Submitted to: Meeting Abstract
Publication Type: Other
Publication Acceptance Date: 9/27/2000
Publication Date: N/A
Technical Abstract: Pasteurella haemolytica is the agent associated with bovine respiratory disease also known as shipping fever. Economic losses due to shipping fever cost the livestock industry one billion dollars annually. Although several commercial and experimental vaccines are available, none are completely effective. We therefore chose to study the production of microbial factors that are produced under different growth conditions and evaluate their immunoreactivity. We believe that immunoreactive products could be valuable as vaccine components. We chose to look at growth conditions and production of microbial factors produced under iron limitation. The production of inducible siderophores under iron limitation is one mechanisms pathogenic organisms use to acquire iron. Organisms belonging to the family of Pasteurellaceae, however, do not produce siderophores. The second known mechanism of iron acquisition depends on the induction of outer membrane and periplasmic transport proteins. In this presentation, we show evidence that under iron limitation P. haemolytica produces outer membrane receptors as well as periplasmic transport proteins, but no siderophores. The periplasmic transport proteins, 31- and 35-kDa proteins, have been purified and characterized. They are expressed only when Fe(III) and Fe(II) are absent and repressible when these metal ions are present. Other divalent metal ions do not repress the production of the transport proteins. Their secondary structure differs as well as their immunoreactivity with sera from convalescent cattle. We also investigated the nature of the activity that releases iron from transferrin and found a membrane-bound ferric reductase that uses flavin mononucleotide and NADH as co-factors.