Bacterial innards glimpsed for first time in 3-D


Washington : Scientists glimpsed a detailed version of a bacterial cell wall, how it is made up of thin layer of carbohydrate chains, linked by peptides, wrapped around the microbe like a belt.

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This first-ever glimpse of the structure in 3-D, was made possible by new high-tech microscopy techniques that enabled the scientists to visualise these biological structures at nanometre scales.

“This is both a technological and biological advance,” said Grant Jensen, associate professor of biology at California Institute of Technology (Caltech) and the study’s principal investigator.

“Bacterial cells rely on a cage-like net that surrounds them to maintain their integrity,” Jensen explained. “If it weren’t for this molecular bag, the bacteria couldn’t survive; they would likely rupture.”

This bag, called a sacculus, is made out of peptidoglycan, a mesh-like structure of carbohydrates (glycans) and amino-acid peptides.

It is the sacculus, Jensen notes, that is targeted by the antibiotic penicillin; penicillin blocks a bacterium’s ability to grow and remodel the bag to fit it as the bacterium itself grows. “If the bug can’t make this bag,” Jensen said. “It can’t multiply, and you get better.”

Researchers have long been interested in understanding the precise architecture of the sacculus. The answer to this debate has eluded the scientists, however, because trying to image such tiny biological objects has been beyond their technological reach. Until now, that is, said a Caltech release.

“Six years ago, a gift from the Moore Foundation allowed us to buy what is arguably the world’s best electron cryomicroscope,” said Jensen. “This allowed us to take a different kind of picture of small biological objects than has ever been possible before.

“These pictures are 3-D images to molecular resolution–you can actually start to see individual biological molecules. Using it, we were able to see this network of glycan strands. It was just remarkable.”

The study appeared in the early online edition of the Proceedings of the National Academy of Sciences (PNAS).