Cryptic plasmid of Neisseria gonorrhoeae: complete nucleotide sequence and genetic organization

Abstract

The naturally occurring cryptic plasmid pJDl of Neisseria gonorrhoeae is 4,207 base pairs long and is found in about 96% of gonococcal strains. The total probable coding capacity of pJDl was determined from the complete nucleotide sequence by using computational probes to identify open reading frames with similar codon usage and by screening for the presence of ribosomal binding sites before the start codons. Candidates for promoters and terminators were also found in the sequence. Based on these findings, we propose a model for the genetic organization of the plasmid. The model predicts two transcriptional units, each composed of five compactly spaced genes. A promoter of one of the transcripts was shown to function in Escherichia coli, and the products of three of the five genes in this operon were identified in minicell expression experiments. Of these, the cppA gene encoded a 9-kilodalton protein, and the cppB and cppC genes both coded for 24-kilodalton proteins. No expression of the other transcriptional unit was detected, but two genes in this operon were expressed in minicells when transcribed from an E. coli promoter. The experimental data were consistent with the model.

Molecular models accounting for the gene conversion reactions mediating gonococcal pilin antigenic variation

“…Different HV L sequences show minimal sequence conservation but are all flanked by the conserved sequences cys1 and cys2 which encode conserved cysteine residues. Finally, the 3 H portion of the gene encodes the hypervariable tail (HV T ) (Hagblom et al, 1985;Segal et al, 1986;Seifert, 1996). Each member of the pilin gene family has also been described as having six variable minicassettes of defined sizes, mc1±mc6, that move as units to mediate pilin Av (Haas and Meyer, 1986).…”

“…10 23 recombinants per cell per generation during in vitro growth (Serkin and Seifert, 1998), and at even higher levels when the bacteria are iron starved . The high frequency, the relatively small segments of silent copy DNA (16± 450 bp) that are transferred during each recombination event (Hagblom et al, 1985;Haas and Meyer, 1986) and the ability to recombine pilin sequences without being able to form extensive regions of heteroduplex all make it unlikely that this system relies solely on homologous recombination functions.…”

Identification of acquired DNA inNeisseria lactamica

“…However, the amount of horizontally transferred DNA in N. meningitidis MC58 was estimated to be over 20% (Nakamura et al, 2004), which may indicate that the threshold of 90% was too conservative. Plasmid pNL01 displays high nucleotide identity to pJD1 previously isolated from N. gonorrhoeae (Korch et al, 1985). Together, this suggests acquisition of this plasmid by a neisserial species and exchange between members of Neisseriae.…”

Isolation of bacterial extrachromosomal DNA from human dental plaque associated with periodontal disease, using transposon-aided capture (TRACA)

“…A putative replication (Rep) protein was identified in all except one (pTRACA61) of the plasmids isolated in this study ( Table 1). The Rep from pTRACA45 shares 71% amino acid identity to that of pJD1, a 4.2-kb cryptic plasmid from Neisseria gonorrhoeae (Korch et al, 1985). Furthermore, the two additional ORFs on pTRACA45 are also closely related to those on pJD1 (Table 1), while its G1C content (50.6%) is similar to that of pJD1 (51.5%) and the genomes of Neisseria spp.…”