Cytoadhesins of Mycoplasma hominis

Unraveling the adaptive strategies of Mycoplasma hominis through proteogenomic profiling of clinical isolates

Introduction

Mycoplasma hominis (M. hominis) belongs to the class Mollicutes, characterized by a very small genome size, reduction of metabolic pathways, including transcription factors, and the absence of a cell wall. Despite this, they adapt well not only to specific niches within the host organism but can also spread throughout the body, colonizing various organs and tissues. The adaptation mechanisms of M. hominis, as well as their regulatory pathways, are poorly understood. It is known that, when adapting to adverse conditions, Mycoplasmas can undergo phenotypic switches that may persist for several generations.

Methods

To investigate the adaptive properties of M. hominis related to survival in the host, we conducted a comparative phenotypic and proteogenomic analysis of eight clinical isolates of M. hominis obtained from patients with urogenital infections and the laboratory strain H-34.

Results

We have shown that clinical isolates differ in phenotypic features from the laboratory strain, form biofilms more effectively and show resistance to ofloxacin. The comparative proteogenomic analysis revealed that, unlike the laboratory strain, the clinical isolates possess several features related to stress survival: they switch carbon metabolism, activating the energetically least advantageous pathway of nucleoside utilization, which allows slowing down cellular processes and transitioning to a starvation state; they reconfigure the repertoire of membrane proteins; they have integrative conjugative elements in their genomes, which are key mediators of horizontal gene transfer. The upregulation of the methylating subunit of the restriction-modification (RM) system type I and the additional components of RM systems found in clinical isolates suggest that DNA methylation may play a role in regulating the adaptation mechanisms of M. hominis in the host organism. It has been shown that based on the proteogenomic profile, namely the genome sequence, protein content, composition of the RM systems and additional subunits HsdM, HsdS and HsdR, composition and number of transposable elements, as well as the sequence of the main variable antigen Vaa, we can divide clinical isolates into two phenotypes: typical colonies (TC), which have a high growth rate, and atypical (aTC) mini-colonies, which have a slow growth rate and exhibit properties similar to persisters.

Discussion

We believe that the key mechanism of adaptation of M. hominis in the host is phenotypic restructuring, leading to a slowing down cellular processes and the formation of small atypical colonies. This is due to a switch in carbon metabolism and activation the pathway of nucleoside utilization. We hypothesize that DNA methylation may play a role in regulating this switch.

Characterisation of Type II DNA Methyltransferases of Metamycoplasma hominis

Bacterial virulence, persistence and defence are affected by epigenetic modifications, including DNA methylation. Solitary DNA methyltransferases modulate a variety of cellular processes and influence bacterial virulence; as part of a restriction-modification (RM) system, they act as a primitive immune system in methylating the own DNA, while unmethylated foreign DNA is restricted. We identified a large family of type II DNA methyltransferases in Metamycoplasma hominis, comprising six solitary methyltransferases and four RM systems. Motif-specific 5mC and 6mA methylations were identified with a tailored Tombo analysis on Nanopore reads. Selected motifs with methylation scores >0.5 fit with the gene presence of DAM1 and DAM2, DCM2, DCM3, and DCM6, but not for DCM1, whose activity was strain-dependent. The activity of DCM1 for C^mCWGG and of both DAM1 and DAM2 for G^mATC was proven in methylation-sensitive restriction and finally for recombinant rDCM1 and rDAM2 against a dam-, dcm-negative background. A hitherto unknown dcm8/dam3 gene fusion containing a (TA) repeat region of varying length was characterized within a single strain, suggesting the expression of DCM8/DAM3 phase variants. The combination of genetic, bioinformatics, and enzymatic approaches enabled the detection of a huge family of type II DNA MTases in M. hominis, whose involvement in virulence and defence can now be characterized in future work.

Detection of Putative Virulence Genes alr, goiB, and goiC in Mycoplasma hominis Isolates from Austrian Patients

In Mycoplasma hominis, two genes (alr and goiB) have been found to be associated with the invasion of the amniotic cavity, and a single gene (goiC) to be associated with intra-amniotic infections and a high risk of preterm birth. The syntopic presence of Ureaplasma spp. in the same patient has been shown to correlate with the absence of goiC in M. hominis. The aim of our study was to investigate the presence of alr, goiB, and goiC genes in two groups of M. hominis isolates collected from symptomatic and asymptomatic male and non-pregnant female patients attending an Outpatients Centre. Group A consisted of 26 isolates from patients with only M. hominis confirmed; group B consisted of 24 isolates from patients with Ureaplasma spp. as the only co-infection. We extracted DNA from all M. hominis isolates and analysed the samples for the presence of alr, goiB, and goiC in a qPCR assay. Additionally, we determined their cytotoxicity against HeLa cells. We confirmed the presence of the alr gene in 85% of group A isolates and in 100% of group B isolates; goiB was detected in 46% of the samples in both groups, whereas goiC was found in 73% of group A and 79% of group B isolates, respectively. It was shown that co-colonisation with Ureaplasma spp. in the same patient had no effect on the presence of goiC in the respective M. hominis isolate. We did not observe any cytotoxic effect of the investigated isolates on human cells, regardless of the presence or absence of the investigated genes.

Diagnosis of Mycoplasma hominis Meningitis with Metagenomic Next-Generation Sequencing: A Case Report

Background

Mycoplasma hominis meningitis is a rare postoperative complication of neurosurgery. Accurate and early diagnosis of M. hominis remains challenging because of the limitations of traditional detection methods. Metagenomic next-generation sequencing (mNGS) is an advanced technique with high sensitivity and specificity for identifying infectious pathogens; however, its application in diagnosing M. hominis meningitis has not been widely studied.

Case Presentation

We report the case of a 61-year-old man who presented with fever and headache after neurosurgical treatment for a cerebral hemorrhage. Empiric antibiotic therapy was ineffective. Traditional culture of pathogens and serological testing yielded negative results, but M. hominis was detected in the cerebrospinal fluid by mNGS. After further verification by polymerase chain reaction (PCR), the patient's clinical treatment was adjusted accordingly. With targeted antibiotic intervention, the patient's symptoms were effectively alleviated, and clinical indicators returned to normal levels. Furthermore, the abundance of M. hominis decreased significantly compared to the initial mNGS reading after targeted treatment, indicating that the infection caused by M. hominis was effectively controlled.

Conclusion

Using mNGS, we found that M. hominis may be a candidate causative agent of meningitis. The technique also has the advantage of timeliness and accuracy that traditional cultures cannot achieve. A combination of mNGS with PCR is recommended to identify pathogens in the early stages of infectious diseases to administer targeted clinical medication.

[Clinical implications of the genus Mycoplasma]

Dentro del género Mycoplasma, las especies que tradicionalmente se han relacionado con cuadros infecciosos han sido principalmente M. pneumoniae, M. genitalium, M. hominis o U. urealyticum. Sin embargo, existen otras muchas que están implicadas y, que muchas veces, son desconocidas para los profesionales sanitarios. El objetivo de esta revisión es identificar todas las especies del género Mycoplasma que se han aislado en el hombre y determinar su participación en la patología infecciosa humana.

Characterisation of mobile genetic elements in Mycoplasma hominis with the description of ICEHo-II, a variant mycoplasma integrative and conjugative element

BACKGROUND

Mobile genetic elements are found in genomes throughout the microbial world, mediating genome plasticity and important prokaryotic phenotypes. Even the cell wall-less mycoplasmas, which are known to harbour a minimal set of genes, seem to accumulate mobile genetic elements. In Mycoplasma hominis, a facultative pathogen of the human urogenital tract and an inherently very heterogeneous species, four different MGE-classes had been detected until now: insertion sequence ISMhom-1, prophage MHoV-1, a tetracycline resistance mediating transposon, and ICEHo, a species-specific variant of a mycoplasma integrative and conjugative element encoding a T4SS secretion system (termed MICE).

RESULTS

To characterize the prevalence of these MGEs, genomes of 23 M. hominis isolates were assembled using whole genome sequencing and bioinformatically analysed for the presence of mobile genetic elements. In addition to the previously described MGEs, a new ICEHo variant was found, which we designate ICEHo-II. Of 15 ICEHo-II genes, five are common MICE genes; eight are unique to ICEHo-II; and two represent a duplication of a gene also present in ICEHo-I. In 150 M. hominis isolates and based on a screening PCR, prevalence of ICEHo-I was 40.7%; of ICEHo-II, 28.7%; and of both elements, 15.3%. Activity of ICEHo-I and -II was demonstrated by detection of circularized extrachromosomal forms of the elements through PCR and subsequent Sanger sequencing.

CONCLUSIONS

Nanopore sequencing enabled the identification of mobile genetic elements and of ICEHo-II, a novel MICE element of M. hominis, whose phenotypic impact and potential impact on pathogenicity can now be elucidated.

Microbiota of the Digestive Gland of Red Abalone (Haliotis rufescens) Is Affected by Withering Syndrome

Withering syndrome (WS), an infectious disease caused by intracellular bacteria Candidatus Xenohaliotis californiensis, has provoked significant economic losses in abalone aquaculture. The pathogen infects gastroenteric epithelia, including digestive gland, disrupting the digestive system and causing a progressive wilting in abalone. Nonetheless, our knowledge about WS implications in digestive gland microbiota, and its role in diseases progress remains largely unknown. This study aims to determine whether digestive gland-associated microbiota differs between healthy red abalone (Haliotis rufescens) and red abalone affected with WS. Using high-throughput sequencing of the V4 region of the 16S rRNA gene, our results revealed differences in microbiota between groups. Bacterial genera, including Mycoplasma, Lactobacillus, Cocleimonas and Tateyamaria were significantly more abundant in healthy abalones, whilst Candidatus Xenohaliotis californiensis and Marinomonas were more abundant in WS-affected abalones. Whilst Mycoplasma was the dominant genus in the healthy group, Candidatus Xenohaliotis californiensis was dominant in the WS group. However, Candidatus Xenohaliotis californiensis was present in two healthy specimens, and thus the Mycoplasma/Candidatus Xenohaliotis californiensis ratio appears to be more determinant in specimens affected with WS. Further research to elucidate the role of digestive gland microbiota ecology in WS pathogenesis is required.

MHO_0730 as a Surface-Exposed Calcium-Dependent Nuclease of Mycoplasma hominis Promoting Neutrophil Extracellular Trap Formation and Escape

Mycoplasma lipoproteins play a relevant role in pathogenicity and directly interact with the host immune system. Among human mycoplasmas, Mycoplasma hominis is described as a commensal bacterium that can be associated with a number of genital and extragenital conditions. Mechanisms of M. hominis pathogenicity are still largely obscure, and only a limited number of proteins have been associated with virulence. The current study focused on investigating the role of MHO_0730 as a virulence factor and demonstrated that MHO_0730 is a surface lipoprotein, potentially expressed in vivo during natural infection, acting both as a nuclease with its amino acidic portion and as a potent inducer of Neutrophil extracellular trapsosis with its N-terminal lipid moiety. Evidence for M. hominis neutrophil extracellular trap escape is also presented. Results highlight the relevance of MHO_0730 in promoting infection and modulation and evasion of innate immunity and provide additional knowledge on M. hominis virulence and survival in the host.

Random transposon insertion in the Mycoplasma hominis minimal genome

Mycoplasma hominis is an opportunistic human pathogen associated with genital and neonatal infections. Until this study, the lack of a reliable transformation method for the genetic manipulation of M. hominis hindered the investigation of the pathogenicity and the peculiar arginine-based metabolism of this bacterium. A genomic analysis of 20 different M. hominis strains revealed a number of putative restriction-modification systems in this species. Despite the presence of these systems, a reproducible polyethylene glycol (PEG)-mediated transformation protocol was successfully developed in this study for three different strains: two clinical isolates and the M132 reference strain. Transformants were generated by transposon mutagenesis with an efficiency of approximately 10^-9 transformants/cell/µg plasmid and were shown to carry single or multiple mini-transposons randomly inserted within their genomes. One M132-mutant was observed to carry a single-copy transposon inserted within the gene encoding P75, a protein potentially involved in adhesion. However, no difference in adhesion was observed in cell-assays between this mutant and the M132 parent strain. Whole genome sequencing of mutants carrying multiple copies of the transposon further revealed the occurrence of genomic rearrangements. Overall, this is the first time that genetically modified strains of M. hominis have been obtained by random mutagenesis using a mini-transposon conferring resistance to tetracycline.

Whole-Genome Characterization of Bacillus cereus Associated with Specific Disease Manifestations

Bacillus cereus remains an important cause of infections, particularly in immunocompromised hosts. While typically associated with enteric infections, disease manifestations can be quite diverse and include skin infections, bacteremia, pneumonia, and meningitis. Whether there are any genetic correlates of bacterial strains with particular clinical manifestations remains unknown. To address this gap in understanding, we undertook whole-genome analysis of B. cereus strains isolated from patients with a range of disease manifestations, including noninvasive colonizing disease, superficial skin infections, and invasive bacteremia. Interestingly, strains involved in skin infection tended to form a distinct genetic cluster compared to isolates associated with invasive disease. Other disease manifestations, despite not being exclusively clustered, nonetheless had unique genetic features. The unique features associated with the specific types of infections ranged from traditional virulence determinants to metabolic pathways and gene regulators. These data represent the largest genetic analysis to date of pathogenic B. cereus isolates with associated clinical parameters.

Production of a chimeric protein and its potential application in sero-diagnosis of Mycoplasma hominis infection

INTRODUCTION

Mycoplasma hominis is an opportunistic pathogen of the human genital tract. Detection of antibodies against this organism in human serum or plasma is theoretically unreliable because of high variation in bacterial surface antigens. In this study, we applied the bioinformatics tools to design a chimeric protein constructed of specific, conserved and predicted immuno-dominant epitopes from two different membrane proteins, P120 and P80.

MATERIAL AND METHODS

Linear B-cell epitopes of P120 and P80 were predicted and evaluated by bioinformatics tools and the designed chimeric protein was expressed in Escherichia coli. The chimeric protein, Mh128, was further analyzed in terms of immuno-reactivity by western blotting and enzyme immuno-sorbent assay (ELISA).

RESULTS

We found eight specific, conserved and immuno-dominant epitopes within P120 and P80 based on the bioinformatic studies. The constructed chimeric protein showed immuno-reaction in both western-blotting and ELISA tests.

DISCUSSION

Because of extensive variation of genomic and antigenic structure, diagnosis of M. hominis infection is difficult. Mh128 as a predicted specific and conserved recombinant protein can be potentially used for sero-diagnosis of M. hominis infection. We plan to develop an immuno-assay based on Mh128 and further evaluate the clinical specificity and sensitivity of the method.

Novel role of Vpmas as major adhesins of Mycoplasma agalactiae mediating differential cell adhesion and invasion of Vpma expression variants

Mycoplasma agalactiae exhibits antigenic variation by switching the expression of multiple surface lipoproteins called Vpmas. Although implicated to have a significant influence on the pathogenicity, their exact role in pathogen-host interactions has not been investigated so far. Initial attachment to host cells is regarded as one of the most important steps for colonization but this pathogen lacks the typical mycoplasma attachment organelle. The aim of this study was to determine the role of Vpmas in adhesion of M. agalactiae to host cells. 'Phase-Locked' Mutants (PLMs) steadily expressing single well-characterized Vpma lipoproteins served as ideal tools to evaluate the role of each of the six Vpmas in cytadhesion, which was otherwise not possible due to the high-frequency switching of Vpmas in the wildtype strain PG2. Using in vitro adhesion assays with HeLa and sheep mammary epithelial (MECs) and stromal (MSCs) cells, we could demonstrate differences in the adhesion capabilities of each of the six PLMs compared to the wildtype strain. The PLMV mutant expressing VpmaV exhibited the highest adhesion rate, whereas PLMU, which expresses VpmaU showed the lowest adhesion values explaining the reduced in vivo fitness of PLMU in sheep during experimental intramammary and conjunctival infections. Furthermore, adhesion inhibition assays using Vpma-specific polyclonal antisera were performed to confirm the role of Vpmas in M. agalactiae cytadhesion. This led to a significant decrease (p<0.05) in the adhesion percentage of each PLM. Immunofluorescence staining of TX-114 phase proteins extracted from each PLM showed binding of the respective Vpma to HeLa cells and MECs proving the direct role of Vpmas in cytadhesion. Furthermore, as adhesion is a prerequisite for cell invasion, the ability of the six PLMs to invade HeLa cells was also evaluated using the gentamicin protection assay. The results showed a strong correlation between the adhesion rates and invasion frequencies of the individual PLMs. This is the first report that describes a novel function of Vpma proteins in cell adhesion and invasion. Besides the variability of these proteins causing surface antigenic variation, the newly identified phenotypes are likely to play critical roles in the pathogenicity potential of this ruminant pathogen.

Comparative genomics of four Mycoplasma species of the human urogenital tract: Analysis of their core genomes and virulence genes

The variation in Mycoplasma lipoproteins attributed to genome rearrangements and genetic insertions leads to phenotypic plasticity that allows for the evasion of the host's defence system and pathogenesis. This paper compared for the first time the genomes of four human urogenital Mycoplasma species (M. penetrans HF-2, M. fermentans JER, M. genitalium G37 and M. hominis PG21) to categorise the metabolic functions of the core genes and to assess the effects of tandem repeats, phage-like genetic elements and prophages on the virulence genes. The results of this comparative in silico genomic analysis revealed that the genes constituting their core genomes can be separated into three distinct categories: nuclear metabolism, protein metabolism and energy generation each making up 52%, 31% and 23%, respectively. The genomes have repeat sequences ranging from 3.7% in M. hominis PG21 to 9.5% in M. fermentans JER. Tandem repeats (mostly minisatellites) and phage-like proteins (including DNA gyrases/topoisomerases) were randomly distributed in the Mycoplasma genomes. Here, we identified a coiled-coil structure containing protein in M. penetrans HF-2 which is significantly similar to the Mem protein of M. fermentans ɸMFV1. Therefore, a Mycoplasma prophage seems to be embedded within M. penetrans HF-2 unannotated genome. To the best of our knowledge, no Mycoplasma phages or prophages have been detected in M. penetrans. This study is important not only in understanding the complex genetic factors involved in phenotypic plasticity and virulence in the relatively understudied Mycoplasma species but also in elucidating the effective arrangement of their redundant minimal genomes.

Validation of a novel Mho microarray for a comprehensive characterisation of the Mycoplasma hominis action in HeLa cell infection

Mycoplasma hominis is the second smallest facultative pathogen of the human urogenital tract. With less than 600 protein-encoding genes, it represents an ideal model organism for the study of host-pathogen interactions. For a comprehensive characterisation of the M. hominis action in infection a customized Mho microarray, which was based on two genome sequences (PG21 and LBD-4), was designed to analyze the dynamics of the mycoplasma transcriptome during infection and validated for M. hominis strain FBG. RNA preparation was evaluated and adapted to ensure the highest recovery of mycoplasmal mRNAs from in vitro HeLa cell infection assays. Following cRNA hybridization, the read-out strategy of the hybridization results was optimized and confirmed by RT-PCR. A statistically robust infection assay with M. hominis strain FBG enabled the identification of differentially regulated key effector molecules such as critical cytoadhesins (4 h post infection (pI)), invasins (48 h pI) and proteins associated with establishing chronic infection of the host (336 h pI). Of the 294 differentially regulated genes (>2-fold) 128 (43.5%) encoded hypothetical proteins, including lipoproteins that seem to play a central role as virulence factors at each stage of infection: P75 as a novel cytoadhesin candidate, which is also differentially upregulated in chronic infection; the MHO_2100 protein, a postulated invasin and the MHO_730-protein, a novel ecto-nuclease and domain of an ABC transporter, the function of which in chronic infection has still to be elucidated. Implementation of the M. hominis microarray strategy led to a comprehensive identification of to date unknown candidates for virulence factors at relevant stages of host cell infection.

The Variable Internal Structure of the Mycoplasma penetrans Attachment Organelle Revealed by Biochemical and Microscopic Analyses: Implications for Attachment Organelle Mechanism and Evolution

Although mycoplasmas have small genomes, many of them, including the HIV-associated opportunist Mycoplasma penetrans, construct a polar attachment organelle (AO) that is used for both adherence to host cells and gliding motility. However, the irregular phylogenetic distribution of similar structures within the mycoplasmas, as well as compositional and ultrastructural differences among these AOs, suggests that AOs have arisen several times through convergent evolution. We investigated the ultrastructure and protein composition of the cytoskeleton-like material of the M. penetrans AO with several forms of microscopy and biochemical analysis, to determine whether the M. penetrans AO was constructed at the molecular level on principles similar to those of other mycoplasmas, such as Mycoplasma pneumoniae and Mycoplasma mobile We found that the M. penetrans AO interior was generally dissimilar from that of other mycoplasmas, in that it exhibited considerable heterogeneity in size and shape, suggesting a gel-like nature. In contrast, several of the 12 potential protein components identified by mass spectrometry of M. penetrans detergent-insoluble proteins shared certain distinctive biochemical characteristics with M. pneumoniae AO proteins, although not with M. mobile proteins. We conclude that convergence between M. penetrans and M. pneumoniae AOs extends to the molecular level, leading to the possibility that the less organized material in both M. pneumoniae and M. penetrans is the substance principally responsible for the organization and function of the AO.IMPORTANCEMycoplasma penetrans is a bacterium that infects HIV-positive patients and may contribute to the progression of AIDS. It attaches to host cells through a structure called an AO, but it is not clear how it builds this structure. Our research is significant not only because it identifies the novel protein components that make up the material within the AO that give it its structure but also because we find that the M. penetrans AO is organized unlike AOs from other mycoplasmas, suggesting that similar structures have evolved multiple times. From this work, we derive some basic principles by which mycoplasmas, and potentially all organisms, build structures at the subcellular level.

Cloning, Stability, and Modification of Mycoplasma hominis Genome in Yeast

Mycoplasma hominis is a minimal human pathogen that is responsible for genital and neonatal infections. Despite many attempts, there is no efficient genetic tool to manipulate this bacterium, limiting most investigations of its pathogenicity and its uncommon energy metabolism that relies on arginine. The recent cloning and subsequent engineering of other mycoplasma genomes in yeast opens new possibilities for studies of the genomes of genetically intractable organisms. Here, we report the successful one-step cloning of the M. hominis PG21 genome in yeast using the transformation-associated recombination (TAR) cloning method. At low passages, the M. hominis genome cloned into yeast displayed a conserved size. However, after ∼60 generations in selective media, this stability was affected, and large degradation events were detected, raising questions regarding the stability of large heterologous DNA molecules cloned in yeast and the need to minimize host propagation. Taking these results into account, we selected early passage yeast clones and successfully modified the M. hominis PG21 genome using the CRISPR/Cas9 editing tool, available in Saccharomyces cerevisiae. Complete M. hominis PG21 genomes lacking the adhesion-related vaa gene were efficiently obtained.

Identification of a gene in Mycoplasma hominis associated with preterm birth and microbial burden in intraamniotic infection

OBJECTIVE

Microbial invasion of the amniotic cavity is associated with spontaneous preterm labor and adverse pregnancy outcome, and Mycoplasma hominis often is present. However, the pathogenic process by which M hominis invades the amniotic cavity and gestational tissues, often resulting in chorioamnionitis and preterm birth, remains unknown. We hypothesized that strains of M hominis vary genetically with regards to their potential to invade and colonize the amniotic cavity and placenta.

STUDY DESIGN

We sequenced the entire genomes of 2 amniotic fluid isolates and a placental isolate of M hominis from pregnancies that resulted in preterm births and compared them with the previously sequenced genome of the type strain PG21. We identified genes that were specific to the amniotic fluid/placental isolates. We then determined the microbial burden and the presence of these genes in another set of subjects from whom samples of amniotic fluid had been collected and were positive for M hominis.

RESULTS

We identified 2 genes that encode surface-located membrane proteins (Lmp1 and Lmp-like) in the sequenced amniotic fluid/placental isolates that were truncated severely in PG21. We also identified, for the first time, a microbial gene of unknown function that is referred to in this study as gene of interest C that was associated significantly with bacterial burden in amniotic fluid and the risk of preterm delivery in patients with preterm labor.

CONCLUSION

A gene in M hominis was identified that is associated significantly with colonization and/or infection of the upper reproductive tract during pregnancy and with preterm birth.

Chlamydia trachomatis and Genital Mycoplasmas: Pathogens with an Impact on Human Reproductive Health

The most prevalent, curable sexually important diseases are those caused by Chlamydia trachomatis (C. trachomatis) and genital mycoplasmas. An important characteristic of these infections is their ability to cause long-term sequels in upper genital tract, thus potentially affecting the reproductive health in both sexes. Pelvic inflammatory disease (PID), tubal factor infertility (TFI), and ectopic pregnancy (EP) are well documented complications of C. trachomatis infection in women. The role of genital mycoplasmas in development of PID, TFI, and EP requires further evaluation, but growing evidence supports a significant role for these in the pathogenesis of chorioamnionitis, premature membrane rupture, and preterm labor in pregnant woman. Both C. trachomatis and genital mycoplasmas can affect the quality of sperm and possibly influence the fertility of men. For the purpose of this paper, basic, epidemiologic, clinical, therapeutic, and public health issue of these infections were reviewed and discussed, focusing on their impact on human reproductive health.

The identification of oppA gene homologues as part of the oligopeptide transport system in mycoplasmas

The lack of an annotated oppA gene as part of many oligopeptide permease (opp) operons has questioned the necessity of the oligopeptide-binding domain (OppA) as a part of the Opp transport system in mycoplasmas. This study investigated the occurrence of an oppA gene as part of the oppBCDF operon in 42 mycoplasma genomes. Except for hemoplasma, all mycoplasmas were found to possess one or more copies of the oppBCDF operon and with the help of similarity searches their oppA genes could be identified. Phylogenetic analysis of the combined OppABCDF amino acid sequences allowed them to be grouped into three types. Each type has a unique set of conserved motifs, which are likely to reflect substrate preference and adaption strategies. Our approach allowed the identification of oppA gene homologues for all mycoplasma opp operons and thereby provides a method for re-evaluating the current annotation of oppA genes in mycoplasma genomes.

An emerging mycoplasma associated with trichomoniasis, vaginal infection and disease

Humans are colonized by thousands of bacterial species, but it is difficult to assess the metabolic and pathogenic potential of the majority of these because they have yet to be cultured. Here, we characterize an uncultivated vaginal mycoplasma tightly associated with trichomoniasis that was previously known by its 16S rRNA sequence as "Mnola." In this study, the mycoplasma was found almost exclusively in women infected with the sexually transmitted pathogen Trichomonas vaginalis, but rarely observed in women with no diagnosed disease. The genomes of four strains of this species were reconstructed using metagenome sequencing and assembly of DNA from four discrete mid-vaginal samples, one of which was obtained from a pregnant woman with trichomoniasis who delivered prematurely. These bacteria harbor several putative virulence factors and display unique metabolic strategies. Genes encoding proteins with high similarity to potential virulence factors include two collagenases, a hemolysin, an O-sialoglycoprotein endopeptidase and a feoB-type ferrous iron transport system. We propose the name "Candidatus Mycoplasma girerdii" for this potential new pathogen.

A potential pathogenic factor from Mycoplasma hominis is a TLR2-dependent, macrophage-activating, P50-related adhesin

PROBLEM

Mycoplasma hominis has been implicated in many inflammatory conditions of the human urogenital tract in particular amniotic infections that lead to fetal and neonatal disease and pre-term labor. The mechanisms responsible are poorly defined.

METHOD OF STUDY

Biochemical and immunological methods were used to extract, purify, and characterize an inflammatory component present in M. hominis.

RESULTS

We isolated and purified to homogeneity a 40-kDa bioactive lipoprotein from M. hominis that was a potent TLR2-dependent, CD14-independent activator of the human THP-1 macrophage cell line. Homology searches of the N-terminal sequence revealed that 22 of the first 23 residues were identical to those seen for the phase-variable M. hominis p50 adhesin. The truncated P50t lipoprotein importantly retained its adhesive properties for human macrophages.

CONCLUSION

The unique adhesin/macrophage activator may play a key role in M. hominis infections by triggering an inflammatory cytokine cascade.

Host cell responses to persistent mycoplasmas--different stages in infection of HeLa cells with Mycoplasma hominis

Mycoplasma hominis is a facultative human pathogen primarily associated with bacterial vaginosis and pelvic inflammatory disease, but it is also able to spread to other sites, leading to arthritis or, in neonates, meningitis. With a minimal set of 537 annotated genes, M. hominis is the second smallest self-replicating mycoplasma and thus an ideal model organism for studying the effects of an infectious agent on its host more closely. M. hominis adherence, colonisation and invasion of HeLa cells were characterised in a time-course study using scanning electron microscopy, confocal microscopy and microarray-based analysis of the HeLa cell transcriptome. At 4 h post infection, cytoadherence of M. hominis to the HeLa cell surface was accompanied by differential regulation of 723 host genes (>2 fold change in expression). Genes associated with immune responses and signal transduction pathways were mainly affected and components involved in cell-cycle regulation, growth and death were highly upregulated. At 48 h post infection, when mycoplasma invasion started, 1588 host genes were differentially expressed and expression of genes for lysosome-specific proteins associated with bacterial lysis was detected. In a chronically infected HeLa cell line (2 weeks), the proportion of intracellular mycoplasmas reached a maximum of 10% and M. hominis-filled protrusions of the host cell membrane were seen by confocal microscopy, suggesting exocytotic dissemination. Of the 1972 regulated host genes, components of the ECM-receptor interaction pathway and phagosome-related integrins were markedly increased. The immune response was quite different to that at the beginning of infection, with a prominent induction of IL1B gene expression, affecting pathways of MAPK signalling, and genes connected with cytokine-cytokine interactions and apoptosis. These data show for the first time the complex, time-dependent reaction of the host directed at mycoplasmal clearance and the counter measures of this pestering pathogen.

Molecular methods for the detection of Mycoplasma and ureaplasma infections in humans: a paper from the 2011 William Beaumont Hospital Symposium on molecular pathology

Mycoplasma and Ureaplasma species are well-known human pathogens responsible for a broad array of inflammatory conditions involving the respiratory and urogenital tracts of neonates, children, and adults. Greater attention is being given to these organisms in diagnostic microbiology, largely as a result of improved methods for their laboratory detection, made possible by powerful molecular-based techniques that can be used for primary detection in clinical specimens. For slow-growing species, such as Mycoplasma pneumoniae and Mycoplasma genitalium, molecular-based detection is the only practical means for rapid microbiological diagnosis. Most molecular-based methods used for detection and characterization of conventional bacteria have been applied to these organisms. A complete genome sequence is available for one or more strains of all of the important human pathogens in the Mycoplasma and Ureaplasma genera. Information gained from genome analyses and improvements in efficiency of DNA sequencing are expected to significantly advance the field of molecular detection and genotyping during the next few years. This review provides a summary and critical review of methods suitable for detection and characterization of mycoplasmas and ureaplasmas of humans, with emphasis on molecular genotypic techniques.

Improved adhesive properties of recombinant bifidobacteria expressing the Bifidobacterium bifidum-specific lipoprotein BopA

Background

Bifidobacteria belong to one of the predominant bacterial groups in the intestinal microbiota of infants and adults. Several beneficial effects on the health status of their human hosts have been demonstrated making bifidobacteria interesting candidates for probiotic applications. Adhesion of probiotics to the intestinal epithelium is discussed as a prerequisite for colonisation of and persistence in the gastrointestinal tract.

Results

In the present study, 15 different strains of bifidobacteria were tested for adhesion. B. bifidum was identified as the species showing highest adhesion to all tested intestinal epithelial cell (IEC) lines. Adhesion of B. bifidum S17 to IECs was strongly reduced after treatment of bacteria with pronase. These results strongly indicate that a proteinaceous cell surface component mediates adhesion of B. bifidum S17 to IECs. In silico analysis of the currently accessible Bifidobacterium genomes identified bopA encoding a lipoprotein as a B. bifidum-specific gene previously shown to function as an adhesin of B. bifidum MIMBb75. The in silico results were confirmed by Southern Blot analysis. Furthermore, Northern Blot analysis demonstrated that bopA is expressed in all B. bifidum strains tested under conditions used to cultivate bacteria for adhesion assays. The BopA gene was successfully expressed in E. coli and purified by Ni-NTA affinity chromatography as a C-terminal His₆-fusion. Purified BopA had an inhibitory effect on adhesion of B. bifidum S17 to IECs. Moreover, bopA was successfully expressed in B. bifidum S17 and B. longum/infantis E18. Strains overexpressing bopA showed enhanced adhesion to IECs, clearly demonstrating a role of BopA in adhesion of B. bifidum strains.

Conclusions

BopA was identified as a B. bifidum-specific protein involved in adhesion to IECs. Bifidobacterium strains expressing bopA show enhanced adhesion. Our results represent the first report on recombinant bifidobacteria with improved adhesive properties.

In Mycoplasma hominis the OppA-mediated cytoadhesion depends on its ATPase activity

Background

In Mycoplasma hominis, a facultative human pathogen of the human genital tract, OppA, the substrate-binding domain of the oligopeptide permease, is a multifunctional protein involved in nutrition uptake, cytoadhesion and hydrolysis of extracellular ATP.

Results

To map the function-related protein regions the ATPase activity and adhesive behavior of OppA mutants were analyzed. Mutations of the Walker BA motifs resulted in an inhibition of up to 8% of the OppA ATPase activity, whereas deletion of the N-terminal CS1 or the CS2 region, structural motifs that are conserved in bacterial OppA proteins, reduced ATPase activity to 60% and deletion of CS3, the third conserved region adjacent to the Walker B motif led to a reduction to 42% ATPase activity.

Interestingly, adhesion of the OppA mutants to immobilized HeLa cells demonstrated that two distal regions are mainly involved in adherence of OppA: the CS1 region, deletion of which led to 35% of the cytoadhesion, and the Walker BA with the adjacent upstream region CS3, deletion of which led to 25% of the cytoadhesion. The influence of the ATPase activity on the adherence of M. hominis to HeLa cells was confirmed by the use of ATPase inhibitors which reduced mycoplasmal cytoadhesion to 50%.

Conclusions

These findings suggest that the OppA-mediated cytoadherence of Mycoplasma hominis depends on both, the topology of the neighbouring CS1 and ATPase domain regions and the functionality of the ecto-ATPase activity in addition.

Fatal outcome of a disseminated dual infection with drug-resistant Mycoplasma hominis and Ureaplasma parvum originating from a septic arthritis in an immunocompromised patient

Mycoplasma hominis and Ureaplasma parvum are rare causes of severe and fatal infections. The diagnosis of infection with mycoplasma is dependent on clinical suspicion and microbiological diagnosis, and often relies on molecular methods that do not readily detect antibiotic resistance. This may be of increasing importance as illustrated in the case below.

OppA, the ecto-ATPase of Mycoplasma hominis induces ATP release and cell death in HeLa cells

Background

In the facultative human pathogen Mycoplasma hominis, which belongs to the cell wall-less Mollicutes, the surface-localised substrate-binding domain OppA of the oligopeptide permease was characterised as the main ecto-ATPase.

Results

With the idea that extra-cellular ATP could only be provided by the infected host cells we analysed the ATP release of HeLa cells after incubation with different preparations of Mycoplasma hominis: intact bacterial cells, the membrane fraction with or without OppA, recombinant OppA as well as an ATPase-deficient OppA mutant. Release of ATP into the supernatant of the HeLa cells was primarily determined in all samples lacking ecto-ATPase activity of OppA. In the presence of the ATPase inhibitor DIDS the amount of ATP in the OppA-containing samples increased. This increase was maximal after incubation with fractions containing OppA protein indicating that OppA is involved in ATP release and subsequent hydrolysis. Real-time PCR analyses revealed that the proliferation of HeLa cells is reduced after infection with M. hominis and flow cytometry experiments established that OppA induces greater apoptosis than necrosis of HeLa cells whereas the preservation of ecto-ATPase activity of OppA induces apoptosis.

Conclusion

The OppA induced ATP-release and -hydrolysis induced cell death of M. hominis infected HeLa cells was predominantly due to apoptosis rather than necrosis. Future work will elucidate whether the induction of apoptosis is indispensable for survival of these non-invasive pathogen.

Characterization of a Novel Adhesin-like Gene and Design of a Real-Time PCR for Rapid, Sensitive, and Specific Detection of Spiroplasma kunkelii

Spiroplasma kunkelii, a cell wall-less bacterium, is the causal agent of corn stunt disease. The pathogen is restricted to phloem sieve cells of infected plants and is transmitted by phloem-feeding leafhoppers. Since symptoms of corn stunt disease may not appear until close to flowering time, early detection of the pathogen in disease-transmitting leafhoppers and in symptomless foliar tissues of host plants is critical to disease forecasting and outbreak management. In this study, a field-deployable real-time polymerase chain reaction (PCR) assay was developed for sensitive and specific detection of S. kunkelii. Nucleotide sequence from a previously unreported adhesin-like gene was used to design primers and a fluorogenic probe. The assay was able to detect the presence of S. kunkelii DNA as low as 5 fg, a sensitivity 100 times more than that of conventional PCR. The assay was found to be highly specific to S. kunkelii, as it did not cross-react with one of the most closely related plant pathogenic spiroplasma species, S. citri. The assay was successfully applied to rapid field detection of S. kunkelii in its plant host and insect vectors.

Mycoplasmas and ureaplasmas as neonatal pathogens

The genital mycoplasmas represent a complex and unique group of microorganisms that have been associated with a wide array of infectious diseases in adults and infants. The lack of conclusive knowledge regarding the pathogenic potential of Mycoplasma and Ureaplasma spp. in many conditions is due to a general unfamiliarity of physicians and microbiology laboratories with their fastidious growth requirements, leading to difficulty in their detection; their high prevalence in healthy persons; the poor design of research studies attempting to base association with disease on the mere presence of the organisms in the lower urogenital tract; the failure to consider multifactorial aspects of diseases; and considering these genital mycoplasmas only as a last resort. The situation is now changing because of a greater appreciation of the genital mycoplasmas as perinatal pathogens and improvements in laboratory detection, particularly with regard to the development of powerful molecular nucleic acid amplification tests. This review summarizes the epidemiology of genital mycoplasmas as causes of neonatal infections and premature birth; evidence linking ureaplasmas with bronchopulmonary dysplasia; recent changes in the taxonomy of the genus Ureaplasma; the neonatal host response to mycoplasma and ureaplasma infections; advances in laboratory detection, including molecular methods; and therapeutic considerations for treatment of systemic diseases.

P80, the HinT interacting membrane protein, is a secreted antigen of Mycoplasma hominis

Background

Mycoplasmas are cell wall-less bacteria which encode a minimal set of proteins. In Mycoplasma hominis, the genes encoding the surface-localized membrane complex P60/P80 are in an operon with a gene encoding a cytoplasmic, nucleotide-binding protein with a characteristic Histidine triad motif (HinT). HinT is found in both procaryotes and eukaryotes and known to hydrolyze adenosine nucleotides in eukaryotes. Immuno-precipitation and BIACore analysis revealed an interaction between HinT and the P80 domain of the membrane complex. As the membrane anchored P80 carries an N-terminal uncleaved signal peptide we have proposed that the N-terminus extends into the cytoplasm and interacts with the cytosolic HinT.

Results

Further characterization of P80 suggested that the 4.7 kDa signal peptide is protected from cleavage only in the membrane bound form. We found several proteins were released into the supernatant of a logarithmic phase mycoplasma culture, including P80, which was reduced in size by 10 kDa. Western blot analysis of recombinant P80 mutants expressed in E. coli and differing in the N-terminal region revealed that mutation of the +1 position of the mature protein (Asn to Pro) which is important for signal peptidase I recognition resulted in reduced P80 secretion. All other P80 variants were released into the supernatant, in general as a 74 kDa protein encompassing the helical part of P80. Incubation of M. hominis cells in phosphate buffered saline supplemented with divalent cations revealed that the release of mycoplasma proteins into the supernatant was inhibited by high concentrations of calciumions.

Conclusions

Our model for secretion of the P80 protein of M. hominis implies a two-step process. In general the P80 protein is transported across the membrane and remains complexed to P60, surface-exposed and membrane anchored via the uncleaved signal sequence. Loss of the 4.7 kDa signal peptide seems to be a pre-requisite for P80 secretion, which is followed by a proteolytic process leading to a helical 74 kDa product. We propose that this novel form of two-step secretion is one of the solutions to a life with a reduced gene set.

The vaa locus of Mycoplasma hominis contains a divergent genetic islet encoding a putative membrane protein

BACKGROUND

The Mycoplasma hominis vaa gene encodes a highly variable, surface antigen involved in the adhesion to host cells. We have analysed the structure of the vaa locus to elucidate the genetic basis for variation of vaa.

RESULTS

Mapping of vaa on existing physical maps of five M. hominis isolates by pulsed field gel electrophoresis revealed that vaa is located in a genomic region containing the majority of other characterized membrane protein genes of M. hominis. Sequencing of an 11 kb region containing the vaa locus of M. hominis isolate 132 showed the presence of conserved housekeeping genes at the borders of the region, uvrA upstream and the hitABL operon downstream to vaa. Analysis of 20 M. hominis isolates revealed that the vaa upstream region was conserved whereas the downstream region was highly variable. In isolate 132 this region contained an open reading frame (ORF) encoding a putative 160 kDa membrane protein. Homologous ORFs were present in half of the isolates, whereas this ORF, termed vmp (variable membrane protein), was deleted from the locus in the remaining isolates. Compellingly, the conserved upstream region and variable downstream region of vaa correlates with the genetic structure of vaa itself which consists of a conserved 5' end and a variable 3' end containing a variable number of exchangeable sequence cassettes.

CONCLUSION

Our data demonstrate that the vaa locus contains a divergent genetic islet, and indicate pronounced intraspecies recombination. The high variability level of the locus indicate that it is a chromosomal 'hot spot', presumably important for sustaining diversity and a high adaptation potential of M. hominis.

OppA, the substrate-binding subunit of the oligopeptide permease, is the major Ecto-ATPase of Mycoplasma hominis

Most ATPases, involved in energy-driven processes, act in the cytoplasm. However, external membrane-bound ATPases have also been described in parasites and eukaryotic cells. In Mycoplasma hominis, a bacterium lacking a cell wall, the surface-exposed substrate-binding protein OppA of an oligopeptide permease (Opp) contains an ATP binding P-loop structure in the C-terminal region. With ATP affinity chromatography and tryptic digestion in the presence or absence of ATP, the functionality of the Mg(2+)-dependent ATP binding site is demonstrated. In addition to ATP, ADP also could bind to OppA. The presence of an ATPase activity on the surface of M. hominis is indicated by the inactivation of ATP hydrolyzing activity of intact mycoplasma cells by the impermeable ATPase inhibitor 4',4'-diisothiocyanostilbene-2',2'-disulfonic acid and influenced by the ATP analog 5'-fluorosulfonyl-benzoyladenosine. Comparing equimolar amounts of OppA in intact mycoplasma cells and in the purified form indicated that more than 80% of the surface-localized ATPase activity is derived from OppA, implying that OppA is the main ATPase on the surface of mycoplasma cells. Together, these data present the first evidence that the cytoadhesive substrate binding protein OppA of the oligopeptide permease also functions as an ecto-ATPase in Mycoplasma hominis.

Characterization of P40, a cytadhesin of Mycoplasma agalactiae

An immunodominant protein, P40, of Mycoplasma agalactiae was analyzed genetically and functionally. The gene encoding P40 was cloned from type strain PG2, sequenced, submitted to point mutagenesis in order to convert mycoplasma-specific TGA(Trp) codon to the universal TGG(Trp) codon, and subsequently expressed in Escherichia coli. Nucleotide sequence-derived amino acid sequence comparisons revealed a similarity of P40 to the adhesin P50 of Mycoplasma hominis and to protein P89 of Spiroplasma citri, which is expected to be involved in adhesion. The amino acid sequence of P40 revealed a recognition site for a signal peptidase and strong antigenic and hydrophilic motifs in the C-terminal domain. Triton X-114 phase partitioning confirmed that P40 is a membrane protein. Fab fragments of antibodies directed against recombinant purified P40 significantly inhibited adherence of M. agalactiae strains PG2 to lamb joint synovial cells LSM 192. Sera taken sequentially from sheep infected with PG2 revealed that P40 induced a strong and persistent immune response that gave strong signals on immunoblots containing recombinant P40 even 3 months after infection. The gene encoding P40 was present in a single copy in all of the 26 field strains of M. agalactiae analyzed and was not detected in closely related mycoplasma species. P40 was expressed as a protein with an apparent molecular mass of 37 kDa on sodium dodecyl sulfate-acrylamide gels by all M. agalactiae strains except for serotype C strains, which showed nonsense mutations in their p40 genes.

Molecular design of Mycoplasma hominis Vaa adhesin

The variable adherence-associated (Vaa) adhesin of the opportunistic human pathogen Mycoplasma hominis is a surface-exposed, membrane-associated protein involved in the attachment of the bacterium to host cells. The molecular masses of recombinant 1 and 2 cassette forms of the protein determined by a light-scattering (LS) method were 23.9 kD and 36.5 kD, respectively, and corresponded to their monomeric forms. Circular dichroism (CD) spectroscopy of the full-length forms indicated that the Vaa protein has an alpha-helical content of approximately 80%. Sequence analysis indicates the presence of coiled-coil domains in both the conserved N-terminal and antigenic variable C-terminal part of the Vaa adhesin. Experimental results obtained with recombinant proteins corresponding to the N- or C-terminal parts of the shortest one-cassette form of the protein were consistent with the hypothesis of two distinct coiled-coil regions. The one-cassette Vaa monomer appears to be an elongated protein with a axial shape ratio of 1:10. Analysis of a two-cassette Vaa type reveals a similar axial shape ratio. The results are interpreted in terms of the topological organization of the Vaa protein indicating the localization of the adherence-mediating structure.

The cytosolic HinT protein of Mycoplasma hominis interacts with two membrane proteins

Histidine triad nucleotide-binding (HinT) proteins are dimeric proteins that bind to purines and are found in all three kingdoms: the eukarya, bacteria and archaea. In eukaryotes, HinT proteins have been detected intracellularly, but their function is unknown. Until now, knowledge about HinT proteins in prokaryotes was restricted to sequence similarities and nucleotide-binding studies. In this study, we provide evidence that, in the cell wall-less prokaryote, Mycoplasma hominis, the gene encoding the HinT protein forms an operon with two other genes. These genes encode the species-specific membrane proteins, P60 and P80, which are associated within the mycoplasma membrane. The finding that HinT interacts with this complex by binding to P80 provides novel insight into the organization of bacterial HinT proteins.

Spiroplasma citri Surface Protein P89 Implicated in Adhesion to Cells of the Vector Circulifer tenellus

ABSTRACT Two microtiter plate assays were developed to study the adherence of the plant-pathogenic mollicute Spiroplasma citri to a monolayer of cultured cells of its leafhopper vector, Circulifer tenellus. Adherence was significantly reduced by prior treatment of the spiroplasmas with proteinase K or pronase. Electrophoresis and western blotting of spiroplasma membrane proteins, before and after exposure of intact spiroplasmas to proteases, revealed the concomitant reduction in intensity of a major membrane protein (P89) and a new polypeptide of approximately 46 kDa in protease-treated preparations (P46). Triton X-114 phase partitioning demonstrated that P89 and P46 are amphiphilic, and labeling of the new polypeptide P46 with anti-P89 serum suggested that this molecule may be a breakdown product of P89. Regeneration of P89 after proteinase K treatment of spiroplasmas was directly associated with restoration of the pathogen's attachment capability. Treatment of spiroplasmas with any of several carbohydrates and glycoconjugates or with tetramethyl-urea, a compound that interferes with hydrophobic associations, had a negligible effect on attachment. These results suggest that a spiroplasma surface protein, P89, has a role in S. citri adherence to C. tenellus cells.

Molecular comparison of Mycoplasma hominis strains isolated from colonized women and women with various urogenital infections

Twenty Mycoplasma hominis strains isolated from colonized women and women with various urogenital infections were investigated for genetic and antigenic homogeneity by different methods. Restriction fragment length polymorphism analysis demonstrated heterogeneity for all strains, with one exception. Two strains sequentially isolated from one patient showed identical patterns. Otherwise, no clonal clustering could be detected within the strains isolated from either of the diagnostic groups. In contrast, SDS-PAGE analysis and the comparison of the immunoblot pattern revealed antigenic similarities of strains isolated from patients with bacterial vaginosis, chorioamnionitis, premature rupture of membranes and preterm delivery as well as endometritis but showed obvious differences in comparison to strains isolated from colonized women.

P48 major surface antigen of Mycoplasma agalactiae is homologous to a malp product of Mycoplasma fermentans and belongs to a selected family of bacterial lipoproteins

A major surface antigenic lipoprotein of Mycoplasma agalactiae, promptly recognized by the host's immune system, was characterized. The mature product, P48, showed significant similarity and shared conserved amino acid motifs with lipoproteins or predicted lipoproteins from Mycoplasma fermentans, Mycoplasma hyorhinis, relapsing fever Borrelia spp., Bacillus subtilis, and Treponema pallidum.

The adherence-associated lipoprotein P100, encoded by an opp operon structure, functions as the oligopeptide-binding domain OppA of a putative oligopeptide transport system in Mycoplasma hominis

Mycoplasma hominis, a cell-wall-less prokaryote, was shown to be cytoadherent by the participation of a 100-kDa membrane protein (P100). To identify the gene encoding P100, peptides of P100 were partially sequenced to enable the synthesis of P100-specific oligonucleotides suitable as probes for the detection of the P100 gene. With this strategy, we identified a genomic region of about 10. 4 kb in M. hominis FBG carrying the P100 gene. Analysis of the complete deduced protein sequence suggests that P100 is expressed as a pre-lipoprotein with a structure in the N-terminal region common to peptide-binding proteins and an ATP- or GTP-binding P-loop structure in the C-terminal region. Downstream of the P100 gene, an additional four open reading frames putatively encoding the four core domains of an active transport system, OppBCDF, were localized. The organization of the P100 gene and oppBCDF in a transcriptionally active operon structure was demonstrated in Northern blot and reverse transcription-PCR analyses, as all gene-specific probes detected a common RNA of 9.5 kb. Primer extension analysis revealed that the transcriptional initiation site was localized 323 nucleotides upstream of the methionine-encoding ATG of the P100 gene. The peptide-binding character of the P100 protein was confirmed by fluorescence spectroscopy and strongly suggests that the cytoadherence-mediating lipoprotein P100 represents OppA, the substrate-binding domain of a peptide transport system in M. hominis.

The phytopathogenic mollicute-insect vector interface: a closer look

ABSTRACT Spiroplasma citri, transmitted by phloem-feeding leafhoppers, moves from the gut lumen through the gut wall, hemolymph, and salivary glands and multiplies in insect tissues. Nontransmissible lines were deficient in their ability to cross these barriers. Molecular analysis revealed extensive chromosomal rearrangements between the transmissible and nontransmissible spiroplasma lines including a large chromosomal inversion and deletions of about 10 kb at each inversion border. One open reading frame of the deleted region, cloned from the transmissible strain BR3-3X, encodes an integral membrane protein of 58 kDa that shares limited sequence similarity with major adhesin proteins of two zoopathogenic mycoplasmas. Adhesion of spiroplasmas to cultured leafhopper cells was inhibited by proteases, suggesting that adherence to host cells is mediated by spiroplasma membrane protein(s). A hypothetical model for insect transmission of phytopathogenic mollicutes is presented.

Molecular biology and pathogenicity of mycoplasmas

The recent sequencing of the entire genomes of Mycoplasma genitalium and M. pneumoniae has attracted considerable attention to the molecular biology of mycoplasmas, the smallest self-replicating organisms. It appears that we are now much closer to the goal of defining, in molecular terms, the entire machinery of a self-replicating cell. Comparative genomics based on comparison of the genomic makeup of mycoplasmal genomes with those of other bacteria, has opened new ways of looking at the evolutionary history of the mycoplasmas. There is now solid genetic support for the hypothesis that mycoplasmas have evolved as a branch of gram-positive bacteria by a process of reductive evolution. During this process, the mycoplasmas lost considerable portions of their ancestors' chromosomes but retained the genes essential for life. Thus, the mycoplasmal genomes carry a high percentage of conserved genes, greatly facilitating gene annotation. The significant genome compaction that occurred in mycoplasmas was made possible by adopting a parasitic mode of life. The supply of nutrients from their hosts apparently enabled mycoplasmas to lose, during evolution, the genes for many assimilative processes. During their evolution and adaptation to a parasitic mode of life, the mycoplasmas have developed various genetic systems providing a highly plastic set of variable surface proteins to evade the host immune system. The uniqueness of the mycoplasmal systems is manifested by the presence of highly mutable modules combined with an ability to expand the antigenic repertoire by generating structural alternatives, all compressed into limited genomic sequences. In the absence of a cell wall and a periplasmic space, the majority of surface variable antigens in mycoplasmas are lipoproteins. Apart from providing specific antimycoplasmal defense, the host immune system is also involved in the development of pathogenic lesions and exacerbation of mycoplasma induced diseases. Mycoplasmas are able to stimulate as well as suppress lymphocytes in a nonspecific, polyclonal manner, both in vitro and in vivo. As well as to affecting various subsets of lymphocytes, mycoplasmas and mycoplasma-derived cell components modulate the activities of monocytes/macrophages and NK cells and trigger the production of a wide variety of up-regulating and down-regulating cytokines and chemokines. Mycoplasma-mediated secretion of proinflammatory cytokines, such as tumor necrosis factor alpha, interleukin-1 (IL-1), and IL-6, by macrophages and of up-regulating cytokines by mitogenically stimulated lymphocytes plays a major role in mycoplasma-induced immune system modulation and inflammatory responses.

Truncation as a novel form of variation of the p50 gene in Mycoplasma hominis

A characteristic feature of the mycoplasmas is the presence of variable surface proteins which may play an important role in the adaptation of the cell-wall-less organisms to their host environments. In addition, this antigen variation may be an important pathogenic property of the organism. The ubiquity of the gene encoding P50, an adhesin of Mycoplasma hominis FBG, and its transcription were analysed in different isolates of M. hominis. The p50 gene was present in all isolates tested. Based on Southern blot analysis and sequencing of the gene, the isolates could be classified into one of three distinct groups. Within two groups specific truncations of the p50 gene occurred. The reduction of the gene size was confirmed in Northern blot analysis of representative isolates from each group, with a decrease in transcript length from 1.6 kb in group G-1 down to 0.76 kb in group G-3. In addition to truncation, a coincidental duplication of some gene segments was detected. This work has provided evidence for the genetic basis of a further variation in the M. hominis P50 adhesin.

Cloning and expression of P60, a conserved surface-localized protein of Mycoplasma hominis, in Escherichia coli

The clp60 gene encoding P60, a conserved lipoprotein of Mycoplasma hominis, was cloned and sequenced from both the type strain PG21 and the isolate FBG. Both open reading frames were identical in length, comprising 1746 nucleotides. The deduced amino acid sequences differed in 16 out of 582 amino acids. As expected, none of these divergences mapped within the epitope that was recognized by mAb CG4 in all of the 198 isolates of M. hominis analyzed so far. This conserved epitope was narrowed down to amino acids 454 through 464 within the C terminus of P60. For the expression of the recombinant homolog P60, P60rec, in E. coli the TGA codons of clp60 were substituted for TGG codons prior to cloning of clp60 into the expression plasmid pQE41. The expression of P60rec as a fusion protein with dihydrofolate reductase carrying an N-terminal His-tag enabled the purification of large amounts of P60rec in a soluble form.

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.

Characterization of membrane surface proteins of Mycoplasma agalactiae during natural infection

We have analyzed antigenic variation of seven M. agalactiae wild strains using different sera from naturally infected sheep. Only 30 day sera recognized all surface proteins and inhibited the growth of mycoplasmas. Furthermore, we have observed that two strongly immunogenic proteins: 55 and 35 kDa were digested using 500 micrograms/ml of trypsin. These two bands are immunoprecipitated together with four other proteins but only the 35 kDa protein is recognized by eluted antibodies.

Mycoplasma synoviae has two distinct phase-variable major membrane antigens, one of which is a putative hemagglutinin

Mycoplasma synoviae is a major pathogen of poultry, causing synovitis and respiratory infection. A cluster of 45- to 50-kDa membrane proteins is immunodominant in strain WVU-1853. Four distinct proteins were identified in this cluster by high-pressure liquid chromatography. Monoclonal antibodies and monospecific antisera against each established that they fell into two groups, MSPA and MSPB, each containing two members distinguishable by a difference in hydrophobicity. A 25- to 30-kDa membrane protein (MSPC) was shown to be antigenically related to the MSPB proteins. Considerable variation in the size and expression of MSPA and MSPB was observed among different strains of M. synoviae. Examination of expression in colonies of strain WVU-1853 established that both MSPA and MSPB (and MSPC) were phase variable. Immunostaining of MSPB (and MSPC) with monoclonal antibodies exhibited quantal variation, with three distinct levels observed between and within colonies. Hemadsorption by M. synoviae colonies was also found to be phase variable, with some colonies exhibiting sectorial expression of hemadsorption. Monospecific antisera against MSPA inhibited hemagglutination, but neither monoclonal antibodies nor monospecific antisera against MSPB could inhibit hemagglutination. However, loss of the capacity to hemadsorb by individual clones was associated with loss of expression of both MSPA and MSPB. These findings have elucidated the complexity of structure, function, and expression of the 45- to 50-kDa membrane protein cluster of M. synoviae, and they suggest that all members of the cluster may be involved in adhesion.

Repetitive elements of the Mycoplasma hominis adhesin p50 can be differentiated by monoclonal antibodies

The gene encoding p50, an adhesin of Mycoplasma hominis, was identified, cloned, and sequenced. Comparison of the derived amino acid sequence with the N-terminal amino acids sequenced by the Edman reaction of the native protein revealed that p50 is expressed as a 467-amino-acid precursor. Posttranslational modification leads to a 441-amino-acid lipoprotein with an extended, predominantly helical structure and a leucine zipper. Computer analysis of the amino acid sequence identified a threefold-repetitive sequence motif comprising approximately three-quarters of the total protein. Different regions of the p50 polypeptide chain were expressed in Escherichia coli. Western blot (immunoblot) analysis of the E. coli lysates revealed that the epitopes of four p50-specific monoclonal antibodies were localized in the middle and C-terminal part of the protein. Epitope mapping by exonuclease III digestion showed that all of the four monoclonal antibodies bound within the same region of the threefold-repetitive amino acid sequence motif. The repeats, which were highly homologous but not identical in structure, could be differentiated by the monoclonal antibodies.