Mitochondrial and Plastid Genomes of the Monoraphid Diatom Schizostauron trachyderma.

We provide for the first time the complete plastid and mitochondrial genomes of a monoraphid diatom: Schizostauron trachyderma. The mitogenome is 41,957 bp in size and displays two group II introns in the cox1 gene. The 187,029 bp plastid genome features the typical quadripartite architecture of diatom genomes. It contains a group II intron in the petB gene that overlaps the large single-copy and the inverted repeat region. There is also a group IB4 intron encoding a putative LAGLIDADG homing endonuclease in the rnl gene. The multigene phylogenies conducted provide more evidence of the proximity between S. trachyderma and fistula-bearing species of biraphid diatoms.

Extreme Enlargement of the Inverted Repeat Region in the Plastid Genomes of Diatoms from the Genus Climaconeis.

We sequenced the plastid genomes of three diatoms from the genus Climaconeis, including two strains formerly designated as Climaconeis scalaris. At 208,097 and 216,580 bp, the plastid genomes of the latter strains are the largest ever sequenced among diatoms and their increased size is explained by the massive expansion of the inverted repeat region. Important rearrangements of gene order were identified among the two populations of Climaconeis cf. scalaris. The other sequenced Climaconeis chloroplast genome is 1.5 times smaller compared with those of the Climaconeis cf. scalaris strains and it features an usual quadripartite structure. The extensive structural changes reported here for the genus Climaconeis are compared with those previously observed for other algae and plants displaying large plastid genomes.

Haslea silbo, A Novel Cosmopolitan Species of Blue Diatoms.

Specimens of a new species of blue diatoms from the genus Haslea Simonsen were discovered in geographically distant sampling sites, first in the Canary Archipelago, then North Carolina, Gulf of Naples, the Croatian South Adriatic Sea, and Turkish coast of the Eastern Mediterranean Sea. An exhaustive characterization of these specimens, using a combined morphological and genomic approach led to the conclusion that they belong to a single new to science cosmopolitan species, Haslea silbo sp. nov. A preliminary characterization of its blue pigment shows similarities to marennine produced by Haslea ostrearia, as evidenced by UV-visible spectrophotometry and Raman spectrometry. Life cycle stages including auxosporulation were also observed, providing data on the cardinal points of this species. For the two most geographically distant populations (North Carolina and East Mediterranean), complete mitochondrial and plastid genomes were sequenced. The mitogenomes of both strains share a rare atp6 pseudogene, but the number, nature, and positions of the group II introns inside its cox1 gene differ between the two populations. There are also two pairs of genes fused in single ORFs. The plastid genomes are characterized by large regions of recombination with plasmid DNA, which are in both cases located between the ycf35 and psbA genes, but whose content differs between the strains. The two sequenced strains hosts three plasmids coding for putative serine recombinase protein whose sequences are compared, and four out of six of these plasmids were highly conserved.

Mitogenome sequence of a Black Sea isolate of the kinetoplastid Bodo saltans.

We obtained the mitogenome sequence of a Black Sea isolate of the kinetoplastid Bodo saltans. This sequence consists of two contigs totaling 24,925 bp and encodes ten protein-coding genes, one conserved ORF and one rRNA gene. Alignment of the Black Sea mitogenome with the limited sequence data currently available in public databases for another strain of B. saltans revealed significant genetic divergence between the two isolates. Maximum likelihood phylogenetic inference clearly resolved the Bodonidae from the Trypanosomatidae.