Characterization of a two-component regulatory system from Acinetobacter baumannii that controls biofilm formation and cellular morphology.

Acinetobacter baumannii forms biofilms on abiotic surfaces, a phenotype that may explain its ability to survive in nosocomial environments and to cause device-related infections in compromised patients. The biofilm proficiency of the 19606 type strain depends on the production of pili, cell-surface appendages assembled via the CsuAB-A-B-C-D-E chaperone-usher secretion system. The screening of a bank of isogenic insertion derivatives led to the identification of a biofilm-deficient derivative in which a transposon insertion disrupted a gene predicted to encode the response regulator of a two-component regulatory system.

Binding specificity of Salmonella plasmid-encoded fimbriae assessed by glycomics.

The Salmonella enterica serotype Typhimurium (S. Typhimurium) genome encodes 12 intestinal colonization factors of the chaperone/usher fimbrial assembly class; however, the binding specificity is known for only one of these adhesins, known as type 1 fimbriae. Here we explored the utility of glycomics to determine the carbohydrate binding specificity of plasmid-encoded fimbriae from S.

Identification of Francisella tularensis Himar1-based transposon mutants defective for replication in macrophages.

Francisella tularensis, the etiologic agent of tularemia in humans, is a potential biological threat due to its low infectious dose and multiple routes of entry. F. tularensis replicates within several cell types, eventually causing cell death by inducing apoptosis.

Sequence and organization of pMAC, an Acinetobacter baumannii plasmid harboring genes involved in organic peroxide resistance.

Acinetobacter baumannii 19606 harbors pMAC, a 9540-bp plasmid that contains 11 predicted open-reading frames (ORFs). Cloning and transformation experiments using Acinetobacter calcoaceticus BD413 mapped replication functions within a region containing four 21-bp direct repeats (ori) and ORF 1, which codes for a predicted replication protein. Subcloning and tri-parental mating experiments mapped mobilization functions to the product of ORF 11 and an adjacent predicted oriT.

Salmonella enterica serotype Typhimurium MisL is an intestinal colonization factor that binds fibronectin.

MisL is an autotransporter protein encoded by Salmonella pathogenicity island 3 (SPI3). To investigate the role of MisL in Salmonella enterica serotype Typhimurium (S. Typhimurium) pathogenesis, we characterized its function during infection of mice and identified a host receptor for this adhesin.

The siderophore-mediated iron acquisition systems of Acinetobacter baumannii ATCC 19606 and Vibrio anguillarum 775 are structurally and functionally related.

The Acinetobacter baumannii type strain, ATCC 19606, secretes acinetobactin, a catechol siderophore highly related to the iron chelator anguibactin produced by the fish pathogen Vibrio anguillarum (Listonella anguillarum). This paper reports the initial characterization of the genes and gene products involved in the acinetobactin-mediated iron-acquisition process. Insertional mutagenesis resulted in the isolation of several derivatives whose ability to grow in medium containing the iron chelator 2,2'-dipyridyl was affected.

Analysis of pVU3695, a plasmid encoding glutathione-dependent formaldehyde dehydrogenase activity and formaldehyde resistance in the Escherichia coli VU3695 clinical strain.

The formaldehyde resistance of Escherichia coli VU3695 is due to the expression of glutathione-dependent formaldehyde dehydrogenase (GSH-FDH) activity, which is encoded by the adhC gene located on the plasmid pVU3695. Conjugation of this plasmid to an unrelated PolA deficient strain of E. coli indicated that it encodes its own replication initiation protein and does not confer resistance to several other antimicrobial agents tested in this work.

Attachment to and biofilm formation on abiotic surfaces by Acinetobacter baumannii: involvement of a novel chaperone-usher pili assembly system.

Acinetobacter baumannii causes severe infections in compromised patients, survives on abiotic surfaces in hospital environments and colonizes different medical devices. In this study the analysis of the processes involved in surface attachment and biofilm formation by the prototype strain 19606 was initiated. This strain attaches to and forms biofilm structures on plastic and glass surfaces, particularly at the liquid-air interface of cultures incubated stagnantly.

Detection and analysis of iron uptake components expressed by Acinetobacter baumannii clinical isolates.

The Acinetobacter baumannii 19606 prototype strain produces a 78-kDa iron-regulated outer membrane protein immunologically related to FatA, which is required for iron acquisition by the fish pathogen Vibrio anguillarum via the anguibactin-mediated system. This A. baumannii strain also secretes histamine, a biosynthetic precursor of the siderophore anguibactin.

Genetic organization of an Acinetobacter baumannii chromosomal region harbouring genes related to siderophore biosynthesis and transport.

The Acinetobacter baumannii 8399 clinical isolate secretes dihydroxybenzoic acid (DHBA) and a high-affinity catechol siderophore, which is different from other bacterial iron chelators already characterized. Complementation assays with enterobactin-deficient Escherichia coli strains led to the isolation of a cosmid clone containing A. baumannii 8399 genes required for the biosynthesis and activation of DHBA.

Genetic and phenotypic analysis of Acinetobacter baumannii insertion derivatives generated with a transposome system.

Acinetobacter baumannii is a metabolically versatile pathogen that causes severe infections in compromised patients. However, little is known about the genes and factors involved in its basic physiology and virulence properties. Insertion mutagenesis was used to initiate the identification and characterization of some of these factors and genes in the prototype strain 19606.

Acinetobacter baumannii has two genes encoding glutathione-dependent formaldehyde dehydrogenase: evidence for differential regulation in response to iron.

The adhC1 gene from Acinetobacter baumannii 8399, which encodes a glutathione-dependent formaldehyde dehydrogenase (GSH-FDH), was identified and cloned after mapping the insertion site of Tn3-HoHo1 in a recombinant cosmid isolated from a gene library. Sequence analysis showed that this gene encodes a protein exhibiting significant similarity to alcohol dehydrogenases in bacterial, yeast, plant and animal cells. The expression of the adhC1 gene was confirmed by the detection of GSH-FDH enzyme activity in A.