FIG. 6.

Analysis of in vitro spore germination pathways utilized by B. anthracis. Spores of parent strain B. anthracis, B. anthracis MIGD101, and B. anthracis ΔgerHA were treated with germinants and cogerminants that stimulate each of the known germination pathways. Spores were incubated in PBS with different germinants at the following concentrations: l-alanine, 0.5 mM; inosine, 1 mM; and all other amino acids (L-proline, l-tryptophan, etc.), 50 mM unless otherwise noted. Germination was monitored spectrophotometrically by changes of refractive index at an optical density at 600 nm for 60 min. The results are the average of three experiments and, for all pathways, the standard deviation did not exceed 2% from the average value and therefore is not presented in the graphs. (A) l-Alanine (0.5 mM); (B) alanine (Ala) pathway (50 mM l-alanine); (C) alanine-proline (AP) pathway (0.5 mM l-alanine, 50 mM l-proline); (D) aromatic amino acid-enhanced alanine (AEA) pathway (0.5 mM l-alanine, 50 mM l-tryptophan); (E) amino acid and inosine dependent pathway (AAID-1) (1 mM concentration of inosine pairs, 0.5 mM l-alanine); (F) 50 mM l-proline pathway (50 mM l-proline); (G) AAID-2 pathway (1 mM inosine, 50 mM l-tryptophan).