A survey for bacteria of the genus
Thiothrix
indicated that they inhabited the area where the water of the Zmeiny geothermal spring (northern basin of Lake Baikal, Russia) mixed with the lake water. ...In the coastal zone of the lake oxygen (8.25 g/L) and hydrogen sulfide (up to 1 mg/L) were simultaneously present at sites of massive growth of these particular
Thiothrix
bacteria. Based on the analysis of the morphological characteristics and sequence of individual genes (16S rRNA,
rpoB
and
tilS
), we could not attribute the
Thiothrix
from Lake Baikal to any of the known species of this genus. To determine metabolic capabilities and phylogenetic position of the
Thiothrix
sp. from Lake Baikal, we analyzed their whole genome. Like all members of this genus, the bacteria from Lake Baikal were capable of organo-heterotrophic, chemolithoheterotrophic, and chemolithoautotrophic growth and differed from its closest relatives in the spectrum of nitrogen and sulfur cycle genes as well as in the indices of average nucleotide identity (ANI < 75–94%), amino acid identity (AAI < 94%) and in silico DNA-DNA hybridization (dDDH < 17–57%), which were below the boundary of interspecies differences, allowing us to identify them as novel candidate species.
In this article, the system of the green microalgal genus Micractinium, based on morphological, physiological, ecological and molecular data, is considered. The main diagnostic species ...characteristics and the taxonomic placement of some taxa are also discussed. Phylogenetic analysis showed that the genus Micractinium is characterized by high cryptic diversity. The algorithms used for species delimitation had different results on the number of potentially species-level clusters allocated. The ABGD method was less "sensitive". The tree-based approaches GMYC and PTP showed a more feasible taxonomy of the genus Micractinium, being an effective additional tool for distinguishing species. The clustering obtained by the latter two methods is in good congruence with morphological (cell size and shape, ability to form colonies, production of bristles, chloroplast type), physiological (vitamin requirements, reaction to high and low temperatures), molecular (presence of introns, level of genetic differences, presence of CBCs or special features of the secondary structure in ITS1 and ITS2) and ecological characteristics (habitat). The polyphyly of the holotype of the genus M. pusillum as well as M. belenophorum is shown. The intron was effective as an additional tool for distinguishing species, and the results of the intron analysis should be taken into account together with other characteristics. The CBC approach, based on the search for compensatory base changes in conservative ITS2 regions, was successful only for distinguishing cryptic species from "true" members of M. pusillum. Therefore, to distinguish species, it is more effective to take into account all the CBC in ITS1 and ITS2 and analyze characteristic structural differences (molecular signatures) in the secondary structure of internal transcribed spacers. The genetic distances analysis of 18S-ITS1-5.8S-ITS2 nucleotide sequences showed that intraspecific differences in the genus ranged from 0 to 0.5 % and interspecific differences, from 0.6 to 4.7 %. Due to the polyphasic approach, it was possible to characterize 29 clusters and phylogenetic lines at the species level within the genus Micractinium and to make assumptions about the species.
The correct identification of species diversity of small single-celled green coccoid microalgae still causes difficulties, since their relatively simple morphology hides a high physiological, ...ecological and genetic diversity. The use of molecular genetic methods has revolutionized the study of the true biodiversity of so-called “small green balls,” allowing the discovery of numerous new taxa. This article presents the results of a study of strains recently isolated from small freshwater urbanized lakes (Vasilievsky Lakes system, Samara region, Russian Federation). Morphologically, these strains were close to the genus
Meyerella:
spherical cells, cup-shaped, or wide girdle-shaped parietal chloroplast without pyrenoid. Analysis of the 18S–ITS1–5.8S–ITS2 sequences also showed that the studied strains belong to this genus. Comparison of morphological characteristics, habitat and lifestyle, analysis of tree topology, genetic distances and secondary structures of the ITS1 and ITS2 spacers of the
Meyerella
members, as well as the delimitation results using the Automatic Barcode Gap Discovery (ABGD) method, the Poisson Tree Processes (PTP) model, the Generalized Mixed Yule The Coalescent (GMYC) method allowed us to establish that the studied strains ACSSI 346, ACSSI 362 and ACSSI 363 are representatives of a new species –
M. similis
sp. nov.
—
This article discusses the system of green microalgae of the clade
Parachlorella
, based on morphological, ecological, and molecular genetic data. The diagnostic characteristics of the selected ...genera and species and the systematic position of some taxa are discussed. Phylogenetic analysis of the
Parachlorella
-clade has shown that, despite the relative simplicity of morphology, it is characterized by high cryptic diversity. The polyphyletic nature of the genus
Dictyosphaerium
and some species (
D. libertatis, D. ehrenbergianum, Compactochlorella kochii, Mucidosphaerium pulchellum, M. palustre,
and
Closteriopsis acicularis
) was shown. Theuse of the intron as a universal criterion for closely related species was effective for representatives of groups II, IV, VII, and VIII, as well as for strains of the species
Compactochlorella kochii
and
D. libertatis
. The application of the classical CBC approach, based on the search for CBC in conservative ITS2 regions, was successful only for the representatives of group II. The results of analysis of genetic distances and the GMYC, PTP, and ABGD species delimitation algorithms are not universal tools for determining species boundaries and need to be confirmed by other characteristics (cell shape, ability to form colonies, the way the cells attach to hyaline interconnecting strands, the type of chloroplast, the number of pyrenoids, the presence of mucilage, the presence/absence of introns, the level of genetic differences, the presence of CBC in ITS1 and ITS2, the habitat). Due to the combined use of morphological, ecological and genetic features, it was possible to characterize 11 groups and 2 phylogenetic lines within the clade
Parachlorella
and to make assumptions about the division of genera and species within the selected groups.
SND tracking system—Tests with cosmic muons Aulchenko, V.M.; Bogdanchikov, A.G.; Botov, A.A. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
2009, 2009-1-00, Letnik:
598, Številka:
1
Journal Article
Recenzirano
Tracking system of the SND detector is fully assembled, equipped and tested with cosmic muons in 2007. During these tests operation conditions of the system were checked and optimized and main ...parameters of the system were measured. Design values of gas gain, detection efficiency and space resolution were achieved. Tracking system is ready for installation into the SND detector and coming data taking at the VEPP-2000
e
+
e
-
-collider in Novosibirsk.
•Our knowledge of their taxonomic and phylogenetic relationships is still deficient.•Some genus and species from Moewusinia clade differ specific feature combinations.•The ITS2 of Eubrownia and ...Chlorococcum genera is unique within the chlorophytes.
Despite that the diversity of chlorophycean microalgae has been studied for a long time, our knowledge of their taxonomic and phylogenetic relationships is still deficient. This study represents one of the first efforts to examine the congruence of the morphological identification of microalgal species from genera Eubrownia, Spongiococcum, and Chlorococcum with DNA-based species delimitation methods. We found unique combinations of morphological, molecular, and ecological features, distinguishing some members of the Moewusinia clade at the genus and species levels. Most genetic groups recovered by GMYC, ABGD, and PTP analyses of 18S rRNA and ITS2 were consistent with their morphological identification. The ITS2 region of genera Eubrownia and Chlorococcum is among the longest within the chlorophytes theretofore studied and has a unique secondary structure with branched helix III and uncommonly long helix IV. Moreover, the molecular signatures were found in the basal stem region of helix I, distinguishing two genera. The CBC analysis is able to effectively discriminate between E. isobilateralis, E. aggregata, and all Chlorococcum species, except for C. infusionum and C. echinozygotum. Thus, we confirmed tentative hypotheses of species, obtained by DNA-based delimitation methods, with morphological data, molecular signatures, ITS2 secondary structure, and CBC criterion.
We present the results of devising new techniques and technical means for utilizing small-sized unmanned aerial vehicles (UAVs) in ecological monitoring of marine water basins in compliance with the ...MARPOL 73/78 international convention. The development of a hardware-software complex is described for the system of recognizing oil spills using elements of artificial intelligence. The laboratory experiments on identifying oil spills by laser induced fluorescence (LIF) methods are presented, as well as the methods of recording the spectrum of upward solar radiation.
The results of the first direct experiments on the passage of pulses of ultra-wideband radiation of subnanosecond duration in the Earth’s atmosphere at a distance of more than 10 km are presented. In ...contrast to the work calculated, the preservation of the amplitude–time shape of the pulses in the process of increasing the distance is shown. The establishment of this fact is of decisive importance in the practical application of ultra-wideband pulses in new technological developments.
—
Two techniques for multielement analysis of liquid-droplet aerosol are compared, which are based on the spectral analysis of the radiation of a laser plasma generated in a laser breakdown (LIBS) or ...during laser pulse filamentation in a liquid droplet aerosol (R-FIBS). A liquid-droplet aerosol containing Na solution is used. It is shown that there are optimal delay times of the start of signal recording relative to the start of plasma generation, at which the signal-to-noise ratio is maximal, for both techniques. The dependence of the signal-to-noise ratio is derived for different laser radiation focusing deep into a liquid-droplet cloud for LIBS. The Na detection limits are determined for both methods.
Magnetic skyrmions are topologically nontrivial particles with a potential application as information elements in future spintronic device architectures. While they are commonly portrayed as two ...dimensional objects, in reality magnetic skyrmions are thought to exist as elongated, tube-like objects extending through the thickness of the host material. The study of this skyrmion tube state (SkT) is vital for furthering the understanding of skyrmion formation and dynamics for future applications. However, direct experimental imaging of skyrmion tubes has yet to be reported. Here, we demonstrate the real-space observation of skyrmion tubes in a lamella of FeGe using resonant magnetic x-ray imaging and comparative micromagnetic simulations, confirming their extended structure. The formation of these structures at the edge of the sample highlights the importance of confinement and edge effects in the stabilisation of the SkT state, opening the door to further investigation into this unexplored dimension of the skyrmion spin texture.
PDF
