Bacteria display a wide diversity of shapes and sizes. Bacterial cells are about one-tenth the size of eukaryotic cells and are typically 0.5–5.0 micrometres in length
The largest bacterium ever discovered previously is Thiomargarita namibiensis, a Gram-negative coccoid Proteobacteriumand it is found in the ocean sediments of the continental shelf of Namibia. It’s size is 0.1–0.3 mm (100–300 μm) in diameter, but sometimes attaining 0.75 mm (750 μm).
But recently a bacteria is discovered that is 5000 times bigger than other common bacteria. Its threadlike single cell is visible to the naked eye, growing up to 2 centimeters—as long as a peanut.
This bacteria has a huge genome that’s not free floating inside the cell as in other bacteria but is instead encased in a membrane, an innovation characteristic of much more complex cells, like those in the human body.
Researchers have long divided life into two groups: prokaryotes, which include bacteria and single-cell microbes called archaea, and eukaryotes, which include everything from yeast to most forms of multicellular life, including humans. Prokaryotes have free-floating DNA, whereas eukaryotes package their DNA in a nucleus. Eukaryotes also compartmentalize various cell functions into vesicles called organelles and can move molecules from one compartment to another—something prokaryotes can’t.
But the newly discovered microbe blurs the line between prokaryotes and eukaryotes.