Mice injected with either of two monoclonal antibodies specific for the 0 polysaccharide of Brucella abortus prior to challenge infection had viable counts in spleens and livers significantly below those in control groups 1 and 4 weeks later. Two monoclonal antibodies specific for the porin of B. abortus failed to confer protection.

The omp2 locus of Brucella abortus is composed of two closely related genes (omp2a and omp2b) that encode, and potentially both express, homologous porin proteins. Genetic variation at this locus is revealed in the form of restriction-fragment-length polymorphisms which can be used to distinguish the type strains of all six Brucella species. Five of the six species contain single copies of omp2a and omp2b, whereas Brucella ovis appears to have two copies of the omp2a gene. The implications of these results with regard to the physiological functions of the omp2a and the omp2b gene products, phylogeny of the genus, and species-specific adaptation are discussed.

Uroporphyrinogen III methylase was purified from a recombinant hemB-strain of E. coli harbouring a plasmid containing the cysG gene. N-terminal analysis of this purified protein gave an amino acid sequence corresponding to that predicted from the genetic code. From the u.v./visible spectrum of the reaction catalysed by this SAM dependent methylase it was possible to observe the sequential appearance of the chromophores of a dipyrrocorphin and subsequently of a pyrrocorphin. Confirmation of this transformation was obtained from W-NMR studies when it was demonstrated, for the first time directly, that uroporphyrinogen is initially converted into dihydrosirohydrochlorin (precorrin-2) and then, by further methylation, into a novel trimethylpyrrocorphin.

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The cloning of the gene(s) encoding a 36-kilodalton (kDa) cell envelope protein of BruceUa abortus has been previously described (T. A. Ficht, S. W. Bearden, B. A. Sowa, and L. G. Adams, Infect. Immun. 56:2036Immun. 56: -2046Immun. 56: , 1988. In an attempt to define the nature of the previously described duplication at this locus we have sequenced 3,500 base pairs of genomic DNA encompassing this region. The duplication represented two similar open reading frames which shared more than 85% homology at the nucleotide level but differed primarily because of the absence of 108 nucleotides from one of the two gene copies. These two genes were read from opposite strands and potentially encoded proteins which are 96% homologous. The predicted gene products were identical over the first 100 amino acids, including 22-amino-acid-long signal sequences. The amino acid composition of the predicted proteins was similar to that obtained for the Brucella porin isolated by Winter, Infect. Immun. 35:979-989, 1982) and presumably represented two copies of the porin gene, tentatively identified as omp 2a (silent) and omp 2b (expressed). The homology between the two genes extended to and included Shine-Dalgarno sequences 7 base pairs upstream from the ATG start codons. Homology at the 3' ends extended only as far as the termination codon, but both genes had putative rho-independent transcription termination sites. Localization of the promoters proved more difficult, since the canonical procaryotic sequences could not be identified in the region upstream of either gene. Promoter activity was MATERIALS AND METHODSBacterial strains and cultivation. B. abortus smooth strains 19 and 2308 were obtained from Billy Deyoe at the National 3281 on August 4, 2020 by guest http://iai.asm.org/ Downloaded from (XAR-5; Eastman Kodak Co.) for 24 to 48 h. RESULTS Restriction mapping. Genomic recombinants in X2001 containing Brucella DNA inserts of approximately 20 kbp were INFECT. IMMUN. on August 4, 2020 by guest http://iai.asm.org/ Downloaded from