Monday, 22 November 2010

Darwinism and biohydrometallurgy

It's hard to believe, but South African schools have been told not to teach evolution, as it is too complex a subject to teach, and too difficult for students to understand!

Naturally this has caused much debate and daily correspondence in the Cape Times. The majority of correspondents support the teaching of evolution, but there are some, including the usual Creationist crackpots, who do not. One correspondent today states that evolution is not a fact, it is a theory, even though it is believed by many. He goes on to state that evolution is not critical to everyday life, and that no major scientific breakthrough owes a debt of gratitude to evolution.

Modern biotechnology is just one example of how Darwinism has been applied to achieve major scientific advances. Only two weeks ago, biohydrometallurgists from around the world came together in Cape Town to discuss the latest developments in what is now an accepted and highly applied mineral processing technique, thanks to evolutionary science.

Someone correct me if I am wrong, as I am not a biotechnologist, but wasn't the Fairview Gold Mine in South Africa one of the first to commercially utilize bioleaching in the 1970s?

I seem to remember that it was not initially a commercial success, as the bacteria, then known as thiobacillus ferrooxidans, were unable to survive above ambient temperatures, low acid concentrations, and low slurry densities, so the leaching rate was very slow. Only by applying Darwinistic principles was the modern strain acidithiobacillus ferrooxidans developed, resistant to high temperatures and low pH, enabling successful utilization in gold, uranium and base metal operations.

The history of this development is of great interest, so I would welcome comments from anyone who was involved in the development of modern biohydrometallurgy.


  1. I think you may have missed my presentation - I talked in detail about how biomining consortia have evolved over time, and my research (done at BRGM, France) focused on understanding at what level. For example, was it evolution of the consortium i.e. the population changed, acquiring 'better' organisms or did the individual species of the consortium evolve themselves i.e. was there a change at the genetic or physiological level of individual species. The results suggested it was both; the bioleaching consortium at the Kasese plant in Uganda acquired a new organism, but also that Acidithiobacillus caldus had evolved at a genetic level - perhaps by acquiring resistance genes etc.

    The big problem is that the original BIOX inoculum was never kept, and so it's very difficult to understand how it may have changed over time.

    On a further note - it must be understood that evolution per se happens in many different ways. Mutation happens very slowly (look up the molecular or evolutionary clock) at the level of nucleotide changes (AGTC etc). Thus the evolution of new genes occurs over geological time-scales. However, microorganisms especially can exchange DNA somewhat 'wholesale'. This means that an organism can acquire a set of genes allowing it to survive in a highly toxic environment better than it's predecessor. This is the sort of thing we expect to see in biox reactors etc. Doug Rawlings has done a lot of work on this.

    The actual mechanism of the evolution is irrelevant to the Darwinian aspect of all this. If an organism becomes better able to survive a certain situation, then when that situation arises it will have an advantage - Survival of the Fittest.

    It is absolutely essential to understand the random nature of all this. There is no 'thought process'; evolution is not directed. An organism doesn't find itself in an environment and then evolve to adapt to it. Rather, these mutations and genetic exchanges happen all the time and if, by chance, it gains an advantage this change will be propagated due to competition.

    (That said, there is some evidence that when bacteria are stressed, they make themselves more amenable to genetic transfer. However, there is still no direction - it doesn't find itself in a high Cu environment and seek out Cu-resistance genes for example, it simply seeks out ANY genes etc.)

  2. Just to add... At ferrooxidans is never found in commercial biox plants. It is a common misconception, but it's not able to compete in such an environment. Who knows, maybe sometime in the future it will become so...!

  3. Thanks for your comments Chris. I look forward ro seeing your paper in the special issue of Minerals Engineering


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