Molecular design of Mycoplasma hominis Vaa adhesin

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.

Correlation between the Colony Phenotype and Amino Acid Sequence of the Variable Vaa Antigen in Clinical Isolates of Mycoplasma hominis

A new Mycoplasma hominis phenotype forming mini-colonies (MC) on agar and distinct from the phenotype forming typical colonies (TC) not only in size, but also in morphology, growth rate, and resistance to adverse factors, has been previously identified. In this study, the phenotype of colonies was determined and a comparative analysis of the amino acid sequence of the main variable antigen Vaa of the laboratory strain N-34 and seven clinical isolates of M. hominis was performed. It is demonstrated that the amino acid sequence of Vaa in clinical isolates forming TC (similar to the laboratory strain N-34) is entirely analogous to that of laboratory strain. Clinical isolates forming MC carry amino acid substitutions in the variable C-terminal region of Vaa, which can contribute to adhesion to eukaryotic cells and immune evasion. The connection between colony phenotype and amino acid sequence of Vaa is established.

[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.

Infection strategies of mycoplasmas: Unraveling the panoply of virulence factors

Mycoplasmas, the smallest bacteria lacking a cell wall, can cause various diseases in both humans and animals. Mycoplasmas harbor a variety of virulence factors that enable them to overcome numerous barriers of entry into the host; using accessory proteins, mycoplasma adhesins can bind to the receptors or extracellular matrix of the host cell. Although the host immune system can eradicate the invading mycoplasma in most cases, a few sagacious mycoplasmas employ a series of invasion and immune escape strategies to ensure their continued survival within their hosts. For instance, capsular polysaccharides are crucial for anti-phagocytosis and immunomodulation. Invasive enzymes degrade reactive oxygen species, neutrophil extracellular traps, and immunoglobulins. Biofilm formation is important for establishing a persistent infection. During proliferation, successfully surviving mycoplasmas generate numerous metabolites, including hydrogen peroxide, ammonia and hydrogen sulfide; or secrete various exotoxins, such as community-acquired respiratory distress syndrome toxin, and hemolysins; and express various pathogenic enzymes, all of which have potent toxic effects on host cells. Furthermore, some inherent components of mycoplasmas, such as lipids, membrane lipoproteins, and even mycoplasma-generated superantigens, can exert a significant pathogenic impact on the host cells or the immune system. In this review, we describe the proposed virulence factors in the toolkit of notorious mycoplasmas to better understand the pathogenic features of these bacteria, along with their pathogenic mechanisms.

Mycoplasma hominis profile in women: Culture, kit, molecular diagnosis, antimicrobial resistance, and treatment

OBJECTIVES

Mycoplasma hominis (M.hominis) infections are sexually transmitted and usually associated with urogenital and respiratory diseases. The aim of our study was to (i) detect M. hominis in the vaginal and urine samples of sexually active women using three different detection methods and (ii) to determine the antimicrobial susceptibility and recurrence after the treatment.

METHODS

Both vaginal and urine samples were collected from 110 sexually active women at the Obstetrics and Gynecology Clinic, Başkent University Ankara Hospital, Turkey, between March 2015 and February 2016. The presence of M. hominis in the vaginal and urine samples was detected by in vitro culture, two biochemical diagnostics kits (Mycoplasma IES (Autobio, China) and Mycoplasma IST-2 (BioMérieux, France) and PCR. The antibiotic susceptibility of each sample was tested using the kits. The women positive for M. hominis were treated either singly or along with their sexual partners by tetracycline.

RESULTS

M. hominis was detected in 72 of 220 (32.7%) samples (both vaginal and urine). Of which 37 showed contrary results with two different kits and then were confirmed by PCR. In 13 samples the IES kit identified M. hominis missed by IST-2, and in 8 samples the MIST-2 kit identified M. hominis missed by IES, while both kits missed 6 samples that were agar culture positive for M. hominis." The highest susceptibility rate was observed against pristinamycin (100%), followed by 91%, 83%, and 75% for doxycycline, tetracycline, and josamycin, respectively. Twenty-five patients treated with tetracycline were followed after one month. The recurrence of M. hominis was not observed in any of the 18 cases where both sexual partners were treated but recurred in 5 of the 7 singly treated women.

CONCLUSIONS

The rate of M. hominis detection was significantly higher in the vaginal samples compared to the urine samples. The probability of detecting M. hominis by IST-2 kit was 1.18 times less than IES kit (p < 0.001). When the relationship between the samples was examined, the difference between IES and IST-2 for detecting M. hominis was statistically significant (p < 0.01). Antibiotic susceptibility tests indicated that the tetracycline group of antibiotics was effective in eliminating M. hominis when given to both the sexual partners.

A novel approach for the identification and phylogenetic delineation of human Mycoplasma species and strains using genomic segment sequence analysis

Human Mycoplasma are opportunistic, facultative pathogens that are site-specific in their colonization of mucosal surfaces. They are responsible for significant annual morbidity in humans by causing acute illnesses and chronic auto-inflammatory diseases via modulation of the host's immune system. Accurate and reliable identification of Mycoplasma species and their strains are thus of upmost importance. This study, analysed for the first time, the effectiveness of a short (50 kb) genome fragment (termed as R-segment), which includes the complete rRNA operon and the flanking region up to 50 kb, as a single phylogenetic marker for assessing the molecular taxonomy and determining the identity of human Mycoplasma species and their strains. The R-segments of human mycoplasmas were shown to have inherent genetic properties [average nucleotide identity (ANI), codon bias index (CBI), genome-to-genome distances (GGD) and % G + C] similar to their whole genome counterparts. Based on the results of our R segment analysis, a species of human Mycoplasma can simply be defined as a group of strains that share R-segments with ANIs ≥97%. Additionally, R-segments offered superiority to 16S rRNA gene sequences and multilocus sequences for the delineation of the human Mycoplasma species and their strains. The overall comparative genomic results suggest that R-segment analysis can be considered as a promising cost-effective tool for the epidemiological surveillance and differentiation of the closely related species and/or strains of human mycoplasmas.

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.

Characterization of the role in adherence of Mycoplasma hyorhinis variable lipoproteins containing different repeat unit copy numbers

Mycoplasma hyorhinis (M. hyorhinis) is an important pathogen of pigs. In previous studies, the variable lipoprotein (Vlp) family has been shown to play a role in mediating M. hyorhinis cytoadhesion. Herein, we performed several experiments to study the function of each Vlp family member in detail, especially examining the cytoadhesion functional domain and how the repeat unit copy number impacts on function. Recombinant proteins rVlpII, composed of region II from all seven Vlp members; rVlpIII, composed of repeat peptides from region III of all of Vlp members; as well as a series of recombinant rVlp proteins for each member containing different repeat unit copy numbers were constructed. All of the proteins were expressed in Escherichia coli and purified by affinity chromatography. The recombinant proteins, as well as seven keyhole limpet hemocyanin-conjugated Vlp peptides containing two copies of the repeat unit, were analyzed for their adherence to swine tracheal epithelial cells using a microtiter plate adherence assay. Both rVlpII and rVlpIII proteins were able to bind to cell membrane proteins. Among the repeat unit peptides, only PepVlpB and PepVlpG were able to bind to cell membrane proteins. All of the Vlp members had cytoadhesion capability. The adhesion abilities of the proteins containing 0 or 3 copies of the repeat unit were stronger than those of the proteins containing 12 copies. For rVlpA, rVlpB, rVlpD, rVlpF and rVlpG, the proteins containing no copies bound stronger than the proteins containing 3 copies. In contrast, the adherence of rVlpC3 was stronger than that of rVlpC0. There was no significant difference between the adherence of rVlpE3 and that of rVlpE0. Our results suggest that the major cytoadhesion sites of Vlps are mainly contained in region II, the function of which would be blocked by region III when region III is longer.

Mycoplasma lipoproteins are major determinants of neutrophil extracellular trap formation

Neutrophil granulocytes are paramount to innate responses as major effectors of acute inflammation. Among the various strategies enacted by neutrophils to eliminate microbes NETosis is a novel distinct antimicrobial activity in which an interlacement of chromatin fibres rich in granule-derived antimicrobial peptides and enzymes is extruded (NETs, neutrophils extracellular traps ). NETs contribute to the pathogenesis of acute and chronic inflammatory disorders. The interactions of mycoplasmas and innate immune cells, in particular neutrophil granulocytes, are poorly defined. Here, we describe NET formation in vivo in the mammary gland and milk of sheep naturally infected by Mycoplasma agalactiae. Also, we assess the contribution of liposoluble proteins, the most abundant component of the Mycoplasma membrane, in inducing NETosis. We demonstrate that Mycoplasma liposoluble proteins induce NET release at levels comparable to what observed with other stimuli, such as lipopolysaccharides and phorbol 12-myristate 13-acetate. Stimulation of neutrophils with synthetic diacylated lipopeptides based on the M. agalactiae P48, P80, and MAG_1000 proteins, combined in a mix or used individually, suggests that NETosis might not be dependent on a specific lipopeptide sequence. Also, NETosis is partially abolished when TLR2 is blocked with specific antibodies. The results presented in this work provide evidences for the mechanisms underlying NET activation in mycoplasma infections, and on their contribution to pathogenesis of mycoplasmosis.

The functions of the variable lipoprotein family of Mycoplasma hyorhinis in adherence to host cells

Mycoplasma hyorhinis (M. hyorhinis) is a swine pathogen that is associated with various human cancers and contamination in cell cultures. However, no studies on the adhesion molecules of this pathogen have yet been reported. The variable lipoprotein (Vlp) family is an important surface component of M. hyorhinis. Herein, we performed several experiments to identify the function of the Vlp family in adherence to host cells. Seven recombinant Vlp (rVlp) proteins were expressed in Escherichia coli and purified by affinity chromatography. The potential role of rVlp adherence to pig kidney (PK-15) and swine tracheal epithelial (STEC) cells was then studied by indirect immunofluorescence assay and microtiter plate adherence assay. Adhesion of M. hyorhinis to PK-15 and STEC cells was specifically inhibited by the addition of a cocktail of rVlp proteins. The rVlp protein mixture was shown to bind to both PK-15 and STEC cells. The binding increased in a dose-dependent manner and could be blocked by antisera against the rVlp proteins. Most of the rVlp proteins could bind individually to both PK-15 and STEC cells except for rVlpD and rVlpF, which bound only to STEC cells. Because Vlp members vary in size among different strains and generations, they may vary in their cytoadhesion capabilities in various strains. In summary, the present results indicate that the Vlp family functions as adhesins of M. hyorhinis.

Genetic variability of genital mycoplasmas and its clinical value

The article presents data on genetic variability of genital mycoplasmas. The author presents the results of genetic variability studies for M. hominis, gene vaa, U. parvum, gene mba, and M. genitalium, gene mg192, sampled from women with different clinical manifestations of inflammatory diseases of the urogenital system. Based on the molecular typing results for 138 samples of genital mycoplasmas, the author revealed a relationship between clinical manifestations of inflammatory diseases of the urogenital system caused by U. parvum and different U. parvum serovars as well as different genetic variations of M. hominis.Infection with 6 U. parvum serovar results in the development of inflammatory diseases of the urogenital tract accompanied by subjective manifestations (р < 0.05). Genetic variant II of М. hominis was revealed more often in patients with clinical manifestations of inflammatory diseases while variant I was revealed more often in patients infected with М. hominis without any signs of inflammation (р < 0.05). Genetic variants of M. genitalium were determined; no significant differences in terms of their prevalence in the examined patients were revealed.

Genetic variants of genital mycoplasmas and their relation to the clinical course of inflammatory diseases of the urogenital system in women

Goal of the study. To study genetic variability of M. hominis (based on the vaa gene) and M. genitalium (based on the mg192 gene) derived from biological material samples taken from women with different clinical manifestations of inflammatory diseases of the urogenital system and clinically healthy women (for M. hominis). Materials and methods. Genetic variability of twenty M. hominis samples taken from patients with inflammatory diseases of the urogenital system and twenty M. hominis samples taken from patients without clinical and laboratory signs of inflammatory processes of the urogenital system was studied by the sequence analysis method. Genetic variability of eight M. genitalium samples taken from patients with different clinical signs of inflammatory diseases of the urogenital system was also examined by the sequence analysis method. Results. Three genetic variants of M. hominis based on the vaa gene were found; variant I was revealed more often in patients with clinical manifestations of inflammatory diseases (65.0%), and variant II - in clinically healthy women (60.0%). Three phylogenetic M. gentium groups based on the mg192 gene were revealed; two samples were referred to Groups I and II, and four samples were referred to Group III. Samples from each phylogenetic groups were taken from patients with clinical and laboratory manifestations of cervicitis and urethritis. Conclusion. The study data demonstrate a potential effect of the VAA surface protein on the virulence of opportunistic M. hominis pathogens.

Sequence TTKF ↓ QE defines the site of proteolytic cleavage in Mhp683 protein, a novel glycosaminoglycan and cilium adhesin of Mycoplasma hyopneumoniae

Mycoplasma hyopneumoniae colonizes the ciliated respiratory epithelium of swine, disrupting mucociliary function and inducing chronic inflammation. P97 and P102 family members are major surface proteins of M. hyopneumoniae and play key roles in colonizing cilia via interactions with glycosaminoglycans and mucin. The p102 paralog, mhp683, and homologs in strains from different geographic origins encode a 135-kDa pre-protein (P135) that is cleaved into three fragments identified here as P45(683), P48(683), and P50(683). A peptide sequence (TTKF↓QE) was identified surrounding both cleavage sites in Mhp683. N-terminal sequences of P48(683) and P50(683), determined by Edman degradation and mass spectrometry, confirmed cleavage after the phenylalanine residue. A similar proteolytic cleavage site was identified by mass spectrometry in another paralog of the P97/P102 family. Trypsin digestion and surface biotinylation studies showed that P45(683), P48(683), and P50(683) reside on the M. hyopneumoniae cell surface. Binding assays of recombinant proteins F1(683)-F5(683), spanning Mhp683, showed saturable and dose-dependent binding to biotinylated heparin that was inhibited by unlabeled heparin, fucoidan, and mucin. F1(683)-F5(683) also bound porcine epithelial cilia, and antisera to F2(683) and F5(683) significantly inhibited cilium binding by M. hyopneumoniae cells. These data suggest that P45(683), P48(683), and P50(683) each display cilium- and proteoglycan-binding sites. Mhp683 is the first characterized glycosaminoglycan-binding member of the P102 family.

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.

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.

Identification and functional mapping of the Mycoplasma fermentans P29 adhesin

Initial adherence interactions between mycoplasmas and mammalian cells are important for host colonization and may contribute to subsequent pathogenic processes. Despite significant progress toward understanding the role of specialized, complex tip structures in the adherence of some mycoplasmas, particularly those that infect humans, less is known about adhesins through which other mycoplasmas of this host bind to diverse cell types, even though simpler surface components are likely to be involved. We show by flow cytometric analysis that a soluble recombinant fusion protein (FP29), representing the abundant P29 surface lipoprotein of Mycoplasma fermentans, binds human HeLa cells and inhibits M. fermentans binding to these cells, in both a quantitative and a saturable manner, whereas analogous fusion proteins representing other mycoplasma surface proteins did not. Constructs representing nested N- or C-terminal truncations of FP29 allowed initial mapping of this specific adherence function to a central region of the P29 sequence containing a 36-amino-acid disulfide loop. A derivative of FP29 containing a mutation converting one participating Cys to Ser, precluding intrachain disulfide bond formation, retained full activity. Together these results suggest that the direct interaction of M. fermentans with a ligand on the HeLa cell surface involves a limited segment of the P29 surface lipoprotein and requires neither the disulfide bond nor the contribution of adjacent portions of the protein. Earlier results indicating phase-variable display of monoclonal antibody surface epitopes on P29, now recognized to be outside this ligand binding region, raise the possibility that variation of mycoplasma surface architecture might alter the presentation of the binding region and the adherence phenotype. Preliminary results further indicated that FP29 could inhibit binding to HeLa cells by Mycoplasma hominis, a distinct human mycoplasma species displaying the phase-variable adhesin Vaa, but not that by Mycoplasma capricolum, an organism infecting caprine species. This result raises the additional, testable possibility that a common host cell ligand for two human mycoplasma species may be recognized through structurally dissimilar adhesins that undergo phase variation by two distinct mechanisms, governing protein expression (Vaa) or surface masking (P29).