Mosaic-like organization of IgA protease genes in Neisseria gonorrhoeae generated by horizontal genetic exchange in vivo.

Abstract

IgA protease is a putative virulence factor that exists in several allelic forms in Neisseria gonorrhoeae. However, extracellular secretion of these variant IgA proteases occurs by the same pathway involving three steps of autoproteolytic maturation from a large precursor. Two principal precursor types (H1 and H2) can be distinguished with respect to the location of autoproteolytic sites and the sizes of the mature products. By partial DNA sequence analysis, additional variations have been detected which are not unique to one particular gene; rather, otherwise unrelated iga genes often share homology, thus revealing a composite organization. In the context of other gonococcal features, this observation implies that recombination has occurred in vivo between iga genes of different strains, probably via the route of species‐specific DNA transformation. This process may be of general significance for the modulation and the natural exchange of virulence properties among pathogenic Neisseriae.

Molecular polymorphism and epidemiology of Neisseria meningitidis immunoglobulin A1 proteases.

“…Among the three 6-base restriction enzymes used to examine all 133 strains, Pst I cleaved the iga gene at three sites (Fig. 1), in agreement with published physical maps of gonococcal and meningococcal iga genes (10,14,17). More than 20 distinct arrangements of Pst I recognition sites were detected in the iga gene region.…”

“…1). Halter et al (14) recently differentiated gonococcal iga genes into two types, Hi and H2, on location of the autoproteolytic sites and by size of the a and f3 proteins (Fig. 1) immune-escape purpose, as appears true for several other virulence factors in gonococci and meningococci (22).…”

The UspA1 Protein and a Second Type of UspA2 Protein Mediate Adherence of Moraxella catarrhalis to Human Epithelial Cells In Vitro

“…In contrast, the 3Ј end of each uspA1 and uspA2 gene is highly conserved, as is the 5Ј end of each gene, including the beginning of the ORF. This clustering of sequence polymorphisms amidst two highly conserved regions is reminiscent of the mosaic structure described for ORFs that encode surface-exposed proteins of other bacterial pathogens, including Neisseria meningitidis (23,29), E. coli (30), and Neisseria gonorrhoeae (17). In these examples, horizontal genetic exchange has been proposed as the major mechanism by which mosaic genes are generated.…”

The physical map of the chromosome of a serogroup A strain of Neisseria meningitidis shows complex rearrangements relative to the chromosomes of the two mapped strains of the closely related species N. gonorrhoeae

“…Although the gonococcal maps for strains FA1090 and MS11 are nearly identical (11,26), other gonococcal strains differ in the arrangement of rRNA operons on the chromosome (24). The natural competence of both meningococci and gonococci for genetic transformation may contribute to variability in chromosome organization as well as to the formation of mosaic genes containing information from different sources (28,33,37,47,55,70,82,95). Although we have not yet identified the endpoints of the rearranged segments of gonococcal or meningococcal DNA or the mechanisms by which such rearrangements are generated, the propensity of pathogenic Neisseria species to undergo such rearrangements may have important consequences for the evolution and pathogenic potential of these bacteria.…”

“…Neisseria spp. are naturally competent for genetic transformation (12), and genetic exchange occurs between pathogenic and commensal Neisseria species, between gonococci and meningococci, and among meningococcal strains (28,33,37,47,55,70,82,95). The impact of frequent recombination and horizontal genetic exchange events on the organization of the gonococcal and meningococcal chromosomes is not known.…”