title: Rescuing chemotaxis of the anticancer agent Salmonella enterica serovar Typhimurium VNP20009.
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.
authors.affiliation: Department of Biological Sciences, Life Sciences I, Virginia Polytechnic Institute and State University, Blacksburg, VA 24,061, USA.
authors.forename: Katherine M
authors.initials: KM
authors.lastname: Broadway
authors.affiliation: Department of Biological Sciences, Life Sciences I, Virginia Polytechnic Institute and State University, Blacksburg, VA 24,061, USA.
authors.forename: Elizabeth A P
authors.initials: EA
authors.lastname: Denson
authors.affiliation: Department of Biological Sciences, Life Sciences I, Virginia Polytechnic Institute and State University, Blacksburg, VA 24,061, USA.
authors.forename: Roderick V
authors.initials: RV
authors.lastname: Jensen
authors.affiliation: Department of Biological Sciences, Life Sciences I, Virginia Polytechnic Institute and State University, Blacksburg, VA 24,061, USA. Electronic address: bscharf@vt.edu.
authors.forename: Birgit E
authors.initials: BE
authors.lastname: Scharf
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D002633:Chemotaxis / Q000187:drug effects*; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D019779:Salmonella enterica / Q000166:cytology* / Q000187:drug effects*; D017422:Sequence Analysis, DNA
chemical_list: D000970:Antineoplastic Agents
keywords: Bacterial cancer therapy; Chemotaxis; Flagellar motor; Tumor-colonizing bacteria