Evelyne Brambilla

Identifying the fundamental units of bacterial diversity: A paradigm shift to incorporate ecology into bacterial systematics

The central questions of bacterial ecology and evolution require a method to consistently demarcate, from the vast and diverse set of bacterial cells within a natural community, the groups playing ecologically distinct roles (ecotypes). Because of a lack of theory-based guidelines, current methods in bacterial systematics fail to divide the bacterial domain of life into meaningful units of ecology and evolution. We introduce a sequence-based approach (“ecotype simulation”) to model the evolutionary dynamics of bacterial populations and to identify ecotypes within a natural community, focusing here on two Bacillus clades surveyed from the “Evolution Canyons” of Israel. This approach has identified multiple ecotypes within traditional species, with each predicted to be an ecologically distinct lineage; many such ecotypes were confirmed to be ecologically distinct, with specialization to different canyon slopes with different solar exposures. Ecotype simulation provides a long-needed natural foundation for microbial ecology and systematics.

16S rDNA diversity of cultured and uncultured prokaryotes of a mat sample from Lake Fryxell, McMurdo Dry Valleys, Antarctica

The prokaryotic diversity of aerobic and anaerobic bacterial isolates and of bacterial and archaeal 16S rDNA clones was determined for a microbial mat sample from the moated region of Lake Fryxell, McMurdo Dry Valleys, Antarctica. Among the anaerobic bacteria, members of Clostridium estertheticum and some other psychrotolerant strains dominated whereas methanogens and other Archaea were lacking. Isolates highly related to Flavobacterium hibernum, Janthinobacterium lividum, and Arthrobacter flavus were among the aerobic bacteria most frequently isolated. Assessment of more than 350 partial 16S rDNA clone sequences of libraries generated by Bacteria- and Archaea-specific PCR primers revealed a rich spectrum of bacterial diversity but only two different archaeal clone sequences. Among the Bacteria, representative sequences belonged to the class Proteobacteria, order Verrucomicrobiales, class Actinobacteria, Clostridium/Bacillus subphylum of Gram-positives, and the Cytophaga-Flavobacterium-Bacteroides phylum. The clones formed about 70 higher taxonomy groups (<98% sequence similarity) and 133 potential species, i.e., groups of clones sharing greater than 98% similarity. Only rarely were clone sequences found to be highly related to Lake Fryxell isolates and to strains of described species. Subsequent analysis of ten sequencing batches of 36 individual clones indicated that the diversity might be still higher than had been assessed.

Aeromonas rivuli sp. nov., isolated from the upstream region of a karst water rivulet.

Two freshwater isolates (WB4.1-19(T) and WB4.4-101), sharing 99.9 % 16S rRNA gene sequence similarity, were highly related to Aeromonas sobria (99.7 % similarity; 6 bp differences). A phylogenetic tree derived from a multi-locus phylogenetic analysis (MLPA) of the concatenated sequences of five housekeeping genes (gyrB, rpoD, recA, dnaJ and gyrA; 3684 bp) revealed that both strains clustered as an independent phylogenetic line next to members of Aeromonas molluscorum and Aeromonas bivalvium. The DNA-DNA reassociation value between the two new isolates was 89.3 %. Strain WB4.1-19(T) had a DNA-DNA relatedness value of <70 % with the type strains of the other species tested. Phenotypic characterization differentiated the two novel strains from all other type strains of species of the genus Aeromonas. It is concluded that the two new strains represent a novel species of the genus Aeromonas, for which the name Aeromonas rivuli sp. nov. is proposed, with the type strain WB4.1-19(T) (=CECT 7518(T)=DSM 22539(T)=MDC 2511(T)).

Flavobacterium rivuli sp. nov., Flavobacterium subsaxonicum sp. nov., Flavobacterium swingsii sp. nov. and Flavobacterium reichenbachii sp. nov., isolated from a hard water rivulet

Strains WB 3.3-2(T), WB 3.2-61(T), WB 4.1-42(T) and WB 2.3-68(T) were isolated from the Westerhöfer Bach hard water rivulet, North Germany. The strains were Gram-staining-negative and catalase-, aminopeptidase- and oxidase-positive. The novel strains lacked flagella and only strain WB3.2-61(T) showed gliding motility. Isolates WB 3.2-61(T), WB 4.1-42(T) and WB 2.3-68(T) produced flexirubin pigments. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the novel strains showed <98.2 % similarity to the type strains of all recognized species of the genus Flavobacterium. Strains WB 3.3-2(T) and WB 4.1-42(T) shared 96.3 % sequence similarity and were only distantly related to the type strains of all of the members of the genus Flavobacterium. Strain WB 3.2-61(T) branched adjacent to Flavobacterium limicola DSM 15094(T) (98.0 %), while strain WB 2.3-68(T) was a neighbour of Flavobacterium psychrophilum DSM 3660(T) (97.1 %). On R2A medium, iso-C(15 : 0) was the common major fatty acid; fatty acids C(15 : 0), C(16 : 0), iso-C(15 : 0) 3-OH, iso-C(17 : 1)omega9c, iso-C(17 : 0) 3-OH and summed feature 3 (comprising C(16 : 1)omega7c and/or iso-C(15 : 0) 2-OH) occurred in all strains though sometimes in low amounts. Metabolic properties revealed clear differences between the four isolates as well as between the isolates and their nearest phylogenetic neighbours. The lack of close relatedness was confirmed by Riboprinter and MALDI-TOF analyses of cell extracts. On the basis of a high number of phenotypic differentiating properties and phylogenetic uniqueness, four novel Flavobacterium species are proposed with the following names: Flavobacterium rivuli (type strain WB 3.3-2(T)=DSM 21788(T)=CIP 109865(T)), Flavobacterium subsaxonicum (type strain WB 4.1-42(T)=DSM 21790(T)=CIP 109867(T)), Flavobacterium swingsii (type strain WB 2.3-68(T)=DSM 21789(T)=CIP 109868(T)) and Flavobacterium reichenbachii (type strain WB 3.2-61(T)=DSM 21791(T)=CIP 109866(T)).

Complete genome sequence of Desulfobulbus propionicus type strain (1pr3 T )

Desulfobulbus propionicus Widdel 1981 is the type species of the genus Desulfobulbus, which belongs to the family Desulfobulbaceae. The species is of interest because of its great implication in the sulfur cycle in aquatic sediments, its large substrate spectrum and a broad versatility in using various fermentation pathways. The species was the first example of a pure culture known to disproportionate elemental sulfur to sulfate and sulfide. This is the first completed genome sequence of a member of the genus Desulfobulbus and the third published genome sequence from a member of the family Desulfobulbaceae. The 3,851,869 bp long genome with its 3,351 protein-coding and 57 RNA genes is a part of the GenomicEncyclopedia ofBacteria andArchaea project.

Complete Genome Sequences of Desulfosporosinus orientis DSM765T, Desulfosporosinus youngiae DSM17734T, Desulfosporosinus meridiei DSM13257T, and Desulfosporosinus acidiphilus DSM22704T

Desulfosporosinus species are sulfate-reducing bacteria belonging to the Firmicutes. Their genomes will give insights into the genetic repertoire and evolution of sulfate reducers typically thriving in terrestrial environments and able to degrade toluene (Desulfosporosinus youngiae), to reduce Fe(III) (Desulfosporosinus meridiei, Desulfosporosinus orientis), and to grow under acidic conditions (Desulfosporosinus acidiphilus).

Complete genome sequence of Cellulophaga lytica type strain (LIM-21(T))

Cellulophaga lytica (Lewin 1969) Johansen et al. 1999 is the type species of the genus Cellulophaga which belongs to the family Flavobacteriaceae within the phylum ‘Bacteroidetes’ and was isolated from marine beach mud in Limon, Costa Rica. The species is of biotechnological interest because its members produce a wide range of extracellular enzymes capable of degrading proteins and polysaccharides. After the genome sequence of Cellulophaga algicola this is the second completed genome sequence of a member of the genus Cellulophaga. The 3,765,936 bp long genome with its 3,303 protein-coding and 55 RNA genes consists of one circular chromosome and is a part of the GenomicEncyclopedia ofBacteria andArchaea project.

Automated fragment length analysis of fluorescently-labeled 16S rDNA after digestion with 4-base cutting restriction enzymes

Abstract An automated restriction fragment length analysis [amplified rDNA restriction analysis (ARDRA)] of fluorescently-labeled 16S rDNA is described. The 16S rDNA of cultured bacterial strains was amplified by the polymerase chain reaction containing additional fluorescently-labeled [F] 2′ deoxyumidine 5′ triphosphates (dUTPs) in the reaction mix. After amplification the fluorescently-labeled polymerase chain reaction products were digested with 4-base site specific restriction endonucleases Hae III, Bst UI, and Hha I which have recognition sites in the 16S rDNA sequences of members of most of the α-, β-, γ-subclasses of Proteobacteria , and members of the Cytophaga-Flexibacter-Bacteroides (CFB)-phylum and the Gram-positive bacteria. Aliquots of 16S rDNA were labeled during amplification with three different [F] dUTPs, and each 16S rDNA was digested with a single restriction enzyme. Combined fragments from the analysis with all three restriction enzymes were loaded onto a single lane of an automated DNA sequencing gel and the fragments separated. This modified version of the ARDRA technique can be used as a rapid method for the assessment of pattern similarity and taxonomic relatedness between organisms.

Complete genome sequence of Odoribacter splanchnicus type strain (1651/6T)

Odoribacter splanchnicus (Werner et al. 1975) Hardham et al. 2008 is the type species of the genus Odoribacter, which belongs to the family Porphyromonadaceae in the order ‘Bacteroidales’. The species is of interest because members of the Odoribacter form an isolated cluster within the Porphyromonadaceae. This is the first completed genome sequence of a member of the genus Odoribacter and the fourth sequence from the family Porphyromonadaceae. The 4,392,288 bp long genome with its 3,672 protein-coding and 74 RNA genes and is a part of the GenomicEncyclopedia ofBacteria andArchaea project.

Complete genome sequence of Truepera radiovictrix type strain (RQ-24T)

Truepera radiovictrix Albuquerque et al. 2005 is the type species of the genus Truepera within the phylum “Deinococcus/Thermus”. T. radiovictrix is of special interest not only because of its isolated phylogenetic location in the order Deinococcales, but also because of its ability to grow under multiple extreme conditions in alkaline, moderately saline, and high temperature habitats. Of particular interest is the fact that, T. radiovictrix is also remarkably resistant to ionizing radiation, a feature it shares with members of the genus Deinococcus. This is the first completed genome sequence of a member of the family Trueperaceae and the fourth type strain genome sequence from a member of the order Deinococcales. The 3,260,398 bp long genome with its 2,994 protein-coding and 52 RNA genes consists of one circular chromosome and is a part of the GenomicEncyclopedia ofBacteria andArchaea project.