Pegethrix sp.

Mai, Truc, Johansen, Jeffrey R., Pietrasiak, Nicole, Bohunická, Markéta & Martin, Michael P., 2018, Revision of the Synechococcales (Cyanobacteria) through recognition of four families including Oculatellaceae fam. nov. and Trichocoleaceae fam. nov. and six new genera containing 14 species, Phytotaxa 365 (1), pp. 1-59 : 27

Pegethrix sp. ANT.LH70.1 & ANT.LMA.1 ( Fig. 6e , 7d , 9e )

Diagnosis: ―Secondary structure of the conserved D1-D1’ domain most similar to P. bostrychoides and P. olivacea in the presence of the largest internal loop at position 20–23/44–48 ( Fig. 6e ). Similar to P. convoluta and P. indistincta in the presence of the internal loop at position 14–15/53–54 of D1-D1’ helix ( Fig. 6e ), the basal mismatch at position 5 on 5’ strand of Box B ( Fig. 7d ) and the basal helix of V3 at position 1–18 on 5’ strand and its 3’ complement especially at the basal internal loop and the 5’ unilateral bulge. Dissimilarities between the structure and sequence of these conserved domains of Antarctic Pegethrix sp. and other species of the genus clearly set them apart.

Description:— Filaments rarely false branched. Sheath present. Trichomes brownish, constricted, without necridia, 1.73 ± 0.23 μm wide. Cells are generally isodiametric, 1.76 ± 0.94 μm long, but Brown et al. (2010) also reported two different morphotypes within one single species culture, with cells both longer and shorter than wide.

D1-D1’ helix 76 nucleotides long, with basal 3’ side loop of 9 unpaired nucleotides (5’-CCAUCCCAA-3’), opposed on the 5’ strand by a single unpaired adenine residue. Mid-helix region with several internal loops at positions 14– 15/53–54, 20–23/44–48 and 26–27/40–41, and one large bilateral bulge at position 20-23/44-48, and a terminal loop of 4 nucleotides, having sequence of 5’-GAAA-3’ ( Fig. 6e ). Box B helix 37 nucleotides long, bearing 5 nucleotides in terminal loop ( Fig. 7d ). No V2 helix present between tRNAAla and tRNAIle. V3 helix 94 nucleotides long, with several internal loops at positions 5–6/90, 21-22/77–78, 30–36/63–69 and 42–44/55–57, with a unilateral bulge at position 12–14 on the 5’ strand. Terminal loop 4 nucleotides, 5’-GUAA-3’ ( Fig. 9e ).

Collection locality:— Strains were collected in a water body of Larsemann Hills, located in the Prydz Bay region, which consists of two major ice-free regions in continental east Antarctica.

Reference strains: ―ANT.LH70.1, ANT.LMA.1.

Taxonomic notes:— The two strains representing this taxon were collected from Antarctic water bodies by others. Based on the description, isolated distribution, molecular data and site information provided by those authors ( Taton et al. 2006, Sabbe et al. 2014), this is likely an undescribed species of Pegethrix . We do not name it here as we do not have the culture in our possession and consequently cannot prepare valid type materials. The description above is taken from the original work.

Figures

FIGURE 6. D1-D1’ stems of species described in Oculatellaceae.The stem structures of genera described previously in other publications (Oculatella, Thermoleptolyngbya, Timaviella) or in publications under provision (Trichotorquatus) are not shown here.

FIGURE 7. Box B helices of species described in Oculatellaceae. The structures of genera described previously in other publications (Oculatella, Thermoleptolyngbya, Timaviella) or in publications under provision (Trichotorquatus) are not shown here.

FIGURE 9. V3 helices of species described in Oculatellaceae. All species described have this structure. The V3 helix of Cartusia aeruginosa is missing because we do not have the full length of its ITS region.