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Updated: Apr 6, 2026
Measuring Growth and Gene Expression Dynamics of Tumor-Targeted S. Typhimurium Bacteria
Published on: July 6, 2013
Rescuing chemotaxis of the anticancer agent Salmonella enterica serovar Typhimurium VNP20009
Katherine M Broadway1, Elizabeth A P Denson1, Roderick V Jensen1
1Department of Biological Sciences, Life Sciences I, Virginia Polytechnic Institute and State University, Blacksburg, VA 24,061, USA.
Abstract:
The role of chemotaxis and motility in Salmonella enterica serovar Typhimurium tumor colonization remains unclear. We determined through swim plate assays that the well-established anticancer agent S. Typhimurium VNP20009 is deficient in chemotaxis, and that this phenotype is suppressible. Through genome sequencing, we revealed that VNP20009 and four selected suppressor mutants had a single nucleotide polymorphism (SNP) in cheY causing a mutation in the conserved proline residue at position 110. CheY is the response regulator that interacts with the flagellar motor-switch complex and modulates rotational bias. The four suppressor mutants additionally carried non-synonymous SNPs in fliM encoding a flagellar switch protein. The CheY-P110S mutation in VNP20009 likely rendered the protein unable to interact with FliM, a phenotype that could be suppressed by mutations in FliM. We replaced the mutated cheY in VNP20009 with the wild-type copy and chemotaxis was partially restored. The swim ring of the rescued strain, VNP20009 cheY(+), was 46% the size of the parental strain 14028 swim ring. When tested in capillary assays, VNP20009 cheY(+) was 69% efficient in chemotaxis towards the attractant aspartate as compared to 14028. Potential reasons for the lack of complete restoration and implications for bacterial tumor colonization will be discussed.
Insights
Salmonella Typhimurium VNP20009
Area of Science:
- Microbiology
- Bacterial Motility
- Cancer Therapy
Background:
- Salmonella Typhimurium is investigated for cancer therapy.
- The role of bacterial chemotaxis and motility in tumor colonization is not fully understood.
- The VNP20009 strain, an anticancer agent, exhibits chemotaxis deficiencies.
Purpose of the Study:
- To investigate the genetic basis of chemotaxis deficiency in S. Typhimurium VNP20009.
- To identify suppressors of this chemotaxis-deficient phenotype.
- To understand the implications for bacterial tumor colonization.
Main Methods:
- Swim plate assays to assess chemotaxis.
- Genome sequencing to identify mutations.
- Capillary assays to measure chemotaxis efficiency.
- Genetic manipulation to restore wild-type gene function.
Main Results:
- VNP20009 has a single nucleotide polymorphism (SNP) in cheY, resulting in a mutation at proline 110 (CheY-P110S).
- Suppressor mutants exhibited additional SNPs in fliM, suggesting interaction between CheY and FliM.
- Restoring wild-type cheY partially restored chemotaxis, achieving 46% of the parental swim ring size and 69% chemotaxis efficiency towards aspartate.
Conclusions:
- The CheY-P110S mutation impairs chemotaxis in VNP20009, likely by disrupting CheY-FliM interaction.
- Mutations in FliM can suppress this defect.
- Partial restoration of chemotaxis suggests complex regulatory mechanisms influencing bacterial tumor colonization.
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