New PhD-project!

Exciting PhD project:

An opportunity exists for a motivated PhD-student to join the Microbes and Heavy Metal Group at University of Adelaide to study the:

Geomicrobiology of gold from arid and subarctic North America

Supervisors: Frank Reith, Jeremiah Shuster (both University of Adelaide), Erik Melchiorre (California State University)

The biogeochemical cycle of gold is driven by geomicrobial processes mediating the dispersion and reconcentration of gold in Earth surface environments. Biogeochemical cycling of gold has been demonstrated in present-day semi-arid, (sub)-tropical and temperate environments, whereby biofilms on gold-bearing mineral and gold-particle surfaces drive the dispersion and reconcentration of gold, thereby (trans)forming the particles. If biogeochemical cycling of gold and associated microbial communities in arid or arctic environments, where air temperatures can reach+40°C or -40°C and soils are very dry or remain frozen for much of the year, respectively, are largely unknown.

Therefore, the aims of this study are to assess:

  • if biofilms are present on placer gold particles from Arizona, California, the Yukon and Alaska;
  • the phylogenetic and putative functional composition of bacterial biofilm communities;
  • the presence of secondary gold morphotypes indicative of biogeochemical gold cycling.

To achieve this, gold particles from a range placer sites in Arizona, California, the Yukon and Alaska will studied using a combination of culture dependent and independent techniques, e.g., Illumina Miseq next generation sequencing and high density functional microarrays (GeoChip). Advanced micro-analytical techniques will be applied, including field emission gun-scanning electron microscopy, focused ion beam-scanning electron microscopy coupled with energy dispersive x-ray spectroscopy, and electron microprobe analyses.

This project is part of a large suite of studies assessing all aspects of biogeochemical gold cycling around the world. Studies are currently underway with samples from South Africa, New Zealand, the UK, Switzerland, Germany, Brazil and The Philippines These provide a molecular-level understanding of the bio(geo)chemical processes underpinning gold mobilisation, dispersion and re-concentration in many environments. Ultimately the implementation of a comprehensive global biogeochemical model for gold cycling, describing its distribution, speciation and bio(geo)chemical turnover in Earth surface environment is the aim of this research.

The successful candidate will have advanced skills in molecular microbiology and/or micro-analytical techniques, experience in a clean laboratory environment, be an excellent writer and communicator, and be high highly self-motivated and organised.

Prospective domestic and international candidates can contact A.Prof. Frank Reith to discuss the project as well as scholarship opportunities.

Neue Studie der Uni Halle: Diese Bakterien verdauen giftige Metalle und bilden dabei Gold

Für die meisten Lebewesen sind größere Mengen von Schwermetallen, wie Kupfer oder Gold, giftig. Nicht für das Bakterium C. metallidurans: Es hat einen Weg gefunden, aus einem Schwermetall-Gemisch wertvolle Spurenelemente zu beziehen, ohne sich dabei selbst zu vergiften. Ein interessanter Nebeneffekt: Dabei bildet es winzige Goldnuggets. Welche molekularen Prozesse dabei in den Bakterien ablaufen, hat nun ein Forscherteam der Martin-Luther-Universität Halle-Wittenberg (MLU), der Technischen Universität München (TUM) und der australischen Universität Adelaide herausgefunden. Ihre Ergebnisse stellt die Gruppe in der renommierten Fachzeitschrift “Metallomics” der Royal Society of Chemistry vor.

Das stäbchenförmige Bakterium C. metallidurans lebt vor allem in Böden, die mit zahlreichen Schwermetallen angereichert sind. Im Lauf der Zeit verwittern einige Mineralien im Boden und geben dabei giftige Schwermetalle und Wasserstoff an ihre Umgebung ab. “Wenn man von den giftigen Schwermetallen absieht, sind die Lebensbedingungen in diesen Böden aber nicht schlecht: Es gibt genügend Wasserstoff zur Energiespeicherung und nahezu keinerlei Konkurrenz. Will ein Organismus hier überleben, muss er jedoch eine Möglichkeit finden, sich gegen diese Gifte zu schützen”, sagt Prof. Dr. Dietrich Nies, Professor für Mikrobiologie an der MLU. Gemeinsam mit seinem australischen Kollegen Prof. Dr. Frank Reith von der Universität Aderlaide konnte er bereits 2009 nachweisen, dass C. metallidurans auf biologischem Weg Gold ablagern kann. Welche genauen Prozesse dabei jedoch ablaufen und warum sie das tun, war bislang unbekannt. Dem sind die Forscher nun auf die Schliche gekommen.

Gold gelangt auf demselben Weg wie Kupfer in das Innere der Bakterien. Kupfer ist für C. metallidurans einerseits ein lebenswichtiges Spurenelement, andererseits ist es in größeren Konzentrationen giftig. Kommen die Kupfer- und Goldteilchen in Berührung mit den Bakterien, laufen vielfältige chemische Prozesse ab. Dabei wird Kupfer, das eigentlich in einer schwerer aufnehmbaren Form vorliegt, in eine für das Bakterium wesentlich leichter aufnehmbare Form umgewandelt und so gelangt es in das Zellinnere. Das Gleiche passiert auch mit den Gold-Verbindungen.

Lesen Sie den Rest des Artikels in der Presse-Mitteilung

New study by the University of Halle: These Bacteria produce gold by digesting toxic metals

High concentrations of heavy metals, like copper and gold, are toxic for most living creatures. This is not the case for the bacterium C. metallidurans, which has found a way to extract valuable trace elements from a compound of heavy metals without poisoning itself. One interesting side-effect: the formation of tiny gold nuggets. A team of researchers from Martin Luther University Halle-Wittenberg (MLU), the Technical University of Munich (TUM) and the University of Adelaide in Australia has discovered the molecular processes that take place inside the bacteria. The group presented their findings in the renowned journal “Metallomics” published by the Royal Society of Chemistry.

The rod-shaped bacterium C. metallidurans primarily lives in soils that are enriched with numerous heavy metals. Over time some minerals break down in the soil and release toxic heavy metals and hydrogen into their environment. “Apart from the toxic heavy metals, living conditions in these soils are not bad. There is enough hydrogen to conserve energy and nearly no competition. If an organism chooses to survive here, it has to find a way to protect itself from these toxic substances,” explains Professor Dietrich H. Nies, a microbiologist at MLU. Together with his Australian counterpart, Professor Frank Reith from the University of Adelaide, he was able to prove in 2009 that C. metallidurans is able to deposit gold biologically. Why it does this and the exact processes that take place remained unknown. Now the researchers have finally been able to solve the mystery.

Read the full article here: press release