**Analysis of the Complete Genome of the Alkaliphilic and Phototrophic Firmicute** *Heliorestis convoluta* **Strain HH<sup>T</sup>**

**Emma D. Dewey 1, Lynn M. Stokes 1, Brad M. Burchell 1, Kathryn N. Sha**ff**er 1,**†**, Austin M. Huntington 1, Jennifer M. Baker 1,**‡**, Suvarna Nadendla 2, Michelle G. Giglio 2, Kelly S. Bender 3, Je**ff**rey W. Touchman 4,§, Robert E. Blankenship 5,**-**, Michael T. Madigan 3 and W. Matthew Sattley 1,\***


Received: 26 January 2020; Accepted: 22 February 2020; Published: 25 February 2020

**Abstract:** Despite significant interest and past work to elucidate the phylogeny and photochemistry of species of the *Heliobacteriaceae*, genomic analyses of heliobacteria to date have been limited to just one published genome, that of the thermophilic species *Heliobacterium* (*Hbt*.) *modesticaldum* str. Ice1T. Here we present an analysis of the complete genome of a second heliobacterium, *Heliorestis* (*Hrs.*) *convoluta* str. HHT, an alkaliphilic, mesophilic, and morphologically distinct heliobacterium isolated from an Egyptian soda lake. The genome of *Hrs. convoluta* is a single circular chromosome of 3.22 Mb with a GC content of 43.1% and 3263 protein-encoding genes. In addition to culture-based observations and insights gleaned from the *Hbt. modesticaldum* genome, an analysis of enzyme-encoding genes from key metabolic pathways supports an obligately photoheterotrophic lifestyle for *Hrs. convoluta*. A complete set of genes encoding enzymes for propionate and butyrate catabolism and the absence of a gene encoding lactate dehydrogenase distinguishes the carbon metabolism of *Hrs. convoluta* from its close relatives. Comparative analyses of key proteins in *Hrs. convoluta*, including cytochrome *c*553 and the Fo alpha subunit of ATP synthase, with those of related species reveal variations in specific amino acid residues that likely contribute to the success of *Hrs. convoluta* in its highly alkaline environment.

**Keywords:** heliobacteria; *Heliorestis convoluta*; alkaliphilic bacteria; soda lake; anoxygenic phototroph; bacteriochlorophyll *g*
