RpoN is not required for chitobiose utilization. Growth of B. burgdorferi strain RR22 in BSK-II lacking GlcNAc and supplemented with 75 μM chitobiose. Late-log phase cells were diluted to 1.0 × 105 cells ml-1 in the appropriate medium (closed circle, 1.5 mM GlcNAc; open circle, No addition, i.e. without GlcNAc; closed triangle, 75 μM chitobiose), incubated at 33°C and enumerated daily as described in the Methods. This is a representative experiment that was repeated three times.