The antigens of Mycoplasma hominis

Cell-Free Expression System Derived from a Near-Minimal Synthetic Bacterium

Cell-free expression (CFE) systems are fundamental to reconstituting metabolic pathways in vitro toward the construction of a synthetic cell. Although an Escherichia coli-based CFE system is well-established, simpler model organisms are necessary to understand the principles behind life-like behavior. Here, we report the successful creation of a CFE system derived from JCVI-syn3A (Syn3A), the minimal synthetic bacterium. Previously, high ribonuclease activity in Syn3A lysates impeded the establishment of functional CFE systems. Now, we describe how an unusual cell lysis method (nitrogen decompression) yielded Syn3A lysates with reduced ribonuclease activity that supported in vitro expression. To improve the protein yields in the Syn3A CFE system, we optimized the Syn3A CFE reaction mixture using an active machine learning tool. The optimized reaction mixture improved the CFE 3.2-fold compared to the preoptimized condition. This is the first report of a functional CFE system derived from a minimal synthetic bacterium, enabling further advances in bottom-up synthetic biology.

Use of immunoblotting to detect antibodies to Mycoplasma crocodyli infection in the sera of crocodiles (Crocodylus niloticus)

An immunoblotting protocol for the detection of antibodies to Mycoplasma crocodyli was developed using sonicated antigen of the reference strain 266/93. Immunoblotting detected nine reacting antigens, of which the 33 and 40kDa antigens were immunodominant. There was no difference in reactivity of the antigens against sera obtained from vaccinated and infected crocodiles. Both antigens are candidates for other serological and molecular studies. This is the first report to develop and apply an immunoblotting test for detection of antibody to M. crocodyli infection in crocodiles.

Development and application of an indirect ELISA test for the detection of antibodies to Mycoplasma crocodyli infection in crocodiles (Crocodylus niloticus)

Non-availability of a standardized rapid serodiagnostic test for quick and accurate diagnosis of Mycoplasma crocodyli (M. crocodyli) infection in crocodiles was the underlining reason for conducting the present study. An indirect enzyme-linked immunosorbent assay (iELISA) for the detection of antibodies (Ab) to M. crocodyli infection in crocodile sera was developed using sonicated antigen (Ag) and anti-crocodile conjugate. The iELISA test was optimised with different reagents and at different steps. A cut-off value of percent positive greater than or equal to 53.47% resulted in an estimated sensitivity and specificity of 85.67 and 100%, respectively. The developed iELISA could be used for detection of Abs to M. crocodyli infection in crocodiles and may enable to understand the transmission of the disease.

Development of real-time PCR for detection of Mycoplasma hominis

BACKGROUND

Mycoplasma hominis is associated with pelvic inflammatory disease, bacterial vaginosis, post partum fever, sepsis and infections of the central nervous system often leading to serious conditions. Association with development of female infertility has also been suggested, but different publications present different results. We developed a sensitive and fast diagnostic real-time PCR to test clinical samples from women undergoing laparoscopic examination before fertility treatment. To develop a test for the detection and quantification of M. hominis we selected a housekeeping gene, glyceraldehyde-3-phosphate dehydrogenase (gap), as a target.

RESULTS

Real-time PCR was optimized to detect 10 copies of M. hominis PG21 genomic DNA. A fluorescence signal was measured for all 20 other M. hominis isolates, and melting curves analysis showed variations in the melting temperature in agreement with sequence variation in the region of the probes. There was no amplification of other mycoplasmal DNA and human DNA. Eighty-three patient cervical swab samples from infertile women were cultured for M. hominis in the BEa medium. Two of the samples (2.4%) were positive after 48 hours of incubation. The real-time PCR detected the same two samples positive, and the DNA concentrations in the clinical specimens were calculated to 37.000 copies/ml and 88.500 copies/ml, respectively.

CONCLUSION

The results demonstrate that real-time PCR may prove to be a rapid alternative to the traditional cultivation method. Information on bacterial load in genital swabs can be obtained. The assay allowed detection of M. hominis in a closed system reducing the risk of contamination by amplicon carry-over.

Recombination in Mycoplasma hominis

Mycoplasma hominis has been previously described as a heterogeneous species, and in the present study intraspecies diversity of 20 M. hominis isolates from different individuals was analyzed using parts of the unlinked gyrase B (gyrB), elongation factor Tu (tuf), SRalpha homolog (ftsY), hitB-hitL, excinuclease ABC subunit A (uvrA) and glyceraldehyde-3-phosphate dehydrogenase (gap) genes. The level of variability of these M. hominis genes was low compared with the housekeeping genes from Helicobacter pylori and Neisseria meningitidis, but only few M. hominis isolates had identical sequences in all genes indicating the presence of recombination. In order to test for intergenic recombination, phylogenetic trees were reconstructed for each of the genes but no well-supported bifurcating phylogenetic trees could be obtained. The genes were tested for intragenic recombination using the correlation between linkage disequilibrium and distance between the segregating sites, by the homoplasy ratio (H ratio), and by compatibility matrices. The gap gene showed well-supported evidence for high levels of recombination, whereas recombination was less frequent and not significant within the other genes. The analysis revealed intergenic and intragenic recombination in M. hominis and this may explain the high intraspecies variability. The results obtained in the present study may be of importance for future population studies of Mycoplasma species.

Cloning, sequencing and variability analysis of the gap gene from Mycoplasma hominis

The gap gene encodes the glycolytic enzyme glyceraldehyde 3-phosphate dehydrogenase (GAPDH). The gene was cloned and sequenced from the Mycoplasma hominis type strain PG21(T). The intraspecies variability was investigated by inspection of restriction fragment length polymorphism (RFLP) patterns after polymerase chain reaction (PCR) amplification of the gap gene from 15 strains and furthermore by sequencing of part of the gene in eight strains. The M. hominis gap gene was found to vary more than the Escherichia coli counterpart, but the variation at nucleotide level gave rise to only a few amino acid substitutions. To verify that the gene was expressed in M. hominis, a polyclonal antibody was produced and tested against whole cell protein from 15 strains. The enzyme was expressed in all strains investigated as a 36-kDa protein. All strains except type strain PG21(T) showed reaction to a 104-kDa band in addition to the expected 36-kDa band. The protein reacting at 104 kDa is a M. hominis protein with either an epitope similar to one on GAPDH, or it is an immunoglobulin binding protein.

The Mycoplasma hominis vaa gene displays a mosaic gene structure

Mycoplasma hominis contains a variable adherence-associated (vaa) gene. To classify variants of the vaa genes, we examined 42 M. hominis isolated by PCR, DNA sequencing and immunoblotting. This uncovered the existence of five gene categories. Comparison of the gene types revealed a modular composition of the Vaa proteins. The proteins constituted a conserved N-terminal part followed by a varying number of interchangeable cassettes encoding approximately 110 amino acids with conserved sequences boxes flanking the cassettes. The interchangeable cassettes showed a high mutual homology and a conserved leucine zipper motif. The smallest product contained only one cassette and the largest five. Additionally, two types of stop mutations caused by substitutions resulting in the expression of truncated Vaa proteins were observed. Our results expand the known potential of the Vaa system in generating antigen variation.

Preparative electroelution of specific protein antigens from Mycoplasma pneumoniae: use in an enzyme-linked immunosorbent assay (ELISA)

A rapid, simple and preparative method is described for the recovery of the seven highest molecular weight proteins (HMWP) from Mycoplasma pneumoniae membrane. The yield of proteins obtained was approximately 90%. The method involved the separation of M. pneumoniae proteins by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE), followed by electroelution of HMWP. These eluted antigens were used in an ELISA to measure IgG antibodies in sera from 9 blood donors and 9 patients with M. pneumoniae infection. The specificity of M. pneumoniae HMWP was examined by competition ELISA and immunoblotting with different mycoplasma species encountered in the respiratory tract.

Characterization of the strain-specific and common surface antigens of Mycoplasma arginini

A combination of quantitative immunoelectrophoresis and sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis was used to determine location and molecular weights of surface membrane antigens of four strains of Mycoplasma arginini. Two major surface antigens were identified for M. arginini by absorption of antiserum with whole cells: one surface antigen was strain specific, electrophoretically fast, and prominently located on the surface, whereas the other surface antigen was common to the four strains and of intermediate electrophoretic mobility. Three of the four strains of M. arginini (G-230, 23243, and 27389) possessed immunologically strain-specific antigens which did not cross-react, whereas the leonis strain lacked an immunologically detectable unique surface antigen. A monospecific antiserum prepared against immune precipitates of the strain-specific antigen of strain G-230 detected three polypeptides of 74,000, 44,000, and 17,000 daltons in SDS-polyacrylamide gels of membrane preparations. All four strains shared the common surface antigen which appeared considerably more hydrophobic than the strain-specific surface antigen because it could only be demonstrated by charge-shift immunoelectrophoretic conditions (addition of deoxycholate to the nonionic detergent). Monospecific antiserum to the common antigen of strain G-230 reacted with all four M. arginini strains, but did not react with two other arginine-utilizing species, and recognized three polypeptides of 40,000, 29,000, and 20,000 daltons in membranes of strain G-230. Whereas the common surface antigen is a likely target for conventional serological reactions used for identification of the species M. arginini, strain-specific antigen cannot fulfill this role but must participate in other surface reactions.

Comparison of antigens of pneumonia-associated mycoplasma species by gel diffusion

Comparison of fluorocarbon-extracted antigens of six mycoplasma species by double immunodiffusion and counterimmunodiffusion techniques revealed a close reciprocal relationship among Mycoplasma dispar, M. ovipneumoniae, and M. hyopneumoniae. A lesser degree of cross-reaction was also demonstrated between these three species and M. hyorhinis and M. bovoculi. The interrelationships were more clearly demonstrated by double immunodiffusion than by counterimmunodiffusion.

Surface parasitism by Mycoplasma pneumoniae of respiratory epithelium

Identification of the attachment factor on virulent Mycoplasma pneumoniae organisms which permits surface parasitism of respiratory epithelium was attempted. Brief pretreatment of M. pneumoniae monolayers with protease prevented mycoplasma attachment ot sensitive host cells without reducing viability of the microorganisms. Gel electrophoretic analysis of mycoplasma proteins before and after exposure of intact mycoplasmas to protease revealed the absence of a major protein species (P1) in enzyme-treated preparations while other protein bands with the exception of P2 were virtually unaffected. The absence of P1 correlated with the failure of enzyme-treated mycoplasmas to attach to tracheal explants. P1 regeneration after protease treatment of mycoplasma monolayers was directly associated with reattachment capabilities in M. pneumoniae. Erythromycin inhibited P1 resynthesis, thus preventing resumed attachment activity by mycoplasmas. Lactoperoxidase-catalyzed iodination of intact M. pneumoniae organisms further confirmed that P1 was an external membrane protein and suggested that his surface component was required for the successful membrane-membrane interaction between host and parasite.

Serological comparison of five arginine-utilizing Mycoplasma species by two-dimensional immunoelectrophoresis

Five arginine-utilizing, nonglycolytic Mycoplasma species were compared serologically by two dimensional immunoelectrophoresis. The survey included: Mycoplasma hominis, Mycoplasma arthritidis, Mycoplasma gateae, Mycoplasma gallinarum, and three strains of Mycoplasma arginini. Although the M. arginini strains showed strong cross-reactions, each strain produced a different antigenic profile which was distinct and which indicated significant antigenic differences between strains. The M. arginini strains showed strong relationships with M. gateae; lesser cross-reactions were observed with other strains. Common antigens were demonstrable in the entire group. When all these species were compared with a glycolytic species, Mycoplasma gallisepticum, no cross-reactions were observed. Two-dimensional immunoelectrophoresis was a far more sensitive technique than double-immunodiffusion since as many as 20 components could be resolved.

Isolation, ultrastructure and antigenicity of Mycoplasma gallisepticum membranes

The cell membrane of Mycoplasma gallisepticum was isolated by lysing the cells with digitonin. Chemical and density-gradient analyses and electron microscopy showed the isolated membranes to be relatively free of cytoplasmic contaminants. The density of the membranes exceeded that of other mycoplasma membranes, indicating a higher protein content. Small vesicular extensions seen in the sectioned membranes were interpreted as empty blebs.The isolated membranes, but not the cytoplasmic fraction, elicited in chickens the production of growth-inhibiting, agglutinating and haemagglutination-inhibition antibodies to M. gallisepticum in titres resembling those obtained by injection of whole cells. The peak of the serological response varied with the serological test employed. The rapid slide-agglutination test became positive as early as 3 days after the first injection of only 50 mug. of membrane protein. The haemagglutination-inhibition antibody titre reached its peak at about 10 days after the first injection, while that of the growth-inhibiting antibodies was reached only at about 25 days. The addition of adjuvant to the membrane antigen did not improve the production of the growth-inhibiting antibodies in chickens, but it produced some improvement in rabbits. Our results support the thesis that the chief immunogens of M. gallisepticum reside in the cell membrane of this organism.

New method for the isolation of membranes from Mycoplasma gallisepticum

Mycoplasma gallisepticum lysed readily in carbonate bicarbonate buffer at pH 9.2 to 10.5. The hemagglutination titer of the lysates was 2- to 16-fold greater than a cell suspension at the same protein concentration in buffered saline. Membranes prepared from cells lysed by this method at pH 10 were relatively free from cytoplasmic contaminants as shown by electron microscopy of thin sections. The membranes retained their hemagglutination activity, gave reactions in immunodiffusion tests identical to those obtained by osmotic lysis and sonic treatment, and showed a similar pattern of protein bands by polyacrylamide disk electrophoresis. When inoculated into rabbits, the membranes gave rise to antibodies active in growth-, metabolic- and hemagglutination-inhibition tests. On the average, membranes obtained by lysis at pH 10 contained 44% of the original cell protein. The method is simple, giving high yields of membranes, and may be adaptable to other mycoplasmas.

Chemical and serological properties of Mycoplasma hyorhinis fractions

Mycoplasma hyorhinis organisms were fractionated into lipid, carbohydrate, and protein fractions by chemical and physiochemical procedures. When all fractions were tested for complement fixation and inhibition of growth inhibition activity, only the protein fractions possessed activity. Thus, it appears that the major antigenic component of M. hyorhinis is a protein.

Immunoelectrophoretic analysis of Mycoplasma mycoides var. mycoides

Acrylamide gel electrophoresis was used to show the similarities and differences in the membrane proteins of two vaccine and two virulent strains of Mycoplasma mycoides var. mycoides. Immunoelectrophoretic (IEP) analysis was also used to partially characterize the associated antigens. Antibody spectra to the antigens of M. mycoides differ in rabbit, pig, and cattle sera. Rabbits produce better precipitating antibody against the anodic migrating protein mycoplasma antigens than cattle and pigs as seen in IEP. However, rabbit anti-M. mycoides serum did not show precipitating antibody against the heat-stable carbohydrate antigen. As judged by IEP, the major carbohydrate antigen extracted from the media, or boiled whole organism, is similar to that present in the sera-infected cattle and knee joints of calves. This carbohydrate antigen has a cathodic migration in IEP at pH 8.6. Periodate oxidation, classically used to destroy carbohydrate, also destroys most of the protein antigens. Heating the antigens to 56 C for 10 min destroys many of the noncarbohydrate antigens and 100 C eliminates all but the carbohydrate antigen. Extraction of M. mycoides with chloroform-methanol, phenol, ethanol, or ethanol-acetone reduced or eliminated most of the protein antigens. Some of the isolated antigenic fractions of M. mycoides were tested to determine their activity in the diagnostic complement fixation test for contagious bovine pleuropneumonia and their inhibitory effect in this test by using bovine anti-M. mycoides antisera having precipitating antibody and circulating antigen. The complement fixation antigen is not the galactan, cannot be extracted by chloroform-methanol, but is stable to boiling at 100 C and may be extracted by phenol and partially precipitated by ethanol-acetone.

Respiratory disease in a colony of rats. II. Isolation of Mycoplasma pulmonis from the natural disease, and the experimental disease induced with a cloned culture of this organism

Mycoplasma pulmonis was isolated from the pneumonic lung of a rat. Two groups of mycoplasma-free rats were inoculated, one with a culture of the M. pulmonis strain which had been cloned four times (group A) and the other with a lung homogenate of the rat from which the strain had been isolated (group B). A third group (C) consisted of uninoculated control animals. Each group was kept in strict isolation and allowed to breed so that the progeny was naturally exposed to any pathogens present in the inoculated animals. After different periods of exposure, rats were autopsied, respiratory tracts and inner ears were cultured for mycoplasmas and bacteria, and sera were tested for complement-fixing antibodies to murine mycoplasmas.In group-A rats, M. pulmonis was consistently isolated from the inner ears or lungs from 50 to 715 days after exposure. Complement-fixing antibody to M. pulmonis was detected 20 days after inoculation, but in the naturally exposed progeny antibody took longer than 50 days to develop. Antibodies to the other known mycoplasmas of murine origin, M. arthritidis and M. neurolyticum, were never found. Purulent otitis interna was consistently found from day 55 onwards, while lung lesions were first observed at 85 days and persisted to 715 days. Pulmonary lesions developed more slowly in inoculated parents than in exposed progeny. Similar results were found in group-B rats, which were examined up to 441 days after inoculation. Uninoculated group-C rats were examined up to 768 days of age, but M. pulmonis was not recovered; of the 54 animals whose serum was tested all were negative to the three species of mycoplasmas, except one which had a titre of 16 with M. pulmonis. Pneumonia, bronchiectasis or lymphoreticular hyperplasia were not seen in any of these control rats. Bacterial respiratory pathogens were not isolated from rats in any of the groups, nor was antibody to Sendai virus detected.The results suggest that M. pulmonis alone can cause pneumonia and bronchiectasis in rats since mechanical carry-over of another pathogen with the initial cloned inoculum is very unlikely and there was no evidence for the participation of any other rat pathogen. The respiratory disease induced by the cloned culture was comparable with that induced by the lung homogenate, and with the well-known syndrome of chronic respiratory disease and bronchiectasis in the rat.

Isolation of mycoplasma membranes by digitonin

The cell membrane of Mycoplasma hominis was isolated by lysing the cells with digitonin. Electron microscopy and chemical, density gradient, and electrophoretic analyses of the membrane proteins showed the membranes so obtained, like those isolated by osmotic lysis, to be relatively free of cytoplasmic contaminants. Sensitivity to digitonin lysis depended on temperature but was not affected by Mg(2+) ions and was only slightly affected by the age of the culture. Accordingly, it seems that digitonin may be used for the isolation of cell membranes from sterol-requiring mycoplasmas that tend to be fairly resistant to osmotic lysis.

Membrane antigens of Mycoplasma hominis

Extraction of membranes of Mycoplasma hominis with n-butanol showed that antigenicity was associated with the non-lipid residue, which probably consisted mainly of protein, and not with the lipid itself.Since many membrane proteins are hydrophobic, membranes were rendered soluble in various ways. Extraction with urea or phenol was the most successful, yielding extracts which were both antigenic and serologically reactive. The urea extract could not be fractionated by polyacrylamide disk electrophoresis or by column chromatography. However, serologically active components identified by gel diffusion were separated from detergent-lysed membranes by polyacrylamide disk electrophoresis. The activities of antisera against these fractions suggested that indirect-haemagglutinating or metabolic-inhibiting antibodies can be directed against several different membrane antigens. However, the antigens identified by gel diffusion probably do not represent all the components participating in indirect haemagglutination.Treatment of membrane suspensions with heat, alkali, periodate and various enzymes showed that the four components identified by gel diffusion could be distinguished by their differing stabilities and properties. On the basis of their lability and susceptibility to proteolytic enzymes, two were identified as proteins.

Antigenic differences within the species Mycoplasma hominis

Membrane and soluble fractions of one genital and two oral strains of Mycoplasma hominis were compared by immunodiffusion and polyacrylamide gel electrophoresis. Differences were demonstrated between the membrane antigens of the three strains by immunodiffusion, and the membrane proteins also gave dissimilar patterns in polyacrylamide gel electrophoresis. The soluble fractions gave identical lines in immunodiffusion tests and similar patterns in polyacrylamide gel electrophoresis.When the strains were cross-titrated in metabolic inhibition (MI) and indirect haemagglutination (IHA) tests, statistical analysis of the results revealed significant differences between the strains. Previously, growth-inhibition, MI and IHA activity was shown to be associated with the membrane antigens of M. hominis, so the intraspecies differences revealed by MI and IHA correlate with the differences in the membrane antigens demonstrated by immunodiffusion. Growth-inhibition tests, which might also have been expected to show intraspecies differences, did not do so, probably because of the insensitivity of the test. In contrast to MI and IHA, complement-fixation (CF) tests revealed a high degree of relatedness between the strains. This is consistent with the observation that the soluble antigens of M. hominis participate in the CF reaction, and that the soluble antigens of different strains are identical in immunodiffusion tests.