Turning seawater into gold

English: Crystaline Gold

English: Crystalline Gold (Photo credit: Wikipedia)

Via a number of news sources, and published in Nature Chemical Biology: a report describing new research with a metallophore bacterium. Researchers at McMaster University in Ontario, Canada have been looking at microorganisms that have been associated with biofilms growing on gold nuggets. Gold, like many heavy metals, is toxic to many organisms. Consequently, it was surmised that any microorganisms that are able live in close proximity to these materials must have a mechanism for being able to survive by them. Sequencing of organisms in gold biofilms identified two species, Cupriavidus metallidurans and Delftia acidovorans that made up over 90% of the biofilm associated microbes. The researchers decided to focus on these two species in order to identify any potential mechanisms that they might have had to assure survival in the presence of lethal levels of soluble gold. 

In order to do this, the full DNA sequences of the two microorganisms were compared, specifically to identify any small-molecule metabolites that might be produced in one of them but not the other that had previously been show to play a role in metal binding. They chose to examine D. acidovorans specifically, as that species was able to grow in significantly higher levels of soluble gold on a chemically defined medium, in comparison to C. metallidurans. DNA sequence analysis identified the delG gene from Delftia acidovorans that was present only that species. Molecular deletion of the delG gene in Delftia produced a bacterial strain unable to grow in the presence of soluble gold. The delG gene product was secreted from bacteria into the culture medium. The secreted material was named delftibactin, and was purified and further analyzed.

Purified delftibactin was found to precipitate gold from solution, and electron microscopy of the precipitated material showed the presence of octahedral gold nanoparticles which resembled the structures found in natural deposits. The authors suggest that biological activity by organisms such as Delftia might contribute to the formation of gold deposits, and that the delG gene enables these organisms to survive in environments that would ordinarily be toxic. If the interaction between delftibactin and soluble gold is specific, this might allow the organism to be used for the industrial purification of gold from very dilute sources. Seawater contains approximately 5 to 50 parts per thousand soluble gold. Scaling up production of delftibactin opens up the possibility that it might be used commercially to extract gold from this very rich source.

Bonus time, to promote additional Microbiology interactions: in the comment thread below, list an industrially important microorganism (scientific name), and the industrial process it is important for! Please note, no repeats allowed.


About ycpmicro

My name is David Singleton, and I am an Associate Professor of Microbiology at York College of Pennsylvania. My main course is BIO230, a course taken by allied-health students at YCP. Views on this site are my own.

Posted on February 12, 2013, in Bonus!, Microbes in the News, Strange but True. Bookmark the permalink. 10 Comments.

  1. OK, I will go first since no one else wants to: Aspergillus oryzae, which is used for the industrial production of the enzyme amylase. (from Bauman, page 754)

  2. Biomass of microbes has industrial application is in the production of single cell proteins (SCP) which are in fact whole cells of Spirullina (an algae), Saccharomyces (a yeast) and Lactobacillus (a bacterium). SCP is essentially rich in amino acids which are either absent in vegetarian food or present in low amounts e.g. lysine, threonine, methionine, leucine, isoleucine. (Prof. Rupinder Tewari, Department of Biotechnology, Panjab University)

  3. Poor sad neglected bonus.
    There there. There there.
    Soft bonus
    Warm bonus
    Little ball of fur
    Happy bonus
    Sleepy bonus
    Purr purr purr

  4. In the food sweetener industry an enzyme called glucose isomerase, extracted from the bacteria Bacillus coagulans, is used to make the sweetener fructose, using glucose as the raw material.

  5. Brocadia anammoxidans (sorry, I couldn’t find how to italicize on this) also known as anammox bacteria, is a bacteria that researchers are looking to use for sewage plants. Most bacteria used today to break down water waste does so through an aerobic process which is very expensive to do for the waste facilities. However, anammox bacteria is able to break down human waste aerobically. Even better yet, they are able to utilize nitrite and ammonia which is found naturally in human waste to form energy. On another note, one of their products from their energy process is rocket fuel! Pretty awesome!)


    • In order to make text appear italicized, you need to put HTML tags around it, like this:
      <em>text to be italicized</em>

      So that <em>E. coli</em> becomes
      E. coli

  6. A bacterium called Thermus aquaticus is found naturally in and around hot springs. It contains an enzyme which is responsible for copying the DNA inside the cell. Forensic scientist can use this enzyme to multiply trace amounts of DNA found at crime scenes. A very handy little enzyme these days!


%d bloggers like this: