Molecular Identification of Thalassionema Strains

Identification of the cultured Thalassionema strains was done according to both morphological observation and molecular identification. For morphological observation, cells were mounted on the glass-slide and observed with a ZEISS IMAGER A2 microscope equipped with differential interference contrast optics. For molecular identification, full-length 18S rDNA was assembled from the clean data using GetOrganelle (v1.7.5) [25 (link)] and SPAdes (v3.14.0) [26 (link)], with publicly available 18S rDNA of Thalassionema species serving as reference sequences. The assembled sequences were validated by the following steps. (1) Aligning reads to the assembled sequences using BWA (v0.7.17-r1188) [27 (link)]. (2) Extracting alignment results using SAMtools (v1.10) [28 (link)]. (3) Inspecting and correcting errors using IGV (v2.7.2) [29 (link)]. The evolutionary relationship of Thalassionema species based on full-length 18S rDNA was inferred using maximum likelihood (ML) method, conducted by MEGA (v7.0). The species Synedra acus (KF959659.1) was chosen as the outgroup taxa.