Primitive microbe lends a hand to high-tech crime fight

A steaming, sulphurous spring in the caldera of the world's coldest, most isolated volcano has yielded a powerful new forensic tool that will make it even tougher for criminals to evade the law.

Prof Roy Daniel and Prof Hugh Morgan, two biologists at New Zealand's Waikato University, chanced upon genetic treasure in an obscure polar microbe, designated Bacillus sp E-A1, during a bioprospecting trip to Antarctica's Mt Erebus in the late 1980s.

Now, Auckland University microbiologist Dr David Saul says Bacillus sp E-A1 makes a remarkable heat-stable enzyme -- a proteinase -- that will greatly simplify the task of extracting and purifying DNA from blood, saliva, hair root cells, epithelial cells or other forensic samples from crime scenes and disaster sites.

Saul says the enzyme, dubbed EA1 Proteinase, will make the extraction and purification of DNA from forensic samples so simple that the process could be automated. The resulting cost reductions could make DNA fingerprinting cheaper than conventional fingerprinting.

Saul predicts "dramatic changes" in the use of DNA forensics during the next decade. "A new law is being passed in New Zealand making DNA sampling mandatory for lesser crimes," he says.

"The prospect is that, if the system can be automated, it will be cheaper to do a DNA profile than standard fingerprinting, and as DNA can be extracted from fingerprints, it will become extremely powerful in its ability to identify criminals.

"Run your fingers through your hair and you leave a couple of kilometres of DNA on the carpet -- criminals cannot avoid leaving their DNA at crime scenes, so automated DNA profiling could actually make it very difficult to commit a crime without being detected. It could actually reduce crime rates."

Saul says forensic investigators will be able to use the new enzyme, to digest away all unwanted proteins in forensic samples in a single step. Currently, removing DNA-degrading enzymes and other proteins from forensic samples requires multiple steps that are difficult to automate, and also expose the sample to potential contamination with the technician's own DNA at each step.

"EA1 proteinase has broad substrate specificity and a very good temperature profile," Saul says. "It rapidly removes the nucleases that degrade your DNA at temperatures where they are inactive." By a simple temperature switch, the EA1 proteinase itself denatures and self-digests.

Furthermore, EA1 proteinase is active only at higher temperatures (70 degrees centigrade) and so can be used in conjunction with other enzymes that work at lower temperatures.

"Normally a proteinase cannot be mixed with other enzymes because these are themselves proteins that would be destroyed", Saul says. Enzymes such as lysozyme and cellulases can be included as a cocktail to digest bacterial or plant cell walls and the different activities can be brought into play by temperature cycling.

"We've verified the effectiveness on many forensic substrates and now have proof of concept that can extract DNA from hair shafts, which is very difficult with current techniques," Saul says.

Three universities -- Waikato and Auckland in NZ and Macquarie University in Sydney -- are involved in the research and development project. Saul says the research partners are about to form a strategic alliance with Environmental Science and Research Ltd, which provides all of New Zealand's forensic science services. "They bring in their expertise in putting together legally validated standard operating procedures and have internationally recognised credibility," Saul says.

Because 'extremophile' microbes are virtually impossible to grow in industrial mass-culture systems, the EA1 Proteinase gene has been transferred into a recombinant E. coli bacteria. Saul says Waikato University has the facilities to produce enough enzymes to meet current global needs.

"The beauty of producing a thermostable enzyme in a low-temperature host is that it minimises the usual problem of purifying the recombinant protein. Heat up the crude extract and the host proteins precipitate, and even better, with a heat-stable proteinase what is left is quickly degraded -- it's a very quick step to get a 95 per cent pure product, and that only needs a final polish with ion-exchange chromatography."