**5. Emended Description of the Family** *Ectothiorhodospiraceae* **Imhoff 1984a, 33VP**

Ec.to.thi'o.rho.do.spi.ra'ce.ae. M.L. fem. n. *Ectothiorhodospira* type genus of the family; -aceae ending to denote a family; M. L. fem. pl. n. Ectothiorhodospiraceae the *Ectothiorhodospira* family.

The family constitutes slightly or moderately halophilic phototrophic bacteria growing under alkaline conditions and their chemotrophic relatives. They are Gram-negative and belong to the *Gammaproteobacteria*. Cells are spiral-, vibrioid- or rod-shaped, motile by means of polar flagella and divide by binary fission. They are either phototrophic purple sulfur bacteria that perform anoxygenic photosynthesis with bacteriochlorophylls and carotenoids as photosynthetic pigments or aerobic chemolithotrophic sulfur-oxidizing bacteria, some of which may use nitrate as alternative electron acceptors. Growth of phototrophic representatives is preferably anaerobic in the light, with reduced sulfur compounds as electron donors. Sulfide is oxidized to elemental sulfur and is deposited outside the cells, eventually also in the peripheral periplasmic space of the cell body. The final oxidation product is sulfate. *Ectothiorhodospiraceae* are found in marine and moderately saline environments containing sulfide and having an alkaline to extremely alkaline pH. Glycine betaine, but not ectoine, is the major compatible solute in these bacteria.

The mol% G + C of the DNA is from 53.8–68.4 (genome sequence).

Type genus: *Ectothiorhodospira* Pelsh 1936, 120.

#### **6. Description of the Family** *Halorhodospiraceae***. fam. nov.**

Ha.lo.rho.do.spi.ra'ce.ae. M.L. fem. n. *Halorhodospira* type genus of the family; -aceae ending to denote a family; M. L. fem. pl. n. *Halorhodospiraceae* the family of *Halorhodospira.*

The family constitutes moderately or extremely halophilic and extremely halotolerant phototrophic bacteria growing under alkaline conditions. They are Gram-negative and belong to the *Gammaproteobacteria*. Cells are spiral-, vibrioid- or rod-shaped, motile by means of polar flagella and divide by binary fission. They are phototrophic purple sulfur bacteria that perform anoxygenic photosynthesis with bacteriochlorophylls and carotenoids as photosynthetic pigments and have internal photosynthetic membranes as lamellar stacks continuous with the cytoplasmic membrane. Photosynthetic pigments are bacteriochlorophyll *a* or *b* and carotenoids. Growth of phototrophic representatives is preferably anaerobic in the light, with reduced sulfur compounds as electron donors. Sulfide is oxidized to elemental sulfur and is deposited outside the cells. The final oxidation product is sulfate. *Halorhodospiraceae* are found in saline, preferably extremely saline environments containing sulfide and having an alkaline to extremely alkaline pH. They are regular inhabitants and represent major groups of the bacterial populations of soda lakes of various salinities. Species of this family are the most halophilic eubacteria. Glycine betaine, ectoine and trehalose accumulate as compatible solutes in response to salt and osmotic stress.

The mol% G + C of the DNA is 55.8–72.0 (genome sequence).

Type genus: *Halorhodospira* Imhoff and Süling 1996, 112; Imhoff and Süling 1997, 915.VP.

#### *6.1. Emended Description of the Genus Halorhodospira*

Ha'lo.rho'do. spi'ra. Gr.gen. n. *halos* of the salt; Gr. n. *rhodon* the rose; Gr. n. *spira* the spiral; M.L fem. n. *Halorhodospira*, the spiral rose from salt lakes.

Cells are spiral- or rod-shaped, 0.6–1.2 µm in diameter, motile by bipolar flagella and multiply by binary fission. They are Gram-negative and belong to the *Gammaproteobacteria* and grow photoautotrophically under anoxic conditions with reduced sulfur compounds as electron donors, or photoheterotrophically with a limited number of simple organic compounds. Sulfide is oxidized to elemental sulfur, which is deposited outside the cells and may be further oxidized to sulfate. Internal photosynthetic membranes appear as lamellar stacks continuous with the cytoplasmic membrane. Photosynthetic pigments are bacteriochlorophyll *a* and carotenoids. Growth is dependent on highly saline and alkaline conditions. Greater than 10% (*w*/*v*) total salt concentration is required for optimal growth in all known species, some of which even grow in saturated salt solutions. Glycine betaine, ectoine and trehalose accumulate as compatible solutes in response to salt and osmotic stress. Growth factors are not required. Storage products are polysaccharides, poly-βhydroxybutyrate and polyphosphate. *Halorhodospira* species are found in hypersaline and extremely saline environments, preferably with moderately to extremely alkaline pH (up to pH 11–12), that contain sulfide and are exposed to light, such as salt flats, salt lakes and soda lakes, but some species may also inhabit salterns and coastal lagoons.

The mol% G + C of the DNA is from 67.9–72.0 (genome sequence).

Type species: *Halorhodospira (Hlr.) halophila* (Raymond and Sistrom) Imhoff and Süling 1996, 110.

#### *6.2. Description of the Genus Halochlorospira gen. nov.*

Ha'lo.chlo'ro. spi'ra. Gr.gen. n. *halos* of the salt; Gr. n. *chloros* green; Gr. n. *spira* the spiral; M.L fem. n. *Halochlorospira*, the green spiral from salt lakes.

Cells are spiral- or rod-shaped, 0.5–1.2 µm in diameter, motile by bipolar flagella and multiply by binary fission. They are Gram-negative and belong to the *Gammaproteobacteria* and grow photoautotrophically under anoxic conditions with reduced sulfur compounds as electron donors, or photoheterotrophically with a limited number of simple organic compounds. Internal photosynthetic membranes appear as lamellar stacks continuous with the cytoplasmic membrane. Photosynthetic pigments are bacteriochlorophyll *b* and carotenoids. Sulfide is oxidized to elemental sulfur, which is deposited outside the cells and may be further oxidized to sulfate. Growth is dependent on highly saline and alkaline conditions. Greater than 10% (*w*/*v*) total salt concentration is required for optimal growth by all known species, some of which grow in saturated salt solutions. Glycine betaine, ectoine and trehalose accumulate as compatible solutes in response to salt and osmotic stress. Growth factors not required. Storage products are polysaccharides, poly-βhydroxybutyrate and polyphosphate. *Halochlorospira* species are found in hypersaline and extremely saline environments with slightly to extremely alkaline pH (up to pH 11–12) that contain sulfide and are exposed to light, such as salt flats, salt lakes and soda lakes.

The mol% G + C of the DNA is from 55.8–62.9 (genome sequence).

Type species: *Halochlorospira (Hcs.) halochloris* (Imhoff and Trüper, 1977).

#### *6.3. Description of Halochlorospira halochloris comb. nov.*

The description is entirely the same as for *Halorhodospira halochloris*.

#### *6.4. Descrition of Halochlorospira abdelmalekii comb. nov.*

The description is entirely the same as for *Halorhodospira abdelmalekii*.

**Author Contributions:** Conceptualization, T.E.M., J.F.I. and J.A.K.; methodology, J.F.I. and J.A.K.; validation, J.F.I. and J.A.K.; investigation, J.F.I. and J.A.K.; data curation, J.A.K.; writing T.E.M., J.F.I. and J.A.K.; supervision, J.F.I. and J.A.K.; funding acquisition, J.A.K. All authors have read and agreed to the published version of the manuscript <sup>+</sup> . + Terrance E. Meyer passed away on 1 August 2020, while the manuscript was in the final stages of preparation.

**Funding:** This work was partially sponsored by the Wilson Enhancement Fund for Applied Research in Science at Bellevue University.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The Whole Genome Shotgun projects have been deposited at DDBJ/ENA/ GenBank under the accession numbers provided in Table 1.

**Conflicts of Interest:** The authors declare that they have no conflict of interest.
