Sequence Diversity and Molecular Evolution of the Heat-Modifiable Outer Membrane Protein Gene ( ompA ) of Mannheimia ( Pasteurella ) haemolytica , Mannheimia glucosida , and Pasteurella trehalosi

Abstract

The OmpA (or heat-modifiable) protein is a major structural component of the outer membranes of gramnegative bacteria. The protein contains eight membrane-traversing ␤-strands and four surface-exposed loops. The genetic diversity and molecular evolution of OmpA were investigated in 31 Mannheimia (Pasteurella) haemolytica, 6 Mannheimia glucosida, and 4 Pasteurella trehalosi strains by comparative nucleotide sequence analysis. The OmpA proteins of M. haemolytica and M. glucosida contain four hypervariable domains located at the distal ends of the surface-exposed loops. The hypervariable domains of OmpA proteins from bovine and ovine M. haemolytica isolates are very different but are highly conserved among strains from each of these two host species. Fourteen different alleles representing four distinct phylogenetic classes, classes I to IV, were identified in M. haemolytica and M. glucosida. Class I, II, and IV alleles were associated with bovine M. haemolytica, ovine M. haemolytica, and M. glucosida strains, respectively, whereas class III alleles were present in certain M. haemolytica and M. glucosida isolates. Class I and II alleles were associated with divergent lineages of bovine and ovine M. haemolytica strains, respectively, indicating a history of horizontal DNA transfer and assortative (entire gene) recombination. Class III alleles have mosaic structures and were derived by horizontal DNA transfer and intragenic recombination. Our findings suggest that OmpA is under strong selective pressure from the host species and that it plays an important role in host adaptation. It is proposed that the OmpA protein of M. haemolytica acts as a ligand and is involved in binding to specific host cell receptor molecules in cattle and sheep. P. trehalosi expresses two OmpA homologs that are encoded by different tandemly arranged ompA genes. The P. trehalosi ompA genes are highly diverged from those of M. haemolytica and M. glucosida, and evidence is presented to suggest that at least one of these genes was acquired by horizontal DNA transfer.Mannheimia (Pasteurella) haemolytica is a commensal of cattle, sheep, and other ruminants, but it also causes bovine and ovine pneumonic pasteurellosis (infecting the respiratory tract), which is responsible for considerable economic losses to the cattle and sheep industries (6,20,21). The organism consists of genetically distinct subpopulations that are differentially adapted to and elicit disease in either cattle or sheep (11,14). M. haemolytica possesses various putative virulence determinants (23), including a transferrin receptor (38, 59) and a leukotoxin (26, 49) which are specific for ruminant transferrin (38, 59) and lymphoid cells (4, 7, 27, 49), respectively, and are thought to contribute to the organism's host specificity. However, the molecular basis of host adaptation in the bovine and ovine lineages of M. haemolytica remains largely unclear. Mannheimia glucosida was previously recognized as the A11 serotype of M. haemolytica and represents a heterogeneous group of organ...

Proteomic Investigation of Photorhabdus Bacteria for Nematode-Host Specificity

“…Transfer of X. nematophila nilABC genes into two species of Xenorhabdus that did not colonize S. carpocapsae (X. poinarii and X. bovienii) enabled these species to symbiotically colonize S. carposapsae [18]. Similarly, in the Gram-negative bacteria, protein OmpA constitutes the outer membranes [26]. OmpA has many functions, including adherence to host tissues in several pathogenic bacteria (summarized in [26]).…”

“…Similarly, in the Gram-negative bacteria, protein OmpA constitutes the outer membranes [26]. OmpA has many functions, including adherence to host tissues in several pathogenic bacteria (summarized in [26]). Difference in OmpA hypervariable domains has been linked to host specificity between cattle and sheep isolates of Mannheimia (Pasteurella) haemolytica, M. glucosida, and P. trehalosi [26].…”

“…OmpA has many functions, including adherence to host tissues in several pathogenic bacteria (summarized in [26]). Difference in OmpA hypervariable domains has been linked to host specificity between cattle and sheep isolates of Mannheimia (Pasteurella) haemolytica, M. glucosida, and P. trehalosi [26]. Therefore, it is possible that Photorhabdus OmpA might be important in establishing symbiosis and host specificity with their nematode-hosts.…”

Serotypic diversity and sequence variation of the ompA gene among Mannheimia haemofytica isolates from domestic ruminants

“…The adherence of respiratory pathogens to the mucosal epithelium is critical in host colonization and infection (Beachey 1981). Based on sequence homology, Davies and Lee (2004) suggested that the OmpA of M haemolytica is involved in binding to bovine and ovine receptors, thus playing an important role in the colonization of the respiratory tracts of cattle and sheep. It has also been demonstrated that OmpA shows a specific interaction with the extracellular matrix (EMC) protein fibroncctin (Lo and Sorenscn 2007) and that it contributes to adher ence of M. haemolytica to bovine bronchial epithelial cells (BBEC) in vitro (Kisiela and Czuprynski 2009).…”

“…It has been shown that the majority of polymorphic nucleotide sites in the ompA gene of M haemolytica occurs in four hypcrvariablc domains within the surface-exposed loops (Davies and Lee 2004).…”