Late Ediacaran Redox Stability and Metazoan Evolution

The Neoproterozoic arrival of animals fundamentally changed Earth's biological and geochemical trajectory. Since the early description of Ediacaran and Cambrian animal fossils, a vigorous debate has emerged about the drivers underpinning their seemingly rapid radiation. Some argue for predation and ecology as central to diversification, whereas others point to a changing chemical environment as the trigger. In both cases, questions of timing and feedbacks remain unresolved. Through these debates, the last fifty years of work has largely converged on the concept that a change in atmospheric oxygen levels, perhaps manifested indirectly as an oxygenation of the deep ocean, was causally linked to the initial diversification of large animals. What has largely been absent, but is provided in this study, is a multi-proxy stratigraphic test of this hypothesis. Here, we describe a coupled geochemical and paleontological investigation of Neoproterozoic sedimentary rocks from northern Russia. In detail, we provide iron speciation data, carbon and sulfur isotope compositions, and major element abundances from a predominantly siliciclastic succession (spanning>1000 m) sampled by the Kel'tminskaya-1 drillcore. Our interpretation of these data is consistent with the hypothesis that the $pO_2$ threshold required for diversification of animals with high metabolic oxygen demands was crossed prior to or during the Ediacaran Period. Redox stabilization of shallow marine environments was, however, also critical and only occurred about 560 million years ago (Ma), when large motile bilaterians first enter the regional stratigraphic record. In contrast, neither fossils nor geochemistry lend support to the hypothesis that ecological interactions altered the course of evolution in the absence of environmental change. Together, the geochemical and paleontological records suggest a coordinated transition from low oxygen oceans sometime before the Marinoan (~635 Ma) ice age, through better oxygenated but still redox-unstable shelves of the early Ediacaran Period, to the fully and persistently oxygenated marine environments characteristic of later Ediacaran successions that preserve the first bilaterian macrofossils and trace fossils.Earth and Planetary SciencesOrganismic and Evolutionary Biolog

РАЗРАБОТКА НОВОЙ СХЕМЫ И СПОСОБА ФЛОТАЦИИ РУД ОЛИМПИАДИНСКОГО МЕСТОРОЖДЕНИЯ

The article presents the results of sulfide ore beneficiation of the «Olympiad» deposit according two flow sheets – the existing plant and the new one according to which the concentrate is produced in two stages: roughing I stream flow concentrate is extracted from 1/2 of raw materials and mixed with another 1/2 part of the raw materials and finished roughing II streamflow concentrate is produced. Mixture of the air (t = 15÷20 °С) with water vapor (t = 104 °С, р = 0,12 MPa) is used in II streamflow as gas phase during flotation. A device for measurement of steam bubble size has been developed. Bubble size is shown to be reduced 2,0–2,5 times under the conditions simulating the air-vapor flotation process. In using streamflow air-vapor flotation flow sheet, the concentrate yield decreases from 4,01 to 2,98 % while maintaining the reached level of gold recovery thus reducing the burden and cost for the subsequent operations of bio-oxidation and cyanidation of the concentrate.Приведены результаты обогащения сульфидных руд Олимпиадинского месторождения по двум схемам – действующей фабрики и новой, по которой черновой концентрат получают в два приема: из 1/2 части исходного сырья выделяют черновой концентрат I-й струи обогащения, смешивают его с другой 1/2 частью исходного сырья и выделяют готовый черновой концентрат II-й струи обогащения. Во II-й струе при флотации в качестве газовой фазы применяют смесь воздуха (t = 15÷20 °С) с водяным паром (t = 104 °С, р = 0,12 МПа). Разработано устройство для измерения размера пузырьков пара. Показано, что в условиях, моделирующих процесс паровоздушной флотации, размер пузырьков сокращается в 2,0– 2,5 раза. При использовании схемы струйной паровоздушной флотации выход концентрата уменьшается с 4,01 до 2,98 % при сохранении достигнутого уровня извлечения золота, что снижает нагрузку и затраты на последующие операции биоокисления и цианирования концентрата

ГРАВИТАЦИОННОЕ РАЗДЕЛЕНИЕ В УСЛОВИЯХ СПЕЦИАЛЬНО ФОРМИРУЕМОГО ВЫСОКОГО СОДЕРЖАНИЯ МЕТАЛЛОВ В ИСХОДНОМ СЫРЬЕ

The article presents the results of researching metal-containing raw material preparation in two-compartment jigging machine, the distinctive feature of which is that the jigging concentrate is extracted in the first compartment, into which initial feed is loaded and the undersize from the second compartment is returned. The subject matter of a new aftertreatment diagram of heavy fraction on concentration tables is that the heavy fraction is divided into two equal parts, which are supplied to the installed parallel tables mixing the concentrate of one them with initial feed of another table where ready gravio-concentrate is produced. It is proved that the concurrent extraction of gold from copper-pyritic ores using the proposed flow sheet diagram allows increasing gold extraction from 5,12 to 9,89 %. As a result of pilot tests of the developed scheme of gravity separation with formation of high metal content in the head of the process, it is determined that its use for extracting lead from slag (4–6 %) from soda smelting of used battery scrap in rotary kilns allows increasing extraction of lead in concentrate by 7,7 % and its content in gravity concentrate by 14,7 %.Приведены результаты исследования обогащения металлсодержащего сырья на двухкамерной отсадочной машине, отличительной особенностью работы которой является то, что концентрат отсадки выделяют в первой камере машины, в которую загружают исходное питание и возвращают подрешетный продукт второй камеры машины. Сущность новой схемы перечистки на концентрационных столах тяжелой фракции отсадки состоит в том, что ее делят на 2 равные части и направляют на параллельно установленные столы, смешивая концентрат одного из них с исходным питанием другого, на котором получают готовый гравиоконцентрат. Доказано, что попутное выделение золота из медно-колчеданных руд с помощью предложенной схемы позволяет увеличить его извлечение с 5,12 до 9,89 %. В результате опытно-промышленных испытаний разработанной технологии гравитационной сепарации с формированием высокого содержания металла в голове процесса установлено, что ее использование для извлечения свинца из шлаков (4–6 %) от содовой плавки лома отработанных аккумуляторных батарей в короткобарабанных печах позволяет повысить извлечение свинца на 7,7 %, а его содержание в концентрате гравитации – на 14,7 %

Chemostratigraphy of Neoproterozoic carbonates: implications for 'blind dating'

The delta C-13(carb) and Sr-87/Sr-86 secular variations in Neoproteozoic seawater have been used for the purpose of 'isotope stratigraphy' but there are a number of problems that can preclude its routine use. In particular, it cannot be used with confidence for 'blind dating'. The compilation of isotopic data on carbonate rocks reveals a high level of inconsistency between various carbon isotope age curves constructed for Neoproteozoic seawater, caused by a relatively high frequency of both global and local delta C-13(carb) fluctuations combined with few reliable age determinations. Further complication is caused by the unresolved problem as to whether two or four glaciations, and associated negative delta C-13(carb) excursions, can be reliably documented. Carbon isotope stratigraphy cannot be used alone for geological correlation and 'blind dating'. Strontium isotope stratigraphy is a more reliable and precise tool for stratigraphic correlations and indirect age determinations. Combining strontium and carbon isotope stratigraphy, several discrete ages within the 590-544 Myr interval, and two age-groups at 660-610 and 740-690 Myr can be resolved

A DAQ-SYSTEM OF THERMOCOUPLE CALORIMETER

The DAQ-system of thermocouple calorimeter was created. System takes the measure-ments of 16 K-type thermocouple signals with a frequency up to 1 kHz. Every thermocouple channel is galvanically isolated. It allows carrying out the measurements under the electromagnet-ic fields of the accelerator.Исследование выполнено при финансовой поддержке гранта РФФИ № 20-21-00153

Pleiotropic Roles of a Ribosomal Protein in Dictyostelium discoideum

The cell cycle phase at starvation influences post-starvation differentiation and morphogenesis in Dictyostelium discoideum. We found that when expressed in Saccharomyces cerevisiae, a D. discoideum cDNA that encodes the ribosomal protein S4 (DdS4) rescues mutations in the cell cycle genes cdc24, cdc42 and bem1. The products of these genes affect morphogenesis in yeast via a coordinated moulding of the cytoskeleton during bud site selection. D. discoideum cells that over- or under-expressed DdS4 did not show detectable changes in protein synthesis but displayed similar developmental aberrations whose intensity was graded with the extent of over- or under-expression. This suggested that DdS4 might influence morphogenesis via a stoichiometric effect – specifically, by taking part in a multimeric complex similar to the one involving Cdc24p, Cdc42p and Bem1p in yeast. In support of the hypothesis, the S. cerevisiae proteins Cdc24p, Cdc42p and Bem1p as well as their D. discoideum cognates could be co-precipitated with antibodies to DdS4. Computational analysis and mutational studies explained these findings: a C-terminal domain of DdS4 is the functional equivalent of an SH3 domain in the yeast scaffold protein Bem1p that is central to constructing the bud site selection complex. Thus in addition to being part of the ribosome, DdS4 has a second function, also as part of a multi-protein complex. We speculate that the existence of the second role can act as a safeguard against perturbations to ribosome function caused by spontaneous variations in DdS4 levels

DnaC Inactivation in Escherichia coli K-12 Induces the SOS Response and Expression of Nucleotide Biosynthesis Genes

Background: Initiation of chromosome replication in E. coli requires the DnaA and DnaC proteins and conditionally-lethal dnaA and dnaC mutants are often used to synchronize cell populations. Methodology/Principal Findings: DNA microarrays were used to measure mRNA steady-state levels in initiation-deficient dnaA46 and dnaC2 bacteria at permissive and non-permissive temperatures and their expression profiles were compared to MG1655 wildtype cells. For both mutants there was altered expression of genes involved in nucleotide biosynthesis at the non-permissive temperature. Transcription of the dnaA and dnaC genes was increased at the non-permissive temperature in the respective mutant strains indicating auto-regulation of both genes. Induction of the SOS regulon was observed in dnaC2 cells at 38uC and 42uC. Flow cytometric analysis revealed that dnaC2 mutant cells at non-permissive temperature had completed the early stages of chromosome replication initiation. Conclusion/Significance: We suggest that in dnaC2 cells the SOS response is triggered by persistent open-complex formation at oriC and/or by arrested forks that require DnaC for replication restart

Stringent response of Escherichia coli: revisiting the bibliome using literature mining

Understanding the mechanisms responsible for cellular responses depends on the systematic collection and analysis of information on the main biological concepts involved. Indeed, the identification of biologically relevant concepts in free text, namely genes, tRNAs, mRNAs, gene products and small molecules, is crucial to capture the structure and functioning of different responses. Results In this work, we review literature reports on the study of the stringent response in Escherichia coli. Rather than undertaking the development of a highly specialised literature mining approach, we investigate the suitability of concept recognition and statistical analysis of concept occurrence as means to highlight the concepts that are most likely to be biologically engaged during this response. The co-occurrence analysis of core concepts in this stringent response, i.e. the (p)ppGpp nucleotides with gene products was also inspected and suggest that besides the enzymes RelA and SpoT that control the basal levels of (p)ppGpp nucleotides, many other proteins have a key role in this response. Functional enrichment analysis revealed that basic cellular processes such as metabolism, transcriptional and translational regulation are central, but other stress-associated responses might be elicited during the stringent response. In addition, the identification of less annotated concepts revealed that some (p)ppGpp-induced functional activities are still overlooked in most reviews. Conclusions In this paper we applied a literature mining approach that offers a more comprehensive analysis of the stringent response in E. coli. The compilation of relevant biological entities to this stress response and the assessment of their functional roles provided a more systematic understanding of this cellular response. Overlooked regulatory entities, such as transcriptional regulators, were found to play a role in this stress response. Moreover, the involvement of other stress-associated concepts demonstrates the complexity of this cellular response

Structure of the gene encoding cyclomaltodextrinase from Clostridium thermohydrosulfuricum 39E and characterization of the enzyme purified from Escherichia coli.

Clostridium thermohydrosulfuricum 39E, a gram-positive thermophilic anaerobic bacterium, produced a cyclodextrin (CD)-degrading enzyme, cyclodextrinase (CDase) (EC 3.2.1.54). The enzyme was purified to homogeneity from Escherichia coli cells carrying a recombinant multicopy plasmid that contained the gene encoding for thermophilic CDase. The purified enzyme was a monomer with an M(r) of 66,000 +/- 2,000. It showed the highest activity at pH 5.9 and 65 degrees C. The enzyme hydrolyzed alpha-, beta-, and gamma-CD and linear maltooligosaccharides to yield maltose and glucose. The Km values for alpha-, beta-, and gamma-CD were 2.5, 2.1, and 1.3 mM, respectively. The rates of hydrolysis for polysaccharides (starch, amylose, amylopectin, and pullulan) were less than 5% of the rate of hydrolysis for alpha-CD. The entire nucleotide sequence of the CDase gene was determined. The deduced amino acid sequence of CDase, consisting of 574 amino acids, showed some similarities with those of various amylolytic enzymes