Characterization of FtsZ-Associated Proteins in Streptomyces Species

Streptomyces coelicolor is a Gram-positive filamentous, sporulating soil bacterium. The large 9.7 Mb linear genome has been sequenced and supplements the already extensive genetic studies. Most prokaryotes use FtsZ to divide and it is the first protein to localize to the division site to initiate division. ZipA and FtsA are the first division proteins to bind directly to FtsZ in Escherichia coli tethering it to the inner membrane, but homologs are not present in S. coelicolor. Since many other homologs of cell division proteins are shared between E. coli, B. subtilis, and S. coelicolor, the absence of ZipA and FtsA raises questions about how FtsZ is tethered to the cell membrane in S. coelicolor. Using in vitro biochemical and molecular techniques, including affinity blots, I was unable to identify novel FtsZ-associated proteins in S. coelicolor, S. venezuelae, and S. griseus. From the affinity blots, I identified by MALDI-TOF possible contaminants that could interact with another protein in the purified FtsZ preparation or the antibody serum. Finally, I created a deletion-insertion mutant and an unmarked deletion mutant of ylmF in S. coelicolor, which is involved in septum formation and was shown to interact directly with FtsZ in B. subtilis. Both mutants were incapable of sporulating, and produced the blue-pigmented antibiotic actinorhodin, which is indicative of some cell division defects. The insertion-deletion mutant resembled depletion and overexpression mutants of an essential downstream gene, divIVA, while the unmarked mutant produced large and undivided aerial filaments