Gold in trees leads to hidden deposits

By Rebecca Morelle

Science reporter, BBC World Service

Money might not grow on trees, but scientists have confirmed that gold is found in the leaves of some plants.

Researchers from Australia say that the presence of the particles in a eucalyptus tree's foliage indicates that deposits are buried many metres below.

They believe that the discovery offers a new way to locate the sought-after metal in difficult-to-reach locations.

The research is published in the journal Nature Communications.

Dr Mel Lintern, a geochemist from Australia's Commonwealth Scientific and Industrial Research Organisation (CSIRO), said: "We've found a lot of the easy deposits in Australia and elsewhere in the world as well.

"Now we are trying to tackle finding these more difficult ones that are buried beneath tens of metres of river sediments and sand dunes.

"And the trees are providing us with a method to be able to do this."

Buried treasure

Gold particles have been found around the soils of eucalyptus trees, but the researchers confirmed that the plants were taking in the element.

Using the Australian synchrotron - a vast machine that uses X-rays to probe matter in remarkable detail - they found traces of gold in the leaves, twigs and bark of some trees.

The amounts of the precious metal were tiny.

"We've done a calculation, and found that we need 500 trees growing over a gold deposit to have enough gold in the trees themselves to make a gold ring," said Dr Lintern.

However, the presence of the particles pointed to greater riches buried more than 30m (100ft) below.

Dr Lintern said: "We believe that the trees are acting like a hydraulic pump. They are bringing life-giving water from their roots, and in so doing, they are taking smaller dissolved gold particles up through the vascular system into the foliage."

Currently, the metal is found in outcrops, where the ore appears at the surface, or it is detected through exploratory drilling.

But the researchers said that analysing vegetation could offer a better method to find untapped gold deposits.

Dr Lintern said: "Not only do we believe it is a way of stretching the exploration dollar further, because exploring for these deposits can be quite expensive, it also minimises the damage to the environment because we are taking a very small sample from the trees themselves, as well as the leaves and twigs on the ground."

The researchers said the technique could also be used to find other minerals such as iron, copper and lead in other parts of the world.

Badgers Responsible For Half Of Tuberculosis Found In Cattle

How many badgers are infected, will enough badgers be culled and is it all worth it? Here is a guide to the recent badger cull

Most badgers aren't infected, is that correct?

The largest study of bovine tuberculosis (TB) in badgers was the randomised badger culling trial, RBCT, which reported in 2007. Nearly 8,900 badgers were culled across large (100 km sq) areas where there was high risk of cattle TB. Their carcasses were subjected to detailed examination and testing, although the standard postmortems missed half of the infections compared with extended postmortems. Overall, 16.6% of the badgers culled between 1998 and 2005 were found to be positive, based on the standard postmortem, indicating that about 33% were actually infected. But this percentage varied geographically and by year in the trial.

Do cattle really catch TB from badgers?

Most badgers are not infected, but those that are can transmit infection to cattle. Using a mathematical model and data from the start of the trial, I estimated that confirmed cattle TB rates would be halved if there were no transmission from badgers (meaning neither direct badger-to-cattle transmission nor onward cattle-to-cattle transmission of those primary infections). But this estimate is quite uncertain. Even without using the model, it is clear that in an 18-month period after widespread culling stopped in the trial, cattle TB in the culling area was reduced by roughly half. This estimate was more precise, being almost certainly between 38% and 66%. Thus, it is very likely that at least 38% of the confirmed cattle TB in trial areas stemmed from badger-to-cattle transmission, with half being the best estimate.

What is "perturbation" and why does it matter for cattle?

The results of the £50m randomized badge culling trial that ended in 2006 showed that, five years after a series of four annual culls, there was a reduction in confirmed TB infections in cattle in the cull zones

There are fewer badgers per square kilometre in recently culled areas (unsurprisingly), but the badgers found there ranged more widely. This behavioural effect has been called social "perturbation". Areas with fewer badgers ranging more widely had reduced cattle risks when the reduction in badger density was large (70%). However, in areas with much smaller reductions in badger densities (in particular, land up to 2km outside extensive culling areas and areas subjected to small, reactive culls) there were increased cattle infections, presumably due to the increase in contact with perturbed, infected badgers. Within the trial, badgers culled in areas previously subjected to recent culling were more likely to be infected, presumably due to the perturbation.

Can we really expect a 16% reduction in cattle TB over several years for a single big cull?

The 16% figure was an estimate for the local impact of repeated culls over 150 km sq, taking into account the assumption that the background risk of cattle TB was higher in the culling area than on the land up to 2km outside it. It is not a 16% reduction nationally. Indeed, the impact of a single such cull would not be visible in national statistics.

16% was an average over several years of the cattle risk reduction, observed inside the culling area during four years of annual culling and in the years after culling stopped, set against the cattle risk increase observed up to 2km outside the culling area during the years of annual culling.

How was the number of badgers to be culled arrived at?

For a particular cull zone, the size of the badger population was estimated (call this estimate N). The minimum cull number was then set sufficiently high to be confident that at least 70% of badgers would be culled. Due to statistical uncertainty in the estimate N, that minimum figure was more than 70% times N.

Will the current pilot culls be able to remove enough badgers?

We will have to wait for the report of the independent panel after the pilot culls have finished. The uncertainty over whether enough badgers can be removed (so that the reduction in badger density more than offsets the impact of badger perturbation) arises due to the use of a badger culling technique not used in the RBCT: shooting of free-running badgers. If substantially fewer than 70% of badgers were removed, there would be a risk that the population reduction was insufficient to reduce TB risks to cattle. In a worst-case scenario, it could conceivably be low enough to increase TB risks to cattle, due it seems to social perturbation of the remaining badger population. The tipping point for a reduction in badger density at which a cattle risk reduction becomes a cattle risk increase is not known. This has been a key concern among scientists arguing against the current culling approach.

The government is culling badgers in England. Why don't they cull cows instead?

The government does cull so-called "reactor" cattle every year, after they "reacted" to a diagnostic skin test for TB. In 2012 more than 28,000 cattle were slaughtered in England to control TB. Cattle slaughtered for consumption are also inspected to detect any evidence of infection. Bovine TB control currently costs the government (in other words taxpayers) about £90m a year.

Is badger culling worth doing?

This is the big question. The answer cannot just be purely scientific. There are ethical, animal welfare and economic aspects, in addition to health and safety issues, that must be considered. However, science can provide quantitative predictions for many of the important "what if we?" questions.

• Christl Donnelly is professor of statistical epidemiology at Imperial College London and was a key member of the randomised badger culling trial (RBCT).

Goat shared common ancestor with cattle about 23mn years ago

A team of researchers has completed the first genome sequence of domestic goat by a robust approach integrated with next-generation sequencing (NGS) and whole-genome mapping (WGM) technologies.

A team of researchers has completed the first genome sequence of domestic goat by a robust approach integrated with next-generation sequencing (NGS) and whole-genome mapping (WGM) technologies.

The goat genome is the first reference genome for small ruminant animals and may help advance the understanding of distinct ruminants' genomic features from non-ruminant species. This work also yields a valuable experience for facilitating the de novo assemblies of large, complex genomes in the future.

It will be also be useful for facilitating the identification of SNP markers for marker-assisted breeding, and improving the utility of the goat as a biomedical model and bioreactor, according to researchers from Kunming Institute of Zoology, Chinese Academy of Sciences, BGI, and other institutes.

With the availability of next-generation sequencing (NGS), draft assemblies are easy to generate nowadays. However, to finish a sequence to the chromosome level remains a hard nut to crack.

In this study, the results show that a single NGS platform, when combined with whole-genome mapping technology, could produce a finished assembly much faster and with high quality than other currently available mapping strategies such as BACs or FISH. Through this integrated approach, researchers obtained the ~2.66 Gb goat reference genome from a female Yunnan black goat.

Transposable elements (TEs) are major components of mammalian genomes and contribute to gene and/or genome evolution. The TEs in goat genome are similar to those of cattle, and contain large numbers of ruminant-specific repeats, such as SINE-tRNA and SINE-BovA. It is reported that SINE-BovA repeat expanded primarily in the cattle genome.

However, in this study, researchers found the SINE-tRNA repeat expanded specifically in the goat genome.

Through constructing a phylogenetic tree among goats, cattle, horses, dogs, opossums and humans, researchers found the goat shared a common ancestor with cattle about 23 million years ago. Further comparison analysis revealed 44 rapidly evolving genes under positive selection, seven of which are immune-related genes and three are pituitary hormone or related genes. The immune-related genes identified also exist in cattle.

The findings suggest that the rapid evolution of pituitary hormones may be related to the different features between goat and cattle in milk production, development rates of the fetus and/or hair variation.

The major histocompatibility complex (MHC) plays an important role in the immune system. In this study, the goat MHC was found to be located on chromosome 23 and contains two regions with length of 2.25 Mb and 360 kb, respectively.

With the high quality genome assembly, further understanding of the goat MHC will be useful for immunological studies and vaccine development.

Researchers conducted transcriptomic analysis on the primary and secondary follicles of a cashmere goat, revealing 51 genes that are differentially expressed between the two types of hair follicles. Keratin and keratin-associated proteins are the main structural proteins of hair fibres, determining the quality of fibre together.

In the study, 29 keratin genes and 30 keratin-associated protein genes were detected in both types of follicles. Interestingly, they found two keratin genes and ten keratin-associated protein genes were consistently differentially expressed between primary and secondary hair follicles, suggesting that the keratin-associated protein genes may be more important in determining the structure of cashmere fibres.

In addition to the keratin genes and keratin-associated protein genes, researchers also found several enzymes of amino acid biosynthesis, with implications in regulating primary hair growth and hair cycle.

Xun Xu, deputy director of BGI, said, "The goat reference genome is an important stepping stone in the molecular breeding of cashmere goats, and will help to advance the comparative studies on ruminants. The transcriptomic analysis on the primary and secondary follicles will open a new way for better improving the quality cashmere wool.

The study was published online in Nature Biotechnology.