and consists of five replicons: one chromosome and four extrachromosomal elements with sizes of 276 kb, 174 kb, 117 kb and 90 kb. Genome analysis showed that TF-218T possesses all of the genes for indigoidine biosynthesis, and on specific media the strain showed a blue pigmentation. We also found genes for dissimilatory nitrate reduction, gene-transfer agents, NRPS/PKS genes and signaling systems homologous to the LuxR/I system.

Kribbella shirazensis sp. nov., isolated from Iranian soil.

The taxonomic position of a strain isolated from soil in Shiraz, Fars province, Iran, was investigated. Strain UTMC 693(T) produced an extensively branched substrate mycelium and aerial hyphae consisting of hyphae that fragment into short to elongated rod-like elements. The chemotaxonomic characteristics of the isolate matched those described for the genus Kribbella. Strain UTMC 693(T) showed the highest 16S rRNA gene sequence similarity to Kribbella karoonensis DSM 17344(T) (98.3%), K. swartbergensis DSM 17345(T) (98.2%), K. hippodromi S1.4(T) (98.0%), K. aluminosa HKI 0478(T) (98.0%) and K. jejuensis HD9(T) (98.0%). DNA-DNA hybridization studies with closely related type strains showed 56.3% relatedness to K. karoonensis, 21.3% to K. swartbergensis, 39.0% to K. jejuensis and 42.0% to K. aluminosa. Thus, strain UTMC 693(T) can be considered to represent a novel Kribbella species. Strain UTMC 693(T) showed the typical morphology found among members of Kribbella, but can be differentiated easily from closely related species by genotypic characteristics, chemotaxonomic results and other phenotypic markers. Based on these results, strain UTMC 693(T) ( =DSM 45490(T) =CCUG 61792(T)) is considered the type strain of a novel species of the genus Kribbella, for which the name Kribbella shirazensis sp. nov. is proposed.