Angel provided me with strain BE39. I would also like to thank all of the members of the Bobik lab for making the lab a pleasant working environment.



      The text of Chapter 3 in this dissertation, in part or in full, is a reprint of the

material as it appears in the Journal of Bacteriology (volume 184, pp. 1253-1261) and Figure 2-8 is from Journal of Bacteriology (volume 181, pp. 5973).