Cross-complementation between the products of the genes P1 and ORF6 of Mycoplasma pneumoniae subtypes 1 and 2

Abstract

The genes P1 (MPN141) and ORF6 (MPN142) are essential for the successful colonization of the human respiratory tract by Mycoplasma pneumoniae. Both genes are located in the P1 operon, which consists of three genes. The P1 gene is the second gene in the operon, followed by the ORF6 gene. The P1 gene contains two (RepMP2/3, RepMP4) and the ORF6 gene one (RepMP5) specific repetitive DNA sequence, of which seven to nine similar but not identical copies are dispersed on the genome. Despite this large potential pool for genetic variation, M. pneumoniae isolates from patients contain only one of two distinct combinations of the genes P1 and ORF6. To analyse the functions of the repetitive DNA sequences, two 'new' combinations of the genes P1 and ORF6 were constructed, keeping the P1 gene constant but exchanging RepMP5 copies of the ORF6 gene. M. pneumoniae was transformed with these constructs and the transformants were tested for their ability to grow and survive under in vitro conditions and in guinea pigs. The two transformants colonized the respiratory tract of guinea pigs and showed no obvious differences in their growth behaviour compared to M. pneumoniae isolates from patients. The results indicate that the subtype-specific combinations of the repetitive elements in the P1 and ORF6 genes are not essential for the successful adherence of M. pneumoniae to host cells and the colonization of the respiratory tract of guinea pigs.

Mycoplasma pneumoniae Large DNA Repetitive Elements RepMP1 Show Type Specific Organization among Strains

“…Impressively, regardless of the presence of this intricate network, our data provide further evidence for the existence of two highly conserved groups of M. pneumoniae strains as demonstrated in the past [12], [34], [35]. Previous experiments clearly indicate that type-specific combinations of the repetitive elements in the P1 and mpn142 genes are not essential for the successful adherence of M. pneumoniae to host cells and the colonization of the respiratory tract of guinea pigs [36]. Therefore, M. pneumoniae virulence does not seem to be considerably influenced by the strictly defined combination of repetitive elements and further studies are required to explain and understand reason(s) behind this lack of sequence divergence.…”

Variation in a surface-exposed region of the Mycoplasma pneumoniae P40 protein as a consequence of homologous DNA recombination between RepMP5 elements

“…The significance of (the variable number of) these repeats is not yet known, in particular because the elements in which they reside have not been shown to be translated into protein. However, it is interesting to note that the part of RepMP5-b that contains the trinucleotide tandem repeat from strain M129 has previously been cloned within the RepMP5-c element such as to mimic a putative recombination event within the MPN142 gene (Catrein et al, 2004). The recombinant M. pneumoniae strain carrying this modified MPN142 gene was found to be virulent in an animal model and to express both the P40 and the P90 protein (Catrein et al, 2004).…”

The gene mpn310 (hmw2) from Mycoplasma pneumoniae encodes two proteins, HMW2 and HMW2-s, which differ in size but use the same reading frame

“…Mycoplasma pneumoniae A3 is a transposon Tn4001‐derived gentamicin‐resistant mutant that neither synthesizes HMW2 and HMW2‐s nor adheres to plastic or glass (Krause et al , 1997). This mutant was grown nonadherently in glass flasks (Catrein et al , 2004). The yield was about 40 mg cells (wet weight) or about 3 mg of total protein from a 500‐mL culture.…”