Spotlight on bacterial immune system

Assistant research fellow Raymond Staals (left) and Dr Peter Fineran, of the University of Otago microbiology and immunology department, continue their research. Photo by Gregor Richardson.
Assistant research fellow Raymond Staals (left) and Dr Peter Fineran, of the University of Otago microbiology and immunology department, continue their research. Photo by Gregor Richardson.
Research involving University of Otago scientists has shed new light on a ''surprisingly flexible'' immune system which has enabled bacteria to survive a multibillion-year-long arms race with viruses.

A team co-led by Dr Peter Fineran, of the Otago department of microbiology and immunology, and by scientists from the Netherlands, have been studying the genetic basis of adaptive immunity in E. coli and other bacteria.

Through their recent collaboration, they have found these bacterial immune systems were much more robust and responsive to viruses than previously thought.

Their ''really exciting'' joint findings had appeared in the leading US journal PNAS, Dr Fineran said.

Better understanding the bacterial immune system could eventually help reduce the growth of bacterial resistance in individual patients and could identify new targets for antimicrobial therapies.

The researchers are investigating an adaptive immune system - termed CRISPR-Cas - which is found in half of all bacterial species and in most single-celled microbes in the archaea domain.

The system creates a genetic memory of specific past infections by viruses and plasmids.

Plasmids are small DNA molecules that can move between organisms.

Dr Fineran said the system stole samples of the invader's genetic material and stored them so it could recognise future exposures and neutralise the attack.

The Otago research showed this detection system could recognise a previously encountered ''invader'', even if later mutation meant the intruder was up to 30% different from before.

This was equivalent to a human being recognised on a security camera during a later visit to a building despite being disguised, such as by wearing sunglasses.

It had previously been thought subsequent immune recognition could occur if there was only about a 3% change in appearance by the invader.

''It's a remarkably flexible and robust immune system for such simple single-celled organisms.''

This system reflected the 3.5 billion-year ''co-evolutionary arms race'' between bacteria on one side, and viruses and plasmids on the other, he said.

Dr Fineran's research was supported by a Rutherford Discovery Fellowship from the Royal Society of New Zealand.

john.gibb@odt.co.nz

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