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Living among Stones

Scientists from Freie Universität and Saint Petersburg State University are researching how biofilms act as weathering agents of stone surfaces and how this process can be stopped.

Jan 18, 2016

Wind und Wetter ausgesetzt. Wie der Verwitterungsprozess beispielsweise auch bei Denkmälern und Gebäuden möglicherweise aufgehalten werden kann, erforscht die Mikrobiologin Anna Gorbushina.
Subjected to wind and weather. Anna Gorbushina, a microbiologist, is researching possibilities for halting weathering processes in statues and buildings. Image Credit: cc by-NC-ND Danneborg, flickr
Mikroorganismen belagern den Stein und greifen ihn dadurch an.
Microorganisms settle on and degrade the stone. Image Credit: Anna Gorbushina
Anna Gorbushina ist an der Bundesanstalt für Materialforschung und -prüfung (BAM) beschäftigt und Professorin für Material und Umwelt am Institut für Geologische Wissenschaften und am Institut für Biologie der Freien Universität.
Anna Gorbushina works for the German Federal Institute for Materials Research and Testing (BAM) and is also a professor of geomicrobiologyat the Institute of Geological Sciences and the Institute of Biology, both at Freie Universität Berlin. Image Credit: Svenja Radtke

Jointly, they are tracking down the microorganisms that attack stones, monuments, and facades and form soils. Recently at a workshop in Dahlem, Berlin-based mineralogists and geomicrobiologists – as well as soil scientists and biologists from Saint Petersburg – got together to pool their insights.

This project is being supported by Joint Seed Funding, a funding scheme set up by Freie Universität’s Center for International Cooperation to facilitate the use of synergies between the university and its strategic partner, Saint Petersburg State University. Campus.leben spoke with Anna Gorbushina. Affiliated with the German Federal Institute for Materials Research and Testing (BAM), she is the initiator of the project and also is a professor of Geomicrobiology at Freie Universität’s Institute of Geological Sciences as well as its Institute of Biology.

Professor Gorbushina, what are you researching with your international team of scientists?

There are two Earth systems that have been interacting with each other since the beginning of life on this planet: the biosphere – or life – and the geosphere, which includes rocks and soils. These two spheres are in permanent contact. Knowing how living organisms and rocks interact can help us understand how rock weathering takes place. Twenty years ago scientists were able to demonstrate that – apart from geological influences – biological influences also play a role here. The details, however, are only gradually being unveiled.

The mechanisms that are responsible for rock weathering can be examined very efficiently and – more importantly – can also be replicated by simulating a complex environmental situation in the lab. Biological laboratory modeling, which allows accelerated studies to be carried out under controlled conditions, facilitates this.

The biofilm models for rock weathering that have recently been been deployed at Freie University and at BAM, consist of a simplified two-species biofilm community – black fungi and corresponding cyanobacteria that can be controlled in a genetically targeted way. When it comes to supplementing existing methods for examining weathering mechanisms, this new instrument is often a decisive component.

To gain sufficient insights into the microbiological “antagonist,” researchers use a technique that is well established in medical microbiology, plant biology, or zoology, namely genetic engineering. This can help clarify what role the individual properties of black fungi or cyanobacteria play in the biologically controlled stone or material degradation process.

To better understand the interplay between biofilms and stones (in nature or in the lab), we need the support of specialists from the Earth and life sciences. Soil scientists know what the products of weathering look like in the soil after an extended period of such interaction. Mineralogists help us to observe and quantify the changes in the stone while biologists research specific organisms that can drive these processes.

What is the impact of your research? Beyond the fundamental research, are there already concrete applications

Both two aspects play a role. On the one hand, we now understand better how soil formation and stone weathering basically take place on Earth. Apart from that, knowledge about the weathering of stones is beneficial when it comes to preserving all stone objects; it comes to bear, for example, in monument preservation. After all, monuments, sculptures, roofs, and facades are all subject to weathering effects.

Similar microorganisms as those in Northern Europe also attack marble sculptures in the Mediterranean region. They also occur in deserts (both hot and Antarctic), in the pseudo desert zone, as well as on the walls and roofs of our houses and on modern materials such as photovoltaic systems. Thus, thanks to the insights gained from basic research we can also protect monuments and solar parks.

Natural environmental processes cannot be stopped. Nevertheless, it may be possible to slow them down; and for some buildings, this would already suffice. The connection to BAM, thus, plays a role in the applied aspect of our research. New materials that are designed to stop the colonization of stone or material surfaces are being tested there using the stone-colonizing biofilm model.

As part of this project, you are also hoping to gain insights into climate change. What is the connection between surface-borne microorganisms and climate change?

The biofilm, in other words, this thin layer of life at the boundary between stones or buildings and the environment, is subjected to all the atmospheric influences. Every change in the atmosphere, for example an increase in temperature and CO2, would immediately be reflected in the colonization by microorganisms. In this context, the biofilm serves as a sensitive bio-indicator of climate change.

There are, in fact, significant differences with regard to colonization in various climactic zones or in rural or urban environments. Owing to climate change, biofilms that previously existed only in deserts will appear in other climate zones as well. Today, we understand the microbial processes involved in weathering and have identified organisms that take part in them.

But often these studies are only phenomenological in the sense that they are based on observations of stones that have already weathered, in other words, on objects in nature. These objects, however, are highly complex and the intricacy of the influencing factors often exceeds our power of imagination. The relationships between cause and effect thus cannot be unequivocally settled.    

To get to the bottom of this issue, we need an experimental system in the laboratory that allows the basic mechanisms to be examined in-depth individually. With our stone-colonizing biofilm model we have developed such a system.

The organism model, which is typical for certain surfaces, can be genetically controlled in the lab; this makes it possible to examine how the biofilm changes under various artificial atmospheric conditions and substrates. And this allows us to make certain predictions and to quantitatively understand the influence of changed climate and environmental conditions on the weathering process of stone.

Interview by Jenny Jörgensen

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