Lipopolysaccharide biosynthesis genes in koala type I Chlamydia: cloning and characterization
A.A. Girjes ^(1, 3)(*), EN. Carrick ^(2) and M.F. Lavin ^(1, 4)
1 Queensland Cancer Fund Research Unit, Queensland Institute of Medical Research, Bancroft Centre, 300 Herston Road, Brisbane 4029 (Australia),
2 Department of Zoology,
3 Department to Anatomical Sciences, University of Queensland, St Lucia, Brisbane 4072 (Australia), and
4 Department of Surgery, University of Queensland, Clinical Science Building, Royal Brisbane Hospital, Herston, Brisbane 4029 (Australia)
We showed in 1966 that there are two strains of Chlamydia psittaci which infect the koala (Phascolarctos cinereus). In order to further investigate the role of these chlamydial strains in pathogenesis, we have attempted to identify genes of koala type I strain chlamydia which are involved in the immunogenic response. Transformation of Escherichia coli with a plasmid containing a 6.3-kb fragment (pKOC-10) of C. psittaci DNA caused the appearance of a specific chlamydial lipopolysaccharide (LPS) epitope on the host strain. The smallest DNA fragment capable 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 gseA genes of C. pneumoniae, C. psittaci 6BC and C. trachomatis, and the kdtA gene of E. coli which code for transferases catalysing the addition 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, within the 2.4-kb fragment, were evident, and mRNA species corresponding to these ORFs were detected by Northern analysis. Both ORF1 and ORF2 are required for the appearance of chlamydia-specific LPS on the surface of recombinant E. coli.