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Infection and Immunity, January 2007, p. 113-121, Vol. 75, No. 1
0019-9567/07/$08.00+0 doi:10.1128/IAI.01016-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

and
Bradford W. Gibson1,4*
The Buck Institute for Age Research, Novato, California 94945,1 Columbus Children's Research Institute,2 Department of Pediatrics, The Ohio State University, Columbus, Ohio 43205-2696,3 Department of Pharmaceutical Chemistry, University of California, San Francisco, California 941434
Received 28 June 2006/ Returned for modification 25 August 2006/ Accepted 29 August 2006
Haemophilus ducreyi is a gram-negative bacterium that is the causative agent of chancroid. Strain 35000HP has been well characterized and is representative of the majority of H. ducreyi strains. Strain 35000HP produces a lipooligosaccharide (LOS) that contains D-glycero-D-manno-heptose in the main oligosaccharide chain extension; the lbgB gene has been shown to encode the DD-heptosyltransferase. The lbgB gene is found in a gene cluster together with the lbgA gene, which encodes for the galactosyltransferase I. These two genes are flanked by two housekeeping genes, rpmE and xthA, encoding the ribosomal protein L31 and the exonuclease III, respectively. Recently, a second group of H. ducreyi strains have been identified. Strain 33921, a representative of the class II strains, produces an LOS that lacks DD-heptose in the oligosaccharide portion of its LOS. To better understand the biosynthesis of the DD-heptose-deficient 33921 LOS, we cloned and sequenced the corresponding lbgAB genomic region from strain 33921. Similar to strain 35000HP, the 33921 genome contains xthA and rpmE. However, between these two genes we identified genes encoding two putative glycosyltransferases that were not highly homologous to the 35000HP lbgAB genes. In this study, we demonstrate that the product of one of these genes encodes a galactosyltransferase. In addition, dot blot hybridization determined that 3 of 35 strains tested had the atypical transferases present, as did 4 strains characterized as class II strains by other criterion. These data indicate that the lbgAB genes can serve as one indicator of the classification of H. ducreyi strains.
Published ahead of print on 9 October 2006.
Present address: USAMRIID, 1425 Porter St., Ft. Detrick, MD 21702.
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