In the given case, the organism most closely resembles a heterotrophic species of Archaea.
Archaea comprise a domain of single-celled microorganisms. These microbes are prokaryotes, they possess unique characteristics that distinguish them from the other domains of life.
They utilize more sources of energy in comparison to eukaryotes, these vary from organic compounds to ammonia, metal ions, or even hydrogen gas. The salt-tolerant Archaea utilize sunlight as a source of energy, and other species of Archaea fix carbon.
Archaea was at the beginning observed as extremophiles, thriving in harsh conditions, like salt lakes and hot springs, but they have since been witnessed in a wide array of habitats, like oceans, soils, and marshlands.