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

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

Investigation on silent bacterial infections in specimens from pregnant women affected by spontaneous miscarriage

Miscarriage is one of the main complications occurring in pregnancy. The association between adverse pregnancy outcomes and silent bacterial infections has been poorly investigated. Ureaplasma parvum and urealiticum, Mycoplasma genitalium and hominis and Chlamydia trachomatis DNA sequences have been investigated by polymerase chain reaction (PCR) methods in chorionic villi tissues and peripheral blood mononuclear cells (PBMCs) from females with spontaneous abortion (SA, n = 100) and females who underwent voluntary interruption of pregnancy (VI, n = 100). U. parvum DNA was detected in 14% and 15% of SA and VI, respectively, with a mean of bacterial DNA load of 1.3 × 10⁻¹ copy/cell in SA and 2.8 × 10 ⁻³ copy/cell in VI; U. urealiticum DNA was detected in 3% and 2% of SA and VI specimens, respectively, with a mean DNA load of 3.3 × 10⁻³ copy/cell in SA and 1.6 × 10⁻³ copy/cell in VI; M. hominis DNA was detected in 5% of SA specimens with a DNA load of 1.3 × 10⁻⁴ copy/cell and in 6% of VI specimens with a DNA load of 1.4 × 10⁻⁴ copy/cell; C. trachomatis DNA was detected in 3% of SA specimens with a DNA load of 1.5 × 10⁻⁴ copy/cell and in 4% of VI specimens with a mean DNA load of 1.4 × 10⁻⁴ copy/cell. In PBMCs from the SA and VI groups, Ureaplasma spp, Mycoplasma spp and C. trachomatis DNAs were detected with a prevalence of 1%–3%. Bacteria were investigated, for the first time, by quantitative real-time PCR (qPCR) in chorionic villi tissues and PBMCs from women affected by SA and VI. These data may help to understand the role and our knowledge of the silent infections in SA.     

产后子宫内膜炎与围生期解脲脲原体感染有关

为了探讨围生期支原体感染与产后子宫内膜炎的关系及治疗,本研究选取产后子宫内膜炎患者73例作为观察组,同时选取正常产妇80例作为对照组。通过检测两组解脲脲原体(Uu)和人型支原体(Mh)感染情况,同时给予观察组常规治疗,本研究发现观察组Uu阳性比例为32.88%,明显高于对照组(p<0.05);观察组和对照组Mh阳性差异比较无统计学意义(p>0.05);观察组Uu阳性和Mh阳性产妇发生早产或胎膜早破的比例分别为62.50%和25.00%,明显高于支原体感染阴性产妇(p<0.05);观察组Uu阳性、Mh阳性和阴性患者治疗效果比较差异无统计学意义(p>0.05);观察组治疗后Uu阳性率为10.96%,明显较治疗前降低(p<0.05);观察组治疗前后Mh阳性率比较差异不显著(p>0.05)。本研究表明,Uu感染与产后子宫内膜炎发生有一定关系,围生期应加强Uu感染筛查,并及时进行治疗。     

Nucleoside-catabolizing Enzymes in Mycoplasma-infected Tumor Cell Cultures Compromise the Cytostatic Activity of the Anticancer Drug Gemcitabine

The intracellular metabolism and cytostatic activity of the anticancer drug gemcitabine (2′,2′-difluoro-2′-deoxycytidine; dFdC) was severely compromised in Mycoplasma hyorhinis-infected tumor cell cultures. Pronounced deamination of dFdC to its less cytostatic metabolite 2′,2′-difluoro-2′-deoxyuridine was observed, both in cell extracts and spent culture medium (i.e. tumor cell-free but mycoplasma-containing) of mycoplasma-infected tumor cells. This indicates that the decreased antiproliferative activity of dFdC in such cells is attributed to a mycoplasma cytidine deaminase causing rapid drug catabolism. Indeed, the cytostatic activity of gemcitabine could be restored by the co-administration of tetrahydrouridine (a potent cytidine deaminase inhibitor). Additionally, mycoplasma-derived pyrimidine nucleoside phosphorylase (PyNP) activity indirectly potentiated deamination of dFdC: the natural pyrimidine nucleosides uridine, 2′-deoxyuridine and thymidine inhibited mycoplasma-associated dFdC deamination but were efficiently catabolized (removed) by mycoplasma PyNP. The markedly lower anabolism and related cytostatic activity of dFdC in mycoplasma-infected tumor cells was therefore also (partially) restored by a specific TP/PyNP inhibitor (TPI), or by exogenous thymidine. Consequently, no effect on the cytostatic activity of dFdC was observed in tumor cell cultures infected with a PyNP-deficient Mycoplasma pneumoniae strain. Because it has been reported that some commensal mycoplasma species (including M. hyorhinis) preferentially colonize tumor tissue in cancer patients, our findings suggest that the presence of mycoplasmas in the tumor microenvironment could be a limiting factor for the anticancer efficiency of dFdC-based chemotherapy. Accordingly, a significantly decreased antitumor effect of dFdC was observed in mice bearing M. hyorhinis-infected murine mammary FM3A tumors compared with uninfected tumors.     

Proteogenomic mapping of Mycoplasma hyopneumoniae virulent strain 232

Background

Mycoplasma hyopneumoniae causes respiratory disease in swine and contributes to the porcine respiratory disease complex, a major disease problem in the swine industry. The M. hyopneumoniae strain 232 genome is one of the smallest and best annotated microbial genomes, containing only 728 annotated genes and 691 known proteins. Standard protein databases for mass spectrometry only allow for the identification of known and predicted proteins, which if incorrect can limit our understanding of the biological processes at work. Proteogenomic mapping is a methodology which allows the entire 6-frame genome translation of an organism to be used as a mass spectrometry database to help identify unknown proteins as well as correct and confirm existing annotations. This methodology will be employed to perform an in-depth analysis of the M. hyopneumoniae proteome.

Results

Proteomic analysis indicates 483 of 691 (70%) known M. hyopneumoniae strain 232 proteins are expressed under the culture conditions given in this study. Furthermore, 171 of 328 (52%) hypothetical proteins have been confirmed. Proteogenomic mapping resulted in the identification of previously unannotated genes gatC and rpmF and 5-prime extensions to genes mhp063, mhp073, and mhp451, all conserved and annotated in other M. hyopneumoniae strains and Mycoplasma species. Gene prediction with Prodigal, a prokaryotic gene predicting program, completely supports the new genomic coordinates calculated using proteogenomic mapping.

Conclusions

Proteogenomic mapping showed that the protein coding genes of the M. hyopneumoniae strain 232 identified in this study are well annotated. Only 1.8% of mapped peptides did not correspond to genes defined by the current genome annotation. This study also illustrates how proteogenomic mapping can be an important tool to help confirm, correct and append known gene models when using a genome sequence as search space for peptide mass spectra. Using a gene prediction program which scans for a wide variety of promoters can help ensure genes are accurately predicted or not missed completely. Furthermore, protein extraction using differential detergent fractionation effectively increases the number of membrane and cytoplasmic proteins identifiable my mass spectrometry.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-15-576) contains supplementary material, which is available to authorized users.     

Mycoplasma Pneumoniae Thymidine Phosphorylase

Mycoplasma pneumoniae (Mpn) is a human pathogen causing acute respiratory diseases and accounts for approximately 30% cases of community-acquired pneumonia. Co-infection with Mycoplasmas compromises the efficacy of anticancer and antiviral nucleoside analog-based drugs due to the presence of Mycoplasma thymidine phosphorylase (TP). In this study, a TP-deficient strain of Mpn was generated in order to study the effect of Mpn TP in the metabolism of nucleoside analogs. Deficiency in TP activity led to increased uptake and incorporation of radiolabeled deoxyuridine and uracil but thymidine uptake was not affected. The activities of enzymes in the salvage of thymidine and deoxyuridine, e.g., thymidine kinase and uracil phosphoribosyltransferase were upregulated in the TP-deficient mutant, which may explain the increased uptake of deoxyuridine and uracil. Thirty FDA-approved anticancer and antiviral nucleoside and nucleobase analogs were used to screen their inhibitory activity toward the TP mutant and the wild type strain. Seven analogs were found to inhibit strongly the growth of both wild type and TP mutant. Differences in the inhibitory effect of several purine analogs between the two strains were observed. Further study is needed in order to understand the mechanism of inhibition caused by these analogs. Our results indicated that TP is not an essential gene for Mpn survival and TP deficiency affects other enzymes in Mpn nucleotide metabolism, and suggested that Mycoplasma nucleotide biosynthesis pathway enzymes are potential targets for future development of antibiotics.     

Polymerase chain reaction as a sensitive and rapid method for specific detection of Mycoplasma pneumoniae in clinical samples

The fast diagnosis of Mycoplasma primary atypical pneumonia is impaired by the lack of routinely available culture methods for isolation of Mycoplasma pneumoniae from clinical specimens. Likewise, serological methods commonly used for diagnosis are insensitive and non-specific. In this study, we have established and applied the polymerase chain reaction (PCR) technique to detect M. pneumoniae DNA in clinical samples originating from the respiratory tract. The PCR results were compared with those from culture and serology tests. To standardize the detection of M. pneumoniae by PCR, we first used DNA from culture grown organisms and clinical samples seeded with M. pneumoniae. PCR amplification was performed with M. pneumoniae-specific primers to amplify 144, 153 and 631 bp DNA fragments by using primer pairs MP5-1/MP5-2, P1-178/P1-331 and P1-178/P1-809, respectively. The amplification of the 631 bp DNA fragment was found to be most sensitive for the detection of M. pneumoniae. Using the most sensitive PCR, a total of 47 respiratory specimens from patients suspected of community acquired pneumonia were tested. While none of the specimens were positive for M. pneumoniae in culture, 6 specimens gave positive results by PCR. In 4 out of the 5 PCR positive samples tested serologically, the results were supported by elevated levels of anti-mycoplasma IgG/IgM/IgA. Thus, these results suggest that PCR is the most sensitive method to detect M. pneumoniae in clinical specimens.     

支原体检测多重定量PCR方法的建立及应用

目的:建立一种快速、准确的方法检测支原体,这不仅可以有效地减少和预防支原体污染,还能为科研工作者提供一定的指导价值。方法:利用荧光定量PCR(TaqMan探针法)检测支原体,反应体系中同时存在标记两种颜色TaqMan探针及相关引物,分别检测支原体DNA和参考基因模板。根据支原体16S核糖体RNA保守区和参考基因TOP3A保守区设计引物和探针。通过对引物浓度、探针浓度和退火温度等反应条件的优化,建立了TaqMan探针多重定量PCR方法,并对该方法的特异性、敏感性和重复性进行了验证。结果:建立的双色荧光探针定量PCR方法的标准曲线相关系数r2和扩增效率分别为0.995和113.36%;该方法最低检测限为10 copies/μL;组内及组间变异系数均小于1%,证明该检测方法高效。利用该方法对随机挑选90例细胞抽提DNA样本进行检测,结果有60例为支原体阳性样本,阳性率67%,阳性率与相关研究报道一致。检测3个细胞培养上清样本,结果 1例支原体阳性,2例支原体阴性。从检测的样本中随机选择3个阳性样本及2个阴性样本使用普通PCR支原体检测试剂盒检测,结果一致;将其测序,测序结果比对正确。结论:本研究建立的多重定量PCR支原体检测方法能够应用于细胞抽提DNA及细胞培养上清的支原体检测,可以实现高效、快速检测支原体污染。