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Biofilm formation; Sensing the differences between Bacillus subtilis and Pseudomonas aeruginosa.

Vries, H.J. de (2011) Biofilm formation; Sensing the differences between Bacillus subtilis and Pseudomonas aeruginosa. Bachelor's Thesis, Biology.

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Bacteria and other microorganisms have, last decades, been thoroughly studied. These organisms are thereby adapted to laboratorial settings, masking their true undomesticated phenotypes. Presumably this contributed to the idea that bacteria exist as unicellular organisms. However, discoveries have shown that undomesticated bacteria tend to act multicellular, by formation of a biofilm. In general, bacteria gain several positive consequences by forming a biofilm. It is therefore not unsurprisingly, that most bacterial species are able to construct a biofilm, and that it is the life-style that bacteria tend to execute in their natural habitat. Important parameters of the biofilm are quorum sensing and the architectural structure of the biofilm. Quorum sensing is an interspecific and intraspecific cell-to-cell communication system. That regulates gene expression balanced by cell densities. It provides a mechanism for cells to jointly act upon environmental differences. Quorum sensing signals trigger the production of extracellular polymeric substances (EPS), that causes the formation of a matrix to encapsulate the cells. The cells and the EPS matrix determine the architectural structure of the biofilm. Which can be seen as a measure of the biofilm-capabilities. Two biofilm forming organisms that are well studied, because of the considerable influence of their biofilm upon mankind. Are the Gram-Negative Pseudomonas aeruginosa (P. aeruginosa) and the Gram-Positive Bacillus subtilis (B. subtilis). The goal of this study is to describe the biofilm features of P. aeruginosa and B. subtilis, highlighting differences in quorum sensing systems and architectural structures. Although sharing the basic elements, due to the different environmental-backgrounds, both organisms organise biofilm formation in two distinct manners. While P. aeruginosa is mostly notorious for infecting the lungs of cystic fibrosis patients, the soil residing B. subtilis is mostly known for releasing high resistant spores. As Gram-Negative requisite, P. aeruginosa executes quorum sensing with highly diffusible acyl-homoserine lactone (HSL) signals. In contrast, the peptide pheromone signal of B. subtilis requires active excretion, and does not always require internalization for gene expression regulation. More specific examples show environmental adaptations. P. aeruginosa excretes signals that deceives organisms that compete for a niche in the cystic fibrosis lung. In addition, quorum sensing regulates the excretion of substances, that facilitate survival in the cystic fibrosis lung. B. subtilis has developed a quorum sensing (like) system, based upon potassium leakage. This system provides a mechanism to indirectly sense the effect of several distinct substances. The main function of the extracellular matrix seems resisting harsh conditions. Depending on environmental differences, the cells adjust the EPS matrix. However, the EPS matrix provides other prospects as well. For example, some of the P. aeruginosa biofilm components act adhesin-like, particularly increasing cell-congregation. Moreover, P. aeruginosa secretes compounds that interfere with the human host defense mechanism. Thus, the biofilm of P.aeruginosa provides distinct attributes to initiate and prolong infection. In contrast, B. subtilis biofilm does not provide such additional attributes. However, the biofilm yields good circumstances to develop highly resistant spores, in this manner the biofilm offers major advantages for B. subtilis survival. Important to note, however, these compounds of P. aeruginosa are mainly discovered because overproducing mutants are highly infectious. Due to this reason, along with the fact that B. subtilis is more domesticated than P. aeruginosa, it seems unsurprising that some of the wild-type biofilm features of B. subtilis remain unnoticed. Nonetheless, the differences between B. subtilis and P. aeruginosa are noteworthy, and provide opportunities to concentrate anti-biofilm operations upon the desired organism.

Item Type: Thesis (Bachelor's Thesis)
Degree programme: Biology
Thesis type: Bachelor's Thesis
Language: English
Date Deposited: 15 Feb 2018 07:45
Last Modified: 15 Feb 2018 07:45

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