Transformation-mediated exchange of virulence determinants by co-cultivation of pathogenic Neisseriae

Abstract

The horizontal flow of genetic material between microbes utilizes three principal routes: conjugation, transduction and transformation. While the significance in nature of the first two pathways is generally accepted, the in vivo role of transformation remains uncertain, despite the early observations by Griffith in 1928 on the transformation of streptococci from an avirulent to a virulent state [1]. Recently, circumstantial evidence was collected suggesting a role for transformation-mediated horizontal exchange in the modulation of virulence determinants of pathogenic Neisseriae and the variation of surface structures. In order to further assess the significance of transformation-mediated exchange we performed simple co-cultivation experiments of different Neisseria strains. We observed an efficient intra- and interspecies transfer of essential virulence determinants; the process was sensitive to the presence of DNaseI in the culture and was blocked in transformation-deficient recipients.

Invasive meningococcal disease associated with a very high case fatality rate in the North-West of Poland

“…Both isolates were characterized by ST3698 but they belonged to two different serogroups, C and B. Although capsular switching as a result of the horizontal transfer of siaD genes has been already described in N. meningitidis isolates in vitro and in vivo , this is the first report of capsule replacement in Polish meningococci (Frosch & Meyer, 1992; Swartley et al , 1997; Kertesz et al , 1998; Alcala et al , 2002; Stefanelli et al , 2003). It was not possible to establish the direction of the capsular switching, because even in this study we found the isolate of ST2177, a single variant locus of ST3698, with the phenotype B:NT:P1.6.…”

“…Because there is no vaccine available against serogroup B meningococci, the C to B capsular switching may have a greater impact for public health, especially if it expresses the same epidemic potential as its serogroup C variant. The phenomenon of the capsule switching has been mostly reported after mass vaccination campaigns; however, it is also known that genetic variants of different serogroups may be produced randomly in a meningococcal population, independent of a vaccination pressure (Frosch & Meyer, 1992; Alcala et al , 2002). This may be the case in our study, because in Poland a mass vaccination against serogroup C meningococci was never implemented.…”

Regulation of capsule inNeisseria meningitidis

“…Transformation and recombination events influence expression of meningococcal capsule (Frosch&Meyer, 1992). Co-colonization of different serogroup strains in the human nasopharynx and genetic exchange of the cps gene clusters by transformation and allelic-exchange result in “capsule switching” in vivo (Swartley et al, 1997).…”

Sequential action of factors involved in natural competence for transformation of Neisseria gonorrhoeae

“…Thus, natural transformation accounts for the rapid exchange and adaptation of virulence factors [2] and antibiotic resistances [3] by generating mosaic genes [3-51, for the exhaustive linkage equilibrium of genetic markers within the N. gonorrhoeae population [6], and contributes as a mechanism of pilin variation to the remarkable structural and antigenic diversity of pili [7-91. The early description of transformation-deficient mutants by Biswas et al [lo] led to a dissection of the transformation process into two steps, a DNA uptake step whereby the transforming DNA is converted to a DNase-resistant state, and any subsequent events. Like many bacterial pathogens, N. gonorrhoeae is naturally competent for DNA transformation [ 11.…”