Figure 6.

Proposed long-chain polyamine (LCPA) biosynthesis pathway in A. flavithermus. Enzymatic reactions are shown as arrows and labeled with A. flavithermus gene products, predicted to catalyze these reactions. Proteins detected on the two-dimensional gels are shown in color: those that were up-regulated after incubation for 8 hours in the presence of 10.7 mM silica are indicated in red; Aflv_2750, whose expression was down-regulated, is indicated in green; blue color indicates proteins whose expression remained unchanged; and black color indicates proteins that were not detected on the two-dimensional gels. The functions of Aflv_0146 as arginase, Aflv_1886 as arginine decarboxylase, Aflv_0024 as ornithine decarboxylase, Aflv_2749 as agmatinase, Aflv_2750 as spermidine synthase, and Aflv_1437 as spermine synthase have been biochemically confirmed.