Scientists Discover Record-Setting Bacteria That Are a Centimeter Long

Bacteria are all around (and even inside) us, but you can’t see them with the naked eye. Unless, however, you’re looking at a newly discovered bacterium called Thiomargarita magnifica. Unlike other bacterial cells, this monster can be a centimeter long. It’s by far the largest bacterial species ever found, but there’s plenty we don’t know about how and why it got so huge.

Scientists found Thiomargarita magnifica clinging to sunken leaves in Caribbean mangrove swamps, but no one on the team even knew the white filaments were bacteria at first. At Lawrence Berkeley National Laboratory (LBNL), researchers analyzed the structures, finding they were actually enormous single-celled organisms. While they have some unusual internal features, they are clearly in the bacterial kingdom based on genetic analysis.

At one centimeter, the new organism is about 5,000 times larger than other bacteria. Most bacterial cells are measured in micrometers — the omnipresent Staphylococcus aureus is only about one micrometer across. LBNL scientist Jean-Marie Volland tells NPR that it would be as if we suddenly discovered a humanoid species the size of Mount Everest.

These are not simply blown-up bacterial cells — there are internal structural differences compared to other bacteria. While smaller prokaryotic cells (e.g. bacteria) allow their genetic material to float freely, Thiomargarita magnifica has it bound up inside a membrane like eukaryotic cells (plants and animals). They also reproduce more like eukaryotic cells, budding to produce new organisms rather than dividing in half like other bacteria.

It is not yet possible to culture Thiomargarita magnifica, so they cannot be grown in the lab. That makes it hard to understand their life cycle and what evolutionary advantage might be conferred by their large size, and how that might expand our understanding of the microbial realm. For instance, the researchers were surprised to find the huge surface area of Thiomargarita magnifica was not covered with lesser bacteria. That might suggest it has antimicrobial properties that could be of use to fight disease.

The full report in Science does not imply these advanced structural features have any connection to the development of eukaryotic life like us — it’s not a missing link. However, understanding the evolutionary origins of Thiomargarita magnifica could help us understand how membrane-bound organelles evolved in the distant past, eventually giving rise to life as we know it today.