Mycoplasma fermentans DNA is infrequently detected in urine specimens from renal transplant recipients

Mycoplasma fermentans is a likely causative agent of HIV-associated nephropathy. In a pilot study, M. fermentans DNA was detected with polymerase chain reaction (PCR) in urine samples from renal allograft recipients; nine (39.1%) out of 23 renal allograft recipients (most of whom had chronic allograft rejection) and none of the 20 controls, were infected with M. fermentans. A cross-sectional study was conducted to investigate the prevalence of M. fermentans in urine samples from renal allograft recipients. Midstream urine samples were centrifuged at 13,000 x g, purified with QIAamp and tested with PCR using RW004/RW005 and an internal control to screen for the presence of inhibitors. Of the 264 participants recruited, 263 completed the questionnaire (172 men, 92 women); 53 had chronic renal allograft rejection, 106 had chronic renal dysfunction without rejection, 69 had a normal renal allograft for more than 3 months and 35 had a renal allograft for less than 3 months. All urine samples yielded positive results for the internal control. Mycoplasma fermentans DNA was detected once i prospectively collected urine samples. The only individual infected with M. fermentans was also seropositive for HIV-1. This study demonstrates that M. fermentans can be at most sporadically detected in urine from patients living with a renal allograft but is not implicated in chronic rejection of allograft.

High-frequency DNA rearrangements in the chromosomes of clinically isolated Mycoplasma fermentans

Mycoplasma fermentans is currently being examined as an agent potentially associated with human disease. Several strains of M. fermentans were isolated from patients with respiratory tract disease and AIDS. Two of these clinical strains, M64 and SK6, were triple-filter-cloned and designated as the parental clones in this study. Genomic DNA of randomly picked subclones in four and five subsequent generations passed from the parental M64 and SK6 clones were analyzed by using a radiolabeled M. fermentans-specific insertion sequence (IS)-like element as the probe. The hybridization patterns of DNA restriction fragments revealed high frequencies of chromosomal changes accompanied with excision or new insertion of the IS-like element in M. fermentans chromosome. The findings indicate M. fermentans has an effective mechanism(s) to produce a rapid gene rearrangement that may be mediated by one or more copies of the IS-like element.

Structural and functional properties of complement-activating protein M161Ag, a Mycoplasma fermentans gene product that induces cytokine production by human monocytes

Human malignant cells are targeted by homologous complement C3b if they express M161Ag, a 43-kDa protein with C3-activating property. cDNA of M161Ag cloned from human leukemia cell lines predicted M161Ag as a novel secretory protein comprised of 428 amino acids including 5 amino acids encoded by TGA codons (Matsumoto M., Takeda, J., Inoue, N., Hara, T., Hatanaka, M., Takahashi, K., Nagasawa, S., Akedo, H., and Seya, T. (1997) Nat. Med. 3, 1266-1270), although the origin of this gene was obscure. Here we clarified this point through genomic and biochemical analysis: 1) 5'-UT and genomic sequences represented the prokaryote promoter and ribosomal binding site; 2) the TGA codons in M161Ag cDNA were translated not into selenocysteines but into tryptophans; 3) M161Ag anchored onto the membrane secondary to its N-terminal palmitoylation like prokaryote lipoproteins; 4) genomic and cDNA clones of M161Ag were highly homologous to Mycoplasma fermentans gene encoding P48, a monocytic differentiation/activation factor, recently released in the data base, although the resultant proteins were different in the amino acid sequences. Additionally, purified soluble M161Ag efficiently provoked IL-1beta, tumor necrosis factor alpha, and IL-6 like P48, and further IL-10 and IL-12 in human peripheral blood monocytes. Thus, M161Ag originates from M. fermentans, and latently infected M. fermentans allows human cells to produce M161Ag. The liberated protein serves as a potent modulator of innate and cellular immune responses via its complement-activating and cytokine-producing activities.

Genotypic and phenotypic analysis of Mycoplasma fermentans strains isolated from different host tissues

A correlation was found between the expression of a specific Mycoplasma fermentans surface antigen (Pra, proteinase-resistant antigen) and the site of isolation of the organism from the infected host. Strains which expressed Pra were most frequently associated with cells of bone marrow origin, and strains which lacked expression of Pra were most commonly isolated from the respiratory tract, genital tract, and arthritic joints, i.e., epithelial cell surfaces. Pra was previously shown to be resistant to degradation by proteinases and was hypothesized to play a protective role at the organism surface and perhaps to influence which host tissue site was colonized by the organism. The methods used for this phenotyping scheme required isolation and growth of the mycoplasma in quantities sufficient for immunoblot analysis using monoclonal antibodies. We wanted to determine a more rapid and less cumbersome technique to supplement this method for determining the Pra phenotype directly in clinical specimens. Here we describe PCR studies to investigate the movement of a previously identified M. fermentans insertion sequence (IS)-like element. These data showed a correlation between a specific IS genotype and the Pra+ phenotype. Production of a 160-bp product using a single set of IS-based primers was associated with expression of Pra. The genomic IS location resulting in the 160-bp product was determined by using Southern blot analysis and was found to be a stable insertion site characteristic of genotype I strains. Additional analyses of sequences within and flanking the IS insertion sites revealed another pair of PCR primer sites which resulted in the consistent production of a 450-bp amplicon. The stability of this site was dependent on the absence of the IS-like element between the primer sites. The production of this 450-bp amplicon correlated with the Pra mutant phenotype and was characteristic of genotype II strains. The data showed that the sequence within the IS may be unstable and that reliable genotyping sequences are more easily found in the stable genomic sites which flank the IS element.

Sequencing multimegabase-template DNA with BigDye terminator chemistry

Using the recently introduced BigDye terminators, large-template DNA can be directly sequenced with custom primers on automated instruments. Cycle sequencing conditions are presented to sequence DNA samples isolated from a number of microbial genomes including 750-kb Ureaplasma urealyticum, 1.2-Mb Mycoplasma fermentans, 2.3-Mb Streptococcus pneumoniae, and 4.6-Mb Escherichia coli. Average read lengths of >700 bp from unique primer annealing sites are often sufficient to fill final gaps in microbial genome sequencing projects without additional manipulations of template DNA. The technique can also be applied to sequence-targeted regions, thereby bypassing tedious subcloning steps.

Absence of mycoplasmal gene in malignant mammalian cells transformed by chronic persistent infection of mycoplasmas

Chronic persistent infections by mycoplasmas induced malignant transformation of C3H mouse embryo cells that normally had never been reported to undergo spontaneous transformation. This mycoplasma-mediated oncogenic process had a long latency (more than 7 weeks of continuous mycoplasmal infection) and showed a multistage progression characterized by reversibility (at least up to 11 weeks of mycoplasmal infection) and irreversibility of malignant properties upon removal of the mycoplasma from culture. Further prolonged infections (18 weeks) by Mycoplasma fermentans or M. penetrans resulted in permanent transformation of these C3H cells that no longer required the continued presence of the transformation-inducing mycoplasmas in cultures to retain their malignant properties. Previous studies of viral oncogenesis revealed that virus-transformed cells always had viral gene(s) present. Integration of viral gene(s) apparently played an important role in the process of oncogenesis. In this study, we examined if the continued presence of any mycoplasmal gene(s) in mammalian cells, in whatever form, was also crucial in causing malignant cell transformation. Representational difference analysis (RDA) was a recently developed powerful technique to compare differences between two complex genomes. In the RDA system, subtractive and kinetic enrichment was used to purify and isolate restriction endonuclease gene fragment(s) of mycoplasmal origin, presumably present only in mycoplasma-transformed C3H cells, but not in nonmycoplasma-exposed control C3H cells. After three rounds of subtractive hybridization following PCR enrichment for each of three different restriction enzymes DNA digests, no gene fragment of mycoplasmal origin was amplified or identified in the permanently transformed C3H cells. Differing from tumorigenesis in animal cells induced by most oncogenic viruses or in plant cells induced by Agrobacteria, mycoplasmas evidently did not cause malignant transformation by integrating their gene(s) into the mammalian cell genome.

Genotypic characterization of seven strains of Mycoplasma fermentans isolated from synovial fluids of patients with arthritis

We performed a genotypic characterization of seven strains of Mycoplasma fermentans which have been isolated from the synovial fluid of patients with rheumatoid arthritis (n = 2), spondyloarthropathy (n = 1), and unclassified arthritis (n = 4). We compared them to three reference strains (strains PG18 and K7 and incognitus strain) and to a clinical isolate from the urethra of a patient with nongonococcal urethritis. The characterization methods included electrophoresis of native DNA, arbitrarily primed PCR, and restriction fragment length polymorphism analysis following conventional and pulsed-field gel electrophoresis. Southern blot analysis with a probe internal to an insertion sequence was performed with the restriction products produced by the last two techniques. No extrachromosomal DNA sequences were detected. The M. fermentans strains identified by these methods did not present a unique profile, but they could be separated into two main categories: four articular isolates were genetically related to PG18 and the three other isolates, the urethral isolate, and the incognitus strain were related to K7. We also looked for the presence of the bacteriophage MAV1 (associated with the arthritogenic property of Mycoplasma arthritidis in rodents) in the M. fermentans strains. MAV1 DNA was not detected in either the clinical isolates or the reference strains of M. fermentans.

The ftsZ gene as a tool for detection of Mycoplasma fermentans

Mycoplasma fermentans was reported as a common contaminant of cell cultures, and was shown to either induce or suppress several immunological functions. A strain of M. fermentans was recently isolated from a mouse T-lymphoma cell line, which differs from other M. fermentans strains by its growth characteristics and was designated (in the authors' records) as strain 609. Using the differential display technique (DD), a differentially expressed gene that was identified as the M. fermentans 609 ftsZ gene was isolated. Comparison of the nucleotide sequence of the M. fermentans 609 ftsZ gene to other ftsZ genes showed a 98% homology with Mycoplasma fermentans strain K7 and approximately 50% homology with Mycoplasma pulmonis and Mycoplasma genitalium. Comparison of the putative amino acid sequences of the FtsZ proteins showed similar homology. A polymerase chain reaction (PCR) assay to detect the presence of this ftsZ gene was established; it is a fast and convenient assay to detect infection of cells by the M. fermentans species. This work demonstrates that: (i) DD can be used as a useful technique to identify and isolate mycoplasmal genes from infected cells; and (ii) the ftsZ gene can be a useful marker to distinguish between different species of mycoplasma.

Variability in the distribution and composition of insertion sequence-like elements in strains of Mycoplasma fermentans

Mycoplasma fermentans has been reported to be pathogenic for man. All fourteen strains tested contain an insertion sequence-like element (ISLE) which may be present in multiple copies. To determine whether ISLE copies are similarly distributed in different strains of M. fermentans, restriction enzyme digest fragments of genomic DNA from 14 isolates, from a variety of sources, were separated by electrophoresis, blotted and hybridized to a biotin labelled polymerase chain reaction (PCR) amplified fragment of ISLE. A range of patterns was observed suggesting that the element has a tendency to undergo rearrangement within the genome. Analysis of ISLE sequences revealed inter- and intra-strain polymorphisms.

Localized frameshift mutation generates selective, high-frequency phase variation of a surface lipoprotein encoded by a mycoplasma ABC transporter operon

The wall-less mycoplasmas have revealed unusual microbial strategies for adaptive variation of antigenic membrane proteins exposed during their surface colonization of host cells. In particular, high-frequency mutations affecting the expression of selected surface lipoproteins have been increasingly documented for this group of organisms. A novel manifestation of mutational phase variation is shown here to occur in Mycoplasma fermentans, a chronic human infectious agent and possible AIDS-associated pathogen. A putative ABC type transport operon encoding four gene products is identified. The 3' distal gene encoding P78, a known surface-exposed antigen and the proposed substrate-binding lipoprotein of the transporter, is subject to localized hypermutation in a short homopolymeric tract of adenine residues located in the N-terminal coding region of the mature product. High-frequency, reversible insertion/deletion frameshift mutations lead to selective phase variation in P78 expression, whereas the putative nucleotide-binding protein, P63, encoded by the most 5' gene of the operon, is continually expressed. Mutation-based phase variation in specific surface-exposed microbial transporter components may provide an adaptive advantage for immune evasion, while continued expression of other elements of the same transporter may preserve essential metabolic functions and confer alternative substrate specificity. These features could be critical in mycoplasmas, where limitations in both transcriptional regulators and transport systems may prevail. This study also documents that P63 contains an uncharacteristic hydrophobic sequence between predicted nucleotide binding motifs and displays an amphiphilic character in detergent fractionation. Both features are consistent with an evolutionary adaptation favoring integral association of this putative energy-transducing component with the single mycoplasma membrane.

Antisignature oligonucleotides and their analogs as inhibitors of mollicutes-cofactors of HIV

Inhibition of mollicutes by synthetic oligonucleotides and their analogs complementary to specific "signature" regions of 16S rRNA and corresponding sequences of ribosomal operon DNA was studied. It was shown that antisignature oligonucleotides inhibited transcription in vitro for above 79% interacting specifically with ribosomal operon and non-specific with DNA-dependent RNA-polymerase. The inhibition efficiency depended on oligonucleotide sequence and type of modification. Translation in vitro was suppressed most efficiently (up to 60%) by oligonucleotides complementary to 3'-end region of 16S rRNA, also depending on their modification. Translation in vivo was inhibited most efficiently (up to 73%) by thiophosphate analogs of oligonucleotides complementary to sequences 499-507 and 523-532 of 16S rRNA responsible for binding of ribosomal "core" protein S4 starting the assembly of 30S ribosome subunit. With the simultaneous use of the last two oligonucleotides, the growth of mollicutes in SM IMV-72 medium rich in exogenous sources of nucleosides was suppressed for over 90%. It is supposed that under conditions where mollicutes have no free access to starting materials for their own synthesis of nucleic acid these nucleotides could suppress microorganisms completely. Antisignature oligonucleotides are considered as superspecific agents not leading to the development of resistance of mollicutes and believed to be the main future remedy against diseased caused by microorganisms lacking the system of nucleoside synthesis.

cDNA and genomic cloning and expression of the P48 monocytic differentiation/activation factor, a Mycoplasma fermentans gene product

P48 is a 48 kDa monocytic differentiation/activation factor previously purified from the conditioned medium of the Reh human pre-B cell leukaemia cell line. It induces growth arrest and differentiation of HL-60 human promyelocytic leukaemia cells along the monocytic pathway and the production of the cytokines interleukin 1, tumour necrosis factor-alpha and interleukin 6 in human monocytes and monocytic cell lines. The cDNA for P48 was cloned from Reh cellular RNA using 3' reverse amplification of cDNA ends. Southern blot probing with P48 cDNA revealed hybridization with DNA from Reh and Molt-4 cells, but not with DNA from human peripheral blood mononuclear cells. Subsequent studies using PCR and Southern analysis revealed P48 sequences in DNA isolated from Mycoplasma fermentans but not M. hominis, M.iowae, M.synoviae or M.lypophilum. Although initial studies using Mycoplasma culture and hybridization techniques had failed to reveal Mycoplasma infection in our Reh and Molt-4 cell lines, subsequent PCR studies using Mycoplasma genus-specific rRNA primrs revealed Mycoplasma sequences in these cell lines. Using the P48 cDNA probe, we isolated a genomic clone from M. fermentans DNA which was found to be 98.5% identical with the P48 cDNA clone, and the deduced amino acid sequence agreed with N-terminal microsequencing data for P48 protein purified from the Reh cell line conditioned medium. The 5' end of the gene has a number of consensus sequences characteristic of prokaryotic genes, and the deduced amino acid sequence has a number of features suggesting that P48 is a lipoprotein. The P48 cDNA was expressed in pMAL in Escherichia coli, and the 60 kDa expressed fusion protein was found to react with anti-P48 antibodies on Western blots. This is consistent with a pMAL fusion protein representing the sum of the 42 kDa maltose-binding protein and 18 kDa of P48 recombinant protein, suggesting that native P48 has significant post-translational modification. Consistent with this, Northern blot studies revealed a single 1 kb transcript. The recombinant fusion protein was found to possess anti-proliferative activity against HL-60 cells, and antibodies against recombinant P48 were found to block the biological activity of native P48 isolated from conditioned medium. These studies demonstrate that P48, a molecule with immunomodulatory and haematopoietic differentiation activities, is derived from M. fermentans or a closely related species. P48 may be important in the pathophysiology of Mycoplasma infections and may be useful in dissecting the mechanisms involved in mammalian haematopoietic cell differentiation, immune function and cytokine biosynthesis.

Search for the presence of six Mycoplasma species in peripheral blood mononuclear cells of subjects seropositive and seronegative for human immunodeficiency virus

The prevalence of Mycoplasma fermentans, Mycoplasma pirum, Mycoplasma genitalium, Mycoplasma pneumoniae, Mycoplasma hominis, and Mycoplasma penetrans was investigated by using specific PCR assays with peripheral blood mononuclear cells from subjects infected or not infected with the human immunodeficiency virus (HIV). Only M. fermentans was detected in 5.8% of 154 HIV-seropositive and 11.1% of 90 HIV-seronegative subjects.

Antigenic topology of the P29 surface lipoprotein of Mycoplasma fermentans: differential display of epitopes results in high-frequency phase variation

Antibodies to P29, a major lipid-modified surface protein of Mycoplasma fermentans, reveal phase variation of surface epitopes occurring with high frequency in clonal lineages of the organism. This occurs despite continuous expression of the entire epitope-bearing P29 product (detected by Western immunoblotting) and contrasts with phase variation of other surface antigens mediated by differential expression of proteins. To understand the structure and antigenic topology of P29, the single-copy p29 gene from strain PG18 was cloned and sequenced. The gene encodes a prolipoprotein containing a signal sequence predicted to be modified with lipid and cleaved at the N-terminal Cys-1 residue of the mature P29 lipoprotein. The remaining 218-residue hydrophilic sequence of P29 is predicted to be located external to the single plasma membrane. Additional Cys residues at positions 91 and 128 in the mature protein were shown to form a 36-residue disulfide loop by selectively labeling sulfhydryl groups that were liberated only after chemical reduction of monomeric P29. Two nearly identical charged amino acid sequences occurred in P29, within the disulfide loop and upstream of this structure. Two distinct epitopes binding different monoclonal antibodies were associated with opposite ends of the P29 protein, by mapping products expressed in Escherichia coli from PCR-generated 3' deletion mutations of the p29 gene. Each monoclonal antibody detected high-frequency and noncoordinate changes in accessibility of the corresponding epitopes in colony immunoblots of clonal variants, yet sequencing of the p29 gene from these variants and analysis of disulfide bonds revealed no associated changes in the primary sequence or disulfide loop structure of P29. These results suggest that P29 surface epitope variation may involve masking of selected regions of P29, possibly by other surface components undergoing phase variation by differential expression. Differential masking may be an important mechanism for altering the antigenic or functional surface topology of this mycoplasma and other wall-less mycoplasmas.

Detection of Mycoplasma fermentans in human saliva with a polymerase chain reaction-based assay

Mycoplasma fermentans and other mycoplasma species may be associated with human immunodeficiency virus infection. Little is known about the ecology of this micro-organism and its natural habitat. A polymerase chain reaction (PCR)-based assay was used to detect M. fermentans in whole saliva. The hypothesis was tested that M. fermentans is present on the mucosal surfaces of the mouth and oropharynx. Whole saliva was collected from 110 adults. The 206-bp amplification product of DNA purified from these samples was detected in ethidium bromide-stained 6% polyacrylamide gels in 49 (44%) samples tested. All samples were confirmed by Southern blotting with a probe based on an internal sequence of the expected amplification product. The data suggest that this organism is often found in saliva and on oropharyngeal mucosal surfaces. Saliva may play a part in its transmission between individuals. Saliva sampling may be helpful in further studies of the ecology and distribution of the micro-organism in human populations.

Development of an amplification and hybridization assay for the specific and sensitive detection of Mycoplasma fermentans DNA

A polymerase-chain-reaction-based detection system for Mycoplasma fermentans was established. The highly conserved tuf gene, which encodes elongation factor Tu of prokaryotes, served as target sequence for the PCR. With two PCR oligodeoxynucleotides, which were selected from M. fermentans specific sequences of the tuf gene, we amplified a 850 base pair DNA fragment. Via the biotin-moiety of one primer the PCR fragments were immobilized on streptavidin-coated microtitre plates. After alkaline denaturation a digoxigenin-labelled M. fermentans specific DNA probe was hybridized to the single stranded immobilized PCR fragment. Detection was performed by addition of an alkaline phosphatase conjugated anti-digoxigenin antibody. 4-methyl-umbelliferyl-phosphate was used as a fluorogenic substrate. Amplification of 10 fg chromosomal target DNA was detected by this 'DNA enzyme immuno assay (DEIA)' technique, corresponding to seven genome copies. Our study supports the presumption that the tuf gene proves to be a suitable target sequence for the PCR based detection of any bacterial species. Furthermore, hybridization of PCR fragments with radio-labelled DNA probes should no longer be necessary, because a very sensitive non-radioactive test system can easily be established with the 'DEIA' technique.

Identification of mycoplasma membrane proteins by systematic Tn phoA mutagenesis of a recombinant library

Wall-less prokaryotes in the genus Mycoplasma include over 90 species of infectious agents whose pathogenicity for humans and other animals is currently being assessed. Molecular characterization of surface proteins is critical in this regard but is hampered by the lack of genetic systems in these organisms. We used TnphoA transposition to systematically mutagenize, in Escherichia coli, a genomic plasmid library constructed from Mycoplasma fermentans, a potential human pathogen. The strategy circumvented problems of expressing mycoplasma genes containing UGA (Trp) codons and relied on the construction of the vector pG7ZCW, designed to reduce TnphoA transposition into vector sequences. Functional phoA gene fusions directly identified genes encoding 19 putative membrane-associated proteins of M. fermentans. Sequences of fusion constructs defined three types of export sequence: (1) non-cleavable, membrane-spanning sequences, (2) signal peptides with signal peptidase (SPase) I-like cleavage sites, and (3) signal peptides with SPase II-like lipoprotein-cleavage sites which, like most other mycoplasmal lipoprotein signals analysed to date, differed from those in several Gram-negative and Gram-positive eubacteria in their lack of a Leu residue at the -3 position. Antibodies to synthetic peptides that were deduced from two fusions to predicted lipoproteins, identified corresponding amphiphilic membrane proteins of 57 kDa and 78 kDa expressed in the mycoplasma. The P57 sequence contained a proline-rich N-terminal region analogous to an adhesin of Mycoplasma gallisepticum. The P78 protein was identical to a serologically defined phase-variant surface lipoprotein. TnphoA mutagenesis provides an efficient means of systematically characterizing functionally diverse lipoproteins and other exported proteins in mycoplasmas.

Molecular biological bases of resistance to HIV/AIDS (the hypothesis with elements of the theory)

Proceeding from the structure and function of the shell glycoprotein gp120 of the human immunodeficiency virus (HIV) and receptor glycoprotein CD4 on target cells for this virus, the author assumes that in nature there is genetically determined human resistance to the HIV infection and AIDS. This resistance manifests itself indirectly via products of the glycosylation system and via the composition and order of amino-acid residues in receptor CD4 sites responsible for interaction between the receptor and glycoprotein gp120. The author thinks that people in whom the glycosylation system determines either B(III) or AB(IV) blood groups are potential subjects of the HIV infection. But development of AIDS necessitates some conditions more, one of them is susceptibility of the human organism to be infected with mollicute Mycoplasma fermentans. This mycoplasma is able to recognize terminal NeuAc alpha 2-3 Gal in the composition of oligosaccharides of gp120, which permits it to adhere HIV virions on itself and then to transport them directly to the cells expressing receptor CD4 and having oligosaccharides of the same terminal structure. Oligosaccharides of glycocalyx of the mycoplasma protect it from the action of the human immune system and the mycoplasma, having "transported" HIV virions to target cells combines with membranes of the latter, stimulates formation by them of interleukin-1 and tumour necrosis factor, the known effectors of this virus reproduction. On the basis of all these factors the author identifies four types of human resistance to HIV/AIDS.

Taxonomy of the feline mycoplasmas Mycoplasma felifaucium, Mycoplasma feliminutum, Mycoplasma felis, Mycoplasma gateae, Mycoplasma leocaptivus, Mycoplasma leopharyngis, and Mycoplasma simbae by 16S rRNA gene sequence comparisons

The nucleotide sequence of the 16S rRNA gene of eight mycoplasmas isolated from felids was determined and used for taxonomic comparisons. A signature nucleotide sequence motif and overall sequence similarity to other mollicutes positioned Mycoplasma felifaucium, Mycoplasma felis, Mycoplasma leocaptivus, Mycoplasma leopharyngis, and Mycoplasma simbae in the Mycoplasma fermentans phylogenetic group of mollicutes. Mycoplasma arginini and Mycoplasma gateae were positioned in the Mycoplasma hominis phylogenetic group of mollicutes, and Mycoplasma feliminutum was positioned in the phylogenetically distant Acholeplasma group of mollicutes, showing that host family preference does not necessarily derive from bacterial phylogenetic closeness.

An unusual rRNA gene organization in Mycoplasma fermentans (incognitus strain)

The macro-restriction map of Mycoplasma fermentans (incognitus strain) was constructed and its rRNA genes were located on the map. It was found that this organism contains two sets of rRNA genes. The 16S and 23S rRNA genes were closely linked as two clusters. However, both 5S rRNA genes were separated from the 16S and 23S genes. The two 16S-23S rRNA gene clusters were arranged in an unusual tail to tail orientation.

[The use of an amplification test system for detecting persistent mycoplasmas]

A DNA amplification test system for the detection of Mycoplasma fermentans in clinical specimens was developed. The system was used for the analysis of biological specimens obtained from experimentally infected animals. The infective agent could be detected during the whole period of observation (6 months). High sensitivity of the polymerase chain reaction made it possible to detect M.fermentans in much greater number of cases than with the use of serological techniques.

Differential protein expression and surface presentation generate high-frequency antigenic variation in Mycoplasma fermentans

Mycoplasma fermentans, a wall-less prokaryote, is currently under investigation as a potential human pathogen. Recently, several surface lipoproteins have been shown to vary in expression between M. fermentans strains. Using specific antibodies to these lipoproteins, we investigated the extent and nature of antigenic variation within this species. Immunoscreening of type strain PG18 agar-grown colonies revealed marked heterogeneity in expression of distinct surface lipoproteins. Subsequent isolation and propagation of clonal isolates established isogenic lineages which displayed high-frequency (10(-2) to 10(-5) per generation) antigenic phase variation. [35S]cysteine-labeled protein profiles and Western immunoblots of phase-variant clones showed that several distinct integral membrane proteins undergo noncoordinate variation in expression. In addition to differential expression of epitope-bearing lipoproteins, differential accessibility of epitopes to antibodies was also documented as a mechanism generating surface phenotypic variation. Examination of one strain-variant antigen showed high-frequency phase variation to underlie previously observed antigenic differences between strains of this species. Thus, M. fermentans has a complex system capable of creating rapid changes in surface mosaics. This may profoundly affect mycoplasma-host interactions and may limit the methods by which populations of M. fermentans may be studied in vivo.

Use of the polymerase chain reaction for detection of Mycoplasma fermentans and Mycoplasma genitalium in the urogenital tract and amniotic fluid

In an attempt to further define the natural history of Mycoplasma genitalium and Mycoplasma fermentans infections in humans, we used cultures and the polymerase chain reaction (PCR) to determine whether these organisms were present in the urethra and cervix of sexually active adults and in the amniotic fluid of women whose membranes were intact and collected at the time of cesarean delivery (to preclude cervical contamination). M. genitalium was detected by PCR but not by culture in 11% of patients with urethritis or cervicitis. It was not detected by either PCR or culture in the 232 amniotic fluid samples analyzed. In contrast, M. fermentans was not detected by either method in patients with urethritis or cervicitis but was detected by PCR in 4 of 232 amniotic fluid samples tested. These results indicate that in these four cases M. fermentans was transferred transplacentally. Histological evidence of chorioamnionitis was present in two of the four patients, a finding suggesting that M. fermentans may be a cause of chorioamnionitis. These results must be confirmed by other investigators, and further studies should be undertaken to determine the potential clinical significance of M. fermentans infection.

Fatal systemic infections of nonhuman primates by Mycoplasma fermentans (incognitus strain)

Four silvered leaf monkeys inoculated with Mycoplasma fermentans (incognitus strain) showed wasting syndromes and died in 7-9 months. Infected animals had a late and transient antibody response to mycoplasmal infection. Three monkeys revealed periodic mycoplasmal antigenemia. The one that had the most persistent antigenemia failed to mount a detectable antibody response and was the first to die of the infection. The control monkey was killed 8 months later, after the last of the infected animals had died, and revealed no evidence of seroconversion or antigenemia. Polymerase chain reaction, immunohistochemical, and electron microscopic studies identified systemic infections of M. fermentans in the infected animals. No other opportunistic infection or neoplastic disease was found. It is interesting to note the absence of an inflammatory reaction to the large number of mycoplasmas in the infected tissues. M. fermentans (incognitus strain) apparently suppressed normal inflammatory or immune responses, produced wasting syndromes, and caused a fatal systemic infection in these monkeys.