Добірка наукової літератури з теми "Achnanthidium saprophilum"

A new monoraphid diatom species Achnanthidium tinea Tseplik, Kulikovskiy, Kociolek & Maltsev, sp. nov. is described from Indonesia. The species is described on the basis of molecular and morphological analyses. According to molecular data the new species belongs to the clade that includes strains of Achnanthidium minutissimum, Achnanthidium saprophilum and Achnanthidium digitatum. Morphologically, the new species differs quite significantly from other species of the same genus because of linear-elliptic valves with almost parallel sides and strongly radiate striae and a butterfly-shaped fascia on the raphe valve. The morphology and phylogeny of the new species are discussed, and thoughts on the current state of the taxonomy of the genus Achnanthidium are expressed. Our work shows the importance of using molecular data in diatom systematics and also demonstrates the need to investigate rarely studied regions of our planet.

AbstractDiversity of hot spring diatoms in northern Thailand was studied. Forty-six diatom species were identified in eight localities. The dominant species according to high relative abundance were Diatomella balfouriana (41.7%), Achnanthidium exiguum (20.9%) and Anomoeoneis sphaerophora (11.2%). Moreover, Caloneis molaris, Craticula acidoclinata, Navicula subrhynchocephala and Pinnularia saprophila were recorded as species new to Thailand. The NMDS ordination revealed variation in species composition of eight different hot springs and correlation with the existing environmental variables. Silicon dioxide (SiO2), pH, conductivity, water temperature and total hardness were statistically significant factors affecting relative abundance of Achnanthidium exiguum, Amphora montana, Caloneis aequatorialis, Cocconeis placentula, Craticula cuspidata, Diploneis elliptica, Gomphonema affine, Gomphonema augur, Halamphora fontinalis, Planothidium lanceolatum, Pinnularia abaujensis, Sellaphora lanceolata and Stauroneis anceps.

The study of phytoplankton in the Nizhny Tagil Reservoir using scanning electron microscopy made it possible to obtain the data on morphology of some representatives of the genus Ashnanthidium: A. catenatum, A. dolomiticum, A. eutrophilum, A. saprophilum. The ranges of variability of the main diagnostic features (length and width of the valve, number of striae and areolae in 10 µm) were found and new values were obtained for some of them; the first data on such an important ultrastructural feature as the number of areolae in 10 µm were obtained for the species A. catenatum, A. dolomiticum, and A. eutrophilum.

We applied DNA metabarcoding to evaluate the ecology of genetic variants within several diatom species that are important for biomonitoring. Benthic diatoms are widely used as bioindicators for biomonitoring programmes, including those for European rivers demanded by Water Framework Directive (WFD). Morphological identification of diatoms at species level is required for assessing the ecological status in biomonitoring programmes. However, this is a time-consuming task and requires expert knowledge. In addition, closely related species, which sometimes are scarcely distinguishable on the basis of their morphology, can show different ecological preferences; these may even vary within a single diatom species. Not being able to identify the different ecological preferences shown by the genetic variants of a single species or closely related species, might have consequences for biomonitoring programmes, especially if such differences occur within common species. The key diatom species that we studied were: Fistulifera saprophila (FSAP), widely regarded as a marker for elevated nutrient levels, organic pollution and hence poor ecological status; Achnanthidium minutissimum (ADMI), which usually indicates good ecological status; and Nitzschia inconspicua (NINC) and N. soratensis (NSTS), two species that are widely separated phylogenetically but almost impossible to distinguish in the light microscope. Our dataset was based on high-throughput sequencing using a 312-bp rbcL marker. We used the denoising pipeline DADA2 to infer amplicon sequence variants (ASVs) from 554 environmental samples from river biomonitoring campaigns in Catalonia (NE Spain) and France. Ecological groupings of ASVs were distinguished according to their environmental responses given by Threshold Indicator Taxa ANalysis (TITAN); the environmental parameters that most influenced the occurrence of these groupings were tested using boosted regression trees. We could distinguish three different ecological groupings of ASVs within ADMI and three within FSAP. In each species two of the groupings were clearly separated by their opposite responses to calcium and conductivity and boosted regression trees showed that for three out of four of these groupings, these two variables were among the most important variables for explaining the ASV distributions. The third grouping in FSAP had a negative response to total organic carbon and a positive response to altitude and hence was better represented in less organically polluted waters and higher ecological status than is generally assumed for FSAP. Our analyses did not identify ecological groupings of ASVs within NINC and NSTS but confirmed earlier studies, based on more limited sampling, that indicated different preferences of these species. Conductivity and calcium were the variables that most influenced the occurrence of NINC and NSTS, NINC being better distributed in waters with higher levels of calcium and conductivity than NSTS. Our findings indicate the potential use of DNA metabarcoding for distinguishing the ecological preferences of genetic variants within a single species or closely related species. This information, coupled with the broad knowledge generated over many years using traditional microscope-based identifications, will facilitate the development of more accurate biological indexes for the biomonitoring programmes of the future.

In freshwater ecosystems, periphytic biofilms include diatom assemblages that depend on environmental conditions (e.g., nutrient concentrations, salinity, temperature etc.). These assemblages respond rapidly to environmental changes, which makes diatoms valuable bioindicators. For this reason, they are currently used in freshwater biomonitoring programs (e.g., EU Water Framework Directive - WFD) (Foster et al., 2000). To date, diatom taxonomic identification is based on morphological criteria, which requires high taxonomic expertise to identify them to the species level needed for biomonitoring. Having this in mind, new strategies have been examined for the development of high-throughput, non-biased identification approaches. Human activities are the leading cause of environmental impairments and appropriate biomonitoring of ecosystems is needed to effectively assess the impact of their activities. In the last ten years, DNA metabarcoding combined with next-generation sequencing and bioinformatics, have been proposed as a complementary approach to morphological identification. In the past ten years, DNA metabarcoding coupled with next-generation sequencing and bioinformatics represents a complementary approach for diatom biomonitoring (Vasselon et al., 2019). In this study, this approach was used for the first time in Cyprus considering the association of environmental and anthropogenic pressures to diatom assemblages using the rbcL 312 bp barcode, next-generation sequencing (MiSeq Illumina), and bioinformatic evaluation (Mothur Software). Statistical analysis was then applied to identify the environmental (i.e., river types, geo-morphological) and anthropogenic (i.e., physical, chemical, human land-use pressures) variables' role in the observed diatom diversity. The Indice de Polluosensibilité Spécifique (IPS) index was used as it was shown to better respond to pressures that affect water quality in Cyprus rivers (WDD, 2014). Results indicate differences in diatom assemblages between intermittent and perennial rivers. Achnanthidium minutissimum was more abundant in intermittent rivers; whereas Amphora pediculus and Planothidium victorii (P. caputium) in perennial ones. Furthermore, we could demonstrate the correlation between nutrients (e.g., nitrogen, phosphorus), characteristics of the individual sampling sites (e.g., elevation), and land use activities on the observed differences in diatom diversity (Pissaridou, 2021). Additionally, results were compared to the morphotaxonomy-based approach which was conducted microscopically. Results show a positive correlation between morphological and molecular IPS scores. Points deviating from the norm are influenced by the limitations of both techniques. Fistulifera saprophila had a key role in this observation, as it negatively influences IPS scores. All in all, we conclude that DNA metabarcoding complements the morphological methodology for the ecological quality assessment of freshwaters in Cyprus. Multi-stressors and anthropogenic pressures have a significant statistical relationship to the observed diatom diversity and play a pivotal role in determining Cyprus' rivers' ecological status (Fig. 1). Foster, D., Wood, A., Griffiths, M., 2000. The Water Framework Directive (2000/60/EC) – An introduction Dave Foster – Policy Advisor (Europe), Aram Wood EP Scientist (Water), Dr Martin Griffiths – Head of Water Quality, Environment Agency, Head Office, Rio House, Waterside Drive, Aztec West, Almon 7–9. Pissaridou, P., Vasselon V., Christou A., Chonova T., Lacroix S., Papatheodoulou A., Drakou K., Tziortzis I., Dörflinger G., Rimet F., Bouchez A. and Vasquez MI. 2021 Deciphering Cyprus’ diatom diversity and the effects of environmental and anthropogenic influences for ecological assessment of rivers using DNA metabarcoding.Chemosphere (In Press) Vasselon, V., Frédéric, R., Isabelle, D., Olivier, M., Yorick, R., Agnès, B., 2019. Assessing pollution of aquatic environments with diatoms’ DNA metabarcoding: Experience and developments from France Water Framework Directive networks. Metabarcoding and Metagenomics 3, 101–115. https://doi.org/10.3897/mbmg.3.39646 WDD, 2014. Review and update of article 5 of Directive 2000/60/EC (Water reservoirs) & Classification of water status (Rivers, natural lakes and water reservoirs), That will establish baseline information and data for the 2nd cyprus river basin management plan.

Les diatomées sont des microalgues unicellulaires omniprésentes sur Terre et utilisées comme bioindicateurs pour évaluer l'impact de contaminations sur les écosystèmes aquatiques. Elles font également l'objet d'une attention croissante en tant que matériel de décontamination de métaux lourds d’effluents contaminés ou à des fins de biorestauration in situ. Cependant, les interactions entre les diatomées et les radioéléments, notamment l'uranium (U) et le radium (Ra), restent peu documentées. Ce travail vise à étudier tant au niveau macroscopique que moléculaire, les interactions de U et du Ra avec une culture xénique de diatomées Achnanthidium saprophilum, dans laquelle une communauté bactérienne est naturellement associée de manière symbiotique. Des expériences de bio-association de U et du Ra sont faites en présence de diatomées afin d’évaluer les fractions en U/Ra adsorbées et incorporées. En parallèle, diverses techniques de microscopie et de spectroscopie sont appliquées pour étudier la localisation et la spéciation de U au niveau cellulaire. Les résultats démontrent une bio-association significative de U et du Ra avec les diatomées et soulignent le rôle important des groupes carboxyliques et phosphates dans l'interaction U-diatomées. Les deux mécanismes d’adsorption et d’incorporation ont pu être mis en évidence pour U et Ra, la répartition entre les fractions adsorbées et incorporées dépendant de la phase de croissance des diatomées et du temps de contact entre les micro-algues est les radioéléments. Ce travail met également en évidence la contribution significative des bactéries symbiotiquement associées aux diatomées aux interactions globales
Diatoms are ubiquitous unicellular microalgae that are commonly used as bioindicators to evaluate the impact of contaminations on the ecological health of aquatic ecosystems. In recent decades, diatoms have received increasing attention as a decontamination material for removing heavy metals from contaminated effluents or for in situ bioremediation purposes. However, the interactions between diatoms and radioelements, e.g., uranium (U) and radium (Ra), remain relatively unclear and poorly documented. Therefore, this work aims to study, at both the macroscopic and molecular level, the interaction of U and Ra with a xenic Achnanthidium saprophilum diatom culture in which a naturally occurring bacterial community is symbiotically associated to diatoms. Batch-type U and Ra bio-association experiments are performed to evaluate the adsorbed and incorporated fractions of U/Ra in the diatom culture. Besides, various microscopic and spectroscopic techniques are applied to investigate the localization and speciation of U at the cellular level. Results demonstrate the significant bioassociation of U and Ra with the diatoms and highlight the important role of carboxylic and phosphate groups in the U-diatoms interaction. Both adsorption and incorporation are observed for U and Ra in the diatom culture, with their distribution depending on the diatom growth phase and on the contact time. This work contributes to a better understanding of the interaction of U and Ra with the xenic diatom culture and also highlights the contribution of the bacteria symbiotically associated with the diatoms to the overall interactions