We examined 46 isolates of Borrelia burgdorferi, the etiologic agent of Lyme disease and related disorders, with polyacrylamide gel electrophoresis and monoclonal antibodies. Our attention was on the OspA proteins, which are major proteins of the spirochete. There were at least four discernible phenotypes of the OspA protein. While 25 North American isolates were, with one exception, homogeneous in the type of OspA protein that they produced, 21 European isolates were heterogeneous in the types of OspA proteins represented. Only three European strains resembled North American strains in their OspA phenotype. Application of a deoxyribonucleic acid probe for an ospA gene demonstrated that the arrangement of ospA-associated sequences in the DNA differed between isolates.

A gene bank of DNA from the Lyme disease spirochete was constructed in the plasmid pBR322. Plasmid pTRH32, a recombinant that in Escherichia coli expresses the two major outer surface proteins of the Lyme disease spirochete, was identified. One of the recombinant products, designated OspA, represents a surface protein that appears to be common to all Lyme disease spirochetes, whereas the other recombinant product, designated OspB, represents a more variable surface protein. This recombinant plasmid provides a foundation for future studies on the epidemiology and pathogenesis of Lyme disease as well as on the genetic organization of the etiologic agent.

Mutants of Pseudomonas aeruginosa are described which are markedly deficient in alkaline protease production. Characterization of these mutants in vitro suggests that the mutations in two of these strains are specific for alkaline protease production. Examination of these mutants in a mouse eye model demonstrates that alkaline protease is required for the establishment of corneal infections with P. aeriuginosa PA103. Mutants deficient in alkaline protease production could not colonize traumatized cornea and did not produce the corneal damage characteristic of infection by the parental strain. Addition of subdamaging amounts of alkaline protease to eyes infected with the protease-deficient mutants resulted in infections which were indistinguishable from infections caused by the parental strain.

OspA and OspB are major outer membrane proteins and antigens of the Lyme disease spirochete, Borrelia burgdorferi. We examined the organization of ospA and ospB, the genes encoding these proteins. The location and direction of transcription of each osp gene was determined by subcloning, deletion analysis, and transposon Tn5 mutagenesis. Transposon Tn5 insertions within the ospA gene abrogated expression of ospB, suggesting that these genes are transcribed from a common promoter. Northern blot analysis of mRNA from B. burgdorferi with two DNA probes individually specific for ospA or ospB identified a 2.2-kilobase transcript that hybridized with each probe. These studies indicate that the two osp genes of B. burgdorferi constitute a single transcriptional unit.