The Thin Pili of Acinetobacter sp. Strain BD413 Mediate Adhesion to Biotic and Abiotic Surfaces

Abstract

Two structurally different appendages, thin and thick pili, are found in members of the genus Acinetobacter. The presence of pilus structures correlates with different phenotypes, such as adherence to surfaces, a trait not only observed in pathogenic Acinetobacter species, as well as motility. However, their distinct individual roles were unknown. To characterize the role of different pili in the physiology of Acinetobacter, we isolated the thin pili from the cell surface of Acinetobacter sp. strain BD413 (recently recognized as representative of Acinetobacter baylyi), a soil bacterium that rapidly takes up naked DNA from its environment. Electron microcopy revealed that the pilus has an external diameter of 2 to 3 nm for single filaments. The filaments are packed into right-handed bundles. The major protein constituting the pilus was purified, and the encoding gene, acuA, was cloned. AcuA was found to be weakly related to the structural subunit of F17 pili of Escherichia coli. Analyses of the acuA flanking DNA region led to the identification of three closely associated genes, acuD, acuC, and acuG, whose deduced proteins are similar to chaperone, usher, and adhesin of F17-related pili, respectively. Transcriptional analyses revealed that acuA expression is maximal in the late-stationary-growth phase. Mutation of acuA led to a loss of thin pili and concomitantly loss of adhesion to polystyrene and erythrocytes but not loss of competence. Therefore, thin pili of Acinetobacter sp. strain BD413 are suggested to be assembled by the chaperone/usher pathway and are involved in adherence to biotic and abiotic surfaces.

Evolution of the Chaperone/Usher Assembly Pathway: Fimbrial Classification Goes Greek

“…6). The acuADCG operon encodes thin (2-to 3-nm) fimbriae that are packed into right-handed bundles (110). The fimABCD operon of B. pertussis (201,(355)(356)(357) encodes serotype 2 fimbriae, which have diameters of 5 to 6 nm and are composed of a helical shaft containing 2.5 copies of the major subunit per turn (313).…”

Fourier Transform Infrared Spectroscopy for Rapid Identification of Nonfermenting Gram-Negative Bacteria Isolated from Sputum Samples from Cystic Fibrosis Patients

“…It has been reported that these fibers are expressed or coexpressed by most of the gram-negative bacteria present in the lungs of CF patients (P. aeruginosa, Burkholderia spp., S. maltophilia, and Acinetobacter spp.) (15,19,21) and that a single pilus is a polymer formed by an ordered association of thousands of identical proteinaceous subunits (pilin), which might be glycosylated (4, 6, 42). Therefore, we studied the spectral heterogeneity obtained after the removal of these pilus or flagella fibers from bacterial cells by vigorous shaking and subsequent centrifugation (21,44).…”

“…Before the spectra were b All clinical isolates were identified by use of the API or the Vitek system and the nine additional phenotypic tests indicated in Materials and Methods (19). BCC clinical isolates were further identified by recA PCR-RFLP analysis with primers BCR1 and BCR2 and the HaeIII restriction enzyme, followed by recA PCR with species-specific primers (50).…”

Safety Assessment of Transgenic Organisms, Volume 4

“…Adherence occurs with various mechanisms including general hydrophobicity, production of extracellular polysaccharides and presence of specialized adherence structures. For example, in Acinetobacter, at least two appendages have been observed (thin and thick pili), and in A.baylyi BD413 thin pili appear to be involved in adherence to biotic and abiotic surfaces (Gohl et al, 2006). In Acinetobacter sp.…”