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microbiology

P

Exploding bacteria

. aeruginosa infections

present a growing risk in hospitals, where people with compromised immune systems are vulnerable to infection. The multidrug-resistant superbug survives in biofilms — groups of cells or microorganisms that stick to each other and adhere to a surface. Associate Professor Cynthia Whitchurch and Dr Lynne Turnbull, from the ithree institute at the University of Technology Sydney (UTS), have spent years researching P. aeruginosa

© iStockphoto.com/Kesu01

Microbiologists have discovered that the superbug Pseudomonas aeruginosa causes infection in a most unusual way — by blowing itself up.

to understand how bacteria release virulence factors such as DNA, proteins and membrane vesicles (MVs) into their environment. Once released, the contents are used by the remaining bacteria as a ‘glue’ to build the biofilm, as a food source and as virulence factors that contribute to the infection process. “We originally thought the extracellular DNA (an important biofilm component) might have been produced through a process where the cells die and slowly leak out their genomic DNA,” said Dr Turnbull. “But by using a special stain that lights up fluorescently when it detects extracellular DNA, we saw cells that were exploding like starbursts or fireworks of DNA.” Dr Turnbull said the Pseudomonas cells undergo an incredible transformation

Membrane vesicles produced by exploding bacteria decorate cells of the bacterial pathogen Pseudomonas aeruginosa. Scale bar is 500 nm. Image credit: L Turnbull, the ithree institute, University of Technology Sydney.

Extracellular DNA (yellow) is released by exploding bacteria in biofilms of the bacterial pathogen Pseudomonas aeruginosa (blue). Image credit: E Gloag and L Turnbull, the ithree institute, University of Technology Sydney.

before exploding, with the whole process taking place in as little as six seconds. “The normal bacteria look like little rods or pills,” she said. “One day, as we looked under the microscope, we saw one of the cells turn from a hard,

Time series showing a cell of the bacterial pathogen Pseudomonas aeruginosa exploding and producing membrane vesicles. Image credit: L Turnbull, the ithree institute, University of Technology Sydney.

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