This giant microbe organizes its DNA in a surprising way

PHILADELPHIA — Deep successful nan mangrove swamps of nan Caribbean lives a elephantine bacterium pinch a astonishment instrumentality for organizing its DNA.

Thiovulum imperiosus wraps its familial worldly successful membranous fingers, squishing it against nan periphery of nan cell, scientists reported December 6 astatine nan Cell Bio meeting. It’s a never-before-seen attack that’s vastly different from astir each different known bacteria.

Scientists deliberation astir germs shop their DNA successful a floating wide wrong nan cell’s interior, not packed neatly successful specialized compartments, said Jean-Marie Volland, a marine microbiologist astatine nan University of California, Santa Barbara. It’s a position that aligns pinch textbook descriptions of germs arsenic “organisms that person not evolved a batch of complexity,” he says.

His team’s activity is challenging that accepted wisdom.

Volland’s collaborators discovered T. imperiosus astir a decade ago while snorkeling among mangrove trees disconnected nan seashore of Guadeloupe. The shallow tropical waters incorporate biodiversity that remains mostly unexplored, Volland says. Mangrove swamps are sulfur-rich, truthful they smell of rotten eggs, he says. But connected a bully day, erstwhile nan h2o is clear and quiet, you tin spot food and sponges and a rainbow of colors.

Amidst that thriving ecosystem, scientists lit upon T. imperiosus, a bacterium truthful ample it’s visible to nan unaided eye. (Think of nan mini dot atop a lowercase i.)

T. imperiosus’ DNA (squiggly lines successful this illustration) resides on nan periphery of nan cell, bundled successful semienclosed pockets. Most of nan cell’s soul abstraction has been taken complete by what’s known arsenic nan periplasm (gray), which is usually restricted to a bladed abstraction betwixt nan soul and outer membranes.J.M. Volland

Using 3-D fluorescence and particle microscopy, Volland’s squad spied a elephantine abstraction successful nan halfway of T. imperiosus, pinch bulbous compartments lining nan cell’s interior edge. Squirreled distant wrong nan compartments were blobs of cytoplasm, nan cellular goo that holds nan bacterium’s molecular machinery and DNA.

Microscopy images propose really nan compartments formed: Imagine nan bacterium arsenic a h2o balloon placed wrong different balloon, pinch a bladed abstraction betwixt nan two. In T. imperiosus, that abstraction has expanded dramatically, squeezing nan interior balloon to nan sides. There, DNA and different cellular components cram together, semienclosed successful membranous pouches.

It’s nan 2nd illustration of DNA compartmentalization Volland has reported successful elephantine bacteria. The first, recovered successful a distantly related organism called Thiomargarita magnifica, appears to confine its DNA successful regularly spaced bubbles. Volland had thought nan T. magnifica study mightiness beryllium specified curiosity. But nan T. imperiosus discovery suggests that DNA compartmentalization successful germs whitethorn beryllium much wide than scientists erstwhile suspected, he says.

“I deliberation there’s a batch of complexity hiding successful nan bacterial world that we person not yet uncovered.”