LIPOPOLYSACCHARIDE BIOSYNTHESIS GENES IN KOALA TYPE-I CHLAMYDIA - CLONING AND CHARACTERIZATION

We showed in 1988 that there are two strains of Chlamydia psittaci whi ch infect the koala (Phascolarctos cinereus). In order to further inve stigate the role of these chlamydial strains in pathogenesis, we have attempted to identify genes of koala type I strain chlamydial which ar e involved in the immunogenic response, Transformation of Escherichia coli with a plasmid containing a 6.3-kb fragment (pKOC-10) of C. psitt aci DNA caused the appearance of a specific chlamydial lipopolysacchar ide (LPS) epitope on the host strain. The smallest DNA fragment capabl e of inducing the expression of chlamydial LPS was an Xbal fragment, 2 .4 kb in size (pKOC-5). DNA sequence analysis of the complete fragment revealed regions of high identity, at the amino acid level, to the gs eA genes of C. pneomoniae, C. psittaci 6BC and C. trachomatis, and the kdtA gene of E. coli which code for transferases catalysing the addit ion of 3-deoxy-D-manno-octulosonic acid (Kdo) residues to lipid A. Two open reading frames (ORFs) of 1,314 and 501 nucleotides in size, with in the 2.4-kb fragment, were evident, and mRNA species corresponding t o these ORFs were detected by Northern analysis. Both ORF1 and ORF2 ar e required for the appearance of chlamydia-specific LPS on the surface of recombinant E. coli.