Search

The relationship between the host and its microbiota is challenging to understand because both microbial communities and their environments are highly variable. We have developed a set of techniques based on population dynamics and information theory to address this challenge. These methods identify additional bacterial taxa associated with pediatric Crohn disease and can detect significant changes in microbial communities with fewer samples than previous statistical approaches required. We have also substantially improved the accuracy of the diagnosis based on the microbiota from stool samples, and we found that the ecological niche of a microbe predicts its role in Crohn disease. Bacteria typically residing in the lumen of healthy individuals decrease in disease, whereas bacteria typically residing on the mucosa of healthy individuals increase in disease. Our results also show that the associations with Crohn disease are evolutionarily conserved and provide a mutual information-based method to depict dysbiosis.

Here, we present the complete 2,003,803-bp genome of a sulfate-reducing thermophilic bacterium, Thermodesulfovibrio yellowstonii strain DSM 11347(T).

Here, we present the complete genome sequence of Thermodesulfobacterium commune DSM 2178(T) of the phylum Thermodesulfobacteria.

Here we present the draft genome of Synergistes jonesii 78-1, ATCC 49833, a member of the Synergistes phylum. This organism was isolated from the rumen of a Hawaiian goat and ferments pyridinediols. The assembly contains 2,747,397 bp in 61 contigs.

In order to enrich the phylogenetic diversity represented in the available sequenced bacterial genomes and as part of an "Assembling the Tree of Life" project, we determined the genome sequence of Thermomicrobium roseum DSM 5159. T. roseum DSM 5159 is a red-pigmented, rod-shaped, Gram-negative extreme thermophile isolated from a hot spring that possesses both an atypical cell wall composition and an unusual cell membrane that is composed entirely of long-chain 1,2-diols. Its genome is composed of two circular DNA elements, one of 2,006,217 bp (referred to as the chromosome) and one of 919,596 bp (referred to as the megaplasmid). Strikingly, though few standard housekeeping genes are found on the megaplasmid, it does encode a complete system for chemotaxis including both chemosensory components and an entire flagellar apparatus. This is the first known example of a complete flagellar system being encoded on a plasmid and suggests a straightforward means for lateral transfer of flagellum-based motility. Phylogenomic analyses support the recent rRNA-based analyses that led to T. roseum being removed from the phylum Thermomicrobia and assigned to the phylum Chloroflexi. Because T. roseum is a deep-branching member of this phylum, analysis of its genome provides insights into the evolution of the Chloroflexi. In addition, even though this species is not photosynthetic, analysis of the genome provides some insight into the origins of photosynthesis in the Chloroflexi. Metabolic pathway reconstructions and experimental studies revealed new aspects of the biology of this species. For example, we present evidence that T. roseum oxidizes CO aerobically, making it the first thermophile known to do so. In addition, we propose that glycosylation of its carotenoids plays a crucial role in the adaptation of the cell membrane to this bacterium's thermophilic lifestyle. Analyses of published metagenomic sequences from two hot springs similar to the one from which this strain was isolated, show that close relatives of T. roseum DSM 5159 are present but have some key differences from the strain sequenced.

Hyphomonas neptunium is a marine prosthecate alpha-proteobacterium currently classified as a member of the order 'Rhodobacterales'. Although this classification is supported by 16S rRNA gene sequence phylogeny, 23S rRNA gene sequence analysis, concatenated ribosomal proteins, HSP70 and EF-Tu phylogenies all support classifying Hyphomonas neptunium as a member of the Caulobacterales instead. The possible reasons why the 16S rRNA gene sequence gives conflicting results in this case are also discussed.

The dimorphic prosthecate bacteria (DPB) are [alpha]-proteobacteria that reproduce in an asymmetric manner rather than by binary fission and are of interest as simple models of development. Prior to this work, the only member of this group for which genome sequence was available was the model freshwater organism Caulobacter crescentus. Here we describe the genome sequence of Hyphomonas neptunium, a marine member of the DPB that differs from C. crescentus in that H. neptunium uses its stalk as a reproductive structure. Genome analysis indicates that this organism shares more genes with C. crescentus than it does with Silicibacter pomeroyi (a closer relative according to 16S rRNA phylogeny), that it relies upon a heterotrophic strategy utilizing a wide range of substrates, that its cell cycle is likely to be regulated in a similar manner to that of C. crescentus, and that the outer membrane complements of H. neptunium and C. crescentus are remarkably similar. H. neptunium swarmer cells are highly motile via a single polar flagellum. With the exception of cheY and cheR, genes required for chemotaxis were absent in the H. neptunium genome. Consistent with this observation, H. neptunium swarmer cells did not respond to any chemotactic stimuli that were tested, which suggests that H. neptunium motility is a random dispersal mechanism for swarmer cells rather than a stimulus-controlled navigation system for locating specific environments. In addition to providing insights into bacterial development, the H. neptunium genome will provide an important resource for the study of other interesting biological processes including chromosome segregation, polar growth, and cell aging.

Thermophilic bacteria and their thermostable enzymes are useful in biotechnology, and several studies have been undertaken on thermophilic environments. Small subunit DNA sequences were established and phylogenetic analysis was conducted for 20 species of the genes Acetogenium, Thermoanaerobacter, Clostricium, Thermoanaerobium, Thermoanaerobacterium and Thermobacteroids. Due to inserts, the molecules present in these species were found to be longer than those found on the E. coli. All the bacteria under study form a supercluster inside the subphylum of gram-positive bacteria that have already been sequenced.

The result from the comparison of complete genomes of three strains from the phylum Acidobacteria which share genomic traits with members of the Proteobacteria, the Cyanobacteria, and the Fungi are presented. The cells of the isolates of Acidobacteria strains are found to be long-lived, divide slowly, exhibit slow metabolic rates under low-nutrient conditions and are well equipped to tolerate fluctuations in soil hydration.