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Pili and Hosts
Published in Paul Pumpens, Single-Stranded RNA Phages, 2020
These conjugative plasmids from Gram-negative bacteria directed the synthesis of the extracellular pili which had an essential role in the recognition of recipient cells and the establishment of cell-to-cell contact, as well in the adsorption of the RNA phages. The pilin subunits, namely the structural units of the pili, often shared no similarity. For simplicity, pili were classified into two broad morphological groups: long flexible (1 μm) and short rigid (0.1 μm). Long pili were like those expressed by cells carrying the F plasmid. Short pili were expressed by plasmids of the IncN, IncP, and IncW incompatibility groups. Some plasmids (Inc groups I1, I2, I5, B, K, and Z) encoded both long and short pili (Encyclopedia of Life Sciences, 2008, p. 2208).
Host Defense II: Acquired Immunity
Published in Constantin A. Bona, Francisco A. Bonilla, Textbook of Immunology, 2019
Constantin A. Bona, Francisco A. Bonilla
Borrelia burgdorferi (which causes Lyme disease) possesses about 25 copies of genes encoding the immunodominant variable major protein. It also appears to undergo genetic drift in the Osp B outer membrane protein. Neisseria gonorrheae pili are a major target for antibody production. The pilin protein is also encoded by multiple genes which are sequentially activated. Gonococci use a similar mechanism where new genes are inserted into an expression site. However, this bacterium often uses exogenous DNA from dead disrupted gonococci for gene conversion.
Neisseria gonorrhoeae
Published in Peter M. Lydyard, Michael F. Cole, John Holton, William L. Irving, Nino Porakishvili, Pradhib Venkatesan, Katherine N. Ward, Case Studies in Infectious Disease, 2010
Peter M. Lydyard, Michael F. Cole, John Holton, William L. Irving, Nino Porakishvili, Pradhib Venkatesan, Katherine N. Ward
The pilin (PilE) protein contains a constant N-terminal domain, a hyper-variable C-terminal domain, and several variable regions termed mini-cassettes, which are encoded by genes with varying DNA sequence. The gonococcus has a single complete copy of the pilin gene termed pilE but as many as 15 truncated genes with variable DNA sequence. The truncation is at the 5′ end, resulting in lack of the sequence encoding the N-terminal constant domain and promoter elements. These truncated genes are termed pilS (silent) and form the pilS locus. By recombination of pilS sequences into the pilE gene the bacterium can express a high number of antigenically distinct pili. In addition to antigenic variation the pili undergo phase variation. In phase variation the bacterium has the ability to turn pilus expression on or off at a high frequency.
High throughput and targeted screens for prepilin peptidase inhibitors do not identify common inhibitors of eukaryotic gamma-secretase
Published in Expert Opinion on Drug Discovery, 2023
Pradip Kumar Singh, Michael S. Donnenberg
Type 4 pili (T4P) are retractile filamentous surface appendages present in numerous Gram-positive and Gram-negative bacteria as well as archaea [1–3]. T4P have many functions, including twitching motility, surface attachment, DNA uptake, biofilm formation, host colonization, auto-aggregation, and environmental sensing. In several bacterial pathogens, such as enteropathogenic Escherichia coli (EPEC), Vibrio cholerae, Pseudomonas aeruginosa, Neisseria meningitidis, N. gonorrhoeae, and Clostridioides difficile, T4P may play a role in pathogenesis [4,5]. The T4P of EPEC and V. cholerae are proven virulence factors in experimental human infection [6,7]. The filament of T4P is composed of pilin proteins in a helical array, and its biogenesis requires a complex multi-protein machine that spans the cytoplasmic membrane and, in Gram-negative bacteria, the outer membrane [8]. Pilin protein is synthesized as a prepilin, which has a class III N-terminal signal peptide sequence. Cleavage of this signal sequence is required before the pilin can be incorporated into the growing pilus [9–11]. A dedicated prepilin peptidase (PPP) cleaves the leader sequence of the prepilin and, in many cases, methylates the nascent N-terminal residue [12–14]. Deletion or active-site mutations in PPP genes preclude T4P expression [11,13,15,16].
Mycobacterial biofilms as players in human infections: a review
Published in Biofouling, 2021
Esmeralda Ivonne Niño-Padilla, Carlos Velazquez, Adriana Garibay-Escobar
Structures of importance in motile species are often overlooked in mycobacteria. Pili have been described as contributors to M. tuberculosis in vitro biofilm formation through the expression of Rv3312A (Ramsugit et al. 2013), whose protein product was later identified during infection, evidenced by serological reactions in patients with TB (Alteri et al. 2007). In that study, pilin protein subunit from pili was confirmed to bind laminin (Ln), a component of the eukaryotic extracellular matrix targeted for adhesion, colonization, and invasion of host tissues, particularly in mucosal-like environments in the respiratory tract (Singh et al. 2012). M. tuberculosis and M. smegmatis produce Ln-binding proteins to effectively achieve this process (Pethe et al. 2001; Esposito et al. 2008); however, it is believed that only MTBC members produce pili (Alteri et al. 2007). These facts imply that mycobacterial biofilms could interact with the host’s extracellular matrix. In addition, pili were found to participate in the adhesion of alveolar epithelial cells (Ramsugit et al. 2015).
Abundant production of exopolysaccharide by EAEC strains enhances the formation of bacterial biofilms in contaminated sprouts
Published in Gut Microbes, 2018
Quintin Borgersen, David T. Bolick, Glynis L. Kolling, Matthew Aijuka, Fernando Ruiz-Perez, Richard L. Guerrant, James P. Nataro, Araceli E. Santiago
We sought to determine if CA in EAEC 042 and 227-11 participates in the formation and maturity of biofilm structures on sprouts (Fig. 7). Alfalfa and broccoli sprouts pre-sterilized with bleach were inoculated with 1 × 104 CFU of the EAEC strains and incubated a room temperature for 48 h, then examined by scanning electron microscopy. Uninoculated sterile sprouts were maintained under the same experimental conditions and used as a negative control (Fig. 7A and G). We observed large biofilm structures on sprouts inoculated with wild type 042 and 227-11 strains (Fig. 7B, C, H, I, J and M). Deletion in wcaE or wcaF-wza region appeared to have a reduced biofilm formation on the sprouts (Fig 7D, K and N). Complementation of wcaE in trans restored biofilm formation to wild type levels (Fig 7L, and O). E. coli HS is incapable of producing CA and showed poor biofilm formation (Fig 7F). We observed the presence of fimbrial structures and CA in the biofilm structures on sprouts (white arrows). Deletion of the major pilin subunit of the AAF/II fimbriae of EAEC 042 appeared to reduce biofilm formation in sprouts (Fig. 7E).