ABSTRACT
Ability of actin to polymerise and depolymerise makes it essential to key functions of eukaryotic cell. The functioning of actin is controlled by a host of regulatory proteins, the repertoire of which in diatoms is known to remarkably differ from other organisms. We have performed a phylogenetic analysis of 521 actin and actin-related proteins' aminoacid sequences, as well as 190 sequences of gelsolin family proteins from various genomic and transcriptomic datasets. Based on the results of this analysis, as well as on the presence of clade-specific indels in some of the actin-related proteins, we describe a novel ARP subfamily, dubbed ARP12, which is specific to heterokonts and related organisms. We also describe two novel diatom-specific subfamilies, dGRC1 and dGRC2, among short gelsolin repeat-containing proteins.
Subject(s)
Actins/genetics , Diatoms/genetics , Gelsolin/genetics , Actins/chemistry , Actins/metabolism , Algal Proteins/chemistry , Algal Proteins/genetics , Algal Proteins/metabolism , Amino Acid Sequence , Calcium-Binding Proteins , Gelsolin/chemistry , Gelsolin/metabolism , Multigene Family , Protozoan Proteins , Sequence AlignmentABSTRACT
Cells of the araphid pennate diatom Synedra acus subsp. radians contain large inclusion (1-15 µm) storing silica, as revealed by transmission electron microscopy and EDX-analysis. The size of the inclusions increases with the time of cultivation of diatoms. Approximate concentration of SiO2 in the inclusions is 1-4%. It is assumed that silica in the inclusions is present as gelatinized silica-gel. These results explain the possible mechanism of transport of silicic acid into the cell against the concentration gradient.
Subject(s)
Cytoplasm/ultrastructure , Diatoms/ultrastructure , Inclusion Bodies/ultrastructure , Silicon Dioxide/metabolism , Cytoplasm/metabolism , Diatoms/metabolism , Inclusion Bodies/metabolismABSTRACT
Diatoms are unicellular microscopic eukaryotes able to form species-specific frustules with micro- and nanostructures of biogenic silica. The morphogenesis of frustules components occurs intracellularly within special organelles under control of cytoskeleton. The mechanisms of morphogenesis control are not clear. The influence of paclitaxel, the microtubule inhibitor, onto morphogenesis of valve of pennate diatom Synedra acus subsp. radians was investigated. It has been shown that microtubule disturbance on the early morphogenesis stages provoke symmetry axis displacement of immature valve followed by curvature of the valve. At subsequent stages of morphogenesis stages, disturbance of the fine silica micro- and submicroscale structures (areolae and velums) occurs. It is supposed that a necessary condition for successful diatom valve morphogenesis is a balance between stable and dynamic microtubules.
Subject(s)
Diatoms/metabolism , Microtubules/metabolism , Paclitaxel/pharmacology , Silicon Dioxide/metabolism , Diatoms/ultrastructure , Microtubules/ultrastructureABSTRACT
High-throughput method of sequencing was applied to determine the complete nucleotide sequence of an araphid pennate diatom Synedra acus subsp. radians from Lake Baikal (East Siberia). The assembled genome has a total length of 98 Mbp, the mean coverage is 33x. Structure-functional annotation of the genome was performed.
Subject(s)
Diatoms/genetics , Cell Nucleus/genetics , Genome , Lakes , Models, Genetic , Sequence Analysis , Siberia , SoftwareABSTRACT
Pyrosequencing of amplicons V3-V4 of the 16S rRNA gene of 30 samples from the photic layer across the three basins of Lake Baikal has revealed 44 958 sequences of the domain Bacteria. The most representative phylums among all classified sequences in the samples were Actinobacteria, Bacteroidetes, Verrucomicrobia, Proteobacteria, Acidobacteria, and Cyanobacteria. As much as 38.5% of the total number of sequences has been determined to the level of genus. The taxonomic composition of bacterial communities was similar regardless of some differences in the composition and abundance of spring phytoplankton. Closely related or identical sequences of bacteria inhabiting the epilimnion of other lakes worldwide have been discovered for most sequences. This confirms the similarity of microbial communities in freshwater ecosystems.
Subject(s)
Bacteria/classification , Lakes/microbiology , Microbiota , Phylogeny , Phytoplankton/microbiology , Bacteria/genetics , Bacteria/isolation & purification , Genome, Bacterial , RNA, Ribosomal, 16S/genetics , Seasons , SiberiaABSTRACT
Addition of germanic acid into the culture medium of the diatom Synedra acus subsp. radians (Kutz.) Skabitsch. had nearly no influence on the culture growth at the Ge/Si molar ratio 0.01, but stopped it at ratios 0.05 and higher. It was shown by mass-spectrometry that at the Ge/Si ratio 0.01 germanium was incorporated in both the cytoplasm and siliceous valves, whereas at Ge/Si 0.05 it was incorporated into the cytoplasm but almost failed to accumulate in the valves. At Ge/Si 0.1 germanium was accumulated in the cytoplasm, but its incorporation into the valves terminated. Studies on the cell morphology by light, epifluorescence, and transmission electron microscopy showed that high concentrations of germanic acid induced disorders in morphogenesis of the siliceous frustule and accumulation of large rhodamine-stainable electron-dense inclusions. Model chemical experiments with over-saturated solutions of silicic acid in the presence of polyallylamine revealed that addition of 5% germanic acid considerably accelerated coagulation of silica. Hence, the toxic effect of germanic acid on diatoms could be caused by changes in coagulation of silica.
