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After more than 10 years of research, Murdoch's new Rumen Biotech Group has achieved a biological world-first by genetically modifying the rumen bacteria in the stomachs of cattle and sheep to protect them from fluoroacetate poisoning.
 Fluoroacetate -- a naturally-occurring plant toxin found in trees and shrubs in pastures throughout Australia, and parts of Africa and Central America -- is also used agriculturally in the form of the pesticide Compound 1080.
The Murdoch Rumen Biotech Group, comprising Director Dr Keith Gregg and four researchers, moved to Murdoch from the University of New England at the end of 1997. The Rumen Biotech Group was founded at the University of New England's Institute of Biotechnology in 1986.
"We started off looking at fibre degradation in ruminants to see if we could make bugs that would break down the fibre more efficiently," said Dr Gregg.
"Ruminants have a four-chambered stomach. The first chamber is just a fermentation pot with bugs digesting all the tricky stuff in grass and feed.
"A well-known cliche amongst animal nutritionists is, 'Cows don't eat grass -- bugs eat grass, and cows eat bugs.' In digestive terms this is quite correct.
"So, if you alter what the bugs do, you may alter the whole physiology of the animal."
Dr Gregg's interest in fluoroacetate poisoning in ruminants began after a consultant from the Northern Territory, Mr Terry McCosker, introduced him to the Georgina Gidgee, an acacia tree growing in the Georgina River basin.
"At certain times of the year the Georgina Gidgee contains fluoroacetate," said Dr Gregg.
"The amount varies according to the season and the location of the plant. A paddock that is highly poisonous one year may be safe the next."
Mr McCosker raised the possibility of altering the bugs in a ruminant's stomach to help protect the animal from fluoroacetate poisoning.
After some investigation, it became clear that soil bacteria could break down fluoroacetate and Dr Gregg believed it might be possible to transfer a detoxification gene from soil bacteria to rumen bacteria.
A search for project funding was begun in earnest.
"When our initial requests for funding were rejected by the Australian Meat Corporation, about 30 Queensland and Northern Territory animal producers got together to set up their own consortium to fund a Masters student to research the issue," said Dr Gregg.
Over the next three years, the Masters researcher -- Ms Helen Sharpe -- turned her attention to a number of questions, including the viability of the project, did the enzyme from soil bacteria have the right properties and, if so, would it work at rumen pH levels?
"She isolated and cloned the gene for the detoxifying enzyme, and showed that the cloned enzyme worked the same as the original and was active under rumen conditions," said Dr Gregg.
"When we approached the Meat Corporation with this information, they agreed to fund a larger research project."
Over the next few years the research team at the University of New England's Institute of Biotechnology successfully sequenced the gene and put it into a rumen bug that could then break down the poison.
"We were able to show that a growing culture of the bug could break down the poison in the surrounding medium," said Dr Gregg.
Further trials followed where the bug was placed directly into the rumen of sheep and tested by feeding the sheep fluoroacetate.
"Of the half-dozen major labs in the world actually putting new DNA into rumen bugs at that time, not one had produced anything agriculturally useful.
"Not only had we shown we could make the bug do something useful, but we also found the levels of any particular bug went up and down like a yo-yo. We identified extreme fluctuations, from 10 million bugs per millilitre one day, to less than one thousand per millilitre the next," said Dr Gregg.
"Importantly, however, we found that by putting four different bacterial strains -- including our genetically-engineered strain -- into the same sheep, and tracking them over a five month period, not only did they fluctuate wildly, but they did so independently."
Dr Gregg said this effectively indicated that when the population of one strain was high, the numbers of another might be low.
"Thus, by using four or five altered bugs, it was possible to obtain an average middle range," he said.
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| Animals that might benefit from this technology include sheep, cattle and goats, even camels and llamas. |
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Dr Gregg put forward a plan for 12 months work, which was recommended by a review panel.
Unfortunately, the Meat Research Corporation could only provide three months funding.
However, the University and the animal producers' group managed to find a further three months worth of funding, still only giving the Group six months to carry out 12 months work.
"Four strains of rumen bug were introduced into two sheep (the test group)," said Dr Gregg.
"Two other sheep (the control group) were left untouched. All four were fed fluoroacetate. The difference between them was dramatic. We deliberately aimed the dose to enable us to discriminate a fairly fine level of protection. One test sheep had levels of bugs that we thought should be successful while the other had levels we thought were marginal.
"But the most interesting thing was that the control sheep showed clear symptoms of fluoroacetate poisoning while the test sheep, although obviously suffering more minor ill effects, remained quiet and composed."
Naturally, when these results were passed onto the farmers, there was great excitement.
However, Dr Gregg was quick to point out these early tests were not conclusive and would need to be repeated with similar results, to have any validity.
"In the second round of experiments, three sheep were used in each group, and a more borderline dose of fluoroacetate was introduced," said Dr Gregg.
"Once again the results were striking. The second group of test sheep, with 1.3 of the lethal dose of fluoroacetate, appeared unaffected. This was in marked contrast to the three control sheep which all displayed obvious physiological signs of poisoning. The results of these two experiments strongly support the effectiveness of the genetically-engineered rumen bug in reducing the impact of fluoroacetate poisoning."
Since arriving at Murdoch, the Rumen Biotech Group has been continuing its work to show that, by using four or five altered bugs, it is possible to obtain a consistent level of modified bacteria within the rumen.
"For best results, we need ten times the detoxifying capability provided by a single modified bacterium. Ideally this would mean using ten bugs, all expressing the same level of activity, or perhaps four bugs, with two-to-three times the activity per bug."
A major part of the Rumen Biotech Group's current work is getting the information needed for Genetic Manipulation Advisory Committee (GMAC) assessment.
"In the long term we hope to obtain approval from the GMAC to release the rumen bugs in the general ruminant population," said Dr Gregg.
"A few years ago I made up a list of criteria, including questions such as how well the bug would survive outside the rumen, whether it might be transferred through water and soil, and if there are any long-term, harmful effects on ruminants. After examining the list the GMAC came back with a raft of useful and important questions. A major one was whether the rumen bug could produce rabbits and foxes that were resistant to the poison bait Compound 1080."
Dr Gregg said he was reasonably confident that rumen bugs would not protect rabbits and foxes.
"The bugs in a monogastric animal are located in the hindgut and fluoroacetate should be absorbed further up the digestive tract. Thus, it would appear to be highly unlikely that the rumen bug could neutralise the poison before it killed the animal," said Dr Gregg.
"The GMAC have accepted this in principle but it will, of course, need to be proved empirically before any release could take place. The possibility of the rumen bug affecting feral goat control by interfering with the effect of the poison bait Compound 1080 must also be addressed."
"There are many avenues open to rumen biotechnology work," said Dr Gregg.
"Almost anything involving the digestive systems of ruminants can be looked at in terms of the modified rumen bug. Animals that might benefit from this technology include sheep, cattle and goats, even camels and llamas."
Dr Gregg added that this technology might even be applied to marsupials, which also have a rumen-like section to their stomachs.
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