S. Karen Collinson

Azotobacter vinelandii strains of disparate origin produce azotobactin siderophores with identical structures

SummaryThe yellow green fluorescent siderophore, azotobactin, was purified from cultures of twoAzotobacter vinelandii strains. Structural analysis of azotobactin from the North AmericanA. vinelandii strains O and its capsule negative variant UW (also called OP) revealed that both strains produced azotobactins with identical structures. Moreover, azotobactin produced by these two strains was structurally identical to azotobactin D, the fluorescent siderophore previously isolated from the EuropeanA. vinelandii strain D (CCM 289). Unlike strains of fluorescentPseudomonas which produce structurally diverse pyoverdins, strains ofA. vinelandii of disparate origin produced azotobactins of identical structure. Lactonization of azotobactin did not interfere with the ability of this compound to function as a siderophore.

CHARACTERIZATION OF THE AGFBA FIMBRIAL OPERON ENCODING THIN AGGREGATIVE FIMBRIAE OF SALMONELLA ENTERITIDIS

Of the several fimbrial types produced by the human enteropathogen Salmonella enteritidis, the thin aggregative fimbriae, SEF17, are particularly interesting being highly immunogenic, aggregative, extremely stable, cell surface structures which are widely distributed among Salmonella serovars (Collinson et al., 1991; Doran et al., 1993). These fimbriae are composed of a 17,000 Da fimbrin, AgfA, and require treatment with 90% formic acid before depolymerization occurs (Collinson et al., 1991). Diarrheagenic Escherichia coli strains produce biochemically and serologically related, thin, aggregative fimbriae (Collinson et al., 1992) called curli which are composed of polymerized CsgA fimbrins (Arnqvist et al., 1994). An agfA-specific, oligonucleotide probe capable of distinguishing agfA from csgA forms the basis for a valuable, new, Salmonella-specific, diagnostic test (Doran et al., 1993). The role(s) of SEF17 in Salmonella pathogenesis remain(s) to be elucidated but purified SEF17 binds fibronectin in vitro suggesting a possible role in facilitating bacterial-tissue interactions (Collinson et al., 1993).

Structure of azoverdin, a pyoverdin-like siderophore of Azomonas macrocytogenes ATCC 12334

Abstract The structure of azoverdin, the major peptidic siderophore of Azomonas macrocytogenes ATCC 12334, was elucidated using FAB-MS and high field NMR techniques. It is a chromopeptide possessing at its N-terminal end a fluorescent chromophore derived from 2,3-diamino-6,7-dihydroxyquinoline and at its C-terminal end 2,4-diaminobutyric acid in the lactam from (cDab). The other amino acids are: homoserine (2), N δ -acetyl,N δ -hydroxyornithine (2) and serine (1). The structure of azoverdin is (Succinamide)-Chromophore-(L)-Hse-(D,L)-N δ Acetyl,N δ OHOrn-(D)-Ser-N δ Acetyl,N δ OHOrn-(D)-Hse-(L)-cDab.