Team:Groningen:Project:Detection

Resistance of anti-microbials, especially antibiotics, cause a major problem in the modern medicine world. The World Health Organization state’s “A post-antibiotic era—in which common infections and minor injuries can kill—far from being an apocalyptic fantasy, is instead a very real possibility for the 21st century” (April, 2014)¹. Therefore we will not use antibiotics against the infections but rather use a set of Infection Preventing Molecules (IPMs). Little resistance has been shown for these molecules (Source, resistantie against Nisin) and are therefore excellent targets for our fight against infections. More about these IPMs can be read in our secretion page. To further lower the chance of resistance we integrate a detection system in our LactoAid. This detection system prevents unnecessary production of the IPMs and thus lowering the chance of resistance development in bacteria.

Our lactoAid focusses primarily on the treatment of burn wounds. The most occurring infections with burn wounds are caused by Staphylococcus aureus and Pseudonomas aeruginosa. Both these pathogenic (i.e. capable of causing disease) bacteria are opportunistic bacteria. Meaning that they hardly infect healthy people, but when immunity is lowered or the skin is damaged they can cause infection. Only when the density of the pathogen is above a certain threshold it starts to transcribe pathogenic genes and produces toxins ².

The reason a single cell or low density population will not start to produce these toxins is because they cannot produce enough toxins to kill surrounding cells in order to start an infection. If a pathogen starts to produce these toxins in a low density population, it would waste energy. Therefore the pathogens wait until the density is high enough to inflict damage by simultaneously producing the toxins. So how do the bacteria know when the optimal density is reached? They secrete signal molecules.The pathogens know how big their population is by secreting those signaling molecules. This signaling is called quorum sensing (QS)². We designed our LactoAid in such a way that it is able to detect the QS of both staphylococcus aureus and Pseudonomas aeruginosa.

The Quorum sensing system of pseudomonas aeruginosa is a multiple hierarchically ordered complex. In one layer of this complex system, two proteins are synthesized, LasR and LasI. The LasI produces PAIs which can bind with the LasR. The LasR-PAI couple induces expression of virulence factors, LasA protease, alkaline protease and exotoxin A. Moreover, the couple acts as autoinducer on the expression of LasI by influencing the promoter pLasI, increasing the synthesis of PAIs.³. PAIs can move from cell to cell and thus influence the QS of other cells in their surrounding.

Because the AHLs defuse from cell to cell we designed a biobrick which produces LasR. This will bind to the PAI and induce the pLasI promoter. Behind the pLasI promoter we placed our secretion system to produce the infection preventing molecules. (Figure 4).