Abstract
Mycoplasma pneumoniae strains traditionally are divided into two types, based on sequence variation in the P1 gene. Recently, however, we have identified 8 P1 subtypes by restriction fragment length polymorphism analysis. In the present study the P1 gene sequences of three P1 type 1 and two P1 type 2 M. pneumoniae strains were analyzed. A new P1 gene sequence in a type 1 strain with partial similarity to a recently reported variable region in the P1 gene of an M. pneumoniae type 2 strain (T. Kenri, R. Taniguchi, Y. Sasaki, N. Okazaki, M. Narita, K. Izumikawa, M. Umetsu, and T.Sasaki, Infect. Immun. 67:4557-4562, 1999) was identified. In addition, the P1 gene of the type 1 strain contained another region with nucleotide polymorphisms identical to a stretch in the P1 gene of one of our type 2 strains. These findings indicate that recombination between sequences specific for P1 type 1 and type 2 had occurred and that P1 type 1 and type 2 hybrid sequences can be present within the P1 gene of an individual strain. Identical or nearly identical variable P1 gene sequences were present in several repetitive regions outside the P1 gene locus in the genome of M. pneumoniae strain M129, implying recombination as a mechanism for generation of the P1 gene variation. Additionally, in the P1 gene sequences of four of the five strains studied, single-nucleotide polymorphisms different from the previously reported P1 type 1 and 2 characteristic sequences were identified. The polymorphic sites are candidate targets for genotyping of M. pneumoniae by direct sequencing of amplicons from clinical specimens.
Highlights
Mycoplasma pneumoniae is a common cause of respiratory infections in humans
We used an extended panel of restriction enzymes in PCR-RFLP analysis, and we recently reported that five subtypes could be discriminated among 13 P1 type 1 strains and that three subtypes could be discriminated among 8 P1 type 2 strains [6]
The promoter and terminator regions of the P1 gene sequences of all five strains were identical to the corresponding regions in the P1 gene sequence of strain M129, the strain used to sequence the entire M. pneumoniae genome [29]
Summary
Mycoplasma pneumoniae is a common cause of respiratory infections in humans. Colonization of the respiratory epithelium by M. pneumoniae is mediated by the attachment organelle, a terminal tip structure of M. pneumoniae cells [17]. Studies showed the existence of only two P1 gene types among M. pneumoniae clinical isolates [22, 27]. We used an extended panel of restriction enzymes in PCR-RFLP analysis, and we recently reported that five subtypes could be discriminated among 13 P1 type 1 strains and that three subtypes could be discriminated among 8 P1 type 2 strains [6]. These findings indicate that more variation in the P1 gene sequence exists than previously anticipated. In order to analyze P1 gene sequence variability, we performed sequence analysis of the P1 genes of two M. pneumoniae reference strains and three M. pneumoniae clinical isolates with variable P1 genes as detected by our PCR-RFLP [6]
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