**Abbreviations**

AAP: aerobic anoxygenic phototrophic; AFM, atomic force microscopy; ANI, average nucleotide identity; BChl a, bacteriochlorophyll a; DSMZ, Deutsche Sammlung für Mikroorganismen und Zellkulturen; GTA, gene transfer agents; iDDH, in silico DNA-DNA hybridization; IR, infrared; ML, maximum likelihood; NJ, neighbor-joining; OD, optical density; PGC, photosynthesis gene cluster; SEM, scanning electron microscopy; TEM, transmission electron microscopy.
