The motility behavior on soft agar plate of up-motile derivatives of MotAS and MotPB. A. Spreading of Δ ABΔ PS (negative control), MotAS-Spac (initial isolate), and MotAS-M (up-motile derivative) after 36 h of incubation at 37 C on TY medium plus 200mM NaCl, pH 8.5, without (left) or with (right) 0.6 mM IPTG, and solidified with 0.3% agar. B. Spreading of Δ ABΔ PS (negative control), MotPB-Spac (original isolate), and MotPB-M (up-motile derivative) after 24 h of incubation at 37 C on TY, pH 6.0, without (left) or with (right) 0.6 mM IPTG and solidified with 0.3% agar.