Updated: Mar 18, 2022
You thought bacteria were teeny tiny little things only a microscope could see. Well, you're wrong.
Take your next vacation to the Caribbean, and be sure to stop by the mangroves. There, you'll find Thiomargarita magnifica, a filamentous prokaryote - erm, eukaryote - er, both?
But that's what's so exciting about this discovery. Not only is this organism huge for a single-celled creature - 5000x the size of your average bacterium, clocking in at ~ 2 cm in length (for reference, that's 3 blue whales compared to a peanut) - but it contains a membranous sac verified to be DNA. That DNA contains 11 million base pairs and 11000 distinct genes - more than most bacterial species.
You see, up 'til now, everyone thought that the difference between prokaryotes (bacteria) and eukaryotes (like you) is membrane-bound organelles, especially a nucleus for storing DNA; a boundary never crossed. But T. magnifica changes all that. “[T. magnifica] could be a missing link in the evolution of complex cells,” says Kazuhiro Takemoto, a computational biologist at the Kyushu Institute of Technology. And Petra Levin, a microbiologist at Washington University in St. Louis, is no less excited. “Perhaps it’s time to rethink our definition of eukaryote and prokaryote!” And honestly, I can't disagree.
And that's not all. The size itself is a near-miracle. What makes T. magnifica's gigantism possible, however, is its second sac, which scientists theorize contains water, and whose volume may take up over 70% of the cell's volume. This vacuole, as water-sacs are called in cells, effectively makes the bacterium thinner, allowing for easier diffusion of molecules across its cell membrane, as diffusion is how cells get their sustenance. “When it comes to bacteria, I never say never, but this one for sure is pushing what we thought was the upper limit [of size] by 10-fold,” says Verena Carvalho, a microbiologist at the University of Massachusetts, Amherst. Indeed.
Every time humans think they've got it, Terra throws them another mystery. She truly is the new frontier.
Credit: Elizabeth Pennisi. (23 Feb 2022). Science. doi: 10.1126/science.ada1620