Rhodothalassium

Abstract

Rho.do.tha.las'si.um. Gr. neut. n. rhodon , the rose; Gr. masc. adj. thalassios , belonging to the sea; N.L. neut. n. Rhodothalassium , the rose belonging to the sea. Proteobacteria / Alphaproteobacteria / Rhodothalassiales / Rhodothalassiaceae / Rhodothalassium The genus Rhodothalassium is represented by a single species and is the only genus of the Rhodothalassiaceae family and Rhodothalassiales order. It is characterized by vibrioid‐ to spiral‐shaped cells which multiply by binary fission and are motile by means of flagella. Internal photosynthetic membranes are present as lamellar stacks lying parallel to the cytoplasmic membrane. Photosynthetic pigments are bacteriochlorophyll a and carotenoids of the spirilloxanthin series. Ubiquinones and menaquinones with 10 isoprene units (Q‐10 and MK‐10) are present. Growth occurs preferably photoheterotrophically under anoxic conditions in the light. Most strains also grow chemoorganotrophically under oxic conditions in the dark. Rhodothalassium species are obligately halophilic, require NaCl or sea salt for growth, and live in anoxic zones of hypersaline environments such as salterns, salt lakes, and evaporated coastal lagoons that are exposed to the light. DNA G + C content (mol%) : 68.5–69.0 (WGS), 60.0–62.8 (HPLC). Type species : Rhodothalassium salexigens Imhoff et al. 1998 VP (basonym: Rhodospirillum salexigens Drews 1981, VL9).