A gonococcal homologue of meningococcal γ-glutamyl transpeptidase gene is a new type of bacterial pseudogene that is transcriptionally active but phenotypically silent

BACKGROUND: It has been speculated that the γ-glutamyl transpeptidase (ggt) gene is present only in Neisseria meningitidis and not among related species such as Neisseria gonorrhoeae and Neisseria lactamica, because N. meningitidis is the only bacterium with GGT activity. However, nucleotide sequences highly homologous to the meningococcal ggt gene were found in the genomes of N. gonorrhoeae isolates. RESULTS: The gonococcal homologue (ggt gonococcal homologue; ggh) was analyzed. The nucleotide sequence of the ggh gene was approximately 95 % identical to that of the meningococcal ggt gene. An open reading frame in the ggh gene was disrupted by an ochre mutation and frameshift mutations induced by a 7-base deletion, but the amino acid sequences deduced from the artificially corrected ggh nucleotide sequences were approximately 97 % identical to that of the meningococcal ggt gene. The analyses of the sequences flanking the ggt and ggh genes revealed that both genes were localized in a common DNA region containing the fbp-ggt (or ggh)-glyA-opcA-dedA-abcZ gene cluster. The expression of the ggh RNA could be detected by dot blot, RT-PCR and primer extension analyses. Moreover, the truncated form of ggh-translational product was also found in some of the gonococcal isolates. CONCLUSION: This study has shown that the gonococcal ggh gene is a pseudogene of the meningococcal ggt gene, which can also be designated as Ψggt. The gonococcal ggh (Ψggt) gene is the first identified bacterial pseudogene that is transcriptionally active but phenotypically silent

Involvement of RNA-binding protein Hfq in the osmotic-response regulation of invE gene expression in Shigella sonnei

<p>Abstract</p> <p>Background</p> <p>The expression of Type III secretion system (TTSS) in <it>Shigella </it>is regulated in response to changes in environmental osmolarity and temperature. Temperature-dependent regulation of <it>virF</it>, the master regulator of TTSS synthesis, is believed to occur at the transcriptional level. We recently demonstrated, however, that TTSS synthesis also involves post-transcriptional regulation of the synthesis of InvE, a target of <it>virF </it>and key regulator of TTSS synthesis. The mRNA levels of <it>invE </it>(<it>virB</it>) are stable at 37°C, but mRNA stability markedly decreases at low temperatures where the TTSS synthesis is tightly repressed. Deletion of <it>hfq</it>, which encodes an RNA chaperone in Gram-negative bacteria, results in the restoration of expression of <it>invE </it>and other TTSS genes at low temperature due to an increase in the stability of <it>invE </it>mRNA. To date, the molecular details of the regulation of TTSS expression in response to osmotic pressure are not known. In the current study, we investigated the mechanism of regulation of TTSS by osmotic pressure.</p> <p>Results</p> <p>Transcription of <it>virF</it>, which encodes the master regulator of TTSS expression, was partially repressed under low osmotic conditions. Several lines of evidence indicated that osmolarity-dependent changes in TTSS synthesis are controlled at the post-transcriptional level, through the regulation of InvE synthesis. First, the expression InvE protein was tightly repressed under low osmotic growth conditions, even though <it>invE </it>mRNA transcripts were readily detectable. Second, under low osmotic conditions, <it>invE </it>mRNA was rapidly degraded, whereas deletion of <it>hfq</it>, which encodes an RNA chaperone, resulted in increased <it>invE </it>mRNA stability and the production of InvE protein. Third, the binding of purified Hfq <it>in vitro </it>to <it>invE </it>RNA was stronger in low-salt buffer, as assessed by gel-shift analysis and surface plasmon resonance (Biacore analysis).</p> <p>Conclusion</p> <p>Osmolarity-dependent changes in TTSS synthesis in <it>Shigella </it>involve the post-transcriptional regulation of InvE expression, in addition to partial transcriptional activation by <it>virF</it>. The stability of <it>invE </it>mRNA is reduced under low osmotic conditions, similar to the effect of temperature. Deletion of an RNA chaperone gene (<it>hfq</it>) abolished the repression of TTSS synthesis at low osmolarity through a mechanism that involved increased stability of <it>invE </it>mRNA. We propose that the expression of <it>Shigella </it>virulence genes in response to both osmolarity and temperature involves the post-transcriptional regulation of expression of InvE, a critical regulator of TTSS synthesis.</p

The hemolytic and cytolytic activities of Serratia marcescens phospholipase A (PhlA) depend on lysophospholipid production by PhlA

<p>Abstract</p> <p>Background</p> <p><it>Serratia marcescens </it>is a gram-negative bacterium and often causes nosocomial infections. There have been few studies of the virulence factors of this bacterium. The only <it>S. marcescens </it>hemolytic and cytotoxic factor reported, thus far, is the hemolysin ShlA.</p> <p>Results</p> <p>An <it>S. marcescens shl</it>AB deletion mutant was constructed and shown to have no contact hemolytic activity. However, the deletion mutant retained hemolytic activity on human blood agar plates, indicating the presence of another <it>S. marcescens </it>hemolytic factor. Functional cloning of <it>S. marcescens </it>identified a phospholipase A (PhlA) with hemolytic activity on human blood agar plates. A <it>phl</it>AB deletion mutant lost hemolytic activity on human blood agar plates. Purified recombinant PhlA hydrolyzed several types of phospholipids and exhibited phospholipase A1 (PLA1), but not phospholipase A2 (PLA2), activity. The cytotoxic and hemolytic activities of PhlA both required phospholipids as substrates.</p> <p>Conclusion</p> <p>We have shown that the <it>S. marcescens phlA </it>gene produces hemolysis on human blood agar plates. PhlA induces destabilization of target cell membranes in the presence of phospholipids. Our results indicated that the lysophospholipids produced by PhlA affected cell membranes resulting in hemolysis and cell death.</p

Solitary Fibrous Tumor Arising from the Sphenoid Sinus

Solitary fibrous tumor (SFT) is an uncommon neoplasm that usually arises from the pleura. To our knowledge, only 30 cases of SFTs in the nasal cavity and paranasal sinuses have been reported in the literature. We describe an SFT that arose from the right sphenoid sinus and extended to the nasal cavity and epipharynx. The tumor was completely removed by endoscopic sinus surgery without complication. The patient is taking an uneventful course without any evidence of recurrence of the disease 8 months after surgery now

Clinical Experience Using a Real Time Autofluorescence Endoscopy System in the Gastrointestinal Tract

Autofluorescence spectra of neoplastic tissues have been reported to be significantly different from those of normal tissues when excited by blue or violet light. From this concept, a light-induced autofluorescence endoscopic imaging system for gastrointestinal mucosa (LIFE-GI; Xillix, Canada and Olympus, Japan) has been newly developed and the clinical evaluation of the prototype system has been conducted in hospitals in Canada, Netherlands and Japan

Extensive genomic diversity and selective conservation of virulence determinants in enterohemorrhagic Escherichia coli strains of O157 and non O157 serotypes

Background: Enterohemorrhagic Escherichia coli (EHEC) O157 causes severe food-borne illness in humans. The chromosome of O157 consists of 4.1 Mb backbone sequences shared by benign E. coli K-12, and 1.4 Mb O157-specific sequences encoding many virulence determinants, such as Shiga toxin genes (stx genes) and the locus of enterocyte effacement (LEE). Non-O157 EHECs belonging to distinct clonal lineages from O157 also cause similar illness in humans. According to the "parallel" evolution model, they have independently acquired the major virulence determinants, the stx genes and LEE. However, the genomic differences between O157 and non-O157 EHECs have not yet been systematically analyzed. Results: Using microarray and whole genome PCR scanning analyses, we performed a whole genome comparison of 20 EHEC strains of O26, O111, and O103 serotypes with O157. In non-O157 EHEC strains, although genome sizes were similar with or rather larger than O157 and the backbone regions were well conserved, O157-specific regions were very poorly conserved. Around only 20% of the O157- specific genes were fully conserved in each non-O157 serotype. However, the non-O157 EHECs contained a significant number of virulence genes that are found on prophages and plasmids in O157, and also multiple prophages similar to, but significantly divergent from, those in O157. Conclusion: Although O157 and non-O157 EHECs have independently acquired a huge amount of serotype- or strain-specific genes by lateral gene transfer, they share an unexpectedly large number of virulence genes. Independent infections of similar but distinct bacteriophages carrying these virulence determinants are deeply involved in the evolution of O157 and non-O157 EHECs

Cochlear implantation in patients with bilateral deafness caused by otitis media with ANCA-associated vasculitis (OMAAV): A report of four cases

Objective: Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) without systemic symptoms but with initial symptoms related to the ear, such as hearing loss, otalgia, and dizziness, has recently been reported. We have categorized this condition as otitis media with AAV (OMAAV), and have recently proposed its diagnostic criteria. Methods: To determine the effectiveness of cochlear implantation (CI) in patients with profound hearing loss due to OMAAV. We examined the language understanding ability of four patients with bilateral profound or total deafness due to OMAAV, who underwent CI. Results: In three of the four patients, the language understanding ability with CI was poor. These three patients with poor performance had characteristic features, including a short interval from the onset of ear symptoms to total deafness and clear enhancement of the cochlea on magnetic resonance imaging (MRI). Conclusion: The poor results observed in patients with a rapidly progressive history of hearing loss were attributed to possible severe and profuse intracochlear bleeding and/or destruction of structures, including the spiral ganglion. All the three patients showed contrast enhancement in the inner ear on MRI. We believe that preoperative evaluation of the history of hearing loss as well as the findings of contrast-enhanced MRI is important for predicting the prognosis after CI

Racemization-free Monomer: α-Hydroxyisobutyric Acid from Bio-based Lactic Acid

In order to solve the important problem of the racemization of poly(L-lactic acid), a high yield of racemization-free monomer: a-hydroxyisobutyric acid (HIBA) was synthesized from bio-based lactic acid by methylation using specific bases with bulky side groups. Obtained HIBA can be converted into poly(tetramethylglycolide), which is racemization-free and has higher melting and glass transition points than poly(L-lactic acid)