Comparative proteomic analysis of a Haemophilus parasuis SC096 mutant deficient in the outer membrane protein P5

Outer membrane protein A (OmpA) is a major structural component of the outer membranes and functions as a multifaceted molecular with many diverse roles in Gram-negative bacteria. In Haemophilus parasuis, OmpA has been recognized and named as OmpP5 in genomic literature. In this study, to determine the precise functions of OmpP5, an ompP5 deficient mutant (ΔompP5) of a H. parasuis serovar 4 filed strain SC096 was constructed using a natural transformation method. Compared to the wild-type SC096 strain, the ΔompP5 mutant displayed a detectable delay in growth. However, the wild-type and mutant strains were indistinguishable with respect to the other phenotypes including resistance to killing by porcine and rabbit sera, adhesion to and invasion of porcine umbilicus veins endothelial cells (PUVEC) and porcine kidney epithelial cells (PK-15). To analyze the differences of proteome expression between wild-type and mutant strains, a 2-dimensional gel electrophoresis (2-DE)-based proteomics comparison was performed. There were 24 differentially expressed proteins which were mainly involved in carbohydrate, lipid, nucleotide and amino acid metabolism, or served as transcription and translation factors and chaperone proteins. Collectively, loss of OmpP5 expression in the H. parasuis SC096 strain resulted in global protein expression changes which might be responsible for novel phenotypes occurred in ΔompP5 mutant.