Investigating the Rcs Phosphorelay in Escherichia coli as a Target for Novel Antibiotic Development
Open Access
- Author:
- Bauer, Bradley William
- Area of Honors:
- Microbiology
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Dr. Sarah Ellen Ades, Thesis Supervisor
Dr. Sarah Ellen Ades, Thesis Honors Advisor
Dr. Teh-hui Kao, Faculty Reader
Dr. Wendy Hanna-Rose, Faculty Reader - Keywords:
- Antibiotic resistance
Escherichia coli
Rcs phosphorelay
RcsB - Abstract:
- Although antibiotics are effective against most bacterial infections, resistance is a growing problem. Diseases that were once considered easily curable are becoming more dangerous as current antibiotic therapies continue to become less reliable. As the need for novel drugs has risen, drug discovery and development is at an all-time low. Antibiotic development is no longer a lucrative business; major drug companies have dramatically reduced their efforts to find novel antibiotics, even when facing a public health emergency. There is a need for new antibiotics in every niche of medicine, but the need for novel drugs to combat gram-negative bacterial infections is especially dire. The Rcs phosphorelay is a stress-sensing pathway found in many gram-negative pathogens and is known to increase bacterial survival during antibiotic treatment. The Rcs phosphorelay can sense peptidoglycan damage in the cell envelope caused by β-lactam antibiotics and produces a signal which results in up-regulation of protective genes. Single-gene deletion strains for genes thought to be associated with the Rcs response were analyzed in order to determine which genes are essential for survival in the presence of antibiotics. Mutant strains were grown on LB agar plates containing the antibiotics mecillinam and cefsulodin. Strains were also grown on regular LB plates and plating efficiencies were calculated to assess growth. No genes were found to be highly significant to the pathway’s protective response. This indicates that the Rcs phosphorelay may act through numerous genes to boost survival or none of the genes tested are important for providing antibiotic resistance to the cell. Since the Rcs phosphorelay increases resistance to antibiotics, it has strong potential as a novel drug target. It is hypothesized that inhibition at any step of the Rcs signal cascade will prevent the cells from becoming resistant to drug treatment. A reporter strain was constructed to test for cyclic peptide inhibitors of the Rcs pathway. The reporter strain is almost complete and screening for inhibitors of the Rcs phosphorelay could identify molecules that could serve as lead compounds in the development of a novel antibiotic therapy.