The single-celled organism in the given case is prokaryote.
A prokaryote is a unicellular species, which is devoid of a membrane-bound nucleus, mitochondria, or any other kind of membrane-bound organelle. Prokaryotes are differentiated into two domains Bacteria and Archaea.
Bacteria are prokaryotes that comprise a single cell with a basic internal composition. Bacteria are microscopic single-celled species, which live in different surroundings. Archaea are also prokaryotes, that is, devoid of the nucleus.
Archaeal cells have unique characteristics, which distinguishes them from the other two domains of life, Eukarya, and Bacteria. They are also known as extremophiles, that is, possessing the tendency to thrive in extreme environments, like salt lakes and hot springs, they are also found in a diverse range of habitats.
