Adherence of Mycoplasma hyopneumoniae to the swine respiratory tract is mediated by the membrane protein P97. This protein is located on the outer membrane surface, and its role in adherence has been firmly established. The general region of P97 that mediates adherence to swine cilia is thought to be the R1 region near the carboxy terminus of the protein, but it was not clear if this region could mediate adherence to swine cilia independently of other P97 sequences. To examine this in more detail, a series of R1 repeat sequences containing different numbers of repeating units cloned in frame with lacZ was used to produce R1-␤-galactosidase fusion proteins. These proteins were then tested for adherence to swine cilia and for reactivity to the adherence-blocking monoclonal antibody F2G5 and convalescent-phase swine sera. In this way it was possible to accurately define the cilium binding epitope of P97 and the minimal epitope recognized by antibody. Our results indicate that eight R1 repeating units are required for cilium binding and that three repeating units are needed for antibody recognition. These results could lead to more effective therapeutic measures against this important swine pathogen.Attachment to host tissue is essential for colonization by most mucosal pathogens, including mycoplasmas (1, 2). The best-defined mycoplasmal adhesins, those of Mycoplasma pneumoniae and Mycoplasma genitalium, are found in a specialized attachment organelle (8). It is clear from numerous studies that their adhesins work in concert with other membrane proteins and accessory factors in a coordinated fashion to form the attachment organelle structure (8). Thus, the process of adherence in these species is multifactorial, requiring both membrane proteins and cytoskeletal elements (8). Most mycoplasmas, however, lack specialized attachment organelles like M. pneumoniae, and consequently, their adherence mechanisms differ. How most mycoplasma species adhere to their respective host tissues is largely unknown, and the genetic mechanisms of adherence are poorly defined.As the etiological agent of porcine mycoplasma pneumonia and a major component of the porcine respiratory disease complex, Mycoplasma hyopneumoniae continues to present significant problems for the swine industry. As is the case for many other mycoplasmal species, it is host specific (for swine), it has no readily apparent external structures or organelles that could be used for attachment, there are no genetic systems for analyzing the adherence phenotype, and studies of adherence have been largely qualitative rather than quantitative in nature. For instance, M. hyopneumoniae closely adheres to swine respiratory epithelium both in vivo and in vitro (3, 9). It has also been demonstrated that M. hyopneumoniae can attach to pig and human lung fibroblasts, to pig kidney cells in culture (15), and to turkey red blood cells (12).Our interests in adherence mechanisms as the prelude to colonization and disease led us to take advantage of the available adherence-blocking ...

The P97 adhesin and P102 genes of Mycoplasma hyopneumoniae each have six paralogs in the genome. We tested whether these genes were expressed during infection. P102 is associated with the mycoplasma and with swine cilia. Further, most of the paralogs were transcribed in vivo in two gene transcriptional units.

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~ LITERATURE REVIEW 1 General Information 1 Molecular Characteristics Genome Alternate codon usage Disease Pathology LITERATURE REVIEW General Information Mycoplasmas, members of the class Mollicutes, are the smallest free-living organisms known. They are unique among the prokaryotes since all mycoplasmas lack cell walls (74). Mycoplasmas are widespread in nature as parasites of humans, mammals, birds, reptiles, fish, arthropods, and plants (73). The primary habitats of human and animal mycoplasmas are the mucous surfaces of the respiratory and urogenital tracts, the eyes, alimentary canal, mammary glands, and joints (76). While mycoplasmas usually exhibit a rather strict host and tissue