As well as being not-bacteria and not-eukaryotes, halobacteria also confound naïve human assumptions about how to make a living. If you look only at multicellular organisms, you find they fall mostly into two camps: photosynthetic organisms like plants, which need light, water, carbon dioxide, and not much else to grow; and heterotrophic organisms like humans and fungi, which steal almost everything they need to grow either directly or indirectly from photosynthetic organisms.
Halobacteria are pink because they contain a pigment called bacteriorhodopsin. They use this pigment to capture light from the Sun. This energy is used to run their biochemistry and to help pump salt into the cell to prevent it from popping from osmotic stress. But unlike green plants, they can’t fix carbon dioxide into sugars and other complex organic compounds. Like us, they have to get their carbon in a fixed organic form, mostly in the form of amino acids. Many bacteria and archaea have metabolisms that don’t fit the dreary ‘plant-like’ vs. ‘animal-like’ division, and this is one of the many reasons I love them so.