A gigantic bacterium found in a mangrove swamp in the Caribbean is about the length of an eyelash, and now scientists think they have figured out how it grew to such an enormous size.
A gigantic bacterium found in a mangrove swamp in the Caribbean is about the length of an eyelash, and now scientists think they have figured out how it grew to such an enormous size.
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This bacterium, Thiomargarita magnifica, is 5,000 times larger than most bacteria and 50 times larger than any other known giant bacterium. (The name Magnifica refers to the Latin word for ‘large’ and the French word ‘magnifique’.)
“To put this in context, for other bacteria it would be like having someone as tall as Mount Everest with another human,” said marine biologist Jean-Marie Volland, lead author of the study. The centimeter-long T. magnifica was discovered in 2009 on one of Guadeloupe’s lush islands.
At the time of the discovery, marine biology professor Olivier Gros was looking for bacteria that use sulfur to produce energy.
However, when he poured a sample of marsh water into a petri dish, he saw something very strange. Thin, ‘noodle-like’ threads, visible to the naked eye, were dragging on leaves and dirt. “When I saw them, I thought ‘weird’,” Oliver says. “At first I thought it was just something interesting.”
More than a decade later, several researchers used microscopes to study bizarre tiny prokaryotes. The unusual organism was confirmed to be a gigantic single-celled bacterium using fluorescence, X-rays, electron microscopy and genome sequencing.
Reporting their findings today in the journal Science, the team published several interesting explanations that could explain how the bulky bacteria push the boundaries of what is theoretically possible in terms of size.
Unlike larger, multicellular organisms, bacteria belong to a group of organisms called prokaryotes, traditionally thought to be “unsegmented bags of enzymes” with no internal membranes to divide. Thiomargarita magnifica tends to have internal membranes to store DNA and ribosomes. The researchers decided to call these tiny bacterial organelles “pepins”.
Other bacteria have no inner membranes, so the only place to put the ATP-producing machinery (ATP synthase) is in the cell envelope, which encloses the whole organism.
This constraint limits the size of most bacterial cells, as it is difficult to transport this energy very far. Unlike other bacteria, T. magnifica detaches a small part of itself to form a daughter cell.
Thiomargarita magnifica has a much larger genome than other bacteria.
A genetic analysis revealed a set of genes for sulfur oxidation and carbon fixation, suggesting that T. magnifica relies on chemoautotrophy (harvesting energy through the oxidation of chemicals).
This article was published in Science.
