Isolation and characterization of P1 adhesin, a leg protein of the gliding bacterium Mycoplasma pneumoniae

Rheotaxis in Mycoplasma gliding

This review describes the upstream-directed movement in the small parasitic bacterium Mycoplasma. Many Mycoplasma species exhibit gliding motility, a form of biological motion over surfaces without the aid of general surface appendages such as flagella. The gliding motility is characterized by a constant unidirectional movement without changes in direction or backward motion. Unlike flagellated bacteria, Mycoplasma lacks the general chemotactic signaling system to control their moving direction. Therefore, the physiological role of directionless travel in Mycoplasma gliding remains unclear. Recently, high-precision measurements under an optical microscope have revealed that three species of Mycoplasma exhibited rheotaxis, that is, the direction of gliding motility is lead upstream by the water flow. This intriguing response appears to be optimized for the flow patterns encountered at host surfaces. This review provides a comprehensive overview of the morphology, behavior, and habitat of Mycoplasma gliding, and discusses the possibility that the rheotaxis is ubiquitous among them.

Molecular Tools for Typing Mycoplasma pneumoniae and Mycoplasma genitalium

Mycoplasma pneumoniae and Mycoplasma genitalium are cell wall-less bacteria with strongly reduced genome content and close phylogenetic relatedness. In humans, the only known natural host, the microorganisms colonize the respiratory or genitourinary mucosa and may cause a broad range of clinical presentations. Besides fundamental differences in their tissue specificity, transmission route, and ability to cause prevalence peaks, both species share similarities such as the occurrence of asymptomatic carriers, preferred populations for infection, and problems with high rates of antimicrobial resistance. To further understand the epidemiology of these practically challenging bacteria, typing of strains is necessary. Since the cultivation of both pathogens is difficult and not performed outside of specialized laboratories, molecular typing methods with adequate discriminatory power, stability, and reproducibility have been developed. These include the characterization of genes containing repetitive sequences, of variable genome regions without the presence of repetitive sequences, determination of single and multi-locus variable-number tandem repeats, and detection of single nucleotide polymorphisms in different genes, respectively. The current repertoire of procedures allows reliable differentiation of strains circulating in different populations and in different time periods as well as comparison of strains occurring subsequently in individual patients. In this review, the methods for typing M. pneumoniae and M. genitalium, including the results of their application in different studies, are summarized and current knowledge regarding the association of typing data with the clinical characteristics of infections is presented.

LoxTnSeq: random transposon insertions combined with cre/lox recombination and counterselection to generate large random genome reductions

The removal of unwanted genetic material is a key aspect in many synthetic biology efforts and often requires preliminary knowledge of which genomic regions are dispensable. Typically, these efforts are guided by transposon mutagenesis studies, coupled to deepsequencing (TnSeq) to identify insertion points and gene essentiality. However, epistatic interactions can cause unforeseen changes in essentiality after the deletion of a gene, leading to the redundancy of these essentiality maps. Here, we present LoxTnSeq, a new methodology to generate and catalogue libraries of genome reduction mutants. LoxTnSeq combines random integration of lox sites by transposon mutagenesis, and the generation of mutants via Cre recombinase, catalogued via deep sequencing. When LoxTnSeq was applied to the naturally genome reduced bacterium Mycoplasma pneumoniae, we obtained a mutant pool containing 285 unique deletions. These deletions spanned from > 50 bp to 28 Kb, which represents 21% of the total genome. LoxTnSeq also highlighted large regions of non-essential genes that could be removed simultaneously, and other non-essential regions that could not, providing a guide for future genome reductions.

Force and Stepwise Movements of Gliding Motility in Human Pathogenic Bacterium Mycoplasma pneumoniae

Mycoplasma pneumoniae, a human pathogenic bacterium, binds to sialylated oligosaccharides and glides on host cell surfaces via a unique mechanism. Gliding motility is essential for initiating the infectious process. In the present study, we measured the stall force of an M. pneumoniae cell carrying a bead that was manipulated using optical tweezers on two strains. The stall forces of M129 and FH strains were averaged to be 23.7 and 19.7 pN, respectively, much weaker than those of other bacterial surface motilities. The binding activity and gliding speed of the M129 strain on sialylated oligosaccharides were eight and two times higher than those of the FH strain, respectively, showing that binding activity is not linked to gliding force. Gliding speed decreased when cell binding was reduced by addition of free sialylated oligosaccharides, indicating the existence of a drag force during gliding. We detected stepwise movements, likely caused by a single leg under 0.2-0.3 mM free sialylated oligosaccharides. A step size of 14-19 nm showed that 25-35 propulsion steps per second are required to achieve the usual gliding speed. The step size was reduced to less than half with the load applied using optical tweezers, showing that a 2.5 pN force from a cell is exerted on a leg. The work performed in this step was 16-30% of the free energy of the hydrolysis of ATP molecules, suggesting that this step is linked to the elementary process of M. pneumoniae gliding. We discuss a model to explain the gliding mechanism, based on the information currently available.

Molecular ruler of the attachment organelle in Mycoplasma pneumoniae

Length control is a fundamental requirement for molecular architecture. Even small wall-less bacteria have specially developed macro-molecular structures to support their survival. Mycoplasma pneumoniae, a human pathogen, forms a polar extension called an attachment organelle, which mediates cell division, cytadherence, and cell movement at host cell surface. This characteristic ultrastructure has a constant size of 250–300 nm, but its design principle remains unclear. In this study, we constructed several mutants by genetic manipulation to increase or decrease coiled-coil regions of HMW2, a major component protein of 200 kDa aligned in parallel along the cell axis. HMW2-engineered mutants produced both long and short attachment organelles, which we quantified by transmission electron microscopy and fluorescent microscopy with nano-meter precision. This simple design of HMW2 acting as a molecular ruler for the attachment organelle should provide an insight into bacterial cellular organization and its function for their parasitic lifestyles.

Mycoplasma pneumoniae, a pathogen of “walking pneumonia”, have a membrane protrusion with a precise length of 250–300 nm specially developed to support their parasitic lifestyles. To date, however, there has been no report focusing on the potential length-control mechanisms of this characteristic architecture called an attachment organelle. Here, we found that the coiled-coil domains of the 200-kDa protein HMW2 are aligned in parallel along the cell axis, and acts as a molecular ruler by the assembly into a physical scaffold. The molecular ruler could be engineered by genetic modification to produce both longer and shorter attachment organelle. The analyses of the length-controlled mutant highlight a simple design principle of cellular organization in a small bacterium.

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 pneumoniae Infections: Pathogenesis and Vaccine Development

Mycoplasma pneumoniae is a major causative agent of community-acquired pneumonia which can lead to both acute upper and lower respiratory tract inflammation, and extrapulmonary syndromes. Refractory pneumonia caused by M. pneumonia can be life-threatening, especially in infants and the elderly. Here, based on a comprehensive review of the scientific literature related to the respective area, we summarize the virulence factors of M. pneumoniae and the major pathogenic mechanisms mediated by the pathogen: adhesion to host cells, direct cytotoxicity against host cells, inflammatory response-induced immune injury, and immune evasion. The increasing rate of macrolide-resistant strains and the harmful side effects of other sensitive antibiotics (e.g., respiratory quinolones and tetracyclines) in young children make it difficult to treat, and increase the health risk or re-infections. Hence, there is an urgent need for development of an effective vaccine to prevent M. pneumoniae infections in children. Various types of M. pneumoniae vaccines have been reported, including whole-cell vaccines (inactivated and live-attenuated vaccines), subunit vaccines (involving M. pneumoniae protein P1, protein P30, protein P116 and CARDS toxin) and DNA vaccines. This narrative review summarizes the key pathogenic mechanisms underlying M. pneumoniae infection and highlights the relevant vaccines that have been developed and their reported effectiveness.

Pathogenic Analysis of the Bronchoalveolar Lavage Fluid Samples With Pediatric Refractory Mycoplasma pneumoniae Pneumonia

Background: We conducted a pathogenic analysis in the bronchoalveolar lavage fluid (BALF) samples from refractory Mycoplasma pneumoniae pneumonia (RMPP) children.

Methods: A total of 150 BALF samples from 60 RMPP patients were analyzed to investigate pathogenic changes. The characteristics of M. pneumoniae were analyzed through culture, real-time PCR, genotyping, antimicrobial susceptibility testing and proteomics. The other pathogens were determined using culture, sequencing and nucleic acid detection.

Results: In 60 RMPP cases, the bacterial co-infection rate was 5%, while that of virus was 33.3%. The poor prognosis rate was 61.7%. The DNA positive rate among the 150 samples was 98.7%, while the culture positive rate was 56.7% for M. pneumoniae. Significant differences were noticed in the positivity of M. pneumoniae culture obtained from samples with a disease course of at least 3 weeks compared with those within 3 weeks. The genotype 1 M. pneumoniae strains showed a macrolide resistant (MLr) rate of 100%, and that for genotype 2 was 90.1%. Proteomics showed that there were 57 proteins up-regulated in the MLs M. pneumoniae, half of which were membrane-associated protein with adhesion or toxicity.

Conclusions: Pediatric RMPP usually presented with viral co-infection, but it caused limited effects on the progression and prognosis of RMPP. Persistent presence of viable M. pneumoniae is not necessary in the later stage of RMPP. The expression of virulence factor in the MLr M. pneumoniae was higher than that of the MLs M. pneumoniae, which was more common in the RMPP children.

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.

Alternative conformation of the C-domain of the P140 protein from Mycoplasma genitalium

The human pathogen Mycoplasma genitalium is responsible for urethritis in men, and for cervicitis and pelvic inflammatory disease in women. The adherence of M. genitalium to host target epithelial cells is mediated through an adhesion complex called Nap, which is essential for infectivity. Nap is a transmembrane dimer of heterodimers of the immunodominant proteins P110 and P140. The M. genitalium genome contains multiple copies of portions that share homology with the extracellular regions of P140 and P110 encoded by the genes mg191 and mg192, respectively. Homologous recombination between the genes and the copies allows the generation of a large diversity of P140 and P110 variants to overcome surveillance by the host immune system. Interestingly, the C-terminal domain (C-domain) of the extracellular region of P140, which is essential for the function of Nap by acting as a flexible stalk anchoring the protein to the mycoplasma membrane, presents a low degree of sequence variability. In the present work, the X-ray crystal structures of two crystal forms of a construct of the P140 C-domain are reported. In both crystal forms, the construct forms a compact octamer with D4 point-group symmetry. The structure of the C-domain determined in this work presents significant differences with respect to the structure of the C-domain found recently in intact P140. The structural plasticity of the C-domain appears to be a possible mechanism that may help in the functioning of the mycoplasma adhesion complex.

Structure and mechanism of the Nap adhesion complex from the human pathogen Mycoplasma genitalium

Mycoplasma genitalium is a human pathogen adhering to host target epithelial cells and causing urethritis, cervicitis and pelvic inflammatory disease. Essential for infectivity is a transmembrane adhesion complex called Nap comprising proteins P110 and P140. Here we report the crystal structure of P140 both alone and in complex with the N-terminal domain of P110. By cryo-electron microscopy (cryo-EM) and tomography (cryo-ET) we find closed and open Nap conformations, determined at 9.8 and 15 Å, respectively. Both crystal structures and the cryo-EM structure are found in a closed conformation, where the sialic acid binding site in P110 is occluded. By contrast, the cryo-ET structure shows an open conformation, where the binding site is accessible. Structural information, in combination with functional studies, suggests a mechanism for attachment and release of M. genitalium to and from the host cell receptor, in which Nap conformations alternate to sustain motility and guarantee infectivity.

Cell surface processing of the P1 adhesin of Mycoplasma pneumoniae identifies novel domains that bind host molecules

Mycoplasma pneumoniae is a genome reduced pathogen and causative agent of community acquired pneumonia. The major cellular adhesin, P1, localises to the tip of the attachment organelle forming a complex with P40 and P90, two cleavage fragments derived by processing Mpn142, and other molecules with adhesive and mobility functions. LC-MS/MS analysis of M. pneumoniae M129 proteins derived from whole cell lysates and eluents from affinity matrices coupled with chemically diverse host molecules identified 22 proteoforms of P1. Terminomics was used to characterise 17 cleavage events many of which were independently verified by the identification of semi-tryptic peptides in our proteome studies and by immunoblotting. One cleavage event released ¹⁵⁹⁷TSAAKPGAPRPPVPPKPGAPKPPVQPPKKPA¹⁶²⁷ from the C-terminus of P1 and this peptide was shown to bind to a range of host molecules. A smaller synthetic peptide comprising the C-terminal 15 amino acids, ¹⁶¹³PGAPKPPVQPPKKPA¹⁶²⁷, selectively bound cytoskeletal intermediate filament proteins cytokeratin 7, cytokeratin 8, cytokeratin 18, and vimentin from a native A549 cell lysate. Collectively, our data suggests that ectodomain shedding occurs on the surface of M. pneumoniae where it may alter the functional diversity of P1, Mpn142 and other surface proteins such as elongation factor Tu via a mechanism similar to that described in Mycoplasma hyopneumoniae.

Application of spherical substrate to observe bacterial motility machineries by Quick-Freeze-Replica Electron Microscopy

3-D Structural information is essential to elucidate the molecular mechanisms of various biological machineries. Quick-Freeze Deep-Etch-Replica Electron Microscopy is a unique technique to give very high-contrast surface profiles of extra- and intra-cellular apparatuses that bear numerous cellular functions. Though the global architecture of those machineries is primarily required to understand their functional features, it is difficult or even impossible to depict side- or highly-oblique views of the same targets by usual goniometry, inasmuch as the objects (e.g. motile microorganisms) are placed on conventional flat substrates. We introduced silica-beads as an alternative substrate to solve such crucial issue. Elongated Flavobacterium and globular Mycoplasmas cells glided regularly along the bead’s surface, similarly to those on a flat substrate. Quick-freeze replicas of those cells attached to the beads showed various views; side-, oblique- and frontal-views, enabling us to study not only global but potentially more detailed morphology of complicated architecture. Adhesion of the targets to the convex surface could give surplus merits to visualizing intriguing molecular assemblies within the cells, which is relevant to a variety of motility machinery of microorganisms.

Behaviors and Energy Source of Mycoplasma gallisepticum Gliding

Mycoplasma gallisepticum, an avian-pathogenic bacterium, glides on host tissue surfaces by using a common motility system with Mycoplasma pneumoniae In the present study, we observed and analyzed the gliding behaviors of M. gallisepticum in detail by using optical microscopes. M. gallisepticum glided at a speed of 0.27 ± 0.09 μm/s with directional changes relative to the cell axis of 0.6 degree ± 44.6 degrees/5 s without the rolling of the cell body. To examine the effects of viscosity on gliding, we analyzed the gliding behaviors under viscous environments. The gliding speed was constant in various concentrations of methylcellulose but was affected by Ficoll. To investigate the relationship between binding and gliding, we analyzed the inhibitory effects of sialyllactose on binding and gliding. The binding and gliding speed sigmoidally decreased with sialyllactose concentration, indicating the cooperative binding of the cell. To determine the direct energy source of gliding, we used a membrane-permeabilized ghost model. We permeabilized M. gallisepticum cells with Triton X-100 or Triton X-100 containing ATP and analyzed the gliding of permeabilized cells. The cells permeabilized with Triton X-100 did not show gliding; in contrast, the cells permeabilized with Triton X-100 containing ATP showed gliding at a speed of 0.014 ± 0.007 μm/s. These results indicate that the direct energy source for the gliding motility of M. gallisepticum is ATP.IMPORTANCE Mycoplasmas, the smallest bacteria, are parasitic and occasionally commensal. Mycoplasma gallisepticum is related to human-pathogenic mycoplasmas-Mycoplasma pneumoniae and Mycoplasma genitalium-which cause so-called "walking pneumonia" and nongonococcal urethritis, respectively. These mycoplasmas trap sialylated oligosaccharides, which are common targets among influenza viruses, on host trachea or urinary tract surfaces and glide to enlarge the infected areas. Interestingly, this gliding motility is not related to other bacterial motilities or eukaryotic motilities. Here, we quantitatively analyze cell behaviors in gliding and clarify the direct energy source. The results provide clues for elucidating this unique motility mechanism.

Production and characterization of recombinant P1 adhesin essential for adhesion, gliding, and antigenic variation in the human pathogenic bacterium, Mycoplasma pneumoniae

Mycoplasma pneumoniae forms an attachment organelle at one cell pole, binds to the host cell surface, and glides via a unique mechanism. A 170-kDa protein, P1 adhesin, present on the organelle surface plays a critical role in the binding and gliding process. In this study, we obtained a recombinant P1 adhesin comprising 1476 amino acid residues, excluding the C-terminal domain of 109 amino acids that carried the transmembrane segment, that were fused to additional 17 amino acid residues carrying a hexa-histidine (6 × His) tag using an Escherichia coli expression system. The recombinant protein showed solubility, and chirality in circular dichroism (CD). The results of analytical gel filtration, ultracentrifugation, negative-staining electron microscopy, and small-angle X-ray scattering (SAXS) showed that the recombinant protein exists in a monomeric form with a uniformly folded structure. SAXS analysis suggested the presence of a compact and ellipsoidal structure rather than random or molten globule-like conformation. Structure model based on SAXS results fitted well with the corresponding structure obtained with cryo-electron tomography from a closely related species, M. genitalium. This recombinant protein may be useful for structural and functional studies as well as for the preparation of antibodies for medical applications.

Mycoplasma genitalium adhesin P110 binds sialic-acid human receptors

Adhesion of pathogenic bacteria to target cells is a prerequisite for colonization and further infection. The main adhesins of the emerging sexually transmitted pathogen Mycoplasma genitalium, P140 and P110, interact to form a Nap complex anchored to the cell membrane. Herein, we present the crystal structures of the extracellular region of the virulence factor P110 (916 residues) unliganded and in complex with sialic acid oligosaccharides. P110 interacts only with the neuraminic acid moiety of the oligosaccharides and experiments with human cells demonstrate that these interactions are essential for mycoplasma cytadherence. Additionally, structural information provides a deep insight of the P110 antigenic regions undergoing programmed variation to evade the host immune response. These results enlighten the interplay of M. genitalium with human target cells, offering new strategies to control mycoplasma infections.

How the Mycoplasma genitalium cytadhesins P140 and P110 promote host cell invasion remains poorly understood. Here, combining structural analysis with functional assays, Aparicio et al. identify the P110 domain that binds to sialylated receptors essential for mycoplasma cytadherence.

Sialylated Receptor Setting Influences Mycoplasma pneumoniae Attachment and Gliding Motility

Mycoplasma pneumoniae is a common cause of human respiratory tract infections, including bronchitis and atypical pneumonia. M. pneumoniae binds glycoprotein receptors having terminal sialic acid residues via the P1 adhesin protein. Here, we explored the impact of sialic acid presentation on M. pneumoniae adherence and gliding on surfaces coated with sialylated glycoproteins, or chemically functionalized with α-2,3- and α-2,6-sialyllactose ligated individually or in combination to a polymer scaffold in precisely controlled densities. In both models, gliding required a higher receptor density threshold than adherence, and receptor density influenced gliding frequency but not gliding speed. However, very high densities of α-2,3-sialyllactose actually reduced gliding frequency over peak levels observed at lower densities. Both α-2,3- and α-2,6-sialyllactose supported M. pneumoniae adherence, but gliding was only observed on the former. Finally, gliding on α-2,3-sialyllactose was inhibited on surfaces also conjugated with α-2,6-sialyllactose, suggesting that both moieties bind P1 despite the inability of the latter to support gliding. Our results indicate that the nature and density of host receptor moieties profoundly influences M. pneumoniae gliding, which could affect pathogenesis and infection outcome. Furthermore, precise functionalization of polymer scaffolds shows great promise for further analysis of sialic acid presentation and M. pneumoniae adherence and gliding.

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.

Molecular characterization of genomic DNA in mycoplasma pneumoniae strains isolated from serious mycoplasma pneumonia cases in 2016, Yunnan, China

Mycoplasma pneumoniae (MP) is particularly prevalent in low-immunity school-age children. Few data have been reported on MP prevalence in Yunnan, China. This study was designed to investigate the prevalence and characterize genomic DNA of MP in a small outbreak in 2016, Southwest China. RepMP4 and RepMP2/3 genes of MP positive samples were amplified for molecular typing through sequence alignment and PCR-RFLP assay. Phylogenetic trees were constructed by MEGA5.0. The results showed that two distinct P1 types (type I and type II) were prevalent in this MP outbreak. Type I was the most prevalent type, and clustered in the same evolutionary branch of C26 (China, 2012). Only 1 MP isolate belonged to type II, and clustered in the branch of KCH405 (Japan, 2016). Fifty-nine nucleotide mutations were observed in P1 genes of type I isolates (51 in RepMP4, 8 in RepMP2/3). Ninety-five nucleotide mutations were observed in P1 genes of the type II isolates (33 in RepMP4, 62 in RepMP2/3). It is noteworthy that 31 mutation sites were clustered in an 84-bp fragment in the RepMP4 gene of type II isolates. One new fragment that appeared in two of the type I strains was not found in NCBI. Nucleotide diversity analyze results showed that RepMP4 was more likely to be genetically diverse than RepMP2/3. Two-tailed Z-test result of RepMP4 suggested positive selection between 6 P1 type I isolates and M29 (China, 2005). According to secondary structure prediction, 36 new possible protein binding sites were found and another 9 sites were lost, 2 helices were missed and 1 new helix appeared in type I isolates. As for type II isolates, 16 protein binding regions were gained and 31 were lost. This study may help to understand the intrinsic geographical relatedness and contributes further to the research of MP.

A sensitive and rapid immunoassay for Mycoplasma pneumoniae in children with pneumonia based on single-walled carbon nanotubes

Mycoplasma pneumoniae(MP) is a leading pathogen of respiratory infection, especially community-acquired pneumonia (CAP), in children worldwide. However, its diagnosis is frequently ineffective because bacterial culture and serology test are usually positive 1–2 weeks or more after the disease onset. To achieve a better detection efficiency, the single-walled carbon nanotubes(SWCNT) were coupled with the colloidal gold-monoclonal antibody immunochromatographic strips(CGIC). Interestingly, the SWCNT/CGIC assay allowed MP identification, with a detection limit of 1 × 10² copies/ml. Using referenced throat swabs of 97 MP and 40 non-MP cases, the assay yielded 72.2% sensitivity, 100.0% specificity, 100.0% positive predictive value (PPV), 59.7% negative predictive value (NPV). In summary, our assay was far more effective than any conventional methods for the diagnosis of acute MP. The ease of use, rapid and stability further enhance its feasibility for clinical use on-site.

Structural characterization of the NAP; the major adhesion complex of the human pathogen Mycoplasma genitalium

Mycoplasma genitalium, the causative agent of non-gonococcal urethritis and pelvic inflammatory disease in humans, is a small eubacterium that lacks a peptidoglycan cell wall. On the surface of its plasma membrane is the major surface adhesion complex, known as NAP that is essential for adhesion and gliding motility of the organism. Here, we have performed cryo-electron tomography of intact cells and detergent permeabilized M. genitalium cell aggregates, providing sub-tomogram averages of free and cell-attached NAPs respectively, revealing a tetrameric complex with two-fold rotational (C2) symmetry. Each NAP has two pairs of globular lobes (named α and β lobes), arranged as a dimer of heterodimers with each lobe connected by a stalk to the cell membrane. The β lobes are larger than the α lobes by 20%. Classification of NAPs showed that the complex can tilt with respect to the cell membrane. A protein complex containing exclusively the proteins P140 and P110, was purified from M. genitalium and was structurally characterized by negative-stain single particle EM reconstruction. The close structural similarity found between intact NAPs and the isolated P140/P110 complexes, shows that dimers of P140/P110 heterodimers are the only components of the extracellular region of intact NAPs in M. genitalium.

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.

Complete Genome Sequences of the p1 Gene Type 2b and 2c Strains Mycoplasma pneumoniae KCH-402 and KCH-405

Here, we present the complete genome sequences of Mycoplasma pneumoniae KCH-402 and KCH-405, which are p1 gene type 2b and 2c strains, respectively. These strains harbor variations in the orf6 gene, which encodes the cytadherence-related proteins P40 and P90.

Mycoplasma fermentans deacetylase promotes mammalian cell stress tolerance

Mycoplasma fermentans is a pathogenic bacterium that infects humans and has potential pathogenic roles in respiratory, genital and rheumatoid diseases. NAD⁺-dependent deacetylase is involved in a wide range of pathophysiological processes and our studies have demonstrated that expression of mycoplasmal deacetylase in mammalian cells inhibits proliferation but promotes anti-starvation stress tolerance. Furthermore, mycoplasmal deacetylase is involved in cellular anti-oxidation, which correlates with changes in the proapoptotic proteins BIK, p21 and BIM. Mycoplasmal deacetylase binds to and deacetylates the FOXO3 protein, similar with mammalian SIRT2, and affects expression of the FOXO3 target gene BIM, resulting in inhibition of cell proliferation. Mycoplasmal deacetylase also alters the performance of cells under drug stress. This study expands our understanding of the potential molecular and cellular mechanisms of interaction between mycoplasmas and mammalian cells.

The effect of Platycodin D on the expression of cytoadherence proteins P1 and P30 in Mycoplasma pneumoniae models

Platycodin D is one of the most important monomers of the Qinbaiqingfei pellet (Qinbai), which has already been approved as the first effective new Traditional Chinese Medicine used to fight against Mycoplasma pneumoniae (M. pneumoniae) in clinic in China. In previous studies, pharmacodynamics experiment has proved that Platycodin D has anti-M. pneumoniae effect and the minimum inhibitory concentration (MIC) is 16mμg/ml. This paper further clarified that the mechanism underlying the anti-M. pneumoniae effect of Platycodin D might be due to M. pneumoniae adhesion proteins P1 and P30. P1 and P30 expression levels in M. pneumoniae strain, M. pneumoniae-infected BALB/c mice, and M. pneumoniae-infected A549 cells were determined by reverse transcription PCR. Platycodin D strongly inhibited P1 and P30 expression in M. pneumonia and high dosage of Platycodin D exhibited a greater effect on reducing P1 and P30 expression than low dose Platycodin D. Platycodin D prevented M. pneumoniae infection through inhibiting the expression of adhesion proteins, which might be one of the mechanisms for the anti-M. pneumoniae properties of Qinbai. These results provide a foundation to further explore the mechanisms of action of Qinbai in future studies.

Two case reports: Whole genome sequencing of two clinical macrolide-resistant Mycoplasma pneumoniae isolates with different responses to azithromycin

BACKGROUND

Cases of macrolide-resistant Mycoplasma pneumoniae have increased rapidly since 2000, especially in Asia. Patients infected with macrolide-resistant M pneumoniae usually present with severe M pneumoniae pneumonia. The aim of this study was to identify indicators for whether children at an early stage of M pneumoniae infection develop mild or severe pneumonia.

CASE SUMMARY

Herein, we retrospectively reviewed 2 pediatric cases caused by macrolide-resistant M pneumoniae, but with markedly different severity of pneumonia. First, we compared the clinical courses of the patients, then isolated the pathogens and tested their response to macrolides, then finally, carried out whole genome sequencing of these isolates. Despite the difference in clinical presentation of the infection, both isolates exhibited a high level of resistance to macrolide antibiotics. Analysis of clinical data showed that the erythrocyte sedimentation rate in blood samples of the patients in the early stages of disease varied greatly. Genome sequence analysis revealed single nucleotide polymorphisms mainly focused on adhesin P1, which is involved in the pathogenicity of M pneumoniae.

CONCLUSION

The differences of erythrocyte sedimentation rate in the early stage of M pneumoniae pneumonia and mutations in P1 protein may help us to distinguish between severe or mild disease after infection with macrolide-resistant M pneumoniae. These findings could lead to the development of screening assays that will allow us to distinguish severe or mild M pneumoniae pneumonia early.

Structural Study of MPN387, an Essential Protein for Gliding Motility of a Human-Pathogenic Bacterium, Mycoplasma pneumoniae

Mycoplasma pneumoniae is a human pathogen that glides on host cell surfaces with repeated catch and release of sialylated oligosaccharides. At a pole, this organism forms a protrusion called the attachment organelle, which is composed of surface structures, including P1 adhesin and the internal core structure. The core structure can be divided into three parts, the terminal button, paired plates, and bowl complex, aligned in that order from the front end of the protrusion. To elucidate the gliding mechanism, we focused on MPN387, a component protein of the bowl complex which is essential for gliding but dispensable for cytadherence. The predicted amino acid sequence showed that the protein features a coiled-coil region spanning residue 72 to residue 290 of the total of 358 amino acids in the protein. Recombinant MPN387 proteins were isolated with and without an enhanced yellow fluorescent protein (EYFP) fusion tag and analyzed by gel filtration chromatography, circular dichroism spectroscopy, analytical ultracentrifugation, partial proteolysis, and rotary-shadowing electron microscopy. The results showed that MPN387 is a dumbbell-shaped homodimer that is about 42.7 nm in length and 9.1 nm in diameter and includes a 24.5-nm-long central parallel coiled-coil part. The molecular image was superimposed onto the electron micrograph based on the localizing position mapped by fluorescent protein tagging. A proposed role of this protein in the gliding mechanism is discussed.

IMPORTANCE

Human mycoplasma pneumonia is caused by a pathogenic bacterium, Mycoplasma pneumoniae This tiny, 2-μm-long bacterium is suggested to infect humans by gliding on the surface of the trachea through binding to sialylated oligosaccharides. 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 and analyzed the structure of a key protein which is directly involved in the gliding mechanism.

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.

Periodicity in Attachment Organelle Revealed by Electron Cryotomography Suggests Conformational Changes in Gliding Mechanism of Mycoplasma pneumoniae

Mycoplasma pneumoniae, a pathogenic bacterium, glides on host surfaces using a unique mechanism. It forms an attachment organelle at a cell pole as a protrusion comprised of knoblike surface structures and an internal core. Here, we analyzed the three-dimensional structure of the organelle in detail by electron cryotomography. On the surface, knoblike particles formed a two-dimensional array, albeit with limited regularity. Analyses using a nonbinding mutant and an antibody showed that the knoblike particles correspond to a naplike structure that has been observed by negative-staining electron microscopy and is likely to be formed as a complex of P1 adhesin, the key protein for binding and gliding. The paired thin and thick plates feature a rigid hexagonal lattice and striations with highly variable repeat distances, respectively. The combination of variable and invariant structures in the internal core and the P1 adhesin array on the surface suggest a model in which axial extension and compression of the thick plate along a rigid thin plate is coupled with attachment to and detachment from the substrate during gliding.

Human mycoplasma pneumonia, epidemic all over the world in recent years, is caused by a pathogenic bacterium, Mycoplasma pneumoniae. This tiny bacterium, about 2 µm in cell body length, glides on the surface of the human trachea to infect the host by binding to sialylated oligosaccharides, which are also the binding targets of influenza viruses. The mechanism of mycoplasmal gliding motility is not related to any other well-studied motility systems, such as bacterial flagella and cytoplasmic motor proteins. Here, we visualized the attachment organelle, a cellular architecture for gliding, three dimensionally by using electron cryotomography and other conventional methods. A possible gliding mechanism has been suggested based on the architectural images.

Potential Molecular Targets for Narrow-Spectrum Agents to Combat Mycoplasma pneumoniae Infection and Disease

As Mycoplasma pneumoniae macrolide resistance grows and spreads worldwide, it is becoming more important to develop new drugs to prevent infection or limit disease. Because other mycoplasma species have acquired resistance to other classes of antibiotics, it is reasonable to presume that M. pneumoniae can do the same, so switching to commonly used antibiotics like fluoroquinolones will not result in forms of therapy with long-term utility. Moreover, broad-spectrum antibiotics can have serious consequences for the patient, as these drugs may have severe impacts on the natural microbiota of the individual, compromising the health of the patient either short-term or long-term. Therefore, developing narrow-spectrum antibiotics that effectively target only M. pneumoniae and no more than a small portion of the microbiota is likely to yield impactful, positive results that can be used perhaps indefinitely to combat M. pneumoniae. Development of these agents requires a deep understanding of the basic biology of M. pneumoniae, in many areas deeper than what is currently known. In this review, we discuss potential targets for new, narrow-spectrum agents and both the positive and negative aspects of selecting these targets, which include toxic molecules, metabolic pathways, and attachment and motility. By gathering this information together, we anticipate that it will be easier for researchers to evaluate topics of priority for study of M. pneumoniae.

Antibody Response to Mycoplasma pneumoniae: Protection of Host and Influence on Outbreaks?

In humans of all ages, the cell wall-less and genome-reduced species Mycoplasma pneumoniae can cause infections of the upper and lower respiratory tract. The well-documented occurrence of major peaks in the incidence of community-acquired pneumonia cases reported world-wide, the multifaceted clinical manifestations of infection and the increasing number of resistant strains provide reasons for ongoing interest in the pathogenesis of mycoplasmal disease. The results of recent studies have provided insights into the interaction of the limited virulence factors of the bacterium with its host. In addition, the availability of complete M. pneumoniae genomes from patient isolates and the development of proteomic methods for investigation of mycoplasmas have not only allowed characterization of sequence divergences between strains but have also shown the importance of proteins and protein parts for induction of the immune reaction after infection. This review focuses on selected aspects of the humoral host immune response as a factor that might influence the clinical course of infections, subsequent protection in cases of re-infections and changes of epidemiological pattern of infections. The characterization of antibodies directed to defined antigens and approaches to promote their induction in the respiratory mucosa are also preconditions for the development of a vaccine to protect risk populations from severe disease due to M. pneumoniae.

P40 and P90 from Mpn142 are Targets of Multiple Processing Events on the Surface of Mycoplasma pneumoniae

Mycoplasma pneumoniae is a significant cause of community acquired pneumonia globally. Despite having a genome less than 1 Mb in size, M. pneumoniae presents a structurally sophisticated attachment organelle that (i) provides cell polarity, (ii) directs adherence to receptors presented on respiratory epithelium, and (iii) plays a major role in cell motility. The major adhesins, P1 (Mpn141) and P30 (Mpn453), are localised to the tip of the attachment organelle by the surface accessible cleavage fragments P90 and P40 derived from Mpn142. Two events play a defining role in the formation of P90 and P40; removal of a leader peptide at position 26 (²³SLA↓NTY²⁸) during secretion to the cell surface and cleavage at amino acid 455 (⁴⁵²GPL↓RAG⁴⁵⁷) generating P40 and P90. Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS) analysis of tryptic peptides generated by digesting size-fractionated cell lysates of M. pneumoniae identified 15 cleavage fragments of Mpn142 ranging in mass from 9–84 kDa. Further evidence for the existence of cleavage fragments of Mpn142 was generated by mapping tryptic peptides to proteins recovered from size fractionated eluents from affinity columns loaded with heparin, fibronectin, fetuin, actin, plasminogen and A549 surface proteins as bait. To define the sites of cleavage in Mpn142, neo-N-termini in cell lysates of M. pneumoniae were dimethyl-labelled and characterised by LC-MS/MS. Our data suggests that Mpn142 is cleaved to generate adhesins that are auxiliary to P1 and P30.

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.

Gliding Direction of Mycoplasma mobile

Mycoplasma mobile glides in the direction of its cell pole by a unique mechanism in which hundreds of legs, each protruding from its own gliding unit, catch, pull, and release sialylated oligosaccharides fixed on a solid surface. In this study, we found that 77% of cells glided to the left with a change in direction of 8.4° ± 17.6° μm(-1) displacement. The cell body did not roll around the cell axis, and elongated, thinner cells also glided while tracing a curved trajectory to the left. Under viscous conditions, the range of deviation of the gliding direction decreased. In the presence of 250 μM free sialyllactose, in which the binding of the legs (i.e., the catching of sialylated oligosaccharides) was reduced, 70% and 30% of cells glided to the left and the right, respectively, with changes in direction of ∼30° μm(-1). The gliding ghosts, in which a cell was permeabilized by Triton X-100 and reactivated by ATP, glided more straightly. These results can be explained by the following assumptions based on the suggested gliding machinery and mechanism: (i) the units of gliding machinery may be aligned helically around the cell, (ii) the legs extend via the process of thermal fluctuation and catch the sialylated oligosaccharides, and (iii) the legs generate a propulsion force that is tilted from the cell axis to the left in 70% and to the right in 30% of cells.

IMPORTANCE

Mycoplasmas are bacteria that are generally parasitic to animals and plants. Some Mycoplasma species form a protrusion at a pole, bind to solid surfaces, and glide. Although these species appear to consistently glide in the direction of the protrusion, their exact gliding direction has not been examined. This study analyzed the gliding direction in detail under various conditions and, based on the results, suggested features of the machinery and the mechanism of gliding.

Comparative genome analysis of Mycoplasma pneumoniae

Background

Mycoplasma pneumoniae is a common pathogen that causes upper and lower respiratory tract infections in people of all ages, responsible for up to 40 % of community-acquired pneumonias. It also causes a wide array of extrapulmonary infections and autoimmune phenomena. Phylogenetic studies of the organism have been generally restricted to specific genes or regions of the genome, because whole genome sequencing has been completed for only 4 strains. To better understand the physiology and pathogenicity of this important human pathogen, we performed comparative genomic analysis of 15 strains of M. pneumoniae that were isolated between the 1940s to 2009 from respiratory specimens and cerebrospinal fluid originating from the USA, China and England.

Results

Illumina MiSeq whole genome sequencing was performed on the 15 strains and all genome sequences were completed. Results from the comparative genomic analysis indicate that although about 1500 SNP and indel variants exist between type1 and type 2 strains, there is an overall high degree of sequence similarity among the strains (>99 % identical to each other). Within the two subtypes, conservation of most genes, including the CARDS toxin gene and arginine deiminase genes, was observed. The major variation occurs in the P1 and ORF6 genes associated with the adhesin complex. Multiple hsdS genes (encodes S subunit of type I restriction enzyme) with variable tandem repeat copy numbers were found in all 15 genomes.

Conclusions

These data indicate that despite conclusions drawn from 16S rRNA sequences suggesting rapid evolution, the M. pneumoniae genome is extraordinarily stable over time and geographic distance across the globe with a striking lack of evidence of horizontal gene transfer.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1801-0) contains supplementary material, which is available to authorized users.

Gliding Motility of Mycoplasma mobile on Uniform Oligosaccharides

The binding and gliding of Mycoplasma mobile on a plastic plate covered by 53 uniform oligosaccharides were analyzed. Mycoplasmas bound to and glided on only 21 of the fixed sialylated oligosaccharides (SOs), showing that sialic acid is essential as the binding target. The affinities were mostly consistent with our previous results on the inhibitory effects of free SOs and suggested that M. mobile recognizes SOs from the nonreducing end with four continuous sites as follows. (i and ii) A sialic acid at the nonreducing end is tightly recognized by tandemly connected two sites. (iii) The third site is recognized by a loose groove that may be affected by branches. (iv) The fourth site is recognized by a large groove that may be enhanced by branches, especially those with a negative charge. The cells glided on uniform SOs in manners apparently similar to those of the gliding on mixed SOs. The gliding speed was related inversely to the mycoplasma's affinity for SO, suggesting that the detaching step may be one of the speed determinants. The cells glided faster and with smaller fluctuations on the uniform SOs than on the mixtures, suggesting that the drag caused by the variation in SOs influences gliding behaviors.

IMPORTANCE

Mycoplasma is a group of bacteria generally parasitic to animals and plants. Some Mycoplasma species form a protrusion at a pole, bind to solid surfaces, and glide in the direction of the protrusion. These procedures are essential for parasitism. Usually, mycoplasmas glide on mixed sialylated oligosaccharides (SOs) derived from glycoprotein and glycolipid. Since gliding motility on uniform oligosaccharides has never been observed, this study gives critical information about recognition and interaction between receptors and SOs.

First identification of proteins involved in motility of Mycoplasma gallisepticum

Mycoplasma gallisepticum, the most pathogenic mycoplasma in poultry, is able to glide over solid surfaces. Although this gliding motility was first observed in 1968, no specific protein has yet been shown to be involved in gliding. We examined M. gallisepticum strains and clonal variants for motility and found that the cytadherence proteins GapA and CrmA were required for gliding. Loss of GapA or CrmA resulted in the loss of motility and hemadsorption and led to drastic changes in the characteristic flask-shape of the cells. To identify further genes involved in motility, a transposon mutant library of M. gallisepticum was generated and screened for motility-deficient mutants, using a screening assay based on colony morphology. Motility-deficient mutants had transposon insertions in gapA and the neighbouring downstream gene crmA. In addition, insertions were seen in gene mgc2, immediately upstream of gapA, in two motility-deficient mutants. In contrast to the GapA/CrmA mutants, the mgc2 motility mutants still possessed the ability to hemadsorb. Complementation of these mutants with a mgc2-hexahistidine fusion gene restored the motile phenotype. This is the first report assigning specific M. gallisepticum proteins to involvement in gliding motility.

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.

Effects of Traditional Chinese Medicine Qinbai Qingfei Concentrated Pellet on Cellular Infectivity of Mycoplasma pneumoniae

Aim. To study the effect and mechanism of traditional Chinese medicine Qinbai Qingfei concentrated pellet (QQCP) against Mycoplasma pneumoniae (MP). Methods. Rat airway smooth muscle (ASM) cells were used to examine the antimycoplasmal activity of QQCP via four drug-adding modes: pre- and postadding drugs, simultaneous-adding after drug and MP mixed, and simultaneous-adding drug and MP; taking roxithromycin dispersive tablets (RDT) as positive control, the cellular A₅₇₀ values were determined by MTT method. Results. All of A₅₇₀ values in QQCP group were significantly higher than those of the corresponding MP control group (P < 0.01) in four drug-adding modes; there was no significant difference in A₅₇₀ values between the QQCP group and that of the positive control group (P > 0.05), confirming that QQCP could significantly inhibit the infectivity of MP to ASM cells. Conclusion. QQCP had significant activity in preventing and treating MP infection, killing MP, and antiabsorption.

Modulation of P1 and EGF expression by Baicalin

Mycoplasma pneumoniae (M. pneumoniae) is increasingly recognized as a major cause of acute respiratory tract infections. Today, macrolides are used in the primary treatment of M. pneumoniae infection. However, with the increasing prevalence of strains resistant to macrolides, as well as reports of toxicity and adverse side effects, it is necessary to develop an alternative therapeutic agent. A compound recipe - Qinbaiqingfei pellets (Qinbai) - have already been approved in China as the first effective traditional Chinese medicine to be used against M. pneumoniae. Herein, we characterize the mechanism by which Qinbai interacts with M. pneumoniae and lung epithelial cells. The fact that Baicalin is the key component of Qingbai leads us to believe its study is important to elucidating the mechanism of the action of Qinbai. In this study, we describe the complex impact of Baicalin on the adhesin protein P1 of M. pneumoniae and on the expression of epidermal growth factor (EGF) in BALB/c mice and A549 cells infected with M. pneumonia. We draw the conclusion that Baicalin not only cured M. pneumoniae infection by inhibiting P1 expression, but also enhanced the repair of lung epithelial cells by upregulating EGF. Finally, we demonstrate that Baicalin plays a role in Qinbai treatment.

Role of binding in Mycoplasma mobile and Mycoplasma pneumoniae gliding analyzed through inhibition by synthesized sialylated compounds

Mycoplasmas, which have been shown to be the causative pathogens in recent human pneumonia epidemics, bind to solid surfaces and glide in the direction of the membrane protrusion at a pole. During gliding, the legs of the mycoplasma catch, pull, and release sialylated oligosaccharides fixed on a solid surface. Sialylated oligosaccharides are major structures on animal cell surfaces and are sometimes targeted by pathogens, such as influenza virus. In the present study, we analyzed the inhibitory effects of 16 chemically synthesized sialylated compounds on the gliding and binding of Mycoplasma mobile and Mycoplasma pneumoniae and concluded the following. (i) The recognition of sialylated oligosaccharide by mycoplasma legs proceeds in a "lock-and-key" fashion, with the binding affinity dependent on structural differences among the sialylated compounds examined. (ii) The binding of the leg and the sialylated oligosaccharide is cooperative, with Hill constants ranging from 2 to 3. (iii) Mycoplasma legs may generate a drag force after a stroke, because the gliding speed decreased and pivoting motion occurred more frequently when the number of working legs was reduced by the addition of free sialylated compounds.

Whole surface image of Mycoplasma mobile, suggested by protein identification and immunofluorescence microscopy

Mycoplasma mobile, a freshwater fish pathogen featured with robust gliding motility, binds to the surface of the gill, where it then colonizes. Here, to obtain a whole image of its cell surface, we identified the proteins exposed on the surface using the following methods. (i) The cell surface was labeled with sulfosuccinimidyl-6-(biotinamido) hexanoate and recovered by an avidin column. (ii) The cells were subjected to phase partitioning using Triton X-114, and the hydrophobic proteins were recovered. (iii) The membrane fraction was analyzed by two-dimensional gel electrophoresis. These recovered proteins were subjected to peptide mass fingerprinting, and a final list of 36 expressed surface proteins was established. The ratio of identified proteins to whole surface proteins was estimated through two-dimensional gel electrophoresis of the membrane fraction. The localization of three newly found proteins, Mvsps C, E, and F, has been clarified by immunofluorescence microscopy. Integrating all information, a whole image of the cell surface showed that the proteins for gliding that were localized at the base of the protrusion of flask-shaped M. mobile account for more than 12% of all surface proteins and that Mvsps, surface variants that were localized at both parts other than the neck, account for 49% of all surface proteins.

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.

Protective immune responses in mice induced by intramuscular and intranasal immunization with a Mycoplasma pneumoniae P1C DNA vaccine

Mycoplasma pneumoniae is an important causative agent of atypical pneumonia. This study was to determine the ability of a DNA expression vector, which encodes the carboxy terminal region of the M. pneumoniae P1 protein (P1C), to induce humoral and cellular immune responses and to protect against M. pneumoniae infection in BALB/c mice. Mice were immunized with pcDNA3.1/P1C by either intramuscular injection (i.m.) or intranasal inoculation (i.n.). Our results showed that p1c DNA immunization generates detectable antibodies specific to M. pneumoniae, and elicits high levels of IgG1, IgG2a, and IgG2b isotypes (P < 0.01). The levels of IFN-γ and IL-4 in spleen cells of the immunized mice were significantly elevated by immunization via both the i.m. and i.n. methods. Moreover, p1c DNA-immunized mice exhibited detectable protection against M. pneumoniae infection. The lung tissue inflammation was relieved and the histopathologic score (HPS) of pcDNA3.1/P1C-immunized mice was significantly decreased than those in phosphate-buffed saline (PBS) or vaccine-vector-immunized mice (P < 0.01), whereas there were no significant differences in HPS between i.m. and i.n. vaccination (P > 0.05). Our results suggest that pcDNA3.1/P1C could be useful for developing a vaccine against M. pneumoniae infection.

Complete genome sequence of Mycoplasma pneumoniae type 2a strain 309, isolated in Japan

Mycoplasma pneumoniae strain 309, a type 2a (subtype 2 variant) strain of this bacterium, has variations in the P1 protein, which is responsible for attachment of the bacterium to host cells. Here, we report the complete genome sequence of M. pneumoniae strain 309 isolated from a pneumonia patient in Japan.