Fig. 1

Construction of aspA mutant of P. multocida C48–1. a Schematic showing deletion of the target aspA gene. b Agarose gel electrophoresis confirmed the genotype of the constructed mutant. The wild-type (WT) and mutant strains (MU) were identified using three primer pairs: T1/2, aspA1/2, and Kan1/2 and C standed for negative control. c Confirmation of the complemented strain by PCR (left) and RT-PCR (right). The WT, MU, CO (complemented strains) and CS (mutant strains harboring an empty vector) were identified using two primer pairs: M1/2 (outside the multiple cloning site of vector) and qaspA1/2