Elongation factor (EF-Tu) gene probe detects polymorphism inMycoplasmastrains

A putative transposase gene in the 16S–23S rRNA intergenic spacer region of Mycoplasma imitans

Examination of the nucleotide sequences of the 16S–23S intergenic transcribed spacer (ITS) region ofMycoplasma imitansandMycoplasma gallisepticumidentified a putative transposase gene located only in the ITS ofM. imitans, which can be used as a genetic marker to distinguish these two species. The relative size of the PCR products of the ITS region allowed a clear distinction to be made between strains ofM. imitansandM. gallisepticum, both of which could be readily discriminated from the type strains of all the other recognized avianMycoplasmaspecies. In addition, the putative transposase gene assigned in the ITS ofM. imitanswas shown to include a sequence homologous to that of the P75 gene ofM. gallisepticum. This is believed to be the first description of an insertion element in the rRNA operon region of a mycoplasma species.

Sequence and RFLP analysis of the elongation factor Tu gene used in differentiation and classification of phytoplasmas

Primers designed from sequences of the gene encoding the elongation factor Tu (tuf gene) of several culturable mollicutes amplified most of the tuf gene from phytoplasmas of the aster yellows, stolbur and X-disease groups. About 85% of the tuf gene from two aster yellows strains and a tomato stolbur phytoplasma was sequenced. The nucleotide sequence similarity between these related phytoplasmas was between 87.8 and 97.0%, whereas the homology with other mollicutes was 66.3-72.7%. The similarity of the deduced amino acid sequence was significantly higher, ranging from 96.0 to 99.4% among the phytoplasmas and 78.5% to 83.3% between phytoplasmas and the culturable mollicutes examined. From the nucleotide sequences of the phytoplasma strains, two pairs of primers were designed; one amplified the phytoplasmas of most phylogenetic groups that were established, the other was specific for the aster yellows and stolbur groups. The phytoplasmas of the various groups that were amplified could be distinguished by RFLP analysis using Sau3AI, Alul and HpaII. The aster yellows group could be divided into five Sau3AI RFLP groups. These results showed that the tuf gene has the potential to be used to differentiate and classify phytoplasmas. Southern blot analysis revealed that the tuf gene is present as a single copy.

Recombinant DNA probes and polymerase chain reaction for detection of Mycoplasma gallisepticum strains

Two recombinant DNA clones, pMG286.2 and pMG301.1, were isolated from the partial genomic library of Mycoplasma gallisepticum strain S6. Recombinant M. gallisepticum specific fragments were used as probes in Southern hybridisation with 10 M. gallisepticum strains whose DNA was digested by EcoRI, HindIII, BglII, RsaI and BamHI. The 1.5 kb fragment pMG301.1 did not show polymorphism in hybridisation patterns with M. gallisepticum strains, while the 3.5 kb fragment pMG286.2 enabled differentiation of M. gallisepticum strains into clusters. The DNA sequence of pMG301.1 was used to design a pair of 27-mer oligonucleotides flanking a 1.3 kb genomic region. These two primers directed specific in vitro amplification of all M. gallisepticum strains assayed giving an expected 1.3 kb product. Digestion of polymerase chain reaction products by DdeI enabled simple differentiation between clusters of M. gallisepticum strains and may be useful for improved epizootiological studies of M. gallisepticum infections in poultry.

Species-specific oligonucleotide probes complementary to 16S rRNA of Mycoplasma gallisepticum and Mycoplasma synoviae

Mycoplasma gallisepticum and M synoviae are important avian pathogens causing respiratory diseases which result in great economic losses in poultry farming. Two oligonucleotide probes, complementary to the variable region V8 of 16S rRNA from the avian mycoplasmas M gallisepticum and M synoviae have, therefore, been designed and used in direct filter hybridisation experiments. Both probes gave strong hybridisation signals with their homologous targets, whereas no cross-hybridisations were obtained with any of the other avian mycoplasmas tested. It was possible to detect 2-3 x 10(4) mycoplasma organisms by direct filter hybridisation experiments with radiolabelled probes. The probes were also used to analyse several laboratory strains and field isolates of M gallisepticum and M synoviae with complete agreement between the probe technique and the other methods used for species determination. Atypical M gallisepticum strains also gave strong hybridisation signals with the M gallisepticum specific probe.

Species differentiation of mycoplasmas by EF-Tu specific monoclonal antibodies

Ten mouse hybridoma cell lines producing IgG monoclonal antibodies to mycoplasmal elongation factor Tu (EF-Tu) were established. These mAbs showed different degrees of cross-reactivity between mollicutes and even other bacteria. This finding, indicating protein structure diversities of pan bacterial EF-Tu should permit species differentiation of mycoplasmas by epitope pattern analysis of a single protein. Epitope patterns of 23 mollicute type strains and of 40 M. hominis isolates were determined by ELISA. All M. hominis patterns were found to be closely related whereas intrageneric patterns differed in a species specific manner.

Nucleotide sequence and codon usage of the elongation factor Tu(EF-Tu) gene from Mycoplasma pneumoniae

The Mycoplasma pneumoniae tuf gene, encoding the elongation factor protein Tu, was cloned and sequenced. The nucleotide sequence of the mycoplasmal gene showed about 60% homology to the sequences of tuf genes of other prokaryotes, yeast mitochondria and Euglena gracilis chloroplasts, and about 75% similarity was found when comparing the deduced amino acid sequences of the various Tu proteins. The relatively low G + C content (40%) of the M. pneumoniae DNA was reflected in a low G + C content (44.6%) of the tuf gene, and in a preferential use of adenine and uracil at the third position of codons, yet codon usage analysis revealed the presence of almost all of the codons of the genetic code in the mycoplasmal gene. Southern blot hybridization of digested DNAs of 11 Mollicutes species with the entire M. pneumoniae tuf gene and with its 5' part suggested the presence of one copy only of this gene in the representative species of the Mollicutes. In this respect, the Mollicutes resemble Gram-positive bacteria and differ from the Gram-negative bacteria, which carry two copies of the tuf gene.

A physical map of the Mycoplasma genitalium genome

We report the construction of a physical map of the genome of the human pathogen Mycoplasma genitalium through the use of pulse-field gel electrophoresis. The small size and relative simplicity of this genome permit the arrangement of restriction fragments without having to construct linking clones. The size of the genome has been calculated to be approximately 600 kb and several important genetic determinants have been assigned specific loci on the map.

DNA probes for Mycoplasma gallisepticum and Mycoplasma synoviae: application in experimentally infected chickens

DNA probes specific for Mycoplasma gallisepticum and M. synoviae were selected from genomic libraries prepared in the pUC13 vector. The probes hybridized with the DNA of a wide spectrum of strains within each homologous species, but did not react with the heterologous species or with DNA from any other avian mycoplasma or bacteria tested. Experimental infection and contact exposure of chickens to M. gallisepticum served as models to test the effectiveness of the DNA probe in diagnosis as compared with serological and culture detection methods carried out in parallel. A correlation was generally found between the level of M. gallisepticum in tracheal swabs and the effectiveness of the probe, although a predictably reactive level of mycoplasmas was not always detected. Treatment of clinical specimens with acetylcysteine to disrupt mucus improved the detection rate. Dot-blot hybridization with probe pMG4 enabled positive identification of M. gallisepticum at an early stage of infection, prior to the development of a serological response in the infected chicken. Results are obtainable within 4 days of sampling, much more rapidly than culture, and also in clinical specimens from which mycoplasma isolation is impossible, such as carcasses. The results indicate that the use of DNA probes for the early and rapid detection of M. gallisepticum infection is feasible; a development which can replace laborious culture techniques and less effective serological methods, and thus reduce the time required for diagnosis.

Genetic and antigenic relatedness between Mycoplasma gallisepticum and Mycoplasma synoviae

The two avian pathogens Mycoplasma gallisepticum and Mycoplasma synoviae were found, by Southern blot hybridization of their digested DNAs, to share genomic nucleotide sequences additional to those of the highly conserved ribosomal RNA genes. The assumption that some of the shared sequences encode for antigens or epitopes common to both mycoplasmas was supported by Western immunoblot analysis of cell proteins of one mycoplasma with specific antiserum to the other mycoplasma. Interestingly, the band patterns of reactive antigens were different for some of the M. gallisepticum strains, supporting the concept that the species is genotypically variable. The results of the present study may explain the cross-reactivity of the two mycoplasmas noted previously in a variety of routine serological tests.