Genetic basis for lipopolysaccharide O-antigen biosynthesis in bordetellae.

Bordetella bronchiseptica and Bordetella parapertussis express a surface polysaccharide, attached to a lipopolysaccharide, which has been called O antigen. This structure is absent from Bordetella pertussis. We report the identification of a large genetic locus in B. bronchiseptica and B. parapertussis that is required for O-antigen biosynthesis. The locus is replaced by an insertion sequence in B. pertussis, explaining the lack of O-antigen biosynthesis in this species. The DNA sequence of the B. bronchiseptica locus has been determined and the presence of 21 open reading frames has been revealed. We have ascribed putative functions to many of these open reading frames based on database searches. Mutations in the locus in B. bronchiseptica and B. parapertussis prevent O-antigen biosynthesis and provide tools for the study of the role of O antigen in infections caused by these bacteria.

The organization of the gamma-glutamyl transferase genes and other low copy repeats in human chromosome 22q11.

A clone map consisting of YACs, cosmids, and fosmids has been constructed covering low copy repeat regions of human chromosome 22q11. A combination of clone restriction digest analysis, single-copy landmark content analysis, HindIII-Sau3AI fingerprinting, and sequencing of PCR products derived from clones was required to resolve the map in this region. Seven repeat-containing contigs were placed in 22q11, five containing gamma-glutamyl transferase (GGT) sequences described previously. In one case, a single interval at the resolution of the YAC map was shown to contain at least three GGT sequences after higher resolution mapping. The sequence information was used to design a rapid PCR/restriction digest technique that distinguishes the GGT loci placed in the YAC map. This approach has allowed us to resolve the previous cDNA and mapping information relating to GGT and link it to the physical map of 22q11.