A garden dedicated to microorganisms

Research in focus November 2011

The biology laboratory at the Fraunhofer Institute for Building Physics IBP has its own special garden. But the specimens that grow and flourish here would not be particularly welcome in the average greenhouse. For some ten years now, the team of biologists led by Dr. Wolfgang Hofbauer has been nurturing algae, mold fungi and other microorganisms. It is not the only collection of this kind in Germany, but it is nonetheless unique in two major respects. The first is its unusually broad scope, for this collection contains both photosynthetically active organisms (algae) and organisms that do not photosynthesize (fungi and bacteria). Secondly, it is devoted to microorganisms that perform the same type of "work", namely invading and attacking building components. The organisms were originally isolated from wild populations found growing in and on buildings being investigated for microbial damage. Today’s descendants of these algae and fungi have been allowed to continue exercising their destructive tendencies in the biology laboratory and outdoor test facilities operated by Fraunhofer IBP in Holzkirchen – albeit under the scientists’ watchful eye.

"It was in the winter of 2001 that we started to collect microorganisms that attack buildings," recalls Dr. Wolfgang Hofbauer. "At the time, we were working on an interdisciplinary, collaborative research project sponsored by the German environmental foundation DBU (Deutsche Bundesstiftung Umwelt) and various industrial partners." The IBP scientists’ role in this project was to investigate possible ways of preventing or at least inhibiting microbial growth on building facades. To help them evaluate the efficacy of the proposed strategies to prevent infestation, they also developed an accelerated test procedure to assess the microbial growth resistance of different exterior finishes. Ever since then, the biologists at Fraunhofer IBP have continued to nurture and add to their unusual collection. Today it comprises around 650 distinct cultures. "But that’s just an estimate," Dr. Wolfgang Hofbauer points out. These cultures in turn originate from approximately 400 individual strains (or subsets) of roughly 250 species. To an outsider that might seem tremendously complicated, but the Fraunhofer IBP biologists are used to such diversity and can identify the traits of every single culture in their care. As Dr. Wolfgang Hofbauer explains, "It’s more or less the same with dogs. Each household has its pet, but they by no means resemble one another. There are different breeds that can be distinguished by their physiognomy, and each breed of dog is suited to a different range of activities. The same is true in the world of algae and fungi." That is why the biology laboratory has such a large collection of different cultures and strains. "Most species consist of multiple strains, each with specific characteristics and preferred habitats. There are thermophilic fungi, for instance, that can withstand extreme temperatures, while other strains are able to survive in environments with a limited supply of nutrients." To keep the Fraunhofer IBP’s collection of microorganisms alive in Petri dishes and test tubes, the lab technicians have to repeatedly transfer them from one container to another. The majority of mold fungi can only be left on the same substrate for a matter of weeks. "After that, they have either exhausted the supply of nutrients or they start to die off, poisoned by the rising concentration of their own metabolic products," explains Dr. Wolfgang Hofbauer. The best-known metabolic products of fungi include ethanol, the alcohol produced by bakers’ and brewers’ yeast, and antibiotics. Algae are less demanding in this respect. They only need to be transferred to a new substrate once every six months or so, because they can survive on fewer nutrients and generate fewer toxic metabolic products.
The laboratory’s microorganisms are used for various purposes including a wide range of tests and experimental studies. Dr. Wolfgang Hofbauer and his team are, for example, conducting research on smart materials that are resistant to microbial growth, and they regularly perform biological tests on building materials according to official standards and customers’ requirements or using proprietary methods.
The most unusual find that Dr. Wolfgang Hofbauer can recall is a fungal spore that he still remembers not so much because of its rarity but on account of the place where it was found. "We had been asked to examine a swimming pool that had problems with mold infestation. In one of our samples, we discovered a single spore of a fungus that normally only grows in forests, on very rotten tree trunks. A single spore can hardly be classed as an infestation, but we kept it anyway," says Dr. Wolfgang Hofbauer. In fact, he not only kept it, he let it grow in the laboratory, "because it develops in such beautiful patterns that look like deer antlers".

More Information

Home Research in Focus

All contributions at a glance