Molecular signatures for the phylum Aquificae and its different clades: proposal for division of the phylum Aquificae into the emended order Aquificales, containing the families Aquificaceae and Hydrogenothermaceae, and a new order Desulfurobacteriales ord. nov., containing the family Desulfurobacteriaceae

AppIndels.com server: a web-based tool for the identification of known taxon-specific conserved signature indels in genome sequences. Validation of its usefulness by predicting the taxonomic affiliation of >700 unclassified strains of Bacillus species

Taxon-specific conserved signature indels (CSIs) in genes/proteins provide reliable molecular markers (synapomorphies) for unambiguous demarcation of taxa of different ranks in molecular terms and for genetic, biochemical and diagnostic studies. Because of their predictive abilities, the shared presence of known taxon-specific CSIs in genome sequences has proven useful for taxonomic purposes. However, the lack of a convenient method for identifying the presence of known CSIs in genome sequences has limited their utility for taxonomic and other studies. We describe here a web-based tool/server (AppIndels.com) that identifies the presence of known and validated CSIs in genome sequences and uses this information for predicting taxonomic affiliation. The utility of this server was tested by using a database of 585 validated CSIs, which included 350 CSIs specific for ≈45 Bacillales genera, with the remaining CSIs being specific for members of the orders Neisseriales, Legionellales and Chlorobiales, family Borreliaceae, and some Pseudomonadaceae species/genera. Using this server, genome sequences were analysed for 721 Bacillus strains of unknown taxonomic affiliation. Results obtained showed that 651 of these genomes contained significant numbers of CSIs specific for the following Bacillales genera/families: Alkalicoccus, 'Alkalihalobacillaceae', Alteribacter, Bacillus Cereus clade, Bacillus Subtilis clade, Caldalkalibacillus, Caldibacillus, Cytobacillus, Ferdinandcohnia, Gottfriedia, Heyndrickxia, Lederbergia, Litchfieldia, Margalitia, Mesobacillus, Metabacillus, Neobacillus, Niallia, Peribacillus, Priestia, Pseudalkalibacillus, Robertmurraya, Rossellomorea, Schinkia, Siminovitchia, Sporosarcina, Sutcliffiella, Weizmannia and Caryophanaceae. Validity of the taxon assignment made by the server was examined by reconstructing phylogenomic trees. In these trees, all Bacillus strains for which taxonomic predictions were made correctly branched with the indicated taxa. The unassigned strains likely correspond to taxa for which CSIs are lacking in our database. Results presented here show that the AppIndels server provides a useful new tool for predicting taxonomic affiliation based on shared presence of the taxon-specific CSIs. Some caveats in using this server are discussed.

Genome-Resolved Metagenomics and Metatranscriptomics Reveal that Aquificae Dominates Arsenate Reduction in Tengchong Geothermal Springs

Elevated arsenic (As) is common in geothermal springs, shaping the evolution of As metabolism genes and As transforming microbes. Herein, genome-level microbial metabolisms and As cycling strategies in Tengchong geothermal springs were demonstrated for the first time based on metagenomic and metatranscriptomic analyses. Sulfur cycling was dominated by Aquificae oxidizing thiosulfate via the sox system, fueling the respiration and carbon dioxide fixation processes. Arsenate reduction via arsC [488.63 ± 271.60 transcripts per million (TPM)] and arsenite efflux via arsB (442.98 ± 284.81 TPM) were the primary detoxification pathway, with most genes and transcripts contributed by the members in phylum Aquificae. A complete arsenotrophic cycle was also transcriptionally active as evidenced by the detection of aioA transcripts and arrA transcript reads mapped onto metagenome-assembled genomes (MAGs) affiliated with Crenarchaeota. MAGs affiliated with Aquificae had great potential of reducing arsenate via arsC and fixing nitrogen and carbon dioxide via nifDHK and reductive tricarboxylic acid (rTCA) cycle, respectively. Aquificae's arsenate reduction potential via arsC was observed for the first time at the transcriptional level. This study expands the diversity of the arsC-based arsenate-reducing community and highlights the importance of Aquificae to As biogeochemistry.

The Evaluation of Bacterial Abundance and Functional Potentials in the Three Major Watersheds, Located in the Hot Spring Zone of the Tatun Volcano Group Basin, Taiwan

The Tatun Volcanic Group (TVG), located in northern Taiwan, is characterized by acidic hot springs where the outflow of the hot springs may affect the properties of the associated lotic water bodies. We investigated the bacterial diversity and functional profiles of the Peihuang (PHC), HuangGang (HGC), and Nanhuang Creeks (NHC) located in the TVG basin using 16S rRNA gene sequencing coupled with statistical analyses. Water samples were collected from various streams of the creeks for two months of the year. The NHC showed the highest diversity, richness, and a unique number of phyla, which was followed by the HGC. A reduced number of phyla and a lower diversity was noticed in the PHC. The NHC was found to be abundant in the genera Armatimonas, Prosthecobacter, Pirellula, and Bdellovibrio, whereas the HGC was rich in Thiomonas, Acidiphilium, Prevotella, Acidocella, Acidithiobacillus, and Metallibacterium. The PHC was abundant in Thiomonsa, Legionella, Acidocella, and Sulfuriferula. The samples did not show any strong seasonal variations with the bacterial diversity and abundance; however, the relative abundance of each sampling site varied within the sampling months. The iron transport protein- and the sulfur metabolism-related pathways were predicted to be the key functions in all the creeks, whereas the heavy metal-related functions, such as the cobalt/nickel transport protein and the cobalt-zinc-cadmium efflux system were found to be abundant in the HGC and PHC, respectively. The abundance of Bdellovibrio in the NHC, Diplorickettsia in the HGC, and Legionella in the PHC samples indicated a higher anthropogenic impact over the creek water quality. This study provides the data to understand the distinct bacterial community structure, as well as the functional potentials of the three major watersheds, and helps the knowledge of the impact of the physicochemical properties of the TVG hot springs upon the watersheds.

Persephonella atlantica sp. nov.: How to adapt to physico-chemical gradients in high temperature hydrothermal habitats

A novel thermophilic, microaerophilic and anaerobic, hydrogen- sulphur- and thiosulphate-oxidising bacterium, designated MO1340^T, was isolated from a deep-sea hydrothermal chimney collected from the Lucky Strike hydrothermal vent field on the Mid-Atlantic Ridge. Cells were short, motile rods of 1.4-2.2μm length and 0.5-0.8μm width. Optimal growth was observed for a NaCl concentration of 2.5 % (w/v) at pH 6.5. As for other members of the genus Persephonella, strain MO1340^T was strictly chemolithoautotrophic and could oxidise hydrogen, elemental sulphur or thiosulphate using oxygen as electron acceptor. Anaerobic nitrate reduction using hydrogen could also be performed. Each catabolic reaction had a different optimal growth temperature (65 to 75°C) and an optimal dissolved oxygen concentration (11.4 to 119.7 μM at 70°C for aerobic reactions) that varied according to the electron donors utilised. These experimental results are consistent with the distribution of these catabolic substrates along the temperature gradient observed in active hydrothermal systems. They strongly suggest that this adaptive strategy could confer a selective advantage for strain MO1340^T in the dynamic part of the ecosystem where hot, reduced hydrothermal fluid mixes with cold, oxygenated seawater. Phylogenetic analysis indicated that strain MO1340^T was a member of the genus Persephonella within the order Hydrogenothermales as it shared a 16S rRNA gene sequence similarity <95.5 % and ANI respectively 75.66 % with closest described Persephonella (P. hydrogeniphila 29W^T). On the basis of the physiological and genomic properties of the new isolate, the name Persephonella atlantica sp. nov. is proposed. The type strain is MO1340^T (=UBOCC-M-3359^T =JCM 34026^T).

Temperature governs the distribution of hot spring microbial community in three hydrothermal fields, Eastern Tibetan Plateau Geothermal Belt, Western China

The eastern Tibetan Plateau geothermal belt in the southwest of China hosts a number of hot springs with a wide range of temperature and hydrogeochemical conditions, which may harbor different niches for the distribution of microbial communities. In this study, we investigated hydrochemical characteristics and microbial community composition in 16 hot springs with a temperature range of 34.6 to 88.2 °C within and across three typical hydrothermal fields (Kangding, Litang, and Batang). According to aquifer lithologic and tectonic differences, the hydrochemical compositions of hot springs displayed an apparent regional-specific pattern with distinct distributions of major and trace elements (e.g., Ca²⁺, Mg²⁺, F^-/B) and were primarily formed by water-rock interaction across the three hydrothermal fields. Nonetheless, microbial communities significantly assembled with the temperature rather than the geographic locations with distinct hydrogeological features. Low temperature (<45 °C), moderate temperature (55-70 °C) and high temperature (>70 °C) groups were identified based on their community compositions. Proteobacteria and Nitrospirae were the predominant phyla in low-temperature hot springs, while in moderate to high-temperature springs they were mainly composed of Aquificae, Deinococcus-Thermus, Thermodesulfobacteria, Thermotogae and Cyanobacteria. Variation partition analysis suggested a higher explanation of temperature (29.6%) than spatial variable (1.8%) and other geochemical variables (2.5%) on the microbial distribution. Microbial co-occurrence network showed >80% negative associations hinting a low co-existence pattern and highlighted the driving force of temperature as well as F^- or total organic carbon (TOC) for microbial interactions. Microbial dissimilarity displayed significant linear correlations with environmental (temperature) and geographic distance in Batang but only with temperature in Kangding area, which might be attributed to the regional-specific hydrogeochemistry. This study may help us to better understand the distribution of the microbial community in hot spring across different hydrothermal fields.

Multidomain ribosomal protein trees and the planctobacterial origin of neomura (eukaryotes, archaebacteria)

Palaeontologically, eubacteria are > 3× older than neomura (eukaryotes, archaebacteria). Cell biology contrasts ancestral eubacterial murein peptidoglycan walls and derived neomuran N-linked glycoprotein coats/walls. Misinterpreting long stems connecting clade neomura to eubacteria on ribosomal sequence trees (plus misinterpreted protein paralogue trees) obscured this historical pattern. Universal multiprotein ribosomal protein (RP) trees, more accurate than rRNA trees, are taxonomically undersampled. To reduce contradictions with genically richer eukaryote trees and improve eubacterial phylogeny, we constructed site-heterogeneous and maximum-likelihood universal three-domain, two-domain, and single-domain trees for 143 eukaryotes (branching now congruent with 187-protein trees), 60 archaebacteria, and 151 taxonomically representative eubacteria, using 51 and 26 RPs. Site-heterogeneous trees greatly improve eubacterial phylogeny and higher classification, e.g. showing gracilicute monophyly, that many 'rDNA-phyla' belong in Proteobacteria, and reveal robust new phyla Synthermota and Aquithermota. Monoderm Posibacteria and Mollicutes (two separate wall losses) are both polyphyletic: multiple outer membrane losses in Endobacteria occurred separately from Actinobacteria; neither phylum is related to Chloroflexi, the most divergent prokaryotes, which originated photosynthesis (new model proposed). RP trees support an eozoan root for eukaryotes and are consistent with archaebacteria being their sisters and rooted between Filarchaeota (=Proteoarchaeota, including 'Asgardia') and Euryarchaeota sensu-lato (including ultrasimplified 'DPANN' whose long branches often distort trees). Two-domain trees group eukaryotes within Planctobacteria, and archaebacteria with Planctobacteria/Sphingobacteria. Integrated molecular/palaeontological evidence favours negibacterial ancestors for neomura and all life. Unique presence of key pre-neomuran characters favours Planctobacteria only as ancestral to neomura, which apparently arose by coevolutionary repercussions (explained here in detail, including RP replacement) of simultaneous outer membrane and murein loss. Planctobacterial C-1 methanotrophic enzymes are likely ancestral to archaebacterial methanogenesis and β-propeller-α-solenoid proteins to eukaryotic vesicle coats, nuclear-pore-complexes, and intraciliary transport. Planctobacterial chaperone-independent 4/5-protofilament microtubules and MamK actin-ancestors prepared for eukaryote intracellular motility, mitosis, cytokinesis, and phagocytosis. We refute numerous wrong ideas about the universal tree.

Multidomain ribosomal protein trees and the planctobacterial origin of neomura (eukaryotes, archaebacteria)

Palaeontologically, eubacteria are > 3× older than neomura (eukaryotes, archaebacteria). Cell biology contrasts ancestral eubacterial murein peptidoglycan walls and derived neomuran N-linked glycoprotein coats/walls. Misinterpreting long stems connecting clade neomura to eubacteria on ribosomal sequence trees (plus misinterpreted protein paralogue trees) obscured this historical pattern. Universal multiprotein ribosomal protein (RP) trees, more accurate than rRNA trees, are taxonomically undersampled. To reduce contradictions with genically richer eukaryote trees and improve eubacterial phylogeny, we constructed site-heterogeneous and maximum-likelihood universal three-domain, two-domain, and single-domain trees for 143 eukaryotes (branching now congruent with 187-protein trees), 60 archaebacteria, and 151 taxonomically representative eubacteria, using 51 and 26 RPs. Site-heterogeneous trees greatly improve eubacterial phylogeny and higher classification, e.g. showing gracilicute monophyly, that many 'rDNA-phyla' belong in Proteobacteria, and reveal robust new phyla Synthermota and Aquithermota. Monoderm Posibacteria and Mollicutes (two separate wall losses) are both polyphyletic: multiple outer membrane losses in Endobacteria occurred separately from Actinobacteria; neither phylum is related to Chloroflexi, the most divergent prokaryotes, which originated photosynthesis (new model proposed). RP trees support an eozoan root for eukaryotes and are consistent with archaebacteria being their sisters and rooted between Filarchaeota (=Proteoarchaeota, including 'Asgardia') and Euryarchaeota sensu-lato (including ultrasimplified 'DPANN' whose long branches often distort trees). Two-domain trees group eukaryotes within Planctobacteria, and archaebacteria with Planctobacteria/Sphingobacteria. Integrated molecular/palaeontological evidence favours negibacterial ancestors for neomura and all life. Unique presence of key pre-neomuran characters favours Planctobacteria only as ancestral to neomura, which apparently arose by coevolutionary repercussions (explained here in detail, including RP replacement) of simultaneous outer membrane and murein loss. Planctobacterial C-1 methanotrophic enzymes are likely ancestral to archaebacterial methanogenesis and β-propeller-α-solenoid proteins to eukaryotic vesicle coats, nuclear-pore-complexes, and intraciliary transport. Planctobacterial chaperone-independent 4/5-protofilament microtubules and MamK actin-ancestors prepared for eukaryote intracellular motility, mitosis, cytokinesis, and phagocytosis. We refute numerous wrong ideas about the universal tree.

Novel Sequence Feature of SecA Translocase Protein Unique to the Thermophilic Bacteria: Bioinformatics Analyses to Investigate Their Potential Roles

SecA is an evolutionarily conserved protein that plays an indispensable role in the secretion of proteins across the bacterial cell membrane. Comparative analyses of SecA homologs have identified two large conserved signature inserts (CSIs) that are unique characteristics of thermophilic bacteria. A 50 aa conserved insert in SecA is exclusively present in the SecA homologs from the orders Thermotogales and Aquificales, while a 76 aa insert in SecA is specific for the order Thermales and Hydrogenibacillus schlegelii. Phylogenetic analyses on SecA sequences show that the shared presence of these CSIs in unrelated groups of thermophiles is not due to lateral gene transfers, but instead these large CSIs have likely originated independently in these lineages due to their advantageous function. Both of these CSIs are located in SecA protein in a surface exposed region within the ATPase domain. To gain insights into the functional significance of the 50 aa CSI in SecA, molecular dynamics (MD) simulations were performed at two different temperatures using ADP-bound SecA from Thermotoga maritima. These analyses have identified a conserved network of water molecules near the 50 aa insert in which the Glu185 residue from the CSI is found to play a key role towards stabilizing these interactions. The results provide evidence for the possible role of the 50 aa CSI in stabilizing the binding interaction of ADP/ATP, which is required for SecA function. Additionally, the surface-exposed CSIs in SecA, due to their potential to make novel protein-protein interactions, could also contribute to the thermostability of SecA from thermophilic bacteria.

Biogeography of thermophiles and predominance of Thermus scotoductus in domestic water heaters

Built systems such as water heaters can harbor extremophiles similar to those residing in natural hot springs, but the extent of colonization is not well understood. To address this, we conducted a survey of thermophilic microorganisms in household water heaters across the United States. Filter samples and inoculated cultures were collected by citizen-scientists from 101 homes. Draft genomes were assembled from cultured isolates and 16S rRNA genes were sequenced from filter samples. 28% of households harbored communities with unambiguous DNA signatures of thermophilic organisms, 36% of households provided viable inocula, and 21% of households had both. All of the recovered cultures as well as the community sequencing results revealed Thermus scotoductus to be the dominant thermophile in domestic water heaters, with a minority of water heaters also containing Meiothermus species and a few containing Aquificae. Sequence distance comparisons show that allopatric speciation does not appear to be a strong control on T. scotoductus distribution. Our results demonstrate that thermophilic organisms are widespread in hot tap water, and that Thermus scotoductus preferentially colonizes water heaters at the expense of local environmental Thermus strains.

Identification of distinctive molecular traits that are characteristic of the phylum "Deinococcus-Thermus" and distinguish its main constituent groups

The phylum "Deinococcus-Thermus" contains two heavily researched groups of extremophilic bacteria: the highly radioresistant order Deinococcales and the thermophilic order Thermales. Very few characteristics are known that are uniquely shared by members of the phylum "Deinococcus-Thermus". Comprehensive phylogenetic and comparative analyses of >65 "Deinococcus-Thermus" genomes reported here have identified numerous molecular signatures in the forms of conserved signature insertions/deletions (CSIs) and conserved signature proteins (CSPs), which provide distinguishing characteristics of the phylum "Deinococcus-Thermus" and its main groups. We have identified 58 unique CSIs and 155 unique CSPs that delineate different phylogenetic groups within the phylum. Of these identified traits, 24 CSIs and 29 CSPs are characteristic of the phylum "Deinococcus-Thermus" and they provide novel and reliable means to circumscribe/describe this phylum. An additional 3 CSIs and 3 CSPs are characteristic of the order Deinococcales, and 6 CSIs and 51 CSPs are characteristic of the order Thermales. The remaining 25 CSIs and 72 CSPs identified in this study are distinctive traits of genus level groups within the phylum "Deinococcus-Thermus". The molecular characteristics identified in this work provide novel and independent support for the common ancestry of the members of the phylum "Deinococcus-Thermus" and provide a new means to distinguish the main constituent clades of the phylum. Additionally, the CSIs and CSPs identified in this work may play a role in the unique extremophilic adaptations of the members of this phylum and further functional analyses of these characteristics could provide novel biochemical insights into the unique adaptations found within the phylum "Deinococcus-Thermus".

Impact of genomics on the understanding of microbial evolution and classification: the importance of Darwin's views on classification

Analyses of genome sequences, by some approaches, suggest that the widespread occurrence of horizontal gene transfers (HGTs) in prokaryotes disguises their evolutionary relationships and have led to questioning of the Darwinian model of evolution for prokaryotes. These inferences are critically examined in the light of comparative genome analysis, characteristic synapomorphies, phylogenetic trees and Darwin's views on examining evolutionary relationships. Genome sequences are enabling discovery of numerous molecular markers (synapomorphies) such as conserved signature indels (CSIs) and conserved signature proteins (CSPs), which are distinctive characteristics of different prokaryotic taxa. Based on these molecular markers, exhibiting high degree of specificity and predictive ability, numerous prokaryotic taxa of different ranks, currently identified based on the 16S rRNA gene trees, can now be reliably demarcated in molecular terms. Within all studied groups, multiple CSIs and CSPs have been identified for successive nested clades providing reliable information regarding their hierarchical relationships and these inferences are not affected by HGTs. These results strongly support Darwin's views on evolution and classification and supplement the current phylogenetic framework based on 16S rRNA in important respects. The identified molecular markers provide important means for developing novel diagnostics, therapeutics and for functional studies providing important insights regarding prokaryotic taxa.

Novel, Deep-Branching Heterotrophic Bacterial Populations Recovered from Thermal Spring Metagenomes

Thermal spring ecosystems are a valuable resource for the discovery of novel hyperthermophilic Bacteria and Archaea, and harbor deeply-branching lineages that provide insight regarding the nature of early microbial life. We characterized bacterial populations in two circumneutral (pH ~8) Yellowstone National Park thermal (T ~80°C) spring filamentous “streamer” communities using random metagenomic DNA sequence to investigate the metabolic potential of these novel populations. Four de novo assemblies representing three abundant, deeply-branching bacterial phylotypes were recovered. Analysis of conserved phylogenetic marker genes indicated that two of the phylotypes represent separate groups of an uncharacterized phylum (for which we propose the candidate phylum name “Pyropristinus”). The third new phylotype falls within the proposed Calescamantes phylum. Metabolic reconstructions of the “Pyropristinus” and Calescamantes populations showed that these organisms appear to be chemoorganoheterotrophs and have the genomic potential for aerobic respiration and oxidative phosphorylation via archaeal-like V-type, and bacterial F-type ATPases, respectively. A survey of similar phylotypes (>97% nt identity) within 16S rRNA gene datasets suggest that the newly described organisms are restricted to terrestrial thermal springs ranging from 70 to 90°C and pH values of ~7–9. The characterization of these lineages is important for understanding the diversity of deeply-branching bacterial phyla, and their functional role in high-temperature circumneutral “streamer” communities.

A phylogenomic reappraisal of family-level divisions within the class Halobacteria: proposal to divide the order Halobacteriales into the families Halobacteriaceae, Haloarculaceae fam. nov., and Halococcaceae fam. nov., and the order Haloferacales into the families, Haloferacaceae and Halorubraceae fam nov

The evolutionary interrelationships between the archaeal organisms which comprise the class Halobacteria have proven difficult to elucidate using traditional phylogenetic tools. The class currently contains three orders. However, little is known about the family level relationships within these orders. In this work, we have completed a comprehensive comparative analysis of 129 sequenced genomes from members of the class Halobacteria in order to identify shared molecular characteristics, in the forms of conserved signature insertions/deletions (CSIs) and conserved signature proteins (CSPs), which can provide reliable evidence, independent of phylogenetic trees, that the species from the groups in which they are found are specifically related to each other due to common ancestry. Here we present 20 CSIs and 31 CSPs which are unique characteristics of infra-order level groups of genera within the class Halobacteria. We also present 40 CSIs and 234 CSPs which are characteristic of Haloarcula, Halococcus, Haloferax, or Halorubrum. Importantly, the CSIs and CSPs identified here provide evidence that the order Haloferacales contains two main groups, one consisting of Haloferax and related genera supported by four CSIs and five CSPs and the other consisting of Halorubrum and related genera supported by four CSPs. We have also identified molecular characteristics that suggest that the polyphyletic order Halobacteriales contains at least two large monophyletic clusters of organisms in addition to the polyphyletic members of the order, one cluster consisting of Haloarcula and related genera supported by ten CSIs and nineteen CSPs and the other group consisting of the members of the genus Halococcus supported by nine CSIs and 23 CSPs. We have also produced a highly robust phylogenetic tree based on the concatenated sequences of 766 proteins which provide additional support for the relationships identified by the CSIs and CSPs. On the basis of the phylogenetic analyses and the identified conserved molecular characteristics presented here, we propose a division of the order Haloferacales into two families, an emended family Haloferacaceae and Halorubraceae fam. nov. and a division of the order Halobacteriales into three families, an emended family Halobacteriaceae, Haloarculaceae fam. nov., and Halococcaceae fam. nov.

Phylogenomic and molecular demarcation of the core members of the polyphyletic pasteurellaceae genera actinobacillus, haemophilus, and pasteurella

The genera Actinobacillus, Haemophilus, and Pasteurella exhibit extensive polyphyletic branching in phylogenetic trees and do not represent coherent clusters of species. In this study, we have utilized molecular signatures identified through comparative genomic analyses in conjunction with genome based and multilocus sequence based phylogenetic analyses to clarify the phylogenetic and taxonomic boundary of these genera. We have identified large clusters of Actinobacillus, Haemophilus, and Pasteurella species which represent the “sensu stricto” members of these genera. We have identified 3, 7, and 6 conserved signature indels (CSIs), which are specifically shared by sensu stricto members of Actinobacillus, Haemophilus, and Pasteurella, respectively. We have also identified two different sets of CSIs that are unique characteristics of the pathogen containing genera Aggregatibacter and Mannheimia, respectively. It is now possible to demarcate the genera Actinobacillus sensu stricto, Haemophilus sensu stricto, and Pasteurella sensu stricto on the basis of discrete molecular signatures. The other members of the genera Actinobacillus, Haemophilus, and Pasteurella that do not fall within the “sensu stricto” clades and do not contain these molecular signatures should be reclassified as other genera. The CSIs identified here also provide useful diagnostic targets for the identification of current and novel members of the indicated genera.

Phylogenetic analysis and molecular signatures defining a monophyletic clade of heterocystous cyanobacteria and identifying its closest relatives

Detailed phylogenetic and comparative genomic analyses are reported on 140 genome sequenced cyanobacteria with the main focus on the heterocyst-differentiating cyanobacteria. In a phylogenetic tree for cyanobacteria based upon concatenated sequences for 32 conserved proteins, the available cyanobacteria formed 8-9 strongly supported clades at the highest level, which may correspond to the higher taxonomic clades of this phylum. One of these clades contained all heterocystous cyanobacteria; within this clade, the members exhibiting either true (Nostocales) or false (Stigonematales) branching of filaments were intermixed indicating that the division of the heterocysts-forming cyanobacteria into these two groups is not supported by phylogenetic considerations. However, in both the protein tree as well as in the 16S rRNA gene tree, the akinete-forming heterocystous cyanobacteria formed a distinct clade. Within this clade, the members which differentiate into hormogonia or those which lack this ability were also separated into distinct groups. A novel molecular signature identified in this work that is uniquely shared by the akinete-forming heterocystous cyanobacteria provides further evidence that the members of this group are specifically related and they shared a common ancestor exclusive of the other cyanobacteria. Detailed comparative analyses on protein sequences from the genomes of heterocystous cyanobacteria reported here have also identified eight conserved signature indels (CSIs) in proteins involved in a broad range of functions, and three conserved signature proteins, that are either uniquely or mainly found in all heterocysts-forming cyanobacteria, but generally not found in other cyanobacteria. These molecular markers provide novel means for the identification of heterocystous cyanobacteria, and they provide evidence of their monophyletic origin. Additionally, this work has also identified seven CSIs in other proteins which in addition to the heterocystous cyanobacteria are uniquely shared by two smaller clades of cyanobacteria, which form the successive outgroups of the clade comprising of the heterocystous cyanobacteria in the protein trees. Based upon their close relationship to the heterocystous cyanobacteria, the members of these clades are indicated to be the closest relatives of the heterocysts-forming cyanobacteria.

Genomewide comparison and novel ncRNAs of Aquificales

Background

The Aquificales are a diverse group of thermophilic bacteria that thrive in terrestrial and marine hydrothermal environments. They can be divided into the families Aquificaceae, Desulfurobacteriaceae and Hydrogenothermaceae. Although eleven fully sequenced and assembled genomes are available, only little is known about this taxonomic order in terms of RNA metabolism.

Results

In this work, we compare the available genomes, extend their protein annotation, identify regulatory sequences, annotate non-coding RNAs (ncRNAs) of known function, predict novel ncRNA candidates, show idiosyncrasies of the genetic decoding machinery, present two different types of transfer-messenger RNAs and variations of the CRISPR systems. Furthermore, we performed a phylogenetic analysis of the Aquificales based on entire genome sequences, and extended this by a classification among all bacteria using 16S rRNA sequences and a set of orthologous proteins.

Combining several in silico features (e.g. conserved and stable secondary structures, GC-content, comparison based on multiple genome alignments) with an in vivo dRNA-seq transcriptome analysis of Aquifex aeolicus, we predict roughly 100 novel ncRNA candidates in this bacterium.

Conclusions

We have here re-analyzed the Aquificales, a group of bacteria thriving in extreme environments, sharing the feature of a small, compact genome with a reduced number of protein and ncRNA genes. We present several classical ncRNAs and riboswitch candidates. By combining in silico analysis with dRNA-seq data of A. aeolicus we predict nearly 100 novel ncRNA candidates.

A phylogenomic and molecular marker based proposal for the division of the genus Borrelia into two genera: the emended genus Borrelia containing only the members of the relapsing fever Borrelia, and the genus Borreliella gen. nov. containing the members of the Lyme disease Borrelia (Borrelia burgdorferi sensu lato complex)

The genus Borrelia contains two groups of organisms: the causative agents of Lyme disease and their relatives and the causative agents of relapsing fever and their relatives. These two groups are morphologically indistinguishable and are difficult to distinguish biochemically. In this work, we have carried out detailed comparative genomic analyses on protein sequences from 38 Borrelia genomes to identify molecular markers in the forms of conserved signature inserts/deletions (CSIs) that are specifically found in the Borrelia homologues, and conserved signature proteins (CSPs) which are uniquely present in Borrelia species. Our analyses have identified 31 CSIs and 82 CSPs that are uniquely shared by all sequenced Borrelia species, providing molecular markers for this group of organisms. In addition, our work has identified 7 CSIs and 21 CSPs which are uniquely found in the Lyme disease Borrelia species and eight CSIs and four CSPs that are specific for members of the relapsing fever Borrelia group. Additionally, 38 other CSIs, in proteins which are uniquely found in Borrelia species, also distinguish these two groups of Borrelia. The identified CSIs and CSPs provide novel and highly specific molecular markers for identification and distinguishing between the Lyme disease Borrelia and the relapsing fever Borrelia species. We also report the results of average nucleotide identity (ANI) analysis on Borrelia genomes and phylogenetic analysis for these species based upon 16S rRNA sequences and concatenated sequences for 25 conserved proteins. These analyses also support the distinctness of the two Borrelia clades. On the basis of the identified molecular markers, the results from ANI and phylogenetic studies, and the distinct pathogenicity profiles and arthropod vectors used by different Borrelia spp. for their transmission, we are proposing a division of the genus Borrelia into two separate genera: an emended genus Borrelia, containing the causative agents of relapsing fever and a novel genus, Borreliella gen. nov., containing the causative agents of Lyme disease.

List of new names and new combinations previously effectively, but not validly, published

The purpose of this announcement is to effect the valid publication of the following effectively published new names and new combinations under the procedure described in the Bacteriological Code (1990 Revision). Authors and other individuals wishing to have new names and/or combinations included in future lists should send three copies of the pertinent reprint or photocopies thereof, or an electronic copy of the published paper to the IJSEM Editorial Office for confirmation that all of the other requirements for valid publication have been met. It is also a requirement of IJSEM and the ICSP that authors of new species, new subspecies and new combinations provide evidence that types are deposited in two recognized culture collections in two different countries. It should be noted that the date of valid publication of these new names and combinations is the date of publication of this list, not the date of the original publication of the names and combinations. The authors of the new names and combinations are as given below. Inclusion of a name on these lists validates the publication of the name and thereby makes it available in the nomenclature of prokaryotes. The inclusion of a name on this list is not to be construed as taxonomic acceptance of the taxon to which the name is applied. Indeed, some of these names may, in time, be shown to be synonyms, or the organisms may be transferred to another genus, thus necessitating the creation of a new combination.

Notification of changes in taxonomic opinion previously published outside the IJSEM

The Bacteriological Code deals with the nomenclature of prokaryotes. This may include existing names (the Approved Lists of Bacterial Names) as well as new names and new combinations. In this sense the Code is also dealing indirectly with taxonomic opinions. However, as with most codes of nomenclature there are no mechanisms for formally recording taxonomic opinions that do not involve the creation of new names or new combinations. In particular, it would be desirable for taxonomic opinions resulting from the creation of synonyms or emended descriptions to be made widely available to the public. In 2004, the Editorial Board of the International Journal of Systematic and Evolutionary Microbiology (IJSEM) agreed unanimously that it was desirable to cover such changes in taxonomic opinions (i.e. the creation of synonyms or the emendation of circumscriptions) previously published outside the IJSEM, and to introduce a List of Changes in Taxonomic Opinion [Notification of changes in taxonomic opinion previously published outside the IJSEM; Euzéby et al. (2004). Int J Syst Evol Microbiol 54, 1429–1430]. Scientists wishing to have changes in taxonomic opinion included in future lists should send one copy of the pertinent reprint or a photocopy or a PDF file thereof to the IJSEM Editorial Office or to the Lists Editor. It must be stressed that the date of proposed taxonomic changes is the date of the original publication not the date of publication of the list. Taxonomic opinions included in the List of Changes in Taxonomic Opinion cannot be considered as validly published nor, in any other way, approved by the International Committee on Systematics of Prokaryotes and its Judicial Commission. The names that are to be used are those that are the ‘correct names’ (in the sense of Principle 6) in the opinion of the bacteriologist, with a given circumscription, position and rank. A particular name, circumscription, position and rank do not have to be adopted in all circumstances. Consequently, the List of Changes in Taxonomic Opinion must be considered as a service to bacteriology and it has no ‘official character’, other than providing a centralized point for registering/indexing such changes in a way that makes them easily accessible to the scientific communit y.

Molecular signatures for the phylum (class) Thermotogae and a proposal for its division into three orders (Thermotogales, Kosmotogales ord. nov. and Petrotogales ord. nov.) containing four families (Thermotogaceae, Fervidobacteriaceae fam. nov., Kosmotogaceae fam. nov. and Petrotogaceae fam. nov.) and a new genus Pseudothermotoga gen. nov. with five new combinations

All species from the phylum Thermotogae, class Thermotogae, are currently part of a single family, Thermotogaceae. Using genomic data from 17 Thermotogae species, detailed phylogenetic and comparative genomic analyses were carried out to understand their evolutionary relationships and identify molecular markers that are indicative of species relationships within the phylum. In the 16S rRNA gene tree and phylogenetic trees based upon two different large sets of proteins, members of the phylum Thermotogae formed a number of well-resolved clades. Character compatibility analysis on the protein sequence data also recovered a single largest clique that exhibited similar topology to the protein trees and where all nodes were supported by multiple compatible characters. Comparative genomic analyses have identified 85 molecular markers, in the form of conserved signature indels (CSIs), which are specific for different observed clades of Thermotogae at multiple phylogenetic depths. Eleven of these CSIs were specific for the phylum Thermotogae whereas nine others supported a clade comprising of the genera Thermotoga, Thermosipho and Fervidobacterium. Ten other CSIs provided evidence that the genera Thermosipho and Fervidobacterium shared a common ancestor exclusive of the other Thermotogae and four and eight CSIs in other proteins were specific for the genera Thermosipho and Fervidobacterium, respectively. Two other deep branching clades, one consisting of the genera Kosmotoga and Mesotoga and the other comprising of the genera Petrotoga and Marinitoga, were also supported by multiple CSIs. Based upon the consistent branching of the Thermotogae species using different phylogenetic approaches, and numerous identified CSIs supporting the distinctness of different clades, it is proposed that the class Thermotogae should be divided into three orders (Thermotogales, Kosmotogales ord. nov. and Petrotogales ord. nov.) containing four families (Thermotogaceae, Fervidobacteriaceae fam. nov., Kosmotogaceae fam. nov. and Petrotogaceae fam. nov.). Additionally, the results of our phylogenetic/compatibility studies along with the species distribution patterns of 22 identified CSIs, provide compelling evidence that the current genus Thermotoga is comprised of two evolutionary distinct groups and that it should be divided into two genera. It is proposed that the emended genus Thermotoga should retain only the species Thermotoga maritima, Tt. neapolitana, Tt. petrophila, Tt. naphthophila, Thermotoga sp. EMP, Thermotoga sp. A7A and Thermotoga sp. RQ2 while the other Thermotoga species (viz. Tt. lettingae, Tt. thermarum, Tt. elfii, Tt. subterranean and Tt. hypogea) be transferred to a new genus, Pseudothermotoga gen. nov.