Team:LMU-Munich/Rathenau

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Contents

Collaboration with the Rathenau Institute

Application Scenario

Download our application scenario as a PDF here.


The BaKillus Concept

Increasing bacterial resistance to classical antibiotics remains a serious threat and urges the development of novel pathogen-killing strategies to treat infectious diseases. Exploiting bacterial communication mechanisms such as quorum sensing is a promising strategy to specifically target certain pathogens. Towards this goal, the synthetic organism BaKillus was designed to specifically target respective QS-dependent pathogenic bacteria. Here, the core element is a pathogen-detection device to detect Staphylococcus aureus and Streptococcus pneumoniae. By utilizing QS-dependent promoters, BaKillus will activate pathogen-killing devices like the production of antimicrobial peptides or biofilm degrading enzymes in the presence of target pathogens (see Fig. 1 for details). As a safety measure, a delayed suicide-switch guarantees non-persistence of genetically modified B. subtilis in the absence of pathogens.

TODO: Fig 1 here

Figure 1: Basic concept of BaKillus: S aureus and S pneumoniae use autoinducer-peptides (AIP) for cell-density dependent regulation of gene expression (quorum sensing), e.g. regulation of pathogenicity. BaKillus with the respective two-component sensing systems AgrAC and ComDE is enabled to activate killing devices in an AIP dependant manner. Uncommon antimicrobial peptides like subtilin or the cannibalism toxin, the peptidase lysostaphin and the hydrolase dispersin will be used to ensure effective killing of the targeted pathogens.

Application

BaKillus could be applied in two independent ways, first as a point-of-care diagnostic tool to identify pathogens and second, as a drug-producing microbe to treat bacterial infections.

Pathogen-identification diagnostic tool:

Problem:

Current tests to identify S. aureus (e.g. coagulase) require a time-consuming (18-24h) culturing step. The BaKillus S. aureus diagnosis tool: If the S. aureus detection device is sensitive enough, a smear of a patient into the BaKillus diagnostic tool would be enough to verify a S. aureus (MRSA) infection. This culture-independent detection provides results within 1-2 hours (just limited by the time for BaKillus spore germination and gene expression) and subsequent treatments could be initiated more quickly. We are planning to develop a ready-to use diagnosis tool for point-of-care testing by the professional staff in hospitals, pharmacies or medical offices (see Fig. 2). We are looking into collaboration with the iGEM-Team Aachen, who are planning something similar (https://2014.igem.org/Team:Aachen).

TODO: Fig. 2 here

Figure 2: Basic concept of the BaKillus diagnostic tool. BaKillus spores are stored separately in a self-contained device. About one hour before use, spores and medium are mixed and incubated for the germination of the spores. The sample of a patient (e.g. a smear) can be applied into the culture and after about 30 minutes the result can be analysed with a simple camera-computer-station.


Table 1: Discussion of the BaKillus diagnostic tool.
Strengths Weaknesses
Detection & Identification of AIP dependent pathogens Application is limited to targets that exhibit QS-dependent pathogenicity.
Initial assessment of the sensitivity of the test and tests for reliability of the tool required
Self-contained/tightly closed device prevents release of GMO and thus a product possibly has little legal barriers for approval. (This is topic of an ongoing discussion with Dr. Ulrich Ehlers (Commissioner for GMO-release in Germany, BVL) and Dr. Hans Schrubar (Commissioner for Bio-Safety in Bavaria)
Easy engineering and handling of the detection devic Maybe too cost-intensive due to the need of high-end technology for measurement, especially for the utilization in developing countries. We seek to minimize this hurdle by using low-cost hardware (e.g. Raspberry Pi instead of a conventional computer).