Essential gaps in key Y. pestis CO92 metabolic pathways. A. The last step during each fatty acid elongation cycle involves the reduction of an enoyl-ACP intermediate. In other Enterobacteria such as E. coli and S. Typhimurium, FabI catalyzes this step; however, the current annotation of the YP CO92 genome does not contain fabI. B. The enzyme ArgD catalyzes the sixth step in the nine-step lysine biosynthesis pathway, but argD (YPO0170) is disrupted in YP CO92. YPO1962 has the greatest homology to YPO0170 within the Y. pestis CO92 genome, and we hypothesize here that YPO1962 can replace the function of YPO0170. Note: although each reaction in each pathway is depicted as unidirectional, some are reversible.