In summer 2024, a Karlsruhe seminar organised an excursion to NATUR sculpture for the second time, this time with students and lecturers from both the Institute of Art and Architectural History at the Karlsruhe Institute of Technology (KIT) and the Karlsruhe University of Arts and Design (HfG). In bright sunshine, the participants were welcomed by goats at the actual destination of the excursion at the Kleinebene hill in Oppenau. Compared to the previous year, visible changes could already be seen with the naked eye on the wooden letters. The silvering had progressed even further, especially in the areas exposed to the weather, giving the various types of timber even more character. In more humid areas, particularly towards the mountain, slightly greenish surface discolouration could be observed, which suggests a colonisation by algae.
However, one of the aims of the excursion was to look at the invisible changes and how the wood transforms at the ‘micro-performative’ level. In order to track down the microorganisms, emeritus bioprocess engineer Prof Clemens Posten from KIT provided sterile equipment and gave an introduction to the sampling procedure and correct documentation. A classic core drill was not used because the boreholes were too large; instead, the students used a narrow 4 mm drill to take samples from the wood of the five letters on both the downhill and uphill sides. The beams were drilled on the lower side in order to avoid future sources of waterlogging. The shavings were collected in sterile tubes and the drill points were disinfected with alcohol after each drilling. Each sample was numbered consecutively so that the letter and respective position could be assigned later in the laboratory.
Julia Ihls finally took the samples to the HfG Karlsruhe. There she manages the Bio Design Lab, where she was able to grow the samples on LB agar plates. Within a few days, various fungi began to spread on the culture medium from the pieces of shavings, depending on the type of wood. As the external appearance was not sufficient to determine exactly which fungus had colonised the respective wood, the samples were transferred to the laboratory of Prof. Peter Nick at the Joseph Gottlieb Kölreuter Institute of Plant Sciences (JKIP) at KIT.* In his Molecular Cell Biology Lab, Dr Gabriele Jürges prepared the samples for sequencing in an elaborate two-day process: For this purpose, the cells were disrupted and the DNA was isolated. A specific section of the ribosomal DNA, which is characteristic of fungi, was then labelled using primers (ITS4 & 5) and amplified using the polymerase chain reaction (PCR). After further purification, these DNA samples were sent to an external company for sequencing.
18 types of fungi
The sequences, which were available after 1-2 days, could finally be compared online with the MYCOBANK database and now shed a first light on the colonisation of the wooden letters by different fungi. Around 18 different species of fungi were identified. Particularly in the samples that were taken from the surface by direct imprinting on a culture medium, some non-wood-specific variants were identified that can also infest grasses or crops. The pathogenic sac fungus Sydowia polyspora was identified conspicuously often in the samples. The latent pathogen, which was first described in 1891, is a so-called endophyte that predominantly attacks the plant tissue of conifers such as pines, Douglas firs and larches without any symptoms. If the conifer gets under stress, the weak parasite - presumably in co-operation with other pathogens - becomes noticeable: Small dot-shaped fruiting bodies form on the needles and brown spots appear. However, so-called saprophytes, such as Cladosporium tenuissium, which infest dead wood, were also detected in the samples. However, according to Prof Peter Nick, the transition between fungi infesting dead wood and pathogens that also occur in living trees is fluid: ‘You can't draw a clear line between disease and health - so decomposition can be a healthy or pathogenic decomposition’.
* Botany is the oldest field of research in Karlsruhe and dates back half a century before the Polytechnic was founded. Botanical research goes back to Joseph Gottlieb Kölreuter (1733-1806), who, as professor of natural history and director of the court gardens in Karlsruhe, studied among other things the sexual reproduction of plants and discovered insect pollination.
Credits cycad pictures: Maren Riemann, drone movie: Aron & Hans Kimmig
