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Escherichia coli: Structure, Function, and Toxoid Vaccine Development
Published in Yoshikatsu Murooka, Tadayuki Imanaka, Recombinant Microbes for Industrial and Agricultural Applications, 2020
W. Neal Burnette, Witold Cieplak, Harvey R. Kaslow, Rino Rappuoli, Elaine I. Tuomanen
One strategy for producing nontoxic analogues involves recombinant site-specific modification of the B oligomer of CT and LT so that these moieties are no longer capable of binding to target cells; several such B oligomer analogues have been produced by Holmes and co-workers [131,132]. An alternative method, employed for the genetic inactivation of PT (see foregoing), is to alter the sequence of the Al polypeptide so that its catalytic ADP-ribosyltransferase activity is reduced or eliminated. The results of such efforts with CT are best considered in light of previous studies with other ADP-ribosyltransferase toxins, such as PT, ETA, and DT [for reviews and discussions, see Refs. 7,144,145]. Each of these toxins uses NAD as the ADP-ribose donor and thus share a functional relationship; nevertheless, the protein substrates they modify are generally quite distinct. Cholera toxin and the LTs ADP-ribosylate an arginine residue in Gsa [1,127,146]; in contrast, PT modifies a cysteine and prefers inhibitory G proteins (GiO) involved in regulation of adenylate cyclase [14]. Exotoxin A and DT regulate translation of mRNA by ADP-ribosylating elongation factor 2 at a unique diphthamide residue found thus far only in this protein [7,145].
Involvement of Pseudomonas aeruginosa in the occurrence of community and hospital acquired diarrhea, and its virulence diversity among the stool and the environmental samples
Published in International Journal of Environmental Health Research, 2022
Parisa Fakhkhari, Elahe Tajeddin, Masoumeh Azimirad, Siavosh Salmanzadeh-Ahrabi, Ahya Abdi-Ali, Bahram Nikmanesh, Babak Eshrati, Mohammad Mehdi Gouya, Parviz Owlia, Mohammad Reza Zali, Masoud Alebouyeh
Although P. aeruginosa is an agent linked to the gastrointestinal infections, it generally causes diseases in exraintestinal sites. P. aeruginosa exploits some virulence factors to establish its infection in the lung (Ballok and O’Toole 2013). P. aeruginosa exotoxins have several functions, including Adenosine diphosphate (ADP)-ribosyltransferase (such as Exotoxin A), cytotoxic (such as pyocyanin), and proteolytic (such as elastase that degrades host defenses) activities (Shi et al. 2012). This bacterium encodes a type III secretions system, a system that can inject toxic effector proteins into the cytoplasm of eukaryotic cells. Currently, four effector proteins are defined in P. aeruginosa: ExoU, ExoS, ExoT, and ExoY. These effector proteins modulate host cell functions, change cytoskeletal organization, and signal transduction. While most of P. aeruginosa strains carry exoT and exoY genes, exoS and exoU show diversity among the isolates.
Characterization of Pseudomonas aeruginosa isolated from various environmental niches: New STs and occurrence of antibiotic susceptible “high-risk clones”
Published in International Journal of Environmental Health Research, 2020
Asma Bel Hadj Ahmed, Mohamed Salah Abbassi, Beatriz Rojo-Bezares, Lidia Ruiz-Roldán, Rabii Dhahri, Ines Mehri, Yolanda Sáenz, Abdennaceur Hassen
Pseudomonas aeruginosa is a versatile, aerobic, non-fermentative, and opportunistic pathogen responsible for a wide spectrum of infections often seen in immuno-compromised and critically ill patients as well as individuals with cystic fibrosis, burns or chronic wounds (Gellatly and Hancock 2013). P. aeruginosa is widely recovered from the environment that is capable of colonizing a number of wet and moist sites in plants and soils and a wide variety of aquatic environments (Bédard et al. 2016). Treatment of P. aeruginosa infections has become a great challenge due to the ability of this bacterium to resist many of the currently available antibiotics especially carbapenem drugs. Moreover, excessive use of antibiotics during treatment accelerates development of multidrug-resistant strains, leading to the ineffectiveness of the empirical antibiotic therapy against this microorganism. P. aeruginosa secretes several virulence factors, including bacterial cell-surface factors and secreted factors that may contribute in its pathogenicity, and to combat the host defense mechanisms (Galle et al. 2012). In P. aeruginosa, the type III secretion system (T3SS) is the most important of the secreted virulence factors. This macromolecular syringe system consists of 43 coordinately regulated genes that encode components of the secretion apparatus, a translocon, and factors that regulate secretion (Galle et al. 2012). The secretion apparatus exports toxins across the bacterial cell envelope, whereas the translocon is responsible for injecting these toxins into the host cell. Four secreted toxins have been identified: ExoS, ExoT, ExoU, and ExoY, which are rarely all present in one strain and different strains have either the exoS or the exoU gene (Galle et al. 2012). The elastase B (also called LasB protease and pseudolysina), encoded by lasB gene, is involved in pathogenesis by degradation of human immunologically competent particles such as complement components, cytokines, and immunoglobulins IgA and IgG. The Exotoxin A, encoded by the exoA gene, is also considered as a major virulence factor playing a key role in cell death (Jaffar-Bandjee et al. 1995). In addition, among the P. aeruginosa virulence factors, pigments such as pyocyanin, pyoverdine, pyorubin, and pyomelanin (Visca et al. 2007; Rodriguez-Rojas et al. 2009) play an important role. Finally, in P. aeruginosa, the quorum sensing systems (Las and Rhl) have the mission of regulating the expression levels of various virulence genes. The LasR system controls the Rhl transcriptional activator gene, rhlR, at transcriptional and posttranscriptional levels (Tashiro et al. 2013).