Auxotrophic Staphylococcus Strain via Triple D-Alanine Pathway Knockout
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Solution Overview
Problem
Existing Staphylococcus bacterium strains do not exhibit D-alanine auxotrophy despite double alanine racemase genes knockout, as they possess glutamate racemase and D-alanine aminotransferase, which provide a bypass for alanine racemase, unlike Bacillus subtilis and Escherichia coli.
Innovation Solution
Development of a recombinant Staphylococcus bacterium with triple gene knockouts, including two alanine racemase genes (Δalr1Δalr2) and the D-alanine aminotransferase (dat) gene, rendering it dependent on D-alanine for growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If double alanine racemase genes knockout is performed in Staphylococcus bacterium, then the bacterial cell wall synthesis pathway is disrupted, but the bacterium does not exhibit D-alanine auxotrophy due to presence of bypass enzymes (glutamate racemase and D-alanine aminotransferase)
Solution Approach 1:
The solution segments the D-alanine biosynthesis pathway by knocking out multiple genes (alr1, alr2, and dat) individually and systematically. Each gene knockout addresses a specific enzymatic step, and the cumulative effect of these segmented knockouts achieves complete D-alanine auxotrophy that cannot be achieved by knocking out alr genes alone.
Solution Approach 2:
The invention extracts and removes the bypass enzymes (glutamate racemase and D-alanine aminotransferase) from the metabolic pathway by knocking out the dat gene. This extraction eliminates the alternative route that would otherwise allow the bacterium to synthesize D-alanine independently, thereby achieving reliable auxotrophy.
2Reliability
If triple gene knockout (alr1Δalr2Δdat) is performed to achieve D-alanine auxotrophy, then the bacterium becomes dependent on exogenous D-alanine, but the manufacturing complexity and time increase
Solution Approach 1:
The solution employs preliminary action by using a structured, stepwise approach to gene knockout. First, alr1 and alr2 are knocked out to disrupt the primary pathway, then dat is knocked out to eliminate bypass routes. This preliminary sequencing of knockout operations prevents the need for extensive troubleshooting later and accelerates the overall strain development process.
Solution Approach 2:
The invention implements feedback mechanisms at each knockout stage to verify successful gene disruption and assess the emergence of auxotrophic phenotypes. By monitoring growth characteristics and D-alanine requirements after each knockout event, researchers can adjust subsequent knockout strategies accordingly, preventing wasted time on redundant experiments.
3Adaptability or versatility
If triple gene knockout is performed to create D-alanine auxotrophic strain, then the strain becomes suitable for therapeutic applications, but the ease of manufacture decreases
Solution Approach 1:
The triple knockout strain design achieves multi-functionality by creating a platform strain that can be adapted for various therapeutic applications (treating skin rashes from radiation therapy and chemotherapy). The complete D-alanine auxotrophy serves multiple purposes: it ensures the strain cannot survive in human tissues (enhancing safety), allows for controlled growth in bioreactors (improving manufacturing), and provides a basis for future genetic engineering (increasing versatility).
Data Source
AI summary
The present disclosure provides recombinant Staphylococcus bacterium (e.g. S. epidermidis) that are dependent on D-alanine for growth. In one aspect, the disclosure features a recombinant Staphylococcus bacterium comprising two inactivated alanine racemase genes (Δalr1 Δalr2); and an inactivated D-alanine aminotransferase (dat) gene. In another aspect, the disclosure features a method of making the recombinant Staphylococcus bacterium. In another aspect, the disclosure features a method of treating or preventing a rash in a subject, comprising administering to the subject a population of the recombinant Staphylococcus bacterium of any one of the aspects or embodiments described herein, in an effective amount to treat or prevent the rash in the subject.