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In nature, bacteria occur predominantly in highly organized multicellular communities called biofilms. Biofilm formation induces a complex developmental process, where cells differ from each other spatially and morphologically. The bacterial cells in such biofilms are composed of phenotypically different bacteria, demonstrating an intriguing example of heterogeneous regulation within an isogenic culture. Gram-positive bacteria have developed different strategies for survival in unfavorable environments, e.g. by getting competent or by sporulating. Biofilms offer an opportunity for the cells to survive extreme conditions as the cells in biofilms are more resistant to antibiotics and harsh circumstances.


A rok bio film showing a high degree of structural complexity

Bacillus subtulis a an ideal cantidate for a bio film coating since it is fast growing and has a very rigid extracellular matrix.

TasA Hydrophobins


The hydrophobic proteins that we are expressing in our bacillus biofilm are called chaplins and are derived from streptomyces. We streptomycyes is sporulating hyfe are trying to grow into the are. Since these hyfe are very small it is very hard to break the water air barrier for these hyfe, this is why streptomyces produces small hydrophobic proteins on the surface of it hyfe.

Three subgroups In total their are eight different chaplins. These eight chaplins can be devided in to three groups.

Chaplin A-C This group of chaplin are the largest and are almost three times these size of the other chaplins ones around ... kD. What makes these chaplins special besides their size is that they have a cell wall anchor and a hydrophilic region as well as a hydrophobic region.

Chaplin D, F-H These chaplin are small and have only a hydrophobic region

Chaplin E This chaplin is also small but is in the vivo relaesed outside the cell to start the watertension lowering before the hyfe actually penetrates the water-air barrier

Physical properties What makes these proteins inteesting is that they are amfipathic, meening that they "in theory" can change hydrophilic surfaces into hydrophobic surfaces but in turn can also change hydrophobic surfaces into hydrophilic surfaces. Chaplin are functional amyloids that will asemble by a catalytic process from monomers in polymerics chain forming rod like structure surfaces called amyloid fibers. These fiber are very rigid and and hard to break down. These fiber can only be broken up by boiling them in SDS. share distinguishing features with the medically important pathogenic amyloid fibers that are the hallmark of many neurodegenerative diseases such as Alzheimer's, Huntington's, systemic amyloidosis and the prion diseases.

Biofilms as a biological coating

The idea to make a biological coating has quite some advantages. For once biological coatings are quick to grow and the raw materials necessary for bio film growth are low in cost and plentiful available. So far there have been many coatings with biological substances but never before has bacteria been used for not only producing the coating material but also executing the coating process thereby saving a lot of effort.

For our bio film we have chosen bacillus subtiulus

Antifouling coating

Envirmentally friendly antifouling coating is When marine micro-organisms like algea or poks adhere to the hall of ships they form a layer greatly increasing drag in the water. This results in higher fuel costs and increased erosion. To prevent organism to form to the hall of ships chemicals often containing copper and tin, are used in antifouling paints. A lot of these chemicals eventually end up in the oceans ecosystems accumulating in all trophic levels of marine life and contaminating estuarial silt near shipping routes . Estimates show that in the Netherlands alone, approximately 19 tuns of organotin and 30 tuns of copper end up in the environment every year.

Because of these environmental objections to chemical antifouling coatingds our hydrophobic bioflm would be a great ecological alternativ. This hydrophobic bio film will prevent the adhesing of spores and plankton to ship halls. Thereby preventing the growth of marine fouling organisms.



Medical coatings