Abstract
144 Adhesive organelles of bacterial pathogens are crucial virulence factors, mediating attachment to the target cells of their hosts and initiating infectious process. They also are involved in biofilm formation making bacteria more resistant to immune response. Gram-negative pathogens possess two major classes of proteinaceous adhesins [1]: • The fimbrial adhesive organelles, represented by the linear homopolymers or hete ro polymers (up to 7 distinct subunits) of hundreds to thousands of protein subunits; • The non-fimbrial adhesins consisted of a single protein or homotrimers. The superfamily of fimbrial organelles, assembled by the chaperone/usher (CU) machinery, is divided in two functionally distinct families: monoadhesins and polyadhesins [1, 2]. Monoadhesins comprises in main the thick rigid and thin flexible adhesive pili of a complex subunit composition (up to 7 distinct subunits), which typically display only one adhesive domain on the tip of the pilus. The assembly of monoadhesins is assisted with the FGS (having a short F1-G1 loop) class of periplasmic chaperones [3, 4]. The monoadhesins are encoded in main by the gene clusters of the γ1-, γ2-, γ4-, and γ-monophyletic groups [5]. Polyadhesins, typically, have non-pilus, amorphous or capsule-like morphology. They either comprise homopolymers, which consist of only one type of subunit, or heteropolymers, which consist up to 6 distinct subunits. The notable property of polyadhesins is that all subunits of homopolymers or one of the main structural subunits of heteropolymers possesses one or two independent binding sites specific to different host cell receptors [1, 2]. Assembly of one subfamily of polyadhesins is assisted with the FGL (having a long F1-G1 loop) class of periplasmic chaperones [3, 4]. FGL chaperone-assembled polyadhesins are encoded exclusively by the gene cluster of the UDK 577.083.3+579.84
Highlights
Е mail: vlazav@utu. fi Received 08.07.2013 The rapid emergence of treatment-resistant bacterial pathogens has become a major threat to public health
Enterotoxigenic E. coli (ETEC), E. coli strains producing enterotoxins, are the most common cause of diarrheal disease in children living in endemic areas, as well as children and adults traveling to these areas
280–400 million enterotoxigenic E. coli (ETEC)-associated diarrhea cases occur annually in children younger than 5 years old, plus 100 million more cases in children older than 5 years, which results in approximately 300,000–500,000 deaths annually [132]
Summary
Adhesive organelles of bacterial pathogens are crucial virulence factors, mediating attachment to the target cells of their hosts and initiating infectious process They are involved in biofilm formation making bacteria more resistant to immune response. FGS chaperone-assembled polyadhesins are encoded in main by the gene cluster of the κ-monophyletic group [5]. The polyadhesin-binding to the target cells triggers subversive signal by aggregation of host cell receptors that allow pathogens to mislead and evade immune defense [1, 2] Their binding is orchestrated with the type III secretion system, which is extremally important for bacterial virulency [8]. The recently accumulated significant knowledge on different aspects of biogenesis of the growing family of Gram-negative polyadhesins and their clinical applications requires a new analysis and generalization
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