Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Veterinary Microbiology and Preventive Medicine

First Advisor

Gregory Phillips


The ftsYEX operon of Escherichia coli historically has been described as a cluster of essential cell division genes. Filamentation temperature-sensitive (fts) designates a class of mutants that displays normal cell morphology at the permissive temperature of 30°C, but filaments and dies at the restrictive temperature of 42°C. The first gene, ftsY, is known to encode an essential component of a protein localization system first described in eukaryotes, the signal recognition particle (SRP) pathway. The function of the following genes, ftsE and ftsX, are much less understood. It has been shown that FtsE and FtsX comprise a two-component ATP-binding cassette (ABC) transporter, but the substrate is unknown. Constructing a null mutant of ftsE, I have demonstrated that ftsE is not an essential gene, although viability depends upon the concentration of NaCl or other compounds in the growth medium. In the characterization of this ftsE mutant, it was found that several predominant proteins were missing in this mutant when compared to wild-type protein profiles. Contrary to previous speculation, we have shown that the cell division septation machinery appears to be intact in an ftsE null mutant and it remains capable of forming septa. Regulation of the ftsYEX operon was investigated with the use of gene fusions. We have also constructed a plasmid shuffling system for the isolation of new mutants to further study the function of this operon. E. coli strains exhibiting a salt-dependent temperature-sensitive phenotype were also identified and investigated. This dissertation summarizes the scientific characterization of the ftsYEX operon of E. coli.



Digital Repository @ Iowa State University,

Copyright Owner

Becky Graham



Proquest ID


File Format


File Size

150 pages