Academic thesis

Annette Sievers: Red Pigmented Bacteria on Architectural Surfaces. The Significance of the Constitution of the Well Wall Concerning Inhibitation and Potential Health Hazards. Back
Language: Original   -   Translation
Abstract: The diploma-dissertation deals with the phenomenon of discolouration on architectural surfaces due to colonisation by red pigmented bacteria. At first, the question of a possible material destruction caused by red pigmented bacteria is being pursued. Surveys demonstrate that some of the isolated cultures (available at the University of Oldenburg, Germany) are able to produce acids from milk and hydrogen sulphides. A secretion of organic acids can cause dissolving mechanism of the material components. A production of hydrogen sulphides can result in redoxreactions. Pigments containing lead may therefore turn black. Besides this potential material destruction the colonisation of red pigmented bacteria first of all can have a negative effect on the appearance and thus on the aesthetical appearance of the object. Based on former surveys on the removal of colonisation it has been so far recommended to use mechanical techniques. Because the bacterial colonisation appears mostly in very large sizes and some of the isolates belonging to the group of gram-negative and therefore possibly endotoxin producing bacteria, a considerable risk to human health must be noted. The so-called "LAL-Test" showed that all grame-negative isolates are able to produce endotoxin. However the test cannot evidence the actual degree of concentration of endotoxins produced on the wall and if a removal of this bacteria includes actually the risk of affecting the human organism. It would be desirable if this matter could be further pursued more comprehensively in the context of a broader research program. At this point it is important that conservators realize that they are possibly exposed to a risk of their health when removing gram-negative bacteria. Therefore alternative methods of removal have to be considered. One alternative could be an application of biocides. The effectiveness of some biocides against some of the red-pigmented isolates was examined with the help of the so-called "agar-diffusion-test" in laboratory. The biocide (mostly used as fungicide) Ketoconazol showed the most effective results. Because Ketoconazol is mostly used for human medical treatment it hardly contains serious health hazards. Comparing the test of biocides in laboratory with a test of the same biocides on the colonised walls of the Lüdingworth St. Jacobi-Church, it could be proofed that here the biocides do not prevent but rather support the growth of these bacteria. Therefore it is inevitable to perform not a test in laboratory but in situ.


  • academic institution: HAWK Hochschule für angewandte Wissenschaft und Kunst Hildesheim/ Holzminden/Göttingen
  • kind of theses:  Diplomarbeit
  • main Tutor:  Prof. Dr. Karin Petersen
  • assistant Tutor:  Prof. Dr. Ivo Hammer
  • date:  2002
  • Language:  German
  • pages:  88
  • pictures:  27

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