(A) The effect of the addition of different six-carbon sugars and hexamines at 2% to YP base medium. H99 was cultured on YP, YP+Glc (glucose), YP+Gal (galactose), YP+Inositol, YP+GlcNMe (N-Methyl-glucosamine), YP+GlcNAc (N-Acetyl-glucosamine), YP+GlcN (glucosamine), and YP+2-Dexoyl-Glc (2-Deoxyl-glucose) for 7 days. (B) The dose-dependent effect of glucosamine on self-filamentation in H99. H99 was cultured on YP+GlcN at final concentration of 0, 0.2%, 0.5%, 1%, and 2% for 7 days. (C) The inhibitory effect of other carbon sources on GlcN-induced filamentation. H99 was cultured on the indicated media for 7 days. H99 cultured on YP+GlcN (2%) was used as control. Other carbon sources, such as glucose, galactose, or N-Acetyl-glucosamine (2%) were added to the YP+GlcN medium. (D) The effect of glucosamine on filamentation is not specific to H99. 92BC2-45 (serotype A), 92BC2-11 (serotype A), 93BC1-53 (serotype D), 35–20 VNI (serotype A), 98BC1-50 (serotype D), Bt3 strain (serotype A), and XL280α (serotype D) were cultured on YP+GlcN medium for 7 days.