At first glance, the slightly murky waters in the tube look like a scoop of stormwater, complete with leaves, debris, and even lighter threads in the mix. But in the Petri dish, the thin vermicelli-like threads floating delicately above the leaf debris are revealed to be single bacterial cells, visible to the naked eye.

Single filament of Ca. Thiomargarita magnifica
Single filament of Ca. Thiomargarita magnifica (Credit: Jean-Marie Volland)


The unusual size is notable because bacteria aren’t usually visible without the assistance of microscope. “It’s 5,000 times bigger than most bacteria. To put it into context, it would be like a human encountering another human as tall as Mount Everest,” said Jean-Marie Volland, a scientist with joint appointments at the U.S. Department of Energy (DOE) Joint Genome Institute (JGI), a DOE Office of Science User Facility located at Lawrence Berkeley National Laboratory (Berkeley Lab) and the Laboratory for Research in Complex Systems (LRC) in Menlo Park, Calif. In the June 24, 2022, issue of the journal Science, Volland and colleagues, including researchers at the JGI and Berkeley Lab, LRC, and at the Université des Antilles, described the morphological and genomic features of this giant filamentous bacterium, along with its life cycle.

For most bacteria, their DNA floats freely within the cytoplasm of their cells. This newly discovered species of bacteria keeps its DNA more organized. “The big surprise of the project was to realize that these genome copies that are spread throughout the whole cell are actually contained within a structure that has a membrane,” Volland said. “And this is very unexpected for a bacterium.” Continue reading…

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