Mycoplasma pneumoniae J-domain protein required for terminal organelle function

Identification of Mycoplasma pneumoniae proteins interacting with NOD2 and their role in macrophage inflammatory response

Mycoplasma pneumoniae (M. pneumoniae, Mp) is a cell wall-deficient microorganism known to cause chronic respiratory infections in both children and adults. Nucleotide-binding oligomerization domain-containing protein 2 (NOD2) is an intracellular pattern recognition receptor primarily responsible for identifying muramyl dipeptide (MDP) found in bacterial cell walls. Previous experiments have demonstrated that Mycoplasma ovipneumoniae induces macrophage autophagy through NOD2. In this study, we conducted RNA-seq analysis on macrophages infected with M. pneumoniae and observed an up-regulation in the expression of genes associated with the NOD2 signaling pathway. Mechanistic investigations further revealed the involvement of the NOD2 signaling pathway in the inflammatory response of macrophages activated by M. pneumoniae. We utilized GST pull-down technology in conjunction with liquid chromatography-tandem mass spectrometry (LC-MS/MS) to pinpoint the M. pneumoniae proteins that interact with NOD2. Additionally, co-immunoprecipitation (Co-IP) and immunofluorescence co-localization techniques were used to confirm the interaction between DUF16 protein and NOD2. We found that DUF16 protein can enter macrophages and induce macrophage inflammatory response through the NOD2/RIP2/NF-κB pathway. Notably, the region spanning amino acids 13-90 was identified as a critical region necessary for DUF16-induced inflammation. This research not only broadens our comprehension of the recognition process of the intracellular receptor NOD2, but also deepens our understanding of the development of M. pneumoniae infection.

Mycoplasma synoviae LP78 is a fibronectin/plasminogen binding protein, putative adhesion, and potential diagnostic antigen

Mycoplasma synoviae (M. synoviae) is one of the major poultry pathogens causing infectious synovitis, airsacculitis, a high incidence of shell breakage, and egg production loss. However, the pathogenesis of M. synoviae remains unclear. Adhesion of mycoplasmas to host cells is a crucial step in infection and colonization. The purpose of this study was to determine the adhesive function of a putative P80 family lipoprotein (LP78) and evaluate its application in the detection of antibodies against M. synoviae. Recombinant LP78 (rLP78) was expressed in the supernatant component of Escherichia coli and mouse anti-rLP78 serum was prepared. Bioinformatic analysis and western blotting results revealed that LP78 was conservative among M. synoviae strains. It was distributed not only in the cytoplasm but also on the membrane of M. synoviae through western blotting and indirect immunofluorescence (IFA). The adherence of M. synoviae to DF-1 cells was significantly inhibited by mouse anti-rLP78 serum (p < 0.01). IFA revealed that rLP78 adhered to DF-1 cells, and this adherence was prevented by mouse anti-rLP78 serum. Furthermore, rLP78 was found to bind to the DF-1 cells membrane proteins in a dose-dependent manner by enzyme-linked immunosorbent assay (ELISA). Screening of DF-1 cells membrane proteins by western blotting showed that proteins with molecular weight of 35-40 kDa and 55-70 kDa bound to rLP78. Moreover, rLP78 was identified to be a fibronectin/plasminogen binding protein. The sensitivity and specificity of rLP78-based iELISA were 85.7 and 94.1%, respectively. The maximum dilution of positive serum (HI titer, 1:128) detected via rLP78-based iELISA was 1:6,400, whereas that detected using a commercial ELISA kit was 1:12,800-1:25,600. Both rLP78-based iELISA and the commercial ELISA kit detected seroconversion after 7 days of challenge and immunization. No cross-reactivity with positive sera against other avian pathogens was observed in rLP78-based iELISA. Collectively, these results indicate that LP78 is a fibronectin/plasminogen-binding adhesion protein of M. synoviae and a potential diagnostic antigen. The present study will facilitate a better understanding of the pathogenesis of M. synoviae and the development of new diagnostic.

Distinct Mycoplasma pneumoniae Interactions with Sulfated and Sialylated Receptors

Mycoplasma pneumoniae is a cell wall-less bacterial pathogen of the conducting airways, causing bronchitis and atypical or "walking" pneumonia in humans. M. pneumoniae recognizes sialylated and sulfated oligosaccharide receptors to colonize the respiratory tract, but the contribution of the latter is particularly unclear. We used chamber slides coated with sulfatide (3-O-sulfogalactosylceramide) to provide a baseline for M. pneumoniae binding and gliding motility. As expected, M. pneumoniae bound to surfaces coated with sulfatide in a manner that was dependent on sulfatide concentration and incubation temperature and inhibited by competing dextran sulfate. However, mycoplasmas bound to sulfatide exhibited no gliding motility, regardless of receptor density. M. pneumoniae also bound lactose 3'-sulfate ligated to an inert polymer scaffold, and binding was inhibited by competing dextran sulfate. The major adhesin protein P1 mediates adherence to terminal sialic acids linked α-2,3, but P1-specific antibodies that blocked M. pneumoniae hemadsorption (HA) and binding to the sialylated glycoprotein laminin by 95% failed to inhibit mycoplasma binding to sulfatide, suggesting that P1 does not mediate binding to sulfated galactose. Consistent with this conclusion, the M. pneumoniae HA-negative mutant II-3 failed to bind to sialylated receptors but adhered to sulfatide in a temperature-dependent manner.

Electron cryotomography of Mycoplasma pneumoniae mutants correlates terminal organelle architectural features and function

The Mycoplasma pneumoniae terminal organelle functions in adherence and gliding motility and is comprised of at least eleven substructures. We used electron cryotomography to correlate impaired gliding and adherence function with changes in architecture in diverse terminal organelle mutants. All eleven substructures were accounted for in the prkC, prpC and P200 mutants, and variably so for the HMW3 mutant. Conversely, no terminal organelle substructures were evident in HMW1 and HMW2 mutants. The P41 mutant exhibits a terminal organelle detachment phenotype and lacked the bowl element normally present at the terminal organelle base. Complementation restored this substructure, establishing P41 as either a component of the bowl element or required for its assembly or stability, and that this bowl element is essential to anchor the terminal organelle but not for leverage in gliding. Mutants II-3, III-4 and topJ exhibited a visibly lower density of protein knobs on the terminal organelle surface. Mutants II-3 and III-4 lack accessory proteins required for a functional adhesin complex, while the topJ mutant lacks a DnaJ-like co-chaperone essential for its assembly. Taken together, these observations expand our understanding of the roles of certain terminal organelle proteins in the architecture and function of this complex structure.

Development of Mycoplasma pneumoniae biofilms in vitro and the limited role of motility

Mycoplasma pneumoniae is a bacterial pathogen of humans that is a major causative agent of chronic respiratory disease. M. pneumoniae infections often recur even after successful treatment of symptoms with antibiotics, and resistance to antibiotics is increasing worldwide, with nearly complete resistance in some places. Although biofilms often contribute to chronicity and resistance, M. pneumoniae biofilms remain poorly characterized. Scanning electron microscopy revealed that cells of wild-type (WT) M. pneumoniae strain M129 biofilms, as well as mutants II-3 and II-3R, in vitro became increasingly rounded as the biofilm towers matured over 5 days. The role of gliding motility in biofilm formation was addressed by analyzing differences in biofilm architecture in non-motile mutant II-3R and hypermotile mutant prpC-and by using time-lapse microcinematography to measure flux of cells around biofilm towers. There were no major differences in biofilm architecture between WT and motility mutants, with perhaps a slight tendency for the prpC- cells to spread outside towers during early stages of biofilm formation. Consistent with an insignificant role of motility in biofilm development, flux of cells near towers, which was low, was dominated by exit of cells. Immunofluorescence microscopy revealed that motility-associated attachment organelle (AO) proteins exhibited no discernable changes in localization to foci over time, but immunoblotting identified a decrease in steady-state levels of protein P200, which is required for normal gliding speed, as the WT culture aged. Non-adherent strain II-3 and non-motile strain II-3R also exhibited a steady decrease in P200 steady-state levels, suggesting that the decrease in P200 levels was not a response to changes in gliding behavior during maturation. We conclude that M. pneumoniae cells undergo morphological changes as biofilms mature, motility plays no major role in biofilm development, and P200 loss might be related to maturation of cells. This study helps to characterize potential therapeutic targets for M. pneumoniae infections.

Coinfection with Haemophilus parasuis serovar 4 increases the virulence of porcine circovirus type 2 in piglets

Background

Postweaning multisystemic wasting syndrome (PMWS) is an emerging disease in swine. Pigs with PMWS are often infected with a variety of other pathogens, including bacteria, viruses and mycoplasm, in addition to porcine circovirus type 2 (PCV2). PCV2 and Haemophilus parasuis serovar 4 (HPS4) coinfection remain epidemic in China.

Methods

Here we report construction of a three-week-old naturally farrowed, colostrum-deprived (NFCD) piglet’s infection model and demonstrate that PCV2-infected piglets with the HPS4 coinfection increased the virulence of PCV2 and these pathogens interact acquired PMWS.

Results

All the single infected piglets were transiently bacteremic or viremic. All the PCV2/HPS4 coinfected piglets developed PMWS, characterized by dyspnea, anorexia, prostration and lose weight severely. Co-infection with PCV2 and HPS4 resulted in an increased amount of virus in serum and tissues, presented a slower generation and lower levels of antibodies against PCV2. Co-infection with PCV2 and HPS4 resulted in further reductions in total and differential peripheral blood leukocyte counts. Meantime, PCV2/ HPS4 coinfection potentiated the severity of lung and lymphoid lesions by PCV2-associated, increased the virulence of PCV2-antigen and enhanced the incidence of PMWS in piglets.

Conclusion

Co-infection with PCV2 and HPS4 induce the exacerbation of system injuries and enhance the pathogenicity of PCV2 in piglets.

Mycoplasma pneumoniae from the Respiratory Tract and Beyond

Mycoplasma pneumoniae is an important cause of respiratory tract infections in children as well as adults that can range in severity from mild to life-threatening. Over the past several years there has been much new information published concerning infections caused by this organism. New molecular-based tests for M. pneumoniae detection are now commercially available in the United States, and advances in molecular typing systems have enhanced understanding of the epidemiology of infections. More strains have had their entire genome sequences published, providing additional insights into pathogenic mechanisms. Clinically significant acquired macrolide resistance has emerged worldwide and is now complicating treatment. In vitro susceptibility testing methods have been standardized, and several new drugs that may be effective against this organism are undergoing development. This review focuses on the many new developments that have occurred over the past several years that enhance our understanding of this microbe, which is among the smallest bacterial pathogens but one of great clinical importance.

Elongation Factor Tu and Heat Shock Protein 70 Are Membrane-Associated Proteins from Mycoplasma ovipneumoniae Capable of Inducing Strong Immune Response in Mice

Chronic non-progressive pneumonia, a disease that has become a worldwide epidemic has caused considerable loss to sheep industry. Mycoplasma ovipneumoniae (M. ovipneumoniae) is the causative agent of interstitial pneumonia in sheep, goat and bighorn. We here have identified by immunogold and immunoblotting that elongation factor Tu (EF-Tu) and heat shock protein 70 (HSP 70) are membrane-associated proteins on M. ovipneumonaiea. We have evaluated the humoral and cellular immune responses in vivo by immunizing BALB/c mice with both purified recombinant proteins rEF-Tu and rHSP70. The sera of both rEF-Tu and rHSP70 treated BALB/c mice demonstrated increased levels of IgG, IFN-γ, TNF-α, IL-12(p70), IL-4, IL-5 and IL-6. In addition, ELISPOT assay showed significant increase in IFN-γ⁺ secreting lymphocytes in the rHSP70 group when compared to other groups. Collectively our study reveals that rHSP70 induces a significantly better cellular immune response in mice, and may act as a Th1 cytokine-like adjuvant in immune response induction. Finally, growth inhibition test (GIT) of M. ovipneumoniae strain Y98 showed that sera from rHSP70 or rEF-Tu-immunized mice inhibited in vitro growth of M. ovipneumoniae. Our data strongly suggest that EF-Tu and HSP70 of M. ovipneumoniae are membrane-associated proteins capable of inducing antibody production, and cytokine secretion. Therefore, these two proteins may be potential candidates for vaccine development against M. ovipneumoniae infection in sheep.

Integrated Information and Prospects for Gliding Mechanism of the Pathogenic Bacterium Mycoplasma pneumoniae

Mycoplasma pneumoniae forms a membrane protrusion at a cell pole and is known to adhere to solid surfaces, including animal cells, and can glide on these surfaces with a speed up to 1 μm per second. Notably, gliding appears to be involved in the infectious process in addition to providing the bacteria with a means of escaping the host's immune systems. However, the genome of M. pneumoniae does not encode any of the known genes found in other bacterial motility systems or any conventional motor proteins that are responsible for eukaryotic motility. Thus, further analysis of the mechanism underlying M. pneumoniae gliding is warranted. The gliding machinery formed as the membrane protrusion can be divided into the surface and internal structures. On the surface, P1 adhesin, a 170 kDa transmembrane protein forms an adhesin complex with other two proteins. The internal structure features a terminal button, paired plates, and a bowl (wheel) complex. In total, the organelle is composed of more than 15 proteins. By integrating the currently available information by genetics, microscopy, and structural analyses, we have suggested a working model for the architecture of the organelle. Furthermore, in this article, we suggest and discuss a possible mechanism of gliding based on the structural model, in which the force generated around the bowl complex transmits through the paired plates, reaching the adhesin complex, resulting in the repeated catch of sialylated oligosaccharides on the host surface by the adhesin complex.

The effects of Mycoplasma hyopneumoniae on porcine circovirus type 2 replication in vitro PK-15 cells

Porcine circovirus type 2 (PCV2) is the causative agent of postweaning multisystemic wasting syndrome (PMWS). Mycoplasma hyopneumoniae (Mhp) is a very well-known co-factor that potentially enhances PCV2 replication and thus the development of PMWS. However, co-infection with Mhp and PCV2 in vivo under different conditions can produce divergent clinical signs and lesions. In this study, PCV2 replication could be enhanced by subsequent co-inoculation with Mhp (PCV2+Mhp) in a time and dose dependent method, but not by prior (Mhp+PCV2) or simultaneous (Mhp/PCV2) co-inoculation. Furthermore, different magnitudes of PCV2-infected cells, varying from 150% ± 14% to 351% ± 28%, were detected when co-infected with different Mhp strains. The relative percentage of PCV2-infected cells greatly decreased from 351% ± 28 to 141% ± 18 when the Mhp strain was treated with UV light for 12 h. These results offer the evidences to better understand the complex clinical syndromes in Mhp/PCV2 co-infection cases, and the occurrence of PMWS.

Systematic Structural Analyses of Attachment Organelle in Mycoplasma pneumoniae

Mycoplasma pneumoniae, a human pathogenic bacterium, glides on host cell surfaces by a unique and unknown mechanism. It forms an attachment organelle at a cell pole as a membrane protrusion composed of surface and internal structures, with a highly organized architecture. In the present study, we succeeded in isolating the internal structure of the organelle by sucrose-gradient centrifugation. The negative-staining electron microscopy clarified the details and dimensions of the internal structure, which is composed of terminal button, paired plates, and bowl complex from the end of cell front. Peptide mass fingerprinting of the structure suggested 25 novel components for the organelle, and 3 of them were suggested for their involvement in the structure through their subcellular localization determined by enhanced yellow fluorescent protein (EYFP) tagging. Thirteen component proteins including the previously reported ones were mapped on the organelle systematically for the first time, in nanometer order by EYFP tagging and immunoelectron microscopy. Two, three, and six specific proteins localized specifically to the terminal button, the paired plates, and the bowl, respectively and interestingly, HMW2 molecules were aligned parallel to form the plate. The integration of these results gave the whole image of the organelle and allowed us to discuss possible gliding mechanisms.

Human mycoplasma pneumonia, an epidemic of which occurred around the world a few years ago, is caused by a pathogenic bacterium, Mycoplasma pneumoniae. This tiny bacterium, about 2 μm long, infects humans by gliding on the surface of the trachea through binding to sialylated oligosaccharides, which are also the binding targets of influenza viruses. The mechanism underlying Mycoplasma "gliding motility" is not related to any other well-studied motility systems, such as bacterial flagella and eukaryotic motor proteins. Here, we isolated the internal structure of “attachment organelle", a cellular architecture, and suggested novel component proteins. The organelle was analyzed systematically by focusing on the protein components under fluorescence and electron microscopy, and a possible gliding mechanism was suggested.

A major determinant for gliding motility in Mycoplasma genitalium: the interaction between the terminal organelle proteins MG200 and MG491

Several mycoplasmas, such as the emergent human pathogen Mycoplasma genitalium, developed a complex polar structure, known as the terminal organelle (TO), responsible for a new type of cellular motility, which is involved in a variety of cell functions: cell division, adherence to host cells, and virulence. The TO cytoskeleton is organized as a multisubunit dynamic motor, including three main ultrastructures: the terminal button, the electrodense core, and the wheel complex. Here, we describe the interaction between MG200 and MG491, two of the main components of the TO wheel complex that connects the TO with the cell body and the cell membrane. The interaction between MG200 and MG491 has a KD in the 80 nm range, as determined by surface plasmon resonance. The interface between the two partners was confined to the "enriched in aromatic and glycine residues" (EAGR) box of MG200, previously described as a protein-protein interaction domain, and to a 25-residue-long peptide from the C-terminal region of MG491 by surface plasmon resonance and NMR spectroscopy studies. An atomic description of the MG200 EAGR box binding surface was also provided by solution NMR. An M. genitalium mutant lacking the MG491 segment corresponding to the peptide reveals specific alterations in cell motility and cell morphology indicating that the MG200-MG491 interaction plays a key role in the stability and functioning of the TO.

Mycoplasma pneumoniae, an underutilized model for bacterial cell biology

In recent decades, bacterial cell biology has seen great advances, and numerous model systems have been developed to study a wide variety of cellular processes, including cell division, motility, assembly of macromolecular structures, and biogenesis of cell polarity. Considerable attention has been given to these model organisms, which include Escherichia coli, Bacillus subtilis, Caulobacter crescentus, and Myxococcus xanthus. Studies of these processes in the pathogenic bacterium Mycoplasma pneumoniae and its close relatives have also been carried out on a smaller scale, but this work is often overlooked, in part due to this organism's reputation as minimalistic and simple. In this minireview, I discuss recent work on the role of the M. pneumoniae attachment organelle (AO), a structure required for adherence to host cells, in these processes. The AO is constructed from proteins that generally lack homology to those found in other organisms, and this construction occurs in coordination with cell cycle events. The proteins of the M. pneumoniae AO share compositional features with proteins with related roles in model organisms. Once constructed, the AO becomes activated for its role in a form of gliding motility whose underlying mechanism appears to be distinct from that of other gliding bacteria, including Mycoplasma mobile. Together with the FtsZ cytoskeletal protein, motility participates in the cell division process. My intention is to bring this deceptively complex organism into alignment with the better-known model systems.

Chaperone networking facilitates protein targeting to the bacterial cytoplasmic membrane

Nascent polypeptides emerging from the ribosome are assisted by a pool of molecular chaperones and targeting factors, which enable them to efficiently partition as cytosolic, integral membrane or exported proteins. Extensive genetic and biochemical analyses have significantly expanded our knowledge of chaperone tasking throughout this process. In bacteria, it is known that the folding of newly-synthesized cytosolic proteins is mainly orchestrated by three highly conserved molecular chaperones, namely Trigger Factor (TF), DnaK (HSP70) and GroEL (HSP60). Yet, it has been reported that these major chaperones are strongly involved in protein translocation pathways as well. This review describes such essential molecular chaperone functions, with emphasis on both the biogenesis of inner membrane proteins and the post-translational targeting of presecretory proteins to the Sec and the twin-arginine translocation (Tat) pathways. Critical interplay between TF, DnaK, GroEL and other molecular chaperones and targeting factors, including SecB, SecA, the signal recognition particle (SRP) and the redox enzyme maturation proteins (REMPs) is also discussed. This article is part of a Special Issue entitled: Protein trafficking and secretion in bacteria. Guest Editors: Anastassios Economou and Ross Dalbey.

Molecular characterization of the heat shock protein 70 gene in Mycoplasma ovipneumoniae

Mycoplasma ovipneumoniae is a species of mycoplasma bacteria that commonly infects the respiratory tract, causing respiratory disease in sheep and goats worldwide. In the current study, the 70-kDa heat shock protein (Hsp70) gene was cloned, sequenced and analyzed in 14 clinical isolates of M. ovipneumoniae. Results showed that, compared to the reference Y98 strain, the open-reading frames (ORFs) of Hsp70 gene in all isolates were 1818 base pairs (bp). Three nucleotides of TCA were inserted at 1,776 bp, resulting in insertion of the amino acid glutamine at amino acid position 593. The neighbor-joining trees, constructed using the Hsp70 gene, exhibited that the closest genetic relationship occurred between M. ovipneumoniae and Mycoplasma hyopneumoniae, which was consistent with the one based on the whole genome comparisons between these two mycoplasma species. Therefore, these results suggest that the Hsp70 gene, rather than 16S ribosomal RNA, was suitable as a potential molecular marker for evaluating the genetic relationship of M. ovipneumoniae with other bacterial species.

Biological database of images and genomes: tools for community annotations linking image and genomic information

Genomic data and biomedical imaging data are undergoing exponential growth. However, our understanding of the phenotype-genotype connection linking the two types of data is lagging behind. While there are many types of software that enable the manipulation and analysis of image data and genomic data as separate entities, there is no framework established for linking the two. We present a generic set of software tools, BioDIG, that allows linking of image data to genomic data. BioDIG tools can be applied to a wide range of research problems that require linking images to genomes. BioDIG features the following: rapid construction of web-based workbenches, community-based annotation, user management and web services. By using BioDIG to create websites, researchers and curators can rapidly annotate a large number of images with genomic information. Here we present the BioDIG software tools that include an image module, a genome module and a user management module. We also introduce a BioDIG-based website, MyDIG, which is being used to annotate images of mycoplasmas.

Protein kinase/phosphatase function correlates with gliding motility in Mycoplasma pneumoniae

Mycoplasma pneumoniae exhibits a novel form of gliding motility that is mediated by the terminal organelle, a differentiated polar structure. Given that genes known to be involved in gliding in other organisms are absent in M. pneumoniae, random transposon mutagenesis was employed to generate mutants with gliding-deficient phenotypes. Transposon insertions in the only annotated Ser/Thr protein kinase gene (prkC; MPN248) and its cognate phosphatase gene (prpC; MPN247) in M. pneumoniae resulted in significant and contrasting effects on gliding frequencies. prkC mutant cells glided at approximately half the frequency of wild-type cells, while prpC mutant cells glided more than twice as frequently as wild-type cells. Phosphoprotein staining confirmed the association between phosphorylation of the cytoskeletal proteins HMW1 and HMW2 and membrane protein P1 and the gliding phenotype. When the prpC mutant was complemented by transposon delivery of a wild-type copy of the prpC allele, gliding frequencies and phosphorylation levels returned to the wild-type standard. Surprisingly, delivery of the recombinant wild-type prkC allele dramatically increased gliding frequency to a level approximately 3-fold greater than that of wild-type in the prkC mutant. Collectively, these data suggest that PrkC and PrpC work in opposition in M. pneumoniae to influence gliding frequency.

P65 truncation impacts P30 dynamics during Mycoplasma pneumoniae gliding

The cell wall-less prokaryote Mycoplasma pneumoniae is a major cause of community-acquired bronchitis and pneumonia in humans. Colonization is mediated largely by a differentiated terminal organelle, which is also the leading end in gliding motility. Cytadherence-associated proteins P30 and P65 appear to traffic concurrently to the distal end of developing terminal organelles. Here, truncation of P65 due to transposon insertion in the corresponding gene resulted in lower gliding velocity, reduced cytadherence, and decreased steady-state levels of several terminal organelle proteins, including P30. Utilizing fluorescent protein fusions, we followed terminal organelle development over time. New P30 foci appeared at nascent terminal organelles in P65 mutants, as in the wild type. However, with forward cell motility, P30 in the P65 mutants appeared to drag toward the trailing cell pole, where it was released, yielding a fluorescent trail to which truncated P65 colocalized. In contrast, P30 was only rarely observed at the trailing end of gliding wild-type cells. Complementation with the recombinant wild-type P65 allele by transposon delivery restored P65 levels and stabilized P30 localization to the terminal organelle.

Vaccination of BALB/c mice with an avirulent Mycoplasma pneumoniae P30 mutant results in disease exacerbation upon challenge with a virulent strain

Mycoplasma pneumoniae is a significant human respiratory pathogen that causes high morbidity worldwide. No vaccine to prevent M. pneumoniae infection currently exists, since the mechanisms of pathogenesis are poorly understood. To this end, we constructed a P30 cytadhesin mutant (P-130) with a drastically reduced capacity for binding to erythrocytes and an inability to glide on glass substrates. This mutant was determined to be avirulent and cannot survive in the lungs of BALB/c mice. We also ascertained that the previously identified P30 gliding motility mutant II-3R is avirulent and also cannot be recovered from the lungs of mice after infection. Mutant P130 was then assessed for its efficacy as a live attenuated vaccine candidate in mice after challenge with wild-type M. pneumoniae. After vaccination with the P-130 P30 mutant, mice showed evidence of exacerbated disease upon subsequent challenge with the wild-type strain PI1428, which appears to be driven by a Th17 response and corresponding eosinophilia. Our results are in accordance with other reports of vaccine-induced disease exacerbation in rodents and emphasize the need to better understand the basic mechanisms of M. pneumoniae pathogenesis.

Loss of co-chaperone TopJ impacts adhesin P1 presentation and terminal organelle maturation in Mycoplasma pneumoniae

Mycoplasma pneumoniae is a wall-less human respiratory tract pathogen that colonizes mucosal epithelium via a polar terminal organelle having a central electron-dense core and adhesin-related proteins clustered at a terminal button. A mutant lacking J-domain co-chaperone TopJ is non-cytadherent and non-motile, despite having a core and normal levels of the major cytadherence-associated proteins. J-domain co-chaperones work with DnaK to catalyse polypeptide binding and subsequent protein folding. Here we compared features of the topJ mutant with other cytadherence mutants to elucidate the contribution of TopJ to cytadherence function. The topJ mutant was similar ultrastructurally to a non-cytadherent mutant lacking terminal organelle proteins B/C, including aberrant core positioning and cell morphology in thin sections, but exhibited a hybrid satellite growth pattern with features of mutants both having and lacking a core. Time-lapse images of mycoplasmas expressing a YFP fusion with terminal organelle protein P41 suggested that terminal organelle formation/positioning was delayed or poorly co-ordinated with cell growth in the absence of TopJ. TopJ required a core for localization, perhaps involving HMW1. P1 trypsin accessibility on other non-cytadherent mutants was significantly enhanced over wild type but unexpectedly was reduced with topJ mutant cells, suggesting impaired processing, translocation and/or folding of this adhesin.

Domain analysis of protein P30 in Mycoplasma pneumoniae cytadherence and gliding motility

The cell wall-less prokaryote Mycoplasma pneumoniae causes bronchitis and atypical pneumonia in humans. Mycoplasma attachment and gliding motility are required for colonization of the respiratory epithelium and are mediated largely by a differentiated terminal organelle. P30 is a membrane protein at the distal end of the terminal organelle and is required for cytadherence and gliding motility, but little is known about the functional role of its specific domains. In the current study, domain deletion and substitution derivatives of P30 were engineered and introduced into a P30 null mutant by transposon delivery to assess their ability to rescue P30 function. Domain deletions involving the extracellular region of P30 severely impacted protein stability and adherence and gliding function, as well as the capacity to stabilize terminal organelle protein P65. Amino acid substitutions in the transmembrane domain revealed specific residues uniquely required for P30 stability and function, perhaps to establish correct topography in the membrane for effective alignment with binding partners. Deletions within the predicted cytoplasmic domain did not affect P30 localization or its capacity to stabilize P65 but markedly impaired gliding motility and cytadherence. The larger of two cytoplasmic domain deletions also appeared to remove the P30 signal peptide processing site, suggesting a larger leader peptide than expected. We propose that the P30 cytoplasmic domain may be required to link P30 to the terminal organelle core, to enable the P30 extracellular domain to achieve a functional conformation, or perhaps both.

Functional domain analysis of the Mycoplasma pneumoniae co-chaperone TopJ

Colonization of conducting airways of humans by the prokaryote Mycoplasma pneumoniae is mediated by a differentiated terminal organelle important in cytadherence, gliding motility and cell division. TopJ is a predicted J-domain co-chaperone also having domains unique to mycoplasma terminal organelle proteins and is essential for terminal organelle function, as well as stabilization of protein P24, which is required for normal initiation of terminal organelle formation. J-domains activate the ATPase of DnaK chaperones, facilitating peptide binding and proper protein folding. We performed mutational analysis of the predicted J-domain, central acidic and proline-rich (APR) domain, and C-terminal domain of TopJ and assessed the phenotypic consequences when introduced into an M. pneumoniae topJ mutant. A TopJ derivative with amino acid substitutions in the canonical J-domain histidine-proline-aspartic acid motif restored P24 levels but not normal motility, morphology or cytadherence, consistent with a J-domain co-chaperone function. In contrast, TopJ derivatives having APR or C-terminal domain deletions were less stable and failed to restore P24, but resulted in normal morphology, intermediate gliding motility and cytadherence levels exceeding that of wild-type cells. Results from immunofluorescence microscopy suggest that both the APR and C-terminal domains, but not the histidine-proline-aspartic acid motif, are critical for TopJ localization to the terminal organelle.