Analysis of Predicted Amino Acid Sequences of Diatom Microtubule Center Components

Diatoms synthesize species-specific exoskeletons inside cells under the control of the cytoskeleton and microtubule center. Previous studies have been conducted with the visualization of the microtubule center; however, its composition has not been studied and reliably established. In the present study, several components of MTOC in diatoms, GCP (gamma complex proteins), Aurora A, and centrins have been identified. Analysis of the predicted amino acid sequences of these proteins revealed structural features typical for diatoms. We analyzed the conserved amino acids and the motives necessary for the functioning of proteins. Phylogenetic analysis of GCP showed that all major groups of diatoms are distributed over phylogenetic trees according to their systematic position. This work is a theoretical study; however, it allows drawing some conclusions about the functioning of the studied components and possible ways to regulate them

Changes in valve morphology of two pennate diatom species during long-term culture

The morphology of diatom siliceous is a primary basis for their species identification. This study aims to measure the range of morphological changes induced in the monoclonal cultures of Fragilaria radians strains 280 and A6 and Ulnaria danica strain BK17 by cultivation in the lab for a year or more. The scanning electron microscopy revealed that the number of abnormal valves increases during the first year of culture maintenance. Specific abnormalities observed include curved valves and apices, axial areas and rimoportulae shifted from their normal positions, disordered or otherwise abnormal striae, and various growths on the valves. Similar morphological abnormalities are known to occur in diatoms exposed to microtubule inhibitors. These results show the limits of morphological variance in studied species and could be used to estimate the effect of toxic agents in natural and experimental conditions

Assessment of diatom growth using fluorescence imaging

Monitoring the growth of diatom microalgae requires sensitive, fast, and easy-to-use methods for selecting the most productive strains for further research and application. Here we propose a novel, rapid and non-destructive approach for monitoring the viability and growth of diatom colonies using the IVIS fluorescence imaging system. The fast-growing Achnanthidium sibiricum diatoms were cultivated in favorable laboratory conditions in a specially designed bioincubator for 100 days. The results showed that the diatoms reached the end of the exponential growth phase after 56 days of culture, after which there was a slight decrease in fluorescence intensity. This method relies on using chlorophyll a fluorescence without any sample preparation and has proved to be successful for monitoring algae growth in an incubator during long-term batch cultivation. This result paves the way towards controlled diatom cultivation aimed at collecting diatom-derived bioactive compounds for various purposes.ISSN:1742-6588ISSN:1742-659

Impact of Algicidal Bacillus mycoides on Diatom Ulnaria acus from Lake Baikal

Algae–bacteria interactions play an important role in water ecosystems. In this work, the BS2-15 algicidal strain was isolated from the bottom sediments of Lake Baikal and identified as Bacillus mycoides on the basis of 16S rDNA sequencing, its described ultrastructure, and biochemical properties. B. mycoides BS2-15 was demonstrated to have a strong algicidal effect against a freshwater diatom culture of Ulnaria acus, inhibiting its growth and increasing frustules fragility. By analyzing the impact of bacterial filtrate onto the cells of U. acus, we demonstrated that perhaps an algicidal compound is produced by bacteria independently in the presence of diatoms in a medium. Using methods of TUNEL and confocal microscopy, we revealed that the bacterial algicidal effect on the diatom cells results in DNA fragmentation, nucleus destruction, and neutral lipid accumulation. This phenomenon highlights the complexity of algae–bacteria interactions and their potential role in regulating water ecosystem microbial populations

Differential Expression of Stress Adaptation Genes in a Diatom <i>Ulnaria acus</i> under Different Culture Conditions

Diatoms are a group of unicellular eukaryotes that are essential primary producers in aquatic ecosystems. The dynamic nature of their habitat necessitates a quick and specific response to various stresses. However, the molecular mechanisms of their physiological adaptations are still underexplored. In this work, we study the response of the cosmopolitan freshwater diatom Ulnaria acus (Bacillariophyceae, Fragilariophycidae, Licmophorales, Ulnariaceae, Ulnaria) in relation to a range of stress factors, namely silica deficiency, prolonged cultivation, and interaction with an algicidal bacterium. Fluorescent staining and light microscopy were used to determine the physiological state of cells under these stresses. To explore molecular reactions, we studied the genes involved in the stress response—type III metacaspase (MC), metacaspase-like proteases (MCP), death-specific protein (DSP), delta-1-pyrroline-5-carboxylate dehydrogenase (ALDH12), and glutathione synthetase (GSHS). We have described the structure of these genes, analyzed the predicted amino acid sequences, and measured their expression dynamics in vitro using qRT-PCR. We demonstrated that the expression of UaMC1, UaMC3, and UaDSP increased during the first five days of silicon starvation. On the seventh day, it was replaced with the expression of UaMC2, UaGSHS, and UaALDH. After 45 days of culture, cells stopped growing, and the expression of UaMC1, UaMC2, UaGSHS, and UaDSP increased. Exposure to an algicidal bacterial filtrate induced a higher expression of UaMC1 and UaGSHS. Thus, we can conclude that these proteins are involved in diatoms’ adaptions to environmental changes. Further, these data show that the molecular adaptation mechanisms in diatoms depend on the nature and exposure duration of a stress factor