How do we know ThiomargaritaMicroorganisms are organisms that are too small to be seen with the unaided eye
Most microorganisms are unicellular (single-celled), but this is not universal, since some multicellular organisms are microscopic, while some unicellular protists and bacteria, like Thiomargarita namibiensis, are macroscopic and visible to the naked eye.
Thiomargarita namibiensis
Thiomargarita namibiensis is a gram-negative coccoid Proteobacterium, found in the ocean sediments of the continental shelf of Namibia. It is the largest bacterium ever discovered - 0.1–0.3 mm (100–300 µm) wide, but sometimes up to 0.75 mm (750 µm). Its size is large enough to be seen by the naked eye.
namibiensis is bacteria not protozoa?