Microbiology Monthly Newsletter for Microbiology at the Department of Cell & Molecular Biology Lundberg Laboratory, Göteborg University [ January 1999 ] [ February 1999 ] [ March 1999 ] [ April 1999 ] [ May 1999 ] [ June 1999 ] [ July-August 1999 ] [ September 1999 ] [ October 1999 ] September 1999 Scientific Contributions This month we have three new papers on our science display. The role of fimbriae in Escherichia coli cell adhesion Type 1 fimbriae is an E. coli organelle that is important for receptor mediated attachment of the bacterial cell. This organelle has also been implicated in non-specific cell adhesion to different surfaces. In a recent paper, Karen Otto, Hans Elwing and Malte Hermansson elegantly clarify the role of type 1 fimbriae and demonstrate that this fimbriae does not facilitate the initial contact of the bacterial cell to a surface but contribute to the subsequent establishment of the bacteria on the surface. This was found to be dependent on the nature of the surface though. In fact, the type 1 fimbriae may actually inhibit attachment or firm adhesion of cells to hydrophilic surfaces while being important on hydrophobic surfaces. A reappraisal of the DLVO theory for microbial adhesion Derjaguin, Landau, Verwey and Overbeek presented a theory, between 1940 and 1950, aimed at explaining colloid stability. This theory, called the DLVO theory, was later made popular by microbiologists, notably by K. Marshall, in explaining and/or predicting microbial adhesion using calculations of adhesion free energy changes. By using this theory, the assumption is made that bacteria behave as inert particles and that bacterial adhesion can be understood by a physico-chemical approach. A well-known disciple of the Marshall school of thought, Malte Hermansson, has recently published a review in which he scrutinizes the classical DLVO model, the extended version and ”competing” thermodynamic models in an updated fashion. So, what is Dr. Hermansson’s idea concerning whether this model is useful or not in the science of bacterial adhesion. Well, I think it is fair to say that the verdict is a big Maybe. It is doubtful, according to Hermansson, that this physico-chemical model will ever be sufficient to explain all the complex aspects of bacterial adhesion but at the same time, this model has been, and will continue to be, of value in forming a framework in which biological factors can be added to form a unifying theory of adhesion. And he concludes by citing Theil: ”models are to be used, not to be believed”. In this respect, the DLVO theory has been successful. Cellular deterioration, growth-arrest and oxidation With the development of sensitive immunochemical methods for the detection of protein oxidation (carbonyl groups), the presence of such groups has been used as a marker of protein oxidation and to demonstrate a correlation between the oxidation of target molecules and aging. Sam Dukan have used such a method in combination with two-dimensional gel electrophoresis to demonstrate that stasis-induced oxidation targets specific proteins and that protein oxidation is both quantitatively and qualitatively different in wild type cells as compared to cells lacking the global regulators OxyR and RpoS and oxidative stress defense genes. Sam goes on to show, using mutant analysis, that there is a close correlation between protein oxidation and the life-span of stationary phase E. coli cells. He also demonstrates that the die-off of wild-type E. coli cells during the first 10 days of stasis can be completely counteracted by omitting oxygen indicating that reactive oxygen species may limit longevity also of wild-type E. coli cells starved under aerobic conditions "Theories pass. The frog remains" Jean Rostand, Notebooks of a Biologist Have a great month!