Comparison of Metabarcoding and Microscopy Methodologies to Analyze Diatom Communities in Five Estuaries Along the Southern Coast of the Korean Peninsula.

The study of microalgal communities is critical for understanding aquatic ecosystems. These communities primarily comprise diatoms (Heterokontophyta), with two methods commonly used to study them: Microscopy and metabarcoding. However, these two methods often deliver different results; thus, their suitability for analyzing diatom communities is frequently debated and evaluated. This study used these two methods to analyze the diatom communities in identical water samples and compare the results. The taxonomy of the species constituting the diatom communities was confirmed, and both methods showed that species belonging to the orders Bacillariales and Naviculales (class Bacillariophyceae) are the most diverse. In the lower taxonomic levels (family, genus, and species), microscopy tended to show a bias toward detecting diatom species (Nitzschia frustulum, Nitzschia inconspicua, Nitzschia intermedia, Navicula gregaria, Navicula perminuta, Navicula recens, Navicula sp.) belonging to the Bacillariaceae and Naviculaceae families. The results of the two methods differed in identifying diatom species in the communities and analyzing their structural characteristics. These results are consistent with the fact that diatoms belonging to the genera Nitzschia and Navicula are abundant in the communities; furthermore, only the Illumina MiSeq data showed the abundance of the Melosira and Entomoneis genera. The results obtained from microscopy were superior to those of Illumina MiSeq regarding species-level identification. Based on the results obtained via microscopy and Illumina MiSeq, it was revealed that neither method is perfect and that each has clear strengths and weaknesses. Therefore, to analyze diatom communities effectively and accurately, these two methods should be combined.

Water quality assessment of the Sinchun stream based on epilithic diatom communities.

Water quality was assessed 11 sites on the Sinchun Stream, in the region of Daegu City (South Korea), from May 2007 to March 2008 using Diatom Assemblage Index to Organic Water Pollution (DAIpo) and Trophic Diatom Index (TDI). The reference sites were unaffected by effluent from a closed mine or treated sewage and had, epilithic diatom communities that were dominated by saproxenous taxa such as Achnanthes convergens and Cocconeisplacentula var. lineata. The water quality of these sites had DAIpo values ranging between 77.5-93.8 and TDI values between 51.3-67.6, indicating ß-oligosaprobic and mesotrophic environments, respectively. Study sites affected by effluent from the closed mine had epilithic diatom communities that were dominated by acidobiontic diatoms, such as Eunotia exigua and Achnanthidium minutissimum. The water quality of these sites had DAlpo values of 45.9-70.8, indicating ß-mesosaprobic to α-oligosaprobic environments, whereas TDI ranged between 1.7-66.9, indicating an oligotrophic to mesotrophic environment. Downstream sites affected by the influx of mine effluent and treated sewage had many species and a high percentage of saprophilous taxa, including Fragilaria construens var. venter and Nitzschia amphibia. The water quality of these regions had DAIpo values ranging between 21.8-33.1 and TDI values between 67.5-76.7, indicating α-mesosaprobic and eutrophic environments, respectively.

Identification of a 42-kDa Group IV cPLA2-activating protein, cPLAPγ, as a GTP-binding protein in the bovine brain.

Brain tissue contains multiple forms of Phospholipase A(2) (PLA(2)) whose activities are involved in intracellular and intercellular signalling related to normal functions such as long-term potentiation, neurotransmitter release, cell growth and differentiation. Among them, we focused on regulatory mechanism of cPLA(2)α (Group IVA cytosolic PLA(2)) in brain tissue. In the present study, we report the identification of a cPLA(2)-activating protein (cPLAP) in the bovine brain. cPLAP activity appeared as two major peaks with molecular masses of 200 and 42 kDa in a Superose 12 gel filtration FPLC column. The 42-kDa form of cPLAP, designated cPLAPγ, was further purified using a Mono S FPLC column to near homogeneity and characterized to as a GTP-binding protein (G protein). Metabolic labelling and immunoprecipitation studies revealed that cPLAPγ associates with cPLA(2) in vitro and co-immunoprecipitates with [(35)S]-cPLA(2). Notably, cPLAPγ rendered cPLA(2) fully activated at submicromolar concentrations of Ca(2+). These results suggest that cPLAPγ may act as a G protein, activating cPLA(2)α prior to reaching full intracellular Ca(2+) concentrations.