Molecular signatures for the class Coriobacteriia and its different clades; proposal for division of the class Coriobacteriia into the emended order Coriobacteriales, containing the emended family Coriobacteriaceae and Atopobiaceae fam. nov., and Eggerthellales ord. nov., containing the family Eggerthellaceae fam. nov

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.

Quantification of Slackia and Eggerthella spp. in Human Feces and Adhesion of Representatives Strains to Caco-2 Cells

Eggerthella and Slackia spp. are gut associated bacteria that have been suggested to play roles in host lipid and xenobiotic metabolism. A quantitative PCR method for the selective enumeration of bacteria belonging to either the genus Eggerthella or Slackia was developed in order to establish the numbers of these bacteria occurring in human feces. The primers developed for selective amplification of these genera were tested first in conventional PCR to test for their specificity. Representative species of Eggerthella and Slackia, as well as closely related genera of the Coriobacteriia, were included in the investigation. The selected primers were shown to be capable of specific amplification of species of the genera Eggerthella and Slackia, but not all species of the genera may be amplified by the respective primers. Their use in qPCR experiments to assess the levels of Slackia equolifaciens and Eggerthella lenta in the feces of 19 human volunteers showed they occurred at mean counts of 7 × 10(5) and 3.1 × 10(5) CFU/g for Eggerthella spp. and Slackia spp., respectively. Electron microscopy investigations showed that while E. lenta cells exhibited slender and very regular shaped rods, Slackia cells showed a remarkably pleomorphic phenotype. Both species did not appear to have fimbriae or pili. Some S. equolifaciens cells showed a characteristic "ribbon" of presumably extracellular material around the cells, particularly at the areas of cell division. The two species also differed markedly in their adhesion behavior to Caco-2 cells in cell culture, as E. lenta DSMZ 15644 showed a high adhesion capacity of 74.2% adherence of the bacterial cells added to Caco-2 cells, while S. equolifaciens DSM 24851(T) on the other hand showed only low adhesion capability, as 6.1% of bacterial cells remained bound. Speculatively, this may imply that the ecological compartments where these bacteria reside in the gut may be different, i.e., E. lenta may be associated more with the gut wall, while Slackia may be free living in the lumen.

Actinobacterial Diversity in Volcanic Caves and Associated Geomicrobiological Interactions

Volcanic caves are filled with colorful microbial mats on the walls and ceilings. These volcanic caves are found worldwide, and studies are finding vast bacteria diversity within these caves. One group of bacteria that can be abundant in volcanic caves, as well as other caves, is Actinobacteria. As Actinobacteria are valued for their ability to produce a variety of secondary metabolites, rare and novel Actinobacteria are being sought in underexplored environments. The abundance of novel Actinobacteria in volcanic caves makes this environment an excellent location to study these bacteria. Scanning electron microscopy (SEM) from several volcanic caves worldwide revealed diversity in the morphologies present. Spores, coccoid, and filamentous cells, many with hair-like or knobby extensions, were some of the microbial structures observed within the microbial mat samples. In addition, the SEM study pointed out that these features figure prominently in both constructive and destructive mineral processes. To further investigate this diversity, we conducted both Sanger sequencing and 454 pyrosequencing of the Actinobacteria in volcanic caves from four locations, two islands in the Azores, Portugal, and Hawai'i and New Mexico, USA. This comparison represents one of the largest sequencing efforts of Actinobacteria in volcanic caves to date. The diversity was shown to be dominated by Actinomycetales, but also included several newly described orders, such as Euzebyales, and Gaiellales. Sixty-two percent of the clones from the four locations shared less than 97% similarity to known sequences, and nearly 71% of the clones were singletons, supporting the commonly held belief that volcanic caves are an untapped resource for novel and rare Actinobacteria. The amplicon libraries depicted a wider view of the microbial diversity in Azorean volcanic caves revealing three additional orders, Rubrobacterales, Solirubrobacterales, and Coriobacteriales. Studies of microbial ecology in volcanic caves are still very limited. To rectify this deficiency, the results from our study help fill in the gaps in our knowledge of actinobacterial diversity and their potential roles in the volcanic cave ecosystems.

Olsenella scatoligenes sp. nov., a 3-methylindole- (skatole) and 4-methylphenol- (p-cresol) producing bacterium isolated from pig faeces

Strain SK9K4(T), which is a strictly anaerobic, non-motile, non-sporulating, Gram-stain-positive, saccharolytic coccobacillus, was isolated from pig faeces. SK9K4(T) metabolized indol-3-acetic acid to 3-methylindole (skatole), which is the main contributor to boar taint; it also produced 4-methylphenol (p-cresol) from p-hydroxyphenylacetic acid. Phylogenetic analyses, based on 16S rRNA gene sequences, revealed that the isolate represented a new lineage within the genus Olsenella of the family Atopobiaceae . Strain SK9K4(T) was most closely related to the type strains of the three species of the genus Olsenella with validly published names; Olsenella profusa DSM 13989(T) (93.6%), Olsenella uli DSM 7084(T) (93.5%) and Olsenella umbonata DSM 22620(T) (92.7%). DNA-DNA relatedness values of strain SK9K4(T) with O. profusa , O. uli and O. umbonata were 28.3%, 69.1% and 27.2%, respectively. The genomic DNA G+C content was 62.1 mol% and the major cellular fatty acids (constituting >10% of the total) were C(14 : 0) and C(18 : 1)ω9c. The major end product of glucose fermentation was lactic acid, with minor amounts of acetic acid and formic acid; no H2 was produced. Discrepancies in the fatty acid profiles, the MALDI-TOF mass spectra of cell extracts and the physiological and biochemical characteristics differentiated strain SK9K4(T) from other species of the genus Olsenella and indicate that the isolate represents a novel species within this genus. The name Olsenella scatoligenes sp. nov., is proposed and the type strain is SK9K4(T) ( = JCM 19907(T) = DSM 28304(T)).

Dynamics and diversity of the 'Atopobium cluster' in the human faecal microbiota, and phenotypic characterization of 'Atopobium cluster' isolates

This study monitored the dynamics and diversity of the human faecal 'Atopobium cluster' over a 3-month period using a polyphasic approach. Fresh faecal samples were collected fortnightly from 13 healthy donors (six males and seven females) aged between 26 and 61 years. FISH was used to enumerate total (EUB338mix) and 'Atopobium cluster' (ATO291) bacteria, with counts ranging between 1.12×10(11) and 9.95×10(11), and 1.03×10(9) and 1.16×10(11) cells (g dry weight faeces)(-1), respectively. The 'Atopobium cluster' population represented 0.2-22 % of the total bacteria, with proportions donor-dependent. Denaturing gradient gel electrophoresis (DGGE) using 'Atopobium cluster'-specific primers demonstrated faecal populations of these bacteria were relatively stable, with bands identified as Collinsella aerofaciens, Collinsella intestinalis/Collinsella stercoris, Collinsella tanakaei, Coriobacteriaceae sp. PEAV3-3, Eggerthella lenta, Gordonibacter pamelaeae, Olsenella profusa, Olsenella uli and Paraeggerthella hongkongensis in the DGGE profiles of individuals. Colony PCR was used to identify 'Atopobium cluster' bacteria isolated from faeces (n = 224 isolates). 16S rRNA gene sequence analysis of isolates demonstrated Collinsella aerofaciens represented the predominant (88 % of isolates) member of the 'Atopobium cluster' found in human faeces, being found in nine individuals. Eggerthella lenta was identified in three individuals (3.6 % of isolates). Isolates of Collinsella tanakaei, an 'Enorma' sp. and representatives of novel species belonging to the 'Atopobium cluster' were also identified in the study. Phenotypic characterization of the isolates demonstrated their highly saccharolytic nature and heterogeneous phenotypic profiles, and 97 % of the isolates displayed lipase activity.

Atopobium deltae sp. nov., isolated from the blood of a patient with Fournier's gangrene

A Gram-stain-positive, obligately anaerobic, short rod, designated strain HHRM1715(T), was isolated from the blood of a patient with Fournier's gangrene, complicated by sepsis. On the basis of 16S rRNA gene sequence analysis, strain HHRM1715(T) was shown to belong to the genus Atopobium and was most closely related to Atopobium minutum (95 % similarity). The results of 16S rRNA-gene-based phylogenetic analysis, cellular fatty acid analysis and differential biochemical tests, showed that strain HHRM1715(T) represented a novel species of the genus Atopobium. We therefore describe Atopobium deltae sp. nov. with HHRM1715(T) ( = LMG 27987(T) = CCUG 65171(T)) as the type strain and propose an emended description of the genus Atopobium with regard to the DNA G+C content.

Developmental biology of Streptomyces from the perspective of 100 actinobacterial genome sequences

To illuminate the evolution and mechanisms of actinobacterial complexity, we evaluate the distribution and origins of known Streptomyces developmental genes and the developmental significance of actinobacteria-specific genes. As an aid, we developed the Actinoblast database of reciprocal blastp best hits between the Streptomyces coelicolor genome and more than 100 other actinobacterial genomes (http://streptomyces.org.uk/actinoblast/). We suggest that the emergence of morphological complexity was underpinned by special features of early actinobacteria, such as polar growth and the coupled participation of regulatory Wbl proteins and the redox-protecting thiol mycothiol in transducing a transient nitric oxide signal generated during physiologically stressful growth transitions. It seems that some cell growth and division proteins of early actinobacteria have acquired greater importance for sporulation of complex actinobacteria than for mycelial growth, in which septa are infrequent and not associated with complete cell separation. The acquisition of extracellular proteins with structural roles, a highly regulated extracellular protease cascade, and additional regulatory genes allowed early actinobacterial stationary phase processes to be redeployed in the emergence of aerial hyphae from mycelial mats and in the formation of spore chains. These extracellular proteins may have contributed to speciation. Simpler members of morphologically diverse clades have lost some developmental genes.

Characterization of new bacterial catabolic genes and mobile genetic elements by high throughput genetic screening of a soil metagenomic library

A mix of oligonucleotide probes was used to hybridize soil metagenomic DNA from a fosmid clone library spotted on high density membranes. The pooled radio-labeled probes were designed to target genes encoding glycoside hydrolases GH18, dehalogenases, bacterial laccases and mobile genetic elements (integrases from integrons and insertion sequences). Positive hybridizing spots were affiliated to the corresponding clones in the library and the metagenomic inserts were sequenced. After assembly and annotation, new coding DNA sequences related to genes of interest were identified with low protein similarity against the closest hits in databases. This work highlights the sensitivity of DNA/DNA hybridization techniques as an effective and complementary way to recover novel genes from large metagenomic clone libraries. This study also supports that some of the identified catabolic genes might be associated with horizontal transfer events.

Non contiguous-finished genome sequence and description of Enorma timonensis sp. nov

Enorma timonensis strain GD5(T) sp. nov., is the type strain of E. timonensis sp. nov., a new member of the genus Enorma within the family Coriobacteriaceae. This strain, whose genome is described here, was isolated from the fecal flora of a 53-year-old woman hospitalized for 3 months in an intensive care unit. E. timonensis is an obligate anaerobic rod. Here we describe the features of this organism, together with the complete genome sequence and annotation. The 2,365,123 bp long genome (1 chromosome but no plasmid) contains 2,060 protein-coding and 52 RNA genes, including 4 rRNA genes.

A phylogenomic and molecular signature based approach for characterization of the phylum Spirochaetes and its major clades: proposal for a taxonomic revision of the phylum

The Spirochaetes species cause many important diseases including syphilis and Lyme disease. Except for their containing a distinctive endoflagella, no other molecular or biochemical characteristics are presently known that are specific for either all Spirochaetes or its different families. We report detailed comparative and phylogenomic analyses of protein sequences from Spirochaetes genomes to understand their evolutionary relationships and to identify molecular signatures for this group. These studies have identified 38 conserved signature indels (CSIs) that are specific for either all members of the phylum Spirochaetes or its different main clades. Of these CSIs, a 3 aa insert in the FlgC protein is uniquely shared by all sequenced Spirochaetes providing a molecular marker for this phylum. Seven, six, and five CSIs in different proteins are specific for members of the families Spirochaetaceae, Brachyspiraceae, and Leptospiraceae, respectively. Of the 19 other identified CSIs, 3 are uniquely shared by members of the genera Sphaerochaeta, Spirochaeta, and Treponema, whereas 16 others are specific for the genus Borrelia. A monophyletic grouping of the genera Sphaerochaeta, Spirochaeta, and Treponema distinct from the genus Borrelia is also strongly supported by phylogenetic trees based upon concatenated sequences of 22 conserved proteins. The molecular markers described here provide novel and more definitive means for identification and demarcation of different main groups of Spirochaetes. To accommodate the extensive genetic diversity of the Spirochaetes as revealed by different CSIs and phylogenetic analyses, it is proposed that the four families of this phylum should be elevated to the order level taxonomic ranks (viz. Spirochaetales, Brevinematales ord. nov., Brachyspiriales ord. nov., and Leptospiriales ord. nov.). It is further proposed that the genera Borrelia and Cristispira be transferred to a new family Borreliaceae fam. nov. within the order Spirochaetales.

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

We report here detailed phylogenetic and comparative analyses on 11 sequenced genomes from the phylum Aquificae to identify molecular markers that are specific for the species from this phylum or its different families (viz. Aquificaceae, Hydrogenothermaceae and Desulfurobacteriaceae). In phylogenetic trees based on 16S rRNA gene or concatenated sequences for 32 conserved proteins, species from the three Aquificae families formed distinct clades. These trees also supported a strong relationship between the Aquificaceae and Hydrogenothermaceae families. In parallel, comparative analyses on protein sequences from Aquificae genomes have identified 46 conserved signature indels (CSIs) in broadly distributed proteins that are either exclusively or mainly found in members of the phylum Aquificae or its different families and subclades. Four of these CSIs, which are found in all sequenced Aquificae species, provide potential molecular markers for this phylum. Twelve, six and thirteen other CSIs that respectively are specific for the sequenced Aquificaceae, Hydrogenothermaceae and Desulfurobacteriaceae species provide molecular markers and novel tools for the identification of members of these families and for genetic and biochemical studies on them. Lastly, these studies have identified 11 CSIs in divergent proteins that are uniquely shared by members of the Aquificaceae and Hydrogenothermaceae families providing strong evidence that these two groups of bacteria shared a common ancestor exclusive of all other Aquificae (bacteria). The species from these two families are also very similar in their metabolic and physiological properties and they consist of aerobic or microaerophilic bacteria, which generally obtain energy by oxidation of hydrogen or reduced sulfur compounds by molecular oxygen. Based upon their strong association in phylogenetic trees, unique shared presence of large numbers of CSIs in different proteins, and similarities in their metabolic and physiological properties, it is proposed that the order Aquificales should be emended to include only the members of the families Aquificaceae and Hydrogenothermaceae. The members of the family Desulfurobacteriaceae, which are obligate anaerobes that strictly use hydrogen as electron donor, are now transferred to a new order Desulfurobacteriales ord. nov. The emended descriptions of the phylum Aquificae and its three families incorporating information for different molecular signatures are also provided.