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As an infectious disease, tuberculosis (TB) is one of the major causes of death worldwide. Paleopathological and paleomicrobiological studies indicate a long standing association of the causative agent Mycobacterium tuberculosis and its human host. Since the occurrence and the epidemic spread of this pathogen seem to be closely linked to social and biological factors, it is of particular interest to understand better the role of TB during periods of social and nutritional change such as the Neolithic. In this study, 118 individuals from three sites in Saxony-Anhalt (Germany) dating to the Linear Pottery Culture (5400-4800 BC) were examined macroscopically to identify TB related bone lesions. In two individuals, Pott's disease was detected. In addition, periosteal reactions of varying degrees and frequency were observed mainly along the neck of the ribs in 6.5% (2/31) of subadults and 35.1% (20/57) of adults, with one site standing out markedly. Rib lesions, however, are not specific indicators of TB as they can also be caused by other diseases; so additional investigations were undertaken using histology and micro-CT scans to say more about the disease process. Supplementary molecular analyses indicate the presence of pathogens belonging to the Mycobacterium tuberculosis complex in individuals of all sites. Furthermore, we discuss the occurrence and spread of TB during the Neolithic with regard to nutritional aspects and possible risks of infection. The data presented provide important insights into the health status of Early Neolithic populations in Central Germany.

Chlorite dismutase (Cld) is a unique heme enzyme catalyzing the conversion of ClO 2 − to Cl − and O 2 . Cld is usually found in perchlorate- or chlorate-reducing bacteria but was also recently identified in a nitrite-oxidizing bacterium of the genus Nitrospira . Here we characterized a novel Cld-like protein from the chemolithoautotrophic nitrite oxidizer Nitrobacter winogradskyi which is significantly smaller than all previously known chlorite dismutases. Its three-dimensional (3D) crystal structure revealed a dimer of two identical subunits, which sharply contrasts with the penta- or hexameric structures of other chlorite dismutases. Despite a truncated N-terminal domain in each subunit, this novel enzyme turned out to be a highly efficient chlorite dismutase ( K m = 90 μM; k cat = 190 s −1 ; k cat / K m = 2.1 × 10 6 M −1 s −1 ), demonstrating a greater structural and phylogenetic diversity of these enzymes than was previously known. Based on comparative analyses of Cld sequences and 3D structures, signature amino acid residues that can be employed to assess whether uncharacterized Cld-like proteins may have a high chlorite-dismutating activity were identified. Interestingly, proteins that contain all these signatures and are phylogenetically closely related to the novel-type Cld of N. winogradskyi exist in a large number of other microbes, including other nitrite oxidizers.

Currently, one of the biggest challenges in microbial and ecosystem ecology is to develop conceptual models that organize the growing body of information on environmental microbiology into a clear mechanistic framework with a direct link to ecosystem processes. Doing so will enable development of testable hypotheses to better direct future research and increase understanding of key constraints on biogeochemical networks. Although the understanding of phenotypic and genotypic diversity of microorganisms in the environment is rapidly accumulating, how controls on microbial physiology ultimately affect biogeochemical fluxes remains poorly understood. We propose that insight into constraints on biogeochemical cycles can be achieved by a more rigorous evaluation of microbial community biomass composition within the context of ecological stoichiometry. Multiple recent studies have pointed to microbial biomass stoichiometry as an important determinant of when microorganisms retain or recycle mineral nutrients. We identify the relevant cellular components that most likely drive changes in microbial biomass stoichiometry by defining a conceptual model rooted in ecological stoichiometry. More importantly, we show how X-ray microanalysis (XRMA), nanoscale secondary ion mass spectroscopy (NanoSIMS), Raman microspectroscopy, and in situ hybridization techniques (for example, FISH) can be applied in concert to allow for direct empirical evaluation of the proposed conceptual framework. This approach links an important piece of the ecological literature, ecological stoichiometry, with the molecular front of the microbial revolution, in an attempt to provide new insight into how microbial physiology could constrain ecosystem processes.

Geothermal environments are a suitable habitat for nitrifying microorganisms. Conventional and molecular techniques indicated that chemolithoautotrophic nitrite-oxidizing bacteria affiliated with the genus Nitrospira are widespread in environments with elevated temperatures up to 55 °C in Asia, Europe, and Australia. However, until now, no thermophilic pure cultures of Nitrospira were available, and the physiology of these bacteria was mostly uncharacterized. Here, we report on the isolation and characterization of a novel thermophilic Nitrospira strain from a microbial mat of the terrestrial geothermal spring Gorjachinsk (pH 8.6; temperature 48 °C) from the Baikal rift zone (Russia). Based on phenotypic properties, chemotaxonomic data, and 16S rRNA gene phylogeny, the isolate was assigned to the genus Nitrospira as a representative of a novel species, for which the name Nitrospira calida is proposed. A highly similar 16S rRNA gene sequence (99.6% similarity) was detected in a Garga spring enrichment grown at 46 °C, whereas three further thermophilic Nitrospira enrichments from the Garga spring and from a Kamchatka Peninsula (Russia) terrestrial hot spring could be clearly distinguished from N. calida (93.6-96.1% 16S rRNA gene sequence similarity). The findings confirmed that Nitrospira drive nitrite oxidation in moderate thermophilic habitats and also indicated an unexpected diversity of heat-adapted Nitrospira in geothermal hot springs.

Stoichiometry of microbial biomass is a key determinant of nutrient recycling in a wide variety of ecosystems. However, little is known about the underlying causes of variance in microbial biomass stoichiometry. This is primarily because of technological constraints limiting the analysis of macromolecular composition to large quantities of microbial biomass. Here, we use Raman microspectroscopy (MS), to analyze the macromolecular composition of single cells of two species of bacteria grown on minimal media over a wide range of resource stoichiometry. We show that macromolecular composition, determined from a subset of identified peaks within the Raman spectra, was consistent with macromolecular composition determined using traditional analytical methods. In addition, macromolecular composition determined by Raman MS correlated with total biomass stoichiometry, indicating that analysis with Raman MS included a large proportion of a cell's total macromolecular composition. Growth phase (logarithmic or stationary), resource stoichiometry and species identity each influenced each organism's macromolecular composition and thus biomass stoichiometry. Interestingly, the least variable peaks in the Raman spectra were those responsible for differentiation between species, suggesting a phylogenetically specific cellular architecture. As Raman MS has been previously shown to be applicable to cells sampled directly from complex environments, our results suggest Raman MS is an extremely useful application for evaluating the biomass stoichiometry of environmental microorganisms. This includes the ability to partition microbial biomass into its constituent macromolecules and increase our understanding of how microorganisms in the environment respond to resource heterogeneity.

Nitrospira are barely studied and mostly uncultured nitrite-oxidizing bacteria, which are, according to molecular data, among the most diverse and widespread nitrifiers in natural ecosystems and biological wastewater treatment. Here, environmental genomics was used to reconstruct the complete genome of “ Candidatus Nitrospira defluvii” from an activated sludge enrichment culture. On the basis of this first-deciphered Nitrospira genome and of experimental data, we show that Ca . N. defluvii differs dramatically from other known nitrite oxidizers in the key enzyme nitrite oxidoreductase (NXR), in the composition of the respiratory chain, and in the pathway used for autotrophic carbon fixation, suggesting multiple independent evolution of chemolithoautotrophic nitrite oxidation. Adaptations of Ca . N. defluvii to substrate-limited conditions include an unusual periplasmic NXR, which is constitutively expressed, and pathways for the transport, oxidation, and assimilation of simple organic compounds that allow a mixotrophic lifestyle. The reverse tricarboxylic acid cycle as the pathway for CO 2 fixation and the lack of most classical defense mechanisms against oxidative stress suggest that Nitrospira evolved from microaerophilic or even anaerobic ancestors. Unexpectedly, comparative genomic analyses indicate functionally significant lateral gene-transfer events between the genus Nitrospira and anaerobic ammonium-oxidizing planctomycetes, which share highly similar forms of NXR and other proteins reflecting that two key processes of the nitrogen cycle are evolutionarily connected.

Lesions consistent with skeletal tuberculosis were found in 13 individuals from an early medieval skeletal sample from Courroux (Switzerland). One case of Pott's disease as well as lytic lesions in vertebrae and joints, rib lesions and endocranial new bone formation were identified. Three individuals with lesions and one without were tested for the presence of Myobacterium tuberculosis complex (MTBC) ancient DNA (aDNA), and in two cases, evidence for MTBC aDNA was detected. Our results suggest the presence of tuberculosis in the analysed material, which is in accordance with other osteological and biomolecular research that reported a high prevalence of tuberculosis in medieval skeletons.

Stomach ache for a European mummy Five thousand years ago in the European Alps, a man was shot by an arrow, then clubbed to death. His body was subsequently mummified by ice until glacier retreat exhumed him in 1991. Subsequently, this ancient corpse has provided a trove of intriguing information about copper-age Europeans. Now, Maixner et al. have identified the human pathogen Helicobacter pylori within the mummy's stomach contents. The strain the “Iceman” hosted appears to most closely resemble pathogenic Asian strains found today in Central and Southern Asia. Science , this issue p. 162

Alsonyek-Bataszek in Southern Hungary is one of the largest late Neolithic settlements and cemeteries excavated in Central Europe. In total, 2,359 burials from the Late Neolithic – Early Copper Age Lengyel culture were found between 2006 and 2009. Anthropological investigations previously carried out on individuals from this site revealed an interesting paleopathological case of tuberculosis in the form of Pott’s disease dated to the early 5th millennium BC. In this study, selected specimens from this osteoarcheological series were subjected to paleomicrobiological analysis to establish the presence of MTBC bacteria. As all individuals showing clear osteological signs of TB infection belonged to a single grave group, 38 individuals from this grave group were analysed. The sample included the case of Pott’s disease as well as individuals both with and without osseous TB manifestations. The presence of TB DNA in the individual with Pott’s disease was established, confirming the occurrence of TB in Neolithic populations of Europe. Moreover, our molecular analysis indicated that several other individuals of the same grave group were also infected with TB, opening the possibility for further analyses of this unique Neolithic skeletal series.

The Tyrolean Iceman is an extraordinarily well-preserved natural mummy that lived south of the Alpine ridge ~5,200 years before present (ybp), during the Copper Age. Despite studies that have investigated his genetic profile, the relation of the Iceman´s maternal lineage with present-day mitochondrial variation remains elusive. Studies of the Iceman have shown that his mitochondrial DNA (mtDNA) belongs to a novel lineage of haplogroup K1 (K1f) not found in extant populations. We analyzed the complete mtDNA sequences of 42 haplogroup K bearing individuals from populations of the Eastern Italian Alps – putatively in genetic continuity with the Tyrolean Iceman—and compared his mitogenome with a large dataset of worldwide K1 sequences. Our results allow a re-definition of the K1 phylogeny and indicate that the K1f haplogroup is absent or rare in present-day populations. We suggest that mtDNA Iceman´s lineage could have disappeared during demographic events starting in Europe from ~5,000 ybp. Based on the comparison of our results with published data, we propose a scenario that could explain the apparent contrast between the phylogeographic features of maternal and paternal lineages of the Tyrolean Iceman within the context of the demographic dynamics happening in Europe from 8,000 ybp. This study was financed by the Provincia Autonoma di Bolzano – Alto Adige, Ripartizione Diritto allo studio, università e ricerca scientifica, funds to VC SI

International audience; Alsónyék-Bátaszék in Southern Hungary is one of the largest late Neolithic settlements and cemeteries excavated in Central Europe. In total, 2359 burials from the Late Neolithic - Early Copper Age Lengyel culture were found between 2006 and 2009 [1]. Anthropological investigations previously carried out on individuals from this site revealed an interesting paleopathological case of tuberculosis in the form of Pott's disease dated to the early 5(th) millennium BC. In this study, selected specimens from this osteoarcheological series were subjected to paleomicrobiological analysis to establish the presence of MTBC bacteria. As all individuals showing clear osteological signs of TB infection belonged to a single grave group, 38 individuals from this grave group were analysed. The sample included the case of Pott's disease as well as individuals both with and without osseous TB manifestations. The detection of TB DNA in the individual with Pott's disease provided further evidence for the occurrence of TB in Neolithic populations of Europe. Moreover, our molecular analysis indicated that several other individuals of the same grave group were also infected with TB, opening the possibility for further analyses of this unique Neolithic skeletal series.

International audience; During the American colonization in the 18th and 19th century, Africans were captured and shipped to America. Harsh living and working conditions often led to chronic diseases and high mortality rates. Slaves in the Caribbean were forced to work mainly on sugar plantations. They were buried in cemeteries like Anse Sainte-Marguerite on the isle of Grande-Terre (Guadeloupe) which was examined by archaeologists and physical anthropologists. Morphological studies on osseous remains of 148 individuals revealed 15 cases with signs for bone tuberculosis and a high frequency of periosteal reactions which indicates early stages of the disease. 11 bone samples from these cemeteries were analysed for ancient DNA. The samples were extracted with established procedures and examined for the cytoplasmic multicopy β-actin gene and Mycobacterium tuberculosis complex DNA (IS 6110) by PCR. An amplification product for M. tuberculosis with the size of 123 bp was obtained. Sequencing confirmed the result. This study shows evidence of M. tuberculosis complex DNA in a Caribbean slave population.

probeBase is a curated database of annotated rRNA-targeted oligonucleotide probes and supporting information. Rapid access to probe, microarray and reference data is achieved by powerful search tools and via different lists that are based on selected categories such as functional or taxonomic properties of the target organism(s) or the hybridization format (fluorescence in situ hybridization or microarray) in which the probes were applied. Additional information on probe coverage and specificity is available through direct submissions of probe sequences from probeBase to RDP-II and Greengenes, two major rRNA sequence databases. A freely editable user comments field for each probe entry allows any user to add, modify or remove information or to report errors in real-time. probeBase entries increased from 700 to more than 1200 during the past three years. Several options for submission of single probes or entire probe sets, even prior to publication of newly developed probes, should further contribute to keeping probeBase an up-to-date and useful resource. probeBase is freely accessible at http://www.microbial-ecology.net/probebase. Email correspondence can be addressed to ten.ygoloce-laiborcim@esabeborp.

International audience; The question of pre-neolithic tuberculosis is still open in paleopathological perspective. One of the major interests is to explore what type of infection could have existed around the early stage of animal domestication. Paleopathological lesions evoking skeletal TB were observed on five human skeletons coming from two PPNB sites in Syria, which belongs to the geographical cradle of agriculture. These sites represent respectively pre-domestication phase (Dja'de el Mughara, Northern Syria, 8800-8300 BCE cal.) and early domestication phase (Tell Aswad, Southern Syria, 8200-7600 BCE cal.). MicroCT scan analyses were performed on two specimens (one per site) and revealed microscopic changes in favor of TB infection. Detection of lipid biomarkers is positive for two specimens (one per site). Initial molecular analysis further indicates the presence of TB in one individual from Dja'de. Interestingly, no morphological evidence of TB was observed on animal remains of wild and newly domesticated species, discovered in these sites. These observations strongly suggest the presence of human tuberculosis before domestication and at its early stages.

Sikora, Martin et al., Genome sequencing of the 5,300-year-old mummy of the Tyrolean Iceman, found in 1991 on a glacier near the border of Italy and Austria, has yielded new insights into his origin and relationship to modern European populations. A key finding of that study was an apparent recent common ancestry with individuals from Sardinia, based largely on the Y chromosome haplogroup and common autosomal SNP variation. Here, we compiled and analyzed genomic datasets from both modern and ancient Europeans, including genome sequence data from over 400 Sardinians and two ancient Thracians from Bulgaria, to investigate this result in greater detail and determine its implications for the genetic structure of Neolithic Europe. Using whole-genome sequencing data, we confirm that the Iceman is, indeed, most closely related to Sardinians. Furthermore, we show that this relationship extends to other individuals from cultural contexts associated with the spread of agriculture during the Neolithic transition, in contrast to individuals from a hunter-gatherer context. We hypothesize that this genetic affinity of ancient samples from different parts of Europe with Sardinians represents a common genetic component that was geographically widespread across Europe during the Neolithic, likely related to migrations and population expansions associated with the spread of agriculture. © 2014 Sikora et al., This project was supported by NIH grant 2R01HG003229. This work was also partially supported by an Erwin Schrödinger Fellowship of the Austrian Science Fund (FWF) to MS (J3375-B19).

The Capuchin Catacombs of Palermo, Italy, contain over 1800 mummies dating from the 16th to 20th centuries AD. Their environment is not conducive to the conservation of the remains due to, among other factors, water infiltration, which is producing salt efflorescences on the walls. A multiphasic approach was applied to investigate the halophilic microbiota present in the Catacombs. Enrichment cultures were conducted on media containing different NaCl concentrations, ranging from 3 to 20 %. For screening of the strains, the following two PCR-based methods were used and compared: fluorescence internal transcribed spacer PCR (f-ITS) and random amplification of polymorphic DNA (RAPD) analyses. Results derived from RAPD profiles were shown to be slightly more discriminative than those derived from f-ITS. In addition, the proteolytic and cellulolytic abilities were screened through the use of plate assays, gelatin agar and Ostazin Brilliant Red H-3B (OBR-HEC), respectively. Many of the strains isolated from the wall samples displayed proteolytic activities, such as all strains belonging to the genera Bacillus, Virgibacillus and Arthrobacter, as well as some strains related to the genera Oceanobacillus, Halobacillus and Idiomarina. In addition, many of the strains isolated from materials employed to stuff the mummies showed cellulolytic activities, such as those related to species of the genera Chromohalobacter and Nesterenkonia, as well as those identified as Staphylococcus equorum and Halomonas sp. Furthermore, many of the strains were pigmented ranging from yellow to a strong pink color, being directly related to the discoloration displayed by the materials.

Ancient hominoid genome studies can be regarded by definition as metagenomic analyses since they represent a mixture of both hominoid and microbial sequences in an environment. Here, we report the molecular detection of the oral spirochete Treponema denticola in ancient human tissue biopsies of the Iceman, a 5,300-year-old Copper Age natural ice mummy. Initially, the metagenomic data of the Iceman’s genomic survey was screened for bacterial ribosomal RNA (rRNA) specific reads. Through ranking the reads by abundance a relatively high number of rRNA reads most similar to T. denticola was detected. Mapping of the metagenome sequences against the T. denticola genome revealed additional reads most similar to this opportunistic pathogen. The DNA damage pattern of specifically mapped reads suggests an ancient origin of these sequences. The haematogenous spread of bacteria of the oral microbiome often reported in the recent literature could already explain the presence of metagenomic reads specific for T. denticola in the Iceman’s bone biopsy. We extended, however, our survey to an Iceman gingival tissue sample and a mouth swab sample and could thereby detect T. denticola and Porphyrimonas gingivalis, another important member of the human commensal oral microflora. Taken together, this study clearly underlines the opportunity to detect disease-associated microorganisms when applying metagenomics- enabled approaches on datasets of ancient human remains.

Great European mountain ranges have acted as barriers to gene flow for resident populations since prehistory and have offered a place for the settlement of small, and sometimes culturally diverse, communities. Therefore, the human groups that have settled in these areas are worth exploring as an important potential source of diversity in the genetic structure of European populations. In this study, we present new high resolution data concerning Y chromosomal variation in three distinct Alpine ethno-linguistic groups, Italian, Ladin and German. Combining unpublished and literature data on Y chromosome and mitochondrial variation, we were able to detect different genetic patterns. In fact, within and among population diversity values observed vary across linguistic groups, with German and Italian speakers at the two extremes, and seem to reflect their different demographic histories. Using simulations we inferred that the joint effect of continued genetic isolation and reduced founding group size may explain the apportionment of genetic diversity observed in all groups. Extending the analysis to other continental populations, we observed that the genetic differentiation of Ladins and German speakers from Europeans is comparable or even greater to that observed for well known outliers like Sardinian and Basques. Finally, we found that in south Tyroleans, the social practice of Geschlossener Hof, a hereditary norm which might have favored male dispersal, coincides with a significant intra-group diversity for mtDNA but not for Y chromosome, a genetic pattern which is opposite to those expected among patrilocal populations. Together with previous evidence regarding the possible effects of “local ethnicity” on the genetic structure of German speakers that have settled in the eastern Italian Alps, this finding suggests that taking socio-cultural factors into account together with geographical variables and linguistic diversity may help unveil some yet to be understood aspects of the genetic structure of European populations.

Nitrospira are the most widespread and diverse known nitrite-oxidizing bacteria and key nitrifiers in natural and engineered ecosystems. Nevertheless, their ecophysiology and environmental distribution are understudied because of the recalcitrance of Nitrospira to cultivation and the lack of a molecular functional marker, which would allow the detection of Nitrospira in the environment. Here we introduce nxrB, the gene encoding subunit beta of nitrite oxidoreductase, as a functional and phylogenetic marker for Nitrospira. Phylogenetic trees based on nxrB of Nitrospira were largely congruent to 16S ribosomal RNA-based phylogenies. By using new nxrB-selective polymerase chain reaction primers, we obtained almost full-length nxrB sequences from Nitrospira cultures, two activated sludge samples, and several geographically and climatically distinct soils. Amplicon pyrosequencing of nxrB fragments from 16 soils revealed a previously unrecognized diversity of terrestrial Nitrospira with 1801 detected species-level operational taxonomic units (OTUs) (using an inferred species threshold of 95% nxrB identity). Richness estimates ranged from 10 to 946 coexisting Nitrospira species per soil. Comparison with an archaeal amoA dataset obtained from the same soils [Environ. Microbiol. 14: 525-539 (2012)] uncovered that ammonia-oxidizing archaea and Nitrospira communities were highly correlated across the soil samples, possibly indicating shared habitat preferences or specific biological interactions among members of these nitrifier groups.

Previous investigations carried out in some parts of the 16th-17th century AD series of Bacsalmas-Oalmas (southern Hungary) have already provided interesting paleopathological cases of tuberculosis (e.g. Molnar & Palfi 1994). These studies were essentially based on macromorphological analysis, biomolecular methods were used only in a few cases (e.g. Haas et al. 2000). From a macromorphological point of view, former investigations have only considered 'classical' tuberculosis (TB) alterations (advanced-stage lesions in common skeletal locations). However, due to the recent development of diagnostic criteria in the field of the paleopathology of infectious diseases, new approaches have been introduced in the identification of skeletal TB lesions (Palfi et al. 1999, Maczel 2003). Molecular methods for the detection of mycobacterial aDNA have also been developed considerably in the last few years (e.g. Donoghue 2008, Donoghue 2011). The good state of preservation of the material, the important chronological period of the series and the relative high prevalence of TB reported in preliminary studies encouraged us to carry out a revision of TB-related lesions in the complete Bacsalmas-Oalmas series. A five year international research program--including both macroscopic and biomolecular studies of the series--was recently started. The present paper summarizes the results ofa pilot project conducted to optimize the further systematic paleopathological and paleomicrobial studies. Skeletal material of 205 individuals was chosen forthe macromorphological test-investigation, which was focused both on classical/advanced stage skeletal TB alterations (tuberculous spondylitis, tuberculous arthritis) and atypical/early-stage TB lesions (rib lesions, superficial vertebral changes, endocranial alterations, early-stage spondylodiscitis). In addition, the association of possible stress factors (long bone periostitis, cribra orbitalia, cribra cranii) were also considered. Paleomicrobiological analysis was used to study the presence of Mycobacterium tuberculosis ancient DNA (aDNA) in morphologically positive and negative cases. A comparative paleomicrobial analysis was carried out on different samples, to test the presence of MTB DNA in different skeletal regions.

We undertook the analysis of Zweeloo Woman, a bog mummy from the Netherlands, to assess her parasitic state.Evidence of infection came from two areas: (1) liver paraffin sections and (2) microfossils washed from an intestinal section. Although the liver had shrunken considerably, objects consistent with operculated trematode eggsvwere found. After evaluating the range of trematode species that produce eggs in liver tissue, we arrived at thevdiagnosis of Dicrocoelium dendriticum . Although only 0.1 ml of sediment was recovered from an intestinal section, eggs of Ascaris lumbricoides and Trichuris trichiurawere also identified. No eggs of D. dendriticum were revealed by the intestinal wash although they were observed in the liver. The lancet fluke, D. dendriticum , is a zoonosis that usually infects ruminants such as cattle. Eggs of D. dendriticum may be found in human coprolites if infected cow liver, for example, was eaten. This is false parasitism. Since eggs of D. dendriticumwere found in the liver of Zweeloo Woman, we are assured this was a true infection. This find is especially significant because it is the old est known, patent infection of D. dendriticum in humans

International audience; The Tyrolean Iceman, a 5,300-year-old Copper age individual, was discovered in 1991 on the Tisenjoch Pass in the Italian part of the Ötztal Alps. Here we report the complete genome sequence of the Iceman and show 100% concordance between the previously reported mitochondrial genome sequence and the consensus sequence generated from our genomic data. We present indications for recent common ancestry between the Iceman and present-day inhabitants of the Tyrrhenian Sea, that the Iceman probably had brown eyes, belonged to blood group O and was lactose intolerant. His genetic predisposition shows an increased risk for coronary heart disease and may have contributed to the development of previously reported vascular calcifications. Sequences corresponding to ~60% of the genome of Borrelia burgdorferi are indicative of the earliest human case of infection with the pathogen for Lyme borreliosis.

International audience

Chlorite dismutase (Cld) is a unique heme enzyme which transforms chlorite to chloride and molecular oxygen (reaction: ClO(2)(-)→Cl(-)+O(2)). Since bacteria with Cld play significant roles in the bioremediation of industrially contaminated sites and also in wastewater treatment, it is of high interest to understand the molecular mechanism of chlorite detoxification. Here we investigate a highly active Cld from Candidatus Nitrospira defluvii (NdCld), a key nitrifier in biological wastewater treatment, using a comprehensive structural, biochemical and bioinformatics approach. We determined the crystal structure of Cld from Candidatus Nitrospira defluvii and showed that functional NdCld is a homopentamer possessing a fold found in other Clds and Cld-like enzymes. To investigate the Cld function in more detail, site-directed mutagenesis of a catalytically important residue (Arg173) was performed and two enzyme mutants were structurally and biochemically characterized. Arginine 173 is demonstrated to play a key role in (i) controlling of ligand and substrate access and binding and (ii) in chlorite dismutation reaction. The flexible residue modulates the electrostatic potential and size of the active site entrance and might be involved in keeping transiently formed hypochlorite in place for final molecular oxygen and chloride formation. Furthermore, using a structure-based sequence alignment, we show that the residue corresponding to Arg173 is conserved in all known active forms of Cld and propose it as a marker for Cld activity in yet uncharacterized Cld-like proteins. Finally, our analysis indicates that all Clds and Cld-like enzymes employ a non-covalently bound heme as a cofactor.

Summary Nitrite-oxidizing bacteria of the genus Nitrospira are ubiquitous in natural ecosystems and also in waste- water treatment plants. Nitrospira are members of a distinct phylum, not closely related to other nitrifiers, and no genomic sequences from this genus have been available so far. Here we applied an environmen- tal genomics approach to sequence and assemble a 137 kbp-long genome fragment of 'Candidatus Nitro- spira defluvii', which had been enriched from acti- vated sludge and belongs to Nitrospira sublineage I without isolated representatives. The annotation of this contig, which carried the 16S rRNA gene of N. defluvii, offered first insight into the genome of Nitrospira. Surprisingly, we found a gene similar to genes encoding chlorite dismutase (CLD), an enzyme degrading chlorite (ClO2 - )t o Cl - and O2. To date, CLDs with high catalytic activity have been found only in perchlorate- and chlorate-reducing bacteria but not in nitrifiers. Heterologous expression in E. coli followed by enzymatic tests confirmed that this gene of Nitro- spira encodes a highly active CLD, which is also expressed in situ by Nitrospira, indicating that this nitrite oxidizer might be involved in the bioremedia- tion of perchlorate and chlorite. Phylogenetic analy- ses showed that CLD and related proteins are widely distributed among the Bacteria and Archaea, and indi- cated that this enzyme family appeared relatively early in evolution, has been subject to functional diversification and might play yet unknown roles in microbial metabolism.

A new isolate of a lithoautotrophic nitrite-oxidizing bacterium was obtained from internal corrosion deposits from a steel pipeline of the Moscow heating system. The organism oxidized nitrite as the sole energy source and fixed carbon dioxide as the only carbon source. The cells were extremely pleomorphic: loosely wound spirals, slightly curved and even straight rods were detected, as well as coccoid cells. The highest rate of nitrite consumption (1.5 mM nitrite as substrate) was measured at 42 degrees C, with a temperature range of 28-44 degrees C. In enrichment cultures with Nocardioides sp. as an accompanying organism, optimal oxidation of 5.8 mM nitrite occurred at 45 degrees C, with a range of 28-48 degrees C. Neither pyruvate nor yeast extract stimulated nitrification. Organotrophic growth was not observed. Phylogenetic analysis of 16S rRNA gene sequences revealed that the novel isolate represents a new sublineage of the genus Nitrospira. On the basis of physiological, chemotaxonomic and molecular characteristics, the name 'Candidatus Nitrospira bockiana' is proposed.

Nitrite-oxidizing bacteria of the genus Nitrospira are key nitrifiers in wastewater treatment plants. Pure cultures of these organisms are unavailable, but cultivation-independent molecular methods make it possible to detect Nitrospira-like bacteria in environmental samples and to investigate their ecophysiology. Comprehensive screening of natural and engineered habitats and of public databases for 16S rRNA sequences of Nitrospira-like bacteria revealed a surprisingly high biodiversity in the genus Nitrospira, which comprises at least four phylogenetic sublineages. All Nitrospira-like bacteria detected in wastewater treatment plants belonged to the sublineages I and II. Subsequently, the population dynamics of different Nitrospira-like bacteria were monitored, by quantitative fluorescence in situ hybridization with rRNA-targeted probes, confocal laser scanning microscopy and digital image analysis, during incubation of nitrifying activated sludge in media containing different nitrite concentrations. These experiments showed that Nitrospira-like bacteria, which were affiliated with the phylogenetic sublineages I or II of the genus Nitrospira, responded differently to nitrite concentration shifts. Previously unknown properties of Nitrospira-like bacteria were discovered in the course of an environmental genomics project. Implications of the obtained results for fundamental understanding of the microbial ecology of nitrite oxidizers as well as for future improvement of nutrient removal in wastewater treatment plants are discussed.

Summary Chemolithoautotrophic nitrite oxidizers of the genus Nitrospira are a monophyletic but diverse group of organisms, are widely distributed in many natural habitats, and play a key role in nitrogen elimination during biological wastewater treatment. Phylogenetic analyses of cloned 16S rRNA genes and fluorescence in situ hybridization with newly developed rRNA-tar- geted oligonucleotide probes revealed coexistence of uncultured members of sublineages I and II of the genus Nitrospira in biofilm and activated sludge samples taken from nitrifying wastewater treatment plants. Quantitative microscopic analyses of their spatial arrangement relative to ammonia oxidizers in the biofilm and activated sludge flocs showed that members of the Nitrospira sublineage I occurred sig- nificantly more often in immediate vicinity to ammo- nia oxidizers than would be expected from random community assembly while such a relationship was not observed for Nitrospira sublineage II. This spatial distribution suggested a niche differentiation of these coexisting Nitrospira populations with respect to their preferred concentrations of nitrite. This hypothesis was tested by mathematical modelling of nitrite con- sumption and resulting nitrite gradients in nitrifying biofilms and by quantifying the abundance of sublin- eage I and II Nitrospira in activated sludge during incubations with nitrite in different concentrations. Consistent with the observed localization patterns, a higher nitrite concentration selected for sublineage I but suppressed sublineage II Nitrospira .

Summary Previously uncultured nitrite-oxidizing bacteria affiliated to the genus Nitrospira have for the first time been successfully enriched from activated sludge from a municipal wastewater treatment plant. During the enrichment procedure, the abundance of the Nitrospira -like bacteria increased to approximately 86% of the total bacterial population. This high degree of purification was achieved by a novel enrichment protocol, which exploits physiological features of Nitrospira like bacteria and includes the selective repression of coexisting Nitrobacter cells and heterotrophic contaminants by application of ampicillin in a final concentration of 50 m g ml - 1 . The enrichment process was monitored by electron microscopy, fluorescence in situ hybridization (FISH) with rRNA-targeted probes and fatty acid profiling. Phylogenetic analysis of 16S rRNA gene sequences revealed that the enriched bacteria represent a novel Nitrospira species closely related to uncultured Nitrospira -like bacteria previously found in wastewater treatment plants and nitrifying bioreactors. The enriched strain is provisionally classified as ‘ Candidatus Nitrospira defluvii’.

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Background Dental calculus (mineralised dental plaque) preserves many types of microfossils and biomolecules, including microbial and host DNA, and ancient calculus are thus an important source of information regarding our ancestral human oral microbiome. In this study, we taxonomically characterised the dental calculus microbiome from 20 ancient human skeletal remains originating from Trentino-South Tyrol, Italy, dating from the Neolithic (6000–3500 BCE) to the Early Middle Ages (400–1000 CE). Results We found a high abundance of the archaeal genus Methanobrevibacter in the calculus. However, only a fraction of the sequences showed high similarity to Methanobrevibacter oralis, the only described Methanobrevibacter species in the human oral microbiome so far. To further investigate the diversity of this genus, we used de novo metagenome assembly to reconstruct 11 Methanobrevibacter genomes from the ancient calculus samples. Besides the presence of M. oralis in one of the samples, our phylogenetic analysis revealed two hitherto uncharacterised and unnamed oral Methanobrevibacter species that are prevalent in ancient calculus samples sampled from a broad range of geographical locations and time periods. Conclusions We have shown the potential of using de novo metagenomic assembly on ancient samples to explore microbial diversity and evolution. Our study suggests that there has been a possible shift in the human oral microbiome member Methanobrevibacter over the last millennia.