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Background: Carboplatin and paclitaxel (CP) have been the standard of care for advanced/recurrent endometrial cancer (EC) for many years. However, this chemotherapy combination shows limited efficacy and recurrences often occur in less than 12 months. ABTL0812 is a novel drug that selectively kill cancer cells by cytotoxic autophagy and has shown anticancer efficacy in preclinical models of EC in combination with CP. Methods: ENDOLUNG was an open-label, phase 1/2 clinical trial designed to determine the safety and efficacy of Ibrilatazar (ABTL0812) with CP in patients with advanced/recurrent EC and non-irradiable stage III and IV squamous non-small cell lung cancer (sq-NSCLC). The phase 1 part consisted of a 3 + 3 de-escalation design followed by an expansion cohort with 12 patients. The primary endpoint was safety. ABTL0812 starting dose was 1300 mg tid combined with carboplatin at area under the curve (AUC) 5 and paclitaxel at 175 mg/m2 both administered every 21 days for up to 8 cycles. The phase 2 part included a total of 51 patients. The primary endpoint was overall response rate (ORR) and the secondary endpoints included duration of response (DOR), progression-free survival (PFS) and overall survival (OS). Results: During the phase 1 only one dose limiting toxicity (DLT), a grade 4 neutropenia, was observed in 1 out of 6 patients, thus no de-escalation was applied. One additional DLT, a grade 3 febrile neutropenia, was observed in the expansion cohort, thus the recommended phase 2 dose (RP2D) for ABTL0812 was established at 1300 mg tid. Most frequent hematological adverse events (AE) of the combination were neutropenia (52.9%), anemia (37.3%) and thrombocytopenia (19.6%). Nausea (66.7%), asthenia (66.7%), diarrhea (54.9%) and vomiting (54.9%) were the most frequent non-hematological adverse events (AEs). The combination of ABTL0812 plus CP showed an ORR of 65.8% (13.2% complete response and 52.6% partial response) with a median DOR of 7.4 months (95% CI: 6.3–10.8 months). Median PFS was 9.8 months (95% CI: 6.6–10.6) and median OS 23.6 months (95% CI 6.4-ND). Pharmacokinetic parameters were compatible with target engagement observed in preclinical studies, and blood pharmacodynamic biomarkers indicated sustained target regulation during, at least, 28 days after starting the treatment. Conclusions: This study suggests that the combination of ABTL0812 with CP is safe and feasible with an encouraging activity in patients with advanced/recurrent EC. Our data warrant further confirmation in prospective randomized trials. Trial registration: EU Clinical Trial Register, EudraCT number 2016-001352-21 and National Clinical Trials Number, NCT03366480. Registration on 19 September 2016. Highlights: ABTL0812 is a novel drug in clinical development that kills tumor cells by cytotoxic autophagy. The recommended phase 1/2 dose of ABTL0812 in combination with paclitaxel/carboplatin is 1300 mg three times a day (tid) by the oral route. The combination of ABTL0812 plus carboplatin and paclitaxel (CP) in patients with advanced/recurrent EC suggests an improved benefit-to-risk ratio vs. CP alone and warrants further clinical evaluation. [ABSTRACT FROM AUTHOR]

A unicellular cyanobacterium, strain VI4D9, was isolated from thermophilic microbial mats thriving in a hot spring of the Ahousaht territory of Vancouver Island, Canada, and characterized using optical and electron microscopy, genome sequencing and cultivation approaches. The cells were elongated rods (5.1 µm in length and 1.2 µm in width, on average). Their UV visible absorption spectra revealed that they contain chlorophyll a, phycocyanin and carotenoids. Transmission electron microscopy showed the presence of thylakoids concentrated on one side of the cells. The strain grew within a temperature range of 37–50°C, with an optimum growth at 45°C. Its genome had a size of 3 049 282 bp and a DNA G + C content of 51.8 mol%. The cells contained numerous intracellular spherical granules easily visible under scanning electron microscopy. Energy dispersive X-ray spectroscopy revealed that these granules were made of Ca-, Ba- and Sr-containing carbonates. A phylogenetic 16S rRNA gene tree robustly placed this strain as sister to several environmental sequences and the described species Gloeomargarita lithophora, also characterized by the possession of intracellular carbonate inclusions. We consider strain VI4D9 to represent a new Gloeomargarita species based on its marked phenotypic differences with G. lithophora, notably, its thermophilic nature and different thylakoid organization, therefore we propose the name Gloeomargarita ahousahtiae sp. nov. The type strain is VI4D9 (Culture Collection of Algae and Protozoa strain 1472/1; Laboratorio de Algas Continentales Mexico strain LAC 140). Gloeomargarita ahousahtiae is the second species described within the recently discovered order Gloeomargaritales. Gloeomargarita ahousahtiae is a new thermophilic cyanobacterium. Growth temperature and thylakoid morphology differentiate G. ahousahtiae and G. lithophora. All described Gloeomargaritales synthesize intracellular carbonate inclusions. [ABSTRACT FROM AUTHOR]

This document is a correction notice for an article titled "ENDOLUNG trial. A phase 1/2 study of the Akt/mTOR inhibitor and autophagy inducer Ibrilatazar (ABTL0812) in combination with paclitaxel/carboplatin in patients with advanced/recurrent endometrial cancer" published in BMC Cancer. The authors reported that the equal contribution statement was missing in the original submission, and they have provided the correct equal contribution statement. The correction does not make any claims about jurisdictional or institutional affiliations. The article was authored by Alexandra Leary, Purificación Estévez-García, Renaud Sabatier, Isabelle Ray-Coquard, Margarita Romeo, Pilar Barretina-Ginesta, Marta Gil-Martin, Elena Garralda, Joaquim Bosch-Barrera, Teresa Morán, Paloma Martin-Martorell, Ernest Nadal, Pere Gascón, Jordi Rodon, Jose M Lizcano, Pau Muñoz-Guardiola, Gemma Fierro-Durán, Oriol Pedrós-Gámez, Héctor Pérez-Montoyo, Marc Yeste-Velasco, Marc Cortal, Antonio Pérez-Campos, Jose Alfon, Carles Domenech, Alejandro Pérez-Fidalgo, and Ana Oaknin. [Extracted from the article]

Eukaryogenesis represented a major evolutionary transition that led to the emergence of complex cells from simpler ancestors. For several decades, the most accepted scenario involved the evolution of an independent lineage of proto-eukaryotes endowed with an endomembrane system, including a nuclear compartment, a developed cytoskeleton and phagocytosis, which engulfed the alphaproteobacterial ancestor of mitochondria. However, the recent discovery by metagenomic and cultural approaches of Asgard archaea, which harbour many genes in common with eukaryotes and are their closest relatives in phylogenomic trees, rather supports scenarios based on the symbiosis of one Asgard-like archaeon and one or more bacteria at the origin of the eukaryotic cell. Here, we review the recent discoveries that led to this conceptual shift, briefly evoking current models of eukaryogenesis and the challenges ahead to discriminate between them and to establish a detailed, plausible scenario that accounts for the evolution of eukaryotic traits from those of their prokaryotic ancestors. [ABSTRACT FROM AUTHOR]

Ovarian cancer is the most lethal of all the gynecological tumors despite remarkable advances in our understanding of its molecular biology. The cornerstone treatment remains cytoreductive surgery followed by platinum-based chemotherapy. Recently, the addition of targeted therapies, such as PARP inhibitors, as first-line maintenance has led to outstanding improvements, mainly in BRCA mutated and homologous recombination deficient tumors. However, a significant proportion of patients will experience recurrence, primarily due to platinum resistance, which ultimately result in fatality. Among these patients, primary platinum-resistant have a particularly dismal prognosis due to their low response to current available therapies, historical exclusion from clinical trials, and the absence of validated biomarkers. In this review, we discuss the concept of platinum resistance in ovarian cancer, the clinical and molecular characteristics of this resistance, and the current and new treatment options for these patients. [Display omitted] • Primary platinum-resistant ovarian cancer (PPROC) patients show bad prognosis and lack available therapies or biomarkers. • PPROC shows specific molecular features and resistance to cisplatin through several mechanisms. • A better understanding of PPROC biology will allow to discover new targets of potential diagnostic or therapeutic interest. [ABSTRACT FROM AUTHOR]

Applied Theatre (AT) is a relatively recently-created interdisciplinary field that includes investigation of the social and educational uses of its practices. Since its emergence as a discipline in the 1990s, research has proliferated. However, to better understand the breadth and depth of AT's social and educational applications, there is a need to review and synthesise the scientific literature in this developing area. We sought to address this gap by providing a qualitative synthesis of relevant literature focusing on theatre as a tool for social and educational intervention with socially disadvantaged groups, capturing some of the key achievements and challenges in the field. A qualitative review of scientific literature published on this issue in the last decade was conducted. After obtaining an overview of the literature, we conducted a thematic analysis to identify the central themes of the research. Scientific discussion on the social and educational uses of theatre has expanded significantly in the last decade. Our thematic analysis identified the documentation of a rich multiplicity of social and educational possibilities for applying theatre to contexts of social vulnerability, including: empowerment and development of critical awareness, promotion of personal and community development, construction of spaces of recognition, development of empathetic attitudes towards human differences, and the recovery of silenced narratives. This review also uncovered a number of challenges and dilemmas inherent to the field, such as the question of power distribution in applied theatre processes or the complexities created by an instrumental vision of the arts. This qualitative synthesis of research demonstrates how AT, as a framework for reflection and action of an interdisciplinary nature, offers useful dialogical, creative and critical tools for generating viable alternatives in diverse social and educational contexts. The review of research draws attention to how AT may provide a platform for the recognition and participation of marginalised groups and individuals, and offer a potentially relevant mechanism for moderating social and educational inequality. [ABSTRACT FROM AUTHOR]

Smartphones (SMPs) play a vital role in the lives of young people and in the university classroom. There are few studies of the use of SMPs by university students, and the existing knowledge is inconsistent and lacking consensus. This article shows the validity of a theoretical model of the use of SMPs in higher education, in the context of the theory of uses and gratifications, and the knowledge gained from previous studies on the use of SMPs by adolescents. The results suggest the existence of a specific educational function for the use of SMPs in university classrooms. Despite the emergent nature of this function, the educational use of SMPs in higher education presents potential consolidation as a source of gratification and satisfaction of educational needs. Their inclusion in the everyday activity of university classrooms will require considerable effort to adapt the educational system, and the training of students and teaching staff must be improved in order to reduce possible interference in learning the communicative and expressive play functions of SMPs. [ABSTRACT FROM AUTHOR]

At the present time, it is of interest to promote reflection on educational and social inclusion within a framework of social justice, in order to promote the quality of education. A scoping review approach is adopted from a critical perspective of inclusion, to deconstruct the predominant judgment of educational inclusion and reveal the processes of exclusion and duality that underlie the school environment. A review of the WOS, SCOPUS and ERIC databases was conducted. Seventy-nine articles published in international journals addressing this topic were obtained. Thematic analysis was conducted using the Nvivo software package. The emerging themes include arguments for: rethink to inclusion within the framework of diversity and social justice; arguing the possibilities of inclusion/exclusion depend on various factors and the sociocultural and professional context; calling for greater commitment, ethics and professionalism to meet the challenges of inclusion; denouncing persistent barriers to be overcome; and, finally, calling for new roles and scenarios for support services. [ABSTRACT FROM AUTHOR]

This study aims to analyze the profile of users in an university clinic (SPA-UNED) during the first COVID-19 19 health alarm. The sample was composed of 124 participants (70.4 % women) with an average age of 41.49 years and four instruments were used: Symptom Assessment-45 Questionnaire (SA-45), Clinical Outcomes in Routine Evaluation-Outcome Measure (CORE-OM), Coping Orientation to Problems Experienced (COPE-28) and the Scale Connor-Davidson Resilience (CD-RISC). The results showed a sociodemographic profile formed mainly by single Spanish women from the service sector. Consistent with the reasons for consultation, participants predominantly showed symptoms of depression, anxiety, and somatization, poor use of coping strategies, and low levels of resilience. These variables may be a possible risk profile in the clinical population that outlines a vulnerable group for which psychological prevention and intervention measures are required. [ABSTRACT FROM AUTHOR]

Despite small freshwater ecosystems being biodiversity reservoirs and contributing significantly to greenhouse fluxes, their microbial communities remain largely understudied. Yet, microorganisms intervene in biogeochemical cycling and impact water quality. Because of their small size, these ecosystems are in principle more sensitive to disturbances, seasonal variation and pluri‐annual climate change. However, how microbial community composition varies over space and time, and whether archaeal, bacterial and microbial eukaryote communities behave similarly remain unanswered. Here, we aim to unravel the composition and intra/interannual temporal dynamic patterns for archaea, bacteria and microbial eukaryotes in a set of small freshwater ecosystems. We monitored archaeal and bacterial community composition during 24 consecutive months in four ponds and one brook from northwestern France by 16S rRNA gene amplicon sequencing (microbial eukaryotes were previously investigated for the same systems). Unexpectedly for oxic environments, bacterial Candidate Phyla Radiation (CPR) were highly diverse and locally abundant. Our results suggest that microbial community structure is mainly driven by environmental conditions acting over space (ecosystems) and time (seasons). A low proportion of operational taxonomic units (OTUs) (<1%) was shared by the five ecosystems despite their geographical proximity (2–9 km away), making microbial communities almost unique in each ecosystem and highlighting the strong selective influence of local environmental conditions. Marked and similar seasonality patterns were observed for archaea, bacteria and microbial eukaryotes in all ecosystems despite strong turnovers of rare OTUs. Over the 2‐year survey, microbial community composition varied despite relatively stable environmental parameters. This suggests that biotic associations play an important role in interannual community assembly. [ABSTRACT FROM AUTHOR]

However, until recently, known cases of prokaryote-prokaryote symbioses were relatively sparse and little understood, with the notable exception of metabolic symbioses (syntrophies) established between certain metabolic guilds (e.g. methanogenic archaea and fermentative bacteria, methanotrophic archaea and sulphate-reducing bacteria) (Fenchel and Finlay, 1995; Lopez-Garcia I et al i ., 2017). Expanding prokaryote - prokaryote symbioses: CPR and DPANN phyla In recent years, it has nonetheless become increasingly clear that obligatory prokaryote-prokaryote symbioses implying a close physical connection are much more widespread than ever thought. Beyond getting information about the biology of CPR bacteria, DPANN archaea and, potentially, other bacterial or archaeal lineages that establish tight physical intercellular connections with other bacteria and/or archaea, we will also learn about the ecological importance of these interactions. [Extracted from the article]

Summary: Plastids evolved from a cyanobacterium that was engulfed by a heterotrophic eukaryotic host and became a stable organelle. Some of the resulting eukaryotic algae entered into a number of secondary endosymbioses with diverse eukaryotic hosts. These events had major consequences on the evolution and diversification of life on Earth. Although almost all plastid diversity derives from a single endosymbiotic event, the analysis of nuclear genomes of plastid‐bearing lineages has revealed a mosaic origin of plastid‐related genes. In addition to cyanobacterial genes, plastids recruited for their functioning eukaryotic proteins encoded by the host nucleus and also bacterial proteins of noncyanobacterial origin. Therefore, plastid proteins and plastid‐localised metabolic pathways evolved by tinkering and using gene toolkits from different sources. This mixed heritage seems especially complex in secondary algae containing green plastids, the acquisition of which appears to have been facilitated by many previous acquisitions of red algal genes (the 'red carpet hypothesis'). [ABSTRACT FROM AUTHOR]

Rhodelphidia is a recently discovered phylum within the supergroup Archaeplastida, comprising only two known representatives (Rhodelphis marinus and Rhodelphis limneticus). Despite its close phylogenetic relatedness to red algae, Rhodelphidia differ markedly by being nonphotosynthetic eukaryotrophic flagellates with gene‐ and intron‐rich genomes. Here, we describe a new freshwater Rhodelphidia species, Rhodelphis mylnikovi sp. n., strain Rhod‐M. It shows clear morphological differences with the two other Rhodelphis species, including larger cell body size, presence of two contractile vacuoles, short and blunt pseudopodia, absence of cysts, and tendency to cannibalism. 18S rRNA‐based phylogenetic analysis placed it sister to the freshwater species R. limneticus. [ABSTRACT FROM AUTHOR]

Our study aims to discover the degree of efficacy of the principal’s performance in relation to the learning objectives, curriculum, and results, and explore the relationship among the perceptions of the inspectors, teachers, and management teams about the principal’s efficacy in promoting students’ learning. The Vanderbilt Assessment of Leadership in Education (VAL-ED) questionnaire was applied. Contingency analyses were calculated. We concluded that the three sectors considered the principal’s work to be effective in actions related to the learning objectives, curriculum planning, and responsibility for the outcomes. [ABSTRACT FROM AUTHOR]

Abstract: The opisthokonts constitute a eukaryotic supergroup divided into two main clades: the holozoans, which include animals and their unicellular relatives, and the holomycotans, which include fungi, opisthosporidians, and nucleariids. Nucleariids are phagotrophic filose amoebae that phenotypically resemble more their distant holozoan cousins than their holomycotan phylogenetic relatives. Despite their evolutionary interest, the diversity and internal phylogenetic relationships within the nucleariids remain poorly studied. Here, we formally describe and characterize by molecular phylogeny and microscopy observations Parvularia atlantis gen. et sp. nov. (formerly Nuclearia sp. ATCC 50694), and compare its features with those of other nucleariid genera. Parvularia is an amoebal genus characterized by radiating knobbed and branching filopodia. It exhibits prominent vacuoles observable under light microscopy, a cyst‐like stage, and completely lacks cilia. P. atlantis possesses one or two nuclei with a central nucleolus, and mitochondria with flat or discoid cristae. These morphological features, although typical of nucleariids, represent a combination of characters different to those of any other described Nuclearia species. Likewise, 18S rRNA‐based phylogenetic analyses show that P. atlantis represents a distinct lineage within the nucleariids. [ABSTRACT FROM AUTHOR]

Educational leadership has become a key factor in the improvement of educational quality. The aim of the work was to describe the adaptation of the Pedagogical Leadership Scale VAL-ED (Vanderbilt Assessment of Leadership in Education) to the Spanish population (cross- cultural adaptation process and validation) and obtain their psychometric characteristics through Rasch analysis. The obtained results confirm that the unidimensionality of each of the six subscales that compose it has been demonstrated, it is guaranteed its usefulness to diagnose the educational leadership, to decide ways of improvement and to measure the effectiveness of its implementation. The conclusion is that the adaptation of the VAL-ED questionnaire to the Spanish population is a valid and reliable tool for the measurement of educational leadership. [ABSTRACT FROM AUTHOR]

The aim of this study is to provide an overview of the development of premature children, including attachment, child psychological adjustment and parental variables. 130 children < 1,500 g or < 32 weeks at birth from two public hospitals, assessed at two years corrected age, together with their parents. Parental socio-demographic data was collected. Infant development, attachment and child psychological adjustment were evaluated, as was parental stress. The percentage of preterm children with developmental delays ranged from 5% to 21%. Girls tend to show higher levels of development than boys with effect sizes ranging from small, η2 p =.02, to medium, η2 p =.07. Secure attachment was the most frequent pattern in the sample. No significant differences, p <.05, between preterm children and the normative population were found on children´s behavioral problems and maternal stress levels. Despite the fact prematurity is considered to be a risk factor for a child´s development, a significant proportion of these children do not show problems in terms of developmental levels, attachment pattern and maternal stress. However, socio-emotional and affective domains, as well as psychological support programs for parenthood, should be followed up from a multidisciplinary perspective. [ABSTRACT FROM AUTHOR]

Fifty years ago, Lynn Margulis, inspiring in early twentieth-century ideas that put forward a symbiotic origin for some eukaryotic organelles, proposed a unified theory for the origin of the eukaryotic cell based on symbiosis as evolutionary mechanism. Margulis was profoundly aware of the importance of symbiosis in the natural microbial world and anticipated the evolutionary significance that integrated cooperative interactions might have as mechanism to increase cellular complexity. Today, we have started fully appreciating the vast extent of microbial diversity and the importance of syntrophic metabolic cooperation in natural ecosystems, especially in sediments and microbial mats. Also, not only the symbiogenetic origin of mitochondria and chloroplasts has been clearly demonstrated, but improvement in phylogenomic methods combined with recent discoveries of archaeal lineages more closely related to eukaryotes further support the symbiogenetic origin of the eukaryotic cell. Margulis left us in legacy the idea of ‘eukaryogenesis by symbiogenesis’. Although this has been largely verified, when, where, and specifically how eukaryotic cells evolved are yet unclear. Here, we shortly review current knowledge about symbiotic interactions in the microbial world and their evolutionary impact, the status of eukaryogenetic models and the current challenges and perspectives ahead to reconstruct the evolutionary path to eukaryotes. [ABSTRACT FROM AUTHOR]

The mother-child relationship has traditionally been studied from the perspective of attachment theory. But in addition, they are a psychological and social phenomenon to which the child gives meaning and tries to understand. To explore the child's understanding of this dimension of the relationship, we interviewed 85 children between 7 and 9 years old through a semistructured interview with four stories, in which the Attachment System and the System of Care were related. The analysis of the children's responses shows that 97% attribute discomfort in the mother in relation to the experience of threat of the child. Children of these ages already have an understanding of the Mother's System of Care in connection with the child's attachment system. The responsibility and empathy of the mother are part of the responses of children of these ages as activators of their behavior of care and protection for the child. Children's representations can be organized at increasingly sophisticated and complex levels of understanding. Knowing the feelings and motivations that children attribute to the mother in her role of primary caregiver and the child's vision of the emotional laws that govern affective mother-child relationships, can offer us new perspectives on how attachment relationships are built and be useful in the detection and intervention in unhealthy attachments, in both members of the dyad. [ABSTRACT FROM AUTHOR]

Disagreement in science exists in a variety of strengths, from doubt-raising articles and issues of non-reproducibility up to raging disputes and major controversies. An often-latent form of disagreement consists of misconceptions whereby false ideas are held that run contrary to what is commonly accepted as knowledge. Misconceptions have been the focus of much research in education science and psychology. Here we draw attention to misconceptions that may arise in the very practice of science. We highlight formal features that can be used to characterize misconceptions and distinguish them from controversies, in addition to how they relate to knowledge creation. [ABSTRACT FROM AUTHOR]

How diverse are marine planktonic protist communities? How much seasonality do they exhibit? For a very long time, these two old and challenging questions in the field of plankton ecology could be addressed only for large‐size protist species, based on cell counting under the microscope. The recent application of molecular techniques, notably massive marker‐gene amplicon sequencing approaches (metabarcoding), has allowed investigating with unprecedented level of resolution the small‐sized (<20 µm) planktonic eukaryotes too. An amazing diversity of these tiny organisms has been unveiled but details about their temporal dynamics remain much more elusive. In a From the Cover article in this issue of Molecular Ecology, Giner et al. (2019) introduce a new Recurrence Index (RI) to specifically look for seasonality in time‐series metabarcoding data. They inspected the temporal dynamics of all operational taxonomic units (OTUs) in a rich sequence data set of pico‐ and nanoplanktonic eukaryotes in samples collected monthly during 10 years. Although most OTUs did not show seasonality, some abundant ones did, which explains why some averaging methods can find seasonality at the less detailed level of whole planktonic communities. Not surprisingly, the very complex small‐sized eukaryotic plankton communities are composed of organisms with miscellaneous temporal dynamics. [ABSTRACT FROM AUTHOR]

The genus Balechina (=subgenus Pachydinium) was established for heterotrophic gymnodinioid dinoflagellates with a thick cell covering. The type species, B. pachydermata (=Gymnodinium pachydermatum), showed numerous fine longitudinal striae, whereas B. coerulea (=G. coeruleum) showed ~24 prominent longitudinal surface ridges or furrows and a distinctive blue pigmentation. We have investigated the morphology and molecular phylogeny of these taxa and the species Gymnodinium cucumis, G. lira and G. amphora from the western Mediterranean, Brazil and Japan. Sudden contractions at the cingulum level were seen in B. pachydermata, which also showed a high morphological variability which included morphotypes that have been described as Amphidinium vasculum, G. amphora, G. dogielii and G. gracile sensu Kofoid and Swezy. Molecular phylogeny based on small subunit rRNA gene sequences revealed that Balechina coerulea, G. cucumis and G. lira formed a clade distantly related to the clade of the type species, B. pachydermata, and G. amphora. We propose the new genus Cucumeridinium for the species with longitudinal ridges and a circular apical groove (Cucumeridinium coeruleum comb. nov., C. lira comb. nov. and C. cucumis comb. nov.), and Gymnodinium canus and G. costatum are considered synonyms of C. coeruleum. The genus Balechina remains for the species with a double-layer cell covering, bossed surface with fine striae, and an elongated elliptical apical groove. At present, the genus is monotypic containing only B. pachydermata. [ABSTRACT FROM AUTHOR]

Despite recent progress, the origin of the eukaryotic cell remains enigmatic. It is now known that the last eukaryotic common ancestor was complex and that endosymbiosis played a crucial role in eukaryogenesis at least via the acquisition of the alphaproteobacterial ancestor of mitochondria. However, the nature of the mitochondrial host is controversial, although the recent discovery of an archaeal lineage phylogenetically close to eukaryotes reinforces models proposing archaea-derived hosts. We argue that, in addition to improved phylogenomic analyses with more comprehensive taxon sampling to pinpoint the closest prokaryotic relatives of eukaryotes, determining plausible mechanisms and selective forces at the origin of key eukaryotic features, such as the nucleus or the bacterial-like eukaryotic membrane system, is essential to constrain existing models. [ABSTRACT FROM AUTHOR]

The recent discovery of diverse very large viruses, such as the mimivirus, has fostered a profusion of hypotheses positing that these viruses define a new domain of life together with the three cellular ones (Archaea, Bacteria and Eucarya). It has also been speculated that they have played a key role in the origin of eukaryotes as donors of important genes or even as the structures at the origin of the nucleus. Thanks to the increasing availability of genome sequences for these giant viruses, those hypotheses are amenable to testing via comparative genomic and phylogenetic analyses. This task is made very difficult by the high evolutionary rate of viruses, which induces phylogenetic artefacts, such as long branch attraction, when inadequate methods are applied. It can be demonstrated that phylogenetic trees supporting viruses as a fourth domain of life are artefactual. In most cases, the presence of homologues of cellular genes in viruses is best explained by recurrent horizontal gene transfer from cellular hosts to their infecting viruses and not the opposite. Today, there is no solid evidence for the existence of a viral domain of life or for a significant implication of viruses in the origin of the cellular domains. [ABSTRACT FROM AUTHOR]

Small eukaryotes have key roles in aquatic ecosystems, influencing their local environment, global biogeochemical cycles and climate. Their impact depends on community structure, which varies along time. However, very few studies take into account temporal variation. This is especially true for small, shallow freshwater systems, which remain largely understudied despite their wide variety, global surface and intense microbial activity. We have monthly followed changes in the community structure of small microbial eukaryotes (0.2-5 μm cell diameter) for 2 years in four ponds and one brook located in North-Western France based on massive 18S rDNA amplicon 454 pyrosequencing. We detected a total of 3742 stringently defined operational taxonomic units (OTUs) encompassing all recognized eukaryotic supergroups and lineages of uncertain affiliation. Although geographically close, protist communities in the five ecosystems were contrasting, with very few shared OTUs, suggesting that environmental selection mainly drives community structure. The temporal dynamics of different high-rank taxa appeared complex and rapid at monthly scales. Despite this, a clear and reproducible seasonality was observed. As expected, low-abundance OTUs dominated the community. Although some of them appeared sporadically or remained at low frequencies during the survey, others occasionally reached relatively high abundances, sometimes recurrently. This shows that at least a fraction of low-abundance eukaryotes constitutes a seed bank. The annual proportion of primary producers, free-living heterotrophs and parasites appeared remarkably constant among the different ecosystems, suggesting underlying trends of ecosystem carrying capacity for these functional groups. [ABSTRACT FROM AUTHOR]

It is widely believed that the archaeal ancestor was hyperthermophilic, but during archaeal evolution, several lineages - including haloarchaea and their sister methanogens, the Thaumarchaeota, and the uncultured Marine Group II and Marine Group III Euryarchaeota (MGII/III) - independently adapted to lower temperatures. Recent phylogenomic studies suggest that the ancestors of these lineages were recipients of massive horizontal gene transfer from bacteria. Many of the acquired genes, which are often involved in metabolism and cell envelope biogenesis, were convergently acquired by distant mesophilic archaea. In this Opinion article, we explore the intriguing hypothesis that the import of these bacterial genes was crucial for the adaptation of archaea to mesophilic lifestyles. [ABSTRACT FROM AUTHOR]

The supergroup Holomycota, composed of Fungi and several related lineages of unicellular organisms (Nucleariida, Rozellida, Microsporidia, and Aphelida), represents one of the major branches in the phylogeny of eukaryotes. Nevertheless, except for the well-established position of Nucleariida as the first holomycotan branch to diverge, the relationships among the other lineages have so far remained unresolved largely owing to the lack of molecular data for some groups. This was notably the case aphelids, a poorly known group of endobiotic phagotrophic protists that feed on algae with cellulose walls. The first molecular phylogenies including aphelids supported their sister relationship with Rozellida and Microsporidia which, collectively, formed a new group called Opisthosporidia (the "Opisthosporidia hypothesis"). However, recent phylogenomic analyses including massive sequence data from two aphelid genera, Paraphelidium and Amoeboaphelidium , suggested that the aphelids are sister to fungi (the "Aphelida |$+$| Fungi hypothesis"). Should this position be confirmed, aphelids would be key to understanding the early evolution of Holomycota and the origin of Fungi. Here, we carry out phylogenomic analyses with an expanded taxonomic sampling for aphelids after sequencing the transcriptomes of two species of the genus Aphelidium (Aphelidium insulamus and Aphelidium tribonematis) in order to test these competing hypotheses. Our new phylogenomic analyses including species from the three known aphelid genera strongly rejected the Opisthosporidia hypothesis. Furthermore, comparative genomic analyses further supported the Aphelida |$+$| Fungi hypothesis via the identification of 19 orthologous genes exclusively shared by these two lineages. Seven of them originated from ancient horizontal gene transfer events predating the aphelid–fungal split and the remaining 12 likely evolved de novo , constituting additional molecular synapomorphies for this clade. Ancestral trait reconstruction based on our well-resolved phylogeny of Holomycota suggests that the progenitor of both fungi and rozellids, was aphelid-like, having an amoeboflagellate state and likely preying endobiotically on cellulose-containing, cell-walled organisms. Two lineages, which we propose to call Phytophagea and Opisthophagea, evolved from this ancestor. Phytophagea, grouping aphelids and classical fungi, mainly specialized in endobiotic predation of algal cells. Fungi emerged from this lineage after losing phagotrophy in favor of osmotrophy. Opisthophagea, grouping rozellids and Microsporidia, became parasites, mostly of chitin-containing hosts. This lineage entered a progressive reductive process that resulted in a unique lifestyle, especially in the highly derived Microsporidia. [Aphelida, fungi, Holomycota, horizontal gene transfer, phylogenomics, synapomorphy.] [ABSTRACT FROM AUTHOR]

Algae are significant members of Earth's biodiversity. Having been studied for a long time, the discovery of new algal phyla is extremely unusual. Recently, the enigmatic 'Picobiliphyta,' a group of uncultured eukaryotes unveiled using molecular tools, were claimed to represent an unrecognized early branching algal lineage with a nucleomorph (remnant nucleus of a secondary algal endosymbiont) in their plastids. However, subsequent studies rejected the presence of a nucleomorph, and single-cell genomic studies failed to detect any plastid-related genes, ruling out the possibility of plastid occurrence. The isolation of the first 'picobiliphyte,' Picomonas judraskeda, a tiny organism that feeds on very small (<150 nm) organic particles, came as final proof of their non-photosynthetic lifestyle. Consequently, the group has been renamed Picozoa. The passage from 'picobiliphytes' to 'picozoa' illustrates the crucial role that classical protistology should play to provide sound biological context for the wealth of data produced by modern molecular techniques. [ABSTRACT FROM AUTHOR]

Highlights: [•] No-tillage registered higher water content in the soil at sowing than in conventional tillage. [•] Grain yield improved with no-tillage system. [•] Water use was superior in the no-tillage system than in the conventional tillage. [ABSTRACT FROM AUTHOR]

The diversity and ecological relevance of small haptophytes in marine systems is increasingly recognized. Similar investigations in freshwater remain scarce, despite some recent studies showing the existence of divergent haptophyte lineages and indicating that these microalgae can occur at high abundance in lakes. We studied the diversity of haptophytes in a wide variety of marine, salty continental and, most particularly, freshwater environments by amplifying, cloning and sequencing 18 S rRNA genes. For this purpose, we designed two sets of primers specific for the two recognized haptophyte classes, Prymnesiophyceae and Pavlovophyceae. We detected pavlovophyte sequences only in freshwater systems as well as several novel prymnesiophyte phylotypes in both freshwater and marine environments. In addition, we retrieved a cluster of sequences ( HAP-3) from the Marmara Sea branching deeply in the haptophyte tree with no clear affiliation to either of the two recognized classes. Five of the freshwater prymnesiophyte phylotypes detected formed a divergent monophyletic group ( EV) without close described representatives that branched within the Isochrysidales, a group of generally marine and most often calcifying coccolithophorids. The presence of several sequences of freshwater haptophytes scattered among marine taxa in phylogenetic trees confirms the occurrence of several independent haptophyte transitions between marine and freshwater environments. [ABSTRACT FROM AUTHOR]

One of the most important aspects in the development of a child is the emotional bonding of attachment. Because this development is considered to be an integrated phenomenon, the type of attachment developed affects all other areas of development. The bond of attachment must be considered to be the main factor in the child's development and change. Therefore, it cannot be seen as subsidiary to other alterations. The main context of disorders of emotional attachment in children is that of the nursery school (with teacher, homework and classmates). This is because at the age of 3, this is the place where children spend most time. Therefore, it is very important to point out and emphasize the teacher's role as an attachment figure and encourage the whole of the school's staff to become involved in this task. [ABSTRACT FROM AUTHOR]

The last decade has seen a revival of old virocentric ideas. These concepts are heterogeneous, extending from proposals that consider viruses functionally as living beings and/or as descendants of viral lineages that preceded cell evolution to other claims that consider viruses and/or some viral families a fourth domain of life. While the debates about whether viruses are alive or not and whether some virus-like replicators preceded the first cells fall under the long-lasting dichotomous view on the nature and origin of life (metabolism-versus replication-first), the claim that some giant viruses form a fourth domain in an organismal tree of life is not consistent with current evidence and can be falsified. [ABSTRACT FROM AUTHOR]

A DNA barcode is a preferrably short and highly variable region of DNA supposed to facilitate a rapid identification of species. In many protistan lineages, a lack of species-specific morphological characters hampers an identification of species by light or electron microscopy, and difficulties to perform mating experiments in laboratory cultures also do not allow for an identification of biological species. Thus, testing candidate barcode markers as well as establishment of accurately working species identification systems are more challenging than in multicellular organisms. In cryptic species complexes the performance of a potential barcode marker can not be monitored using morphological characters as a feedback, but an inappropriate choice of DNA region may result in artifactual species trees for several reasons. Therefore a priori knowledge of the systematics of a group is required. In addition to identification of known species, methods for an automatic delimitation of species with DNA barcodes have been proposed. The Cryptophyceae provide a mixture of systematically well characterized as well as badly characterized groups and are used in this study to test the suitability of some of the methods for protists. As species identification method the performance of blast in searches against badly to well-sampled reference databases has been tested with COI-5P and 59-partial LSU rDNA (domains A to D of the nuclear LSU rRNA gene). In addition the performance of two different methods for automatic species delimitation, fixed thresholds of genetic divergence and the general mixed Yule- coalescent model (GMYC), have been examined. The study demonstrates some pitfalls of barcoding methods that have to be taken care of. Also a best- practice approach towards establishing a DNA barcode system in protists is proposed. [ABSTRACT FROM AUTHOR]

All cell membranes are composed of glycerol phosphate phospholipids, and this commonality argues for the presence of such phospholipids in the last common ancestor, or cenancestor. However, phospholipid biosynthesis is very different between bacteria and archaea, leading to the suggestion that the cenancestor was devoid of phospholipid membranes. Recent phylogenomic studies challenge this view, suggesting that the cenancestor did possess complex phospholipid membranes. Here, we discuss the implications of these recent findings for membrane evolution in archaea and bacteria, and for the origin of the eukaryotic cell. [ABSTRACT FROM AUTHOR]

The dinoflagellate genus Heterodinium has unusual morphological characters such as a mid-ventral intercalary plate with a pore, a small plate in the left side of the dorsal epitheca, three antapical plates, and a well-developed anterior cingular list. We obtained the first SSU rDNA sequences from single cells of six species of Heterodinium from Mediterranean coastal and open waters. They included the type species H. scrippsii and H. rigdeniae and representatives of the other subgenera, Sphaerodinium (H. doma, H. milneri, H. globosum) and Platydinium (H. pavillardii). SSU rDNA phylogeny showed that Heterodinium spp. formed a well-supported monophyletic group (100% bootstrap support) composed of two subclades: one comprising H. doma, H. pavillardii, H. globosum and H. rigdeniae, and another comprising H. milneri and H. scrippsii. This whole heterodiniacean clade branched among the poorly resolved short-branching sequences of the lineage comprising groups of Gymnodiniales, Peridiniales, Dinophysales and Prorocentrales. The current classification into subgenera, and even into morphological groups, is not supported by the molecular data. In contrast to previous classifications, our SSU rDNA phylogeny suggests that the genus Heterodinium is divergent from the clade of Gonyaulacales. Accordingly, the supposed homology of pores and plate patterns of Heterodinium and gonyaulacoids may require revision. In Heterodinium, the first antapical and postcingular plates may be interpreted as sulcal plates, suggesting a more typical hypothecal tabulation (5′′′, 2′′′′). Our new data and analysis indicate that the systematic position of Heterodinium is uncertain at present. [ABSTRACT FROM PUBLISHER]

This study analizes the psychometric properties of a new instrument about the working model of children's attachment. The sample was composed of 60 subjects (30 from normal population and 30 from a social risk population). The age of children ranges from 3 to 7 years old. This instrument is an interview based on the completion story task, however it includes new contents as well as a new procedure in regarding to previous attachment measures. The findings show good validity and reliability. The found results are going to be the beginning of future studies. [ABSTRACT FROM AUTHOR]

The dinophysoid dinoflagellates are currently divided into three families: Amphisoleniaceae, Dinophysaceae (mainly Dinophysis Ehrenb. and Phalacroma F. Stein), and Oxyphysaceae, the latter including only one member, Oxyphysis oxytoxoides Kof. Phalacroma has been recently reinstated separately from Dinophysis, and its amended description is currently restricted to cells whose epithecae were large but <1/4 of the cell length. With the aim of improving the phylogeny of Dinophysales, we obtained 54 new SSU rRNA gene sequences of 28 species. Taxon-rich SSU rDNA phylogenetic analysis showed that Dinophysales split into two major clades, one containing the Amphisoleniaceae ( Amphisolenia F. Stein- Triposolenia Kof.) and the other containing the Dinophysaceae. The latter are divided into two well-supported sister groups, the Dinophysaceae sensu stricto (s.s.) ( Dinophysis, Ornithocercus F. Stein, Histioneis F. Stein) and, tentatively, a separate family for the clade of the type and most of the Phalacroma species . Based on combined phylogenies of new SSU rDNA and available LSU rDNA data, O. oxytoxoides (elongated epitheca, >1/4 of the cell length) branched with a strong support with the type of Phalacroma. We therefore propose Phalacroma oxytoxoides comb. nov. for O. oxytoxoides. Our SSU rDNA phylogeny also suggests that the assumed high intraspecific variability of Dinophysis hastata F. Stein hides a number of cryptic species. According to their distinct phylogenetic placement, the forms D. hastata f. phalacromides Jørg. and D. hastata f. uracanthides Jørg. should be erected at the species level. We propose for them the names Dinophysis phalacromoides comb. nov. and Dinophysis uracanthoides comb. nov. [ABSTRACT FROM AUTHOR]

Evaporite accumulations produced by artesian waters in the arid zones of southern Tunisia led to the formation of subrounded, gypsiferous mounds consisting of irregular alternations of mineral precipitates and aeolian sand. The joint occurrence of gypsum crusts and plant colonization determined the stabilization of their top surface. Careful examination of the pigmented (green-brown) crusts revealed endolithic microbial communities just below the surface. In previous optical and scanning electron microscope studies cyanobacteria were the dominant component of these communities. Molecular diversity studies based on small subunit ribosomal RNA (SSU rRNA) gene analysis revealed that Flavobacteria, Actinobacteria, Deinococcales, Alpha- and Gamma- Proteobacteria are also important components of the microbial assemblage. Their pigment analyses, determined by high performance liquid chromatography (HPLC), detected the presence of carotenoids and chlorophyll (chl) a and b. Microbial communities that produce pigmentation and display an endolithic lifestyle typify the extreme environments as those found in arid/semiarid and hot desert regions. [ABSTRACT FROM AUTHOR]

The recent introduction of molecular techniques in eukaryotic microbial diversity studies, in particular those based in the amplification and sequencing of small-subunit ribosomal DNA (SSU rDNA), has revealed the existence of an unexpected variety of new phylotypes. The taxonomic ascription of the organisms bearing those sequences is generally deduced from phylogenetic analysis. Unfortunately, the SSU rDNA sequence alone has often not enough phylogenetic information to resolve the phylogeny of fast-evolving or very divergent sequences, leading to their misclassification. To address this problem, we tried to increase the phylogenetic signal by amplifying the complete eukaryotic rDNA cluster [i.e. the SSU rDNA, the internal transcribed spacers, the 5.8S rDNA and the large-subunit (LSU) rDNA] from environmental samples, and sequencing the SSU and LSU rDNA part of the clones. Using marine planktonic samples, we showed that surveys based on either SSU or SSU + LSU rDNA retrieved comparable diversity patterns. In addition, phylogenetic trees based on the concatenated SSU + LSU rDNA sequences showed better resolution, yielding good support for major eukaryotic groups such as the Opisthokonta, Rhizaria and Excavata. Finally, highly divergent SSU rDNA sequences, whose phylogenetic position was impossible to determine with the SSU rDNA data alone, could be placed correctly with the SSU + LSU rDNA approach. These results suggest that this method can be useful, in particular for the analysis of eukaryotic microbial communities rich in phylotypes of difficult phylogenetic ascription. [ABSTRACT FROM AUTHOR]

Members of the family Warnowiaceae are unarmored phagotrophic dinoflagellates that possess an ocelloid. The genus Erythropsidinium (= Erythropsis) has also developed a unique dynamic appendage, the piston, which is able to independently retract and extend for at least 2 min after the cell lyses. We provide the first small subunit ribosomal RNA gene sequences of warnowiid dinoflagellates, those of the type Erythropsidinium agile and one species of Warnowia. Phylogenetic analyses show that warnowiid dinoflagellates branch within the Gymnodinium sensu stricto group, forming a cluster separated from the Polykrikos clade and with autotrophic Pheopolykrikos beauchampii as closest relative. This reinforces their classification as unarmored dinoflagellates based on the shape of the apical groove, despite the strong ecological and ultrastructural diversity of the Gymnodinium s.s. group. Other structures, such as the ocelloid and piston, have no systematic value above the genus level. [ABSTRACT FROM AUTHOR]

When viruses were discovered, they were accepted as missing links between the inert world and living organisms. However, this idea was soon abandoned as information about their molecular parasitic nature accumulated. Recently, the notion that viruses are living organisms that have had a role in the evolution of some essential features of cells has experienced a renaissance owing to the discovery of unusually large and complex viruses that possess typical cellular genes. Here, we contend that there is strong evidence against the notion that viruses are alive and represent ancient lineages of the tree of life. [ABSTRACT FROM AUTHOR]

Acidobacteria constitute a still poorly studied phylum that is well represented in soils. Recent studies suggest that members of this phylum may be also abundant in deep-sea plankton, but their relative abundance and ecological role in this ecosystem are completely unknown. A recent screening of three metagenomic deep-sea libraries of bathypelagic plankton from the South Atlantic (1000 m depth), the Adriatic (1000 m depth) and the Ionian (3000 m depth) seas in the Mediterranean revealed an unexpected relative proportion of acidobacterial fosmids, which affiliated to the Solibacterales (Group 3), to the Group 11 and, most frequently, to the Group 6 of this diverse phylum. Here, we present the comparative analysis of 11 acidobacterial genome fragments containing the rrn operon from these Mediterranean libraries. A highly conserved syntenic region spanning up to 30 kb and containing up to 25 open reading frames was shared by Group 6 Acidobacteria. Synteny was also partially conserved in distantly related acidobacterial genome fragments derived from a metagenomic soil library, indicating a remarkable conservation of this genomic region within these Acidobacteria. A search for Acidobacteria-specific hits in directly comparable, available fosmid-end sequences from soil and marine metagenomic libraries showed a significant increase of their relative proportion in plankton libraries as a function of increasing depth reaching, at high depth, levels nearly comparable to those of soil. Thus, our results suggest that Acidobacteria are abundant and represent a significant proportion of the microbial community in the deep-sea ecosystem. [ABSTRACT FROM AUTHOR]

Abstract: Molecular ecology and metagenomics applied to the study of microbial biodiversity are changing our comprehension of the biosphere. An impressive diversity of archaea, bacteria and, more recently, protists has been uncovered by molecular tools. Efforts to couple function to the phylogenetic diversity observed in natural environments are leading to the discovery of novel metabolisms and to a re-evaluation of the global ecological impact of known ones. Interesting questions relating to mechanisms of speciation and evolutionary trends at the smallest and largest phylogenetic scales are emerging. [Copyright &y& Elsevier]

Lost City is a unique off-axis hydrothermal vent field characterized by highly alkaline and relatively low-temperature fluids that harbours huge carbonate chimneys. We have carried out a molecular survey based on 18S rDNA sequences of the eukaryotic communities associated with fluid–seawater interfaces and with carbonates from venting areas and the chimney wall. Our study reveals a variety of lineages belonging to eight major taxa: Metazoa, Fungi, Heterokonta (Stramenopiles), Alveolata, Radiolaria, Cercozoa, Heterolobosea and Euglenozoa. We detected one fungal lineage that appears to be widespread in hydrothermal systems both submarine and continental. Alveolates were the most abundant and diverse group in Lost City samples, although their distribution was very different in carbonate, where ciliates dominated, and in fluid–seawater libraries, where dinoflagellates, Group I and Group II (Syndiniales) marine alveolates were profuse. Similarly, Euglenozoa also displayed a differential distribution, kinetoplastids being present on carbonates and a novel group of diplonemids so far exclusively observed in the deep sea being dominant in fluid–seawater libraries. Protist lineages identified in this ecosystem likely correspond to grazers, decomposers and parasites, playing key roles in the food web of the Lost City ecosystem. [ABSTRACT FROM AUTHOR]

Lake Van harbors the largest known microbialites on Earth. The surface of these huge carbonate pinnacles is covered by coccoid cyanobacteria whereas their central axis is occupied by a channel through which neutral, relatively Ca-enriched, groundwater flows into highly alkaline (pH ~9.7) Ca-poor lake water. Previous microscopy observations showed the presence of aragonite globules composed by rounded nanostructures of uncertain origin that resemble similar bodies found in some meteorites. Here, we have carried out fine-scale mineralogical and microbial diversity analyses from surface and internal microbialite samples. Electron transmission microscopy revealed that the nanostructures correspond to rounded aragonite nanoprecipitates. A progressive mineralization of cells by the deposition of nanoprecipitates on their surface was observed from external towards internal microbialite areas. Molecular diversity studies based on 16S rDNA amplification revealed the presence of bacterial lineages affiliated to the Alpha-, Beta- and Gammaproteobacteria, the Cyanobacteria, the Cytophaga-Flexibacter-Bacteroides (CFB) group, the Actinobacteria and the Firmicutes. Cyanobacteria and CFB members were only detected in surface layers. The most abundant and diverse lineages were the Firmicutes (low GC Gram positives). To the exclusion of cyanobacteria, the closest cultivated members to the Lake Van phylotypes were most frequently alkaliphilic and/or heterotrophic bacteria able to degrade complex organics. These heterotrophic bacteria may play a crucial role in the formation of Lake Van microbialites by locally promoting carbonate precipitation. [ABSTRACT FROM AUTHOR]

Eukaryotic thiolases are essential enzymes located in three different compartments (peroxisome, mitochondrion, and cytosol) that can display catabolic or anabolic functions. They are responsible for the thiolytic cleavage of oxidized acyl-CoA (thiolase I; EC 2.3.1.16) and the synthesis or degradation of acetoacetyl-CoA (thiolase II; EC 2.3.1.9). Phylogenetic analysis of eukaryotic thiolase sequences showed that they form six distinct clusters, one of them highly divergent, which are in good correlation with their class and subcellular location. When analyzed together with a representative sample of prokaryotic thiolases, all eukaryotic thiolase groups emerged close to proteobacterial sequences. Metazoan cytosolic thiolase II was related to α-proteobacterial sequences, suggesting a mitochondrial origin. Unexpectedly, cytosolic thiolases from green plants and fungi as well as at least one member of all eukaryotic peroxisomal and mitochondrial thiolases had δ-proteobacteria as closest relatives. Our analysis suggests that these eukaryotic peroxisomal and mitochondrial thiolases may have been acquired from δ-proteobacteria prior to the ancestor of all known eukaryotes. [ABSTRACT FROM AUTHOR]

Archaea possess unique membrane phospholipids that generally comprise isoprenoid ethers built on sn-glycerol-1-phosphate (G1P). By contrast, bacterial and eukaryal membrane phospholipids are fatty acid esters linked to sn-glycerol-3-phosphate (G3P). The two key dehydrogenase enzymes that produce G1P and G3P, G1PDH and G3PDH, respectively, are not homologous. Various models propose that these enzymes originated during the speciation of the two prokaryotic domains, and the nature (and even the very existence) of lipid membranes in the last universal common ancestor (cenancestor) is subject to debate. G1PDH and G3PDH belong to two separate superfamilies that are universally distributed, suggesting that members of both superfamilies existed in the cenancestor. Furthermore, archaea possess homologues to known bacterial genes involved in fatty acid metabolism and synthesize fatty acid phospholipids. The cenancestor seems likely to have been endowed with membrane lipids whose synthesis was enzymatic but probably non-stereospecific. [Copyright &y& Elsevier]

The initiation factor 5A (IF-5A) of archaea and eukaryotes undergoes an unusual post-translational modification consisting of the transformation of a specific conserved lysine residue into the amino acid hypusine. This occurs in a two-step reaction catalysed by the enzymes deoxyhypusine synthase (DHS) and deoxyhypusine hydroxylase. Bacteria do not have IF-5A but only a very distant homologue, the elongation factor P (EF-P). Consequently, all bacteria appeared to also lack genes with significant homology to DHS genes. However, we have carried out BLAST searches and found DHS-like genes in a number of bacterial species. The phylogenetic analysis of these sequences strongly suggests that they have been acquired from archaea by horizontal gene transfer (HGT). Our analysis also suggests, although with weaker support, that a single HGT event from archaea, followed by several HGT between bacterial species, accounts for the patchy distribution of DHS-like genes in bacteria. The activity of these genes in bacteria is enigmatic, since we have not found any evidence of interaction between this protein and the bacterial EF-P. Nevertheless, we cannot discard that it exists, since it appears that the interaction between the DHS and its natural substrate, the IF-5A, is rather weak. This is exemplified by the fact that, in archaea, the complex evolutionary history of the DHS is not paralleled by that of the IF-5A, indicating that these proteins do not follow a perfect co-evolution. [Copyright &y& Elsevier]

Marine planktonic crenarchaeota have escaped all cultivation attempts to date, all crenarchaeota growing in pure culture so far being hyperthermophiles. Here, we present a comparative genomic analysis of a 16S- plus 23S-rDNA-containing fragment of a crenarchaeote retrieved from an environmental genomic library constructed from picoplankton collected at 500 m depth in the Antarctic Polar Front. The clone DeepAnt-EC39 contained an insert of 33.3 kbp, which was completely sequenced. DeepAnt-EC39 appears to represent a lineage specific to deep-sea waters but widespread geographically, as revealed by the analysis of the 16S-23S-rDNA intergenic spacer region. A comparison with previously sequenced marine crenarchaeotal genomic clones also containing an rrn operon (74A4, 4B7 and Cenarchaeum symbiosum strains A and B) revealed a highly variable structure involving gene rearrangements and insertions/deletions. The surroundings of the rrn operon and the contiguous glutamate-1-semialdehyde aminotransferase gene appear hot spots for recombination. Phylogenetic analyses of all individual predicted proteins revealed the existence of several likely cases of horizontal gene transfer both, between the two archaeal kingdoms and between the two prokaryotic domains. The most frequent horizontal transfers appear to involve genes from mesophilic methanogenic euryarchaeota related to Methanosarcinales. We hypothesise that the acquisition of genes from mesophilic bacteria and euryarchaeota has played a major role in the adaptation of Group I crenarchaeota to life at lower temperatures. [ABSTRACT FROM AUTHOR]

Summary We report here a molecular survey based on 16S rRNA genes of the bacterial diversity found in two deep-sea vent niches at the Mid-Atlantic Ridge: hydrothermal sediment (Rainbow site), and microcolonizers made of three different substrates (organic-rich, iron-rich and pumice) that were exposed for 15 days to a vent emission. Bacterial diversity in sediment samples was scattered through many bacterial divisions. The most abundant and diverse environmental sequences (phylotypes) in our libraries corresponded to the Gammaproteobacteria, followed by the Acidobacteria. We detected members of all the subdivisions within the Proteobacteria. Myxobacterial lineages were the most represented within the delta subdivision. Phylotypes ascribing to the Cytophaga-Flavobacterium-Bacteroides , Planctomycetales, high and low G + C Gram-positives, Nitrospirae, and the candidate division TM7 were also identified. Compared to this broad taxonomic coverage, microcolonizers were almost exclusively colonized by epsilonproteobacteria, although these exhibited considerable morphological and phylogenetic in-group diversity. No specificity for any of the substrates tested was seen. This observation further supports the idea of the ecological dominance of epsilonproteobacteria in the fluid–seawater interface environment. Because oxidation of reduced S species and/or sulphur-reduction is thought to be essential for their energetic metabolism in these areas, we mapped different oxidation states of S in individual bacterial filaments from the iron-rich microcolonizer. For this, we used high-resolution, non-destructive synchrotron micro-X-ray Absorption Near-Edge Spectroscopy (micro-XANES), which revealed the co-existence of different S oxidation states, from sulphide to sulphate, at the level of individual cells. This suggests that these cells were metabolizing sulphur in situ . [ABSTRACT FROM AUTHOR]