Probing 23S ribosomal RNA cleavage sites in coccoid Helicobacter pylori

Transformation of Helicobacter pylori into Coccoid Forms as a Challenge for Research Determining Activity of Antimicrobial Substances

Morphological variability is one of the phenotypic features related to adaptation of microorganisms to stressful environmental conditions and increased tolerance to antimicrobial substances. Helicobacter pylori, a gastric mucosal pathogen, is characterized by a high heterogeneity and an ability to transform from a spiral to a coccoid form. The presence of the coccoid form is associated with the capacity to avoid immune system detection and to promote therapeutic failures. For this reason, it seems that the investigation for new, alternative methods combating H. pylori should include research of coccoid forms of this pathogen. The current review aimed at collecting information about the activity of antibacterial substances against H. pylori in the context of the morphological variability of this bacterium. The collected data was discussed in terms of the type of substances used, applied research techniques, and interpretation of results. The review was extended by a polemic on the limitations in determining the viability of coccoid H. pylori forms. Finally, recommendations which can help in future research aiming to find new compounds with a potential to eradicate H. pylori have been formulated.

Maturation of atypical ribosomal RNA precursors in Helicobacter pylori

In most bacteria, ribosomal RNA is transcribed as a single polycistronic precursor that is first processed by RNase III. This double-stranded specific RNase cleaves two large stems flanking the 23S and 16S rRNA mature sequences, liberating three 16S, 23S and 5S rRNA precursors, which are further processed by other ribonucleases. Here, we investigate the rRNA maturation pathway of the human gastric pathogen Helicobacter pylori. This bacterium has an unusual arrangement of its rRNA genes, the 16S rRNA gene being separated from a 23S-5S rRNA cluster. We show that RNase III also initiates processing in this organism, by cleaving two typical stem structures encompassing 16S and 23S rRNAs and an atypical stem–loop located upstream of the 5S rRNA. Deletion of RNase III leads to the accumulation of a large 23S-5S precursor that is found in polysomes, suggesting that it can function in translation. Finally, we characterize a cis-encoded antisense RNA overlapping the leader of the 23S-5S rRNA precursor. We present evidence that this antisense RNA interacts with this precursor, forming an intermolecular complex that is cleaved by RNase III. This pairing induces additional specific cleavages of the rRNA precursor coupled with a rapid degradation of the antisense RNA.

Cloning and sequencing of cagA gene fragment of Helicobacter pylori with coccoid form

AIM: To clone and sequence the cagA gene fragment of Helicobacter pylori (H pylori) with coccoid form.

METHODS: H pylori strain NCTC11637 were transformed to coccoid form by exposure to antibiotics in subinhibitory concentrations. The coccoid H pylori was collected. cagA gene of the coccoid H pylori strain was amplified by PCR. After purified, the target fragment was cloned into plasmid pMD-18T. The recombinant plasmid pMD-18T-cagA was transformed into E.coli JM109. Positive clones were screened and identified by PCR and digestion with restriction endonucleases. The sequence of inserted fragment was then analysed.

RESULTS: cagA gene of 3 444 bp was obtained from the coccoid H pylori genome DNA. The recombinant plasmid pMD-18T-cagA was constructed, then it was digested by BamH I+Sac I, and the product of digestion was identical with the predicted one. Sequence analysis showed that the homology of coccoid and the reported original sequence H pylori was 99.7%.

CONCLUSION: The recombinant plasmid containing cagA gene from coccoid H pylori has been constructed successfully. The coccoid H pylori contain completed cagA gene, which may be related to pathogenicity of them.

Chronic inactive gastritis and coccoid Helicobacter pylori in patients treated for gastroesophageal reflux disease or with H pylori eradication therapy

Gastric biopsy specimens from 105 consecutive adults with persistent dyspepsia who did not have changes due to esophageal reflux disease changes or gastric or duodenal ulcers at endoscopy were scored using the updated Sydney gastritis classification system. The medication history of proton pump inhibitors (PPIs) or Helicobacter pylori eradication therapy during the month before endoscopy was retrieved. Of the patients, 72 (68.6%) had chronic inactive gastritis, and 7 (6.7%) had antral-predominant, chronic mild active gastritis. H pylori infection was present in 36 patients (34.3%), of whom 29 had chronic inactive gastritis. Forty-six patients (43.8%) had a positive medication history, including 40 (56%) of 72 with chronic inactive gastritis. The most common morphologic feature associated with H pylori infection was moderate chronic inactive gastritis, which was found most often in patients who had received recent PPIs or H pylori eradication therapy. Pathologists should be aware of the extensive use of these medications, their association with chronic inactive gastritis, and rare H pylori thatfrequently are coccoid shaped. Modified Giemsa stain may not be the optimal method to detect H pylori in this group of patients.

Differential virulence-gene mRNA expression in coccoid forms of Helicobacter pylori

Controversy exists whether coccoid forms of Helicobacter pylori maintain transcriptional and translational processes. The aim of the present study was to investigate mRNA levels in coccoid H. pylori and, if possible, to establish a correlation with the state of nonrandom fragmentation of rRNA in those cells. For that purpose, UreA, UreI, CagA, VacA, SodB, and Hsp60 mRNA levels in bacillary and coccoid forms of H. pylori CCUG 17874(T), H. pylori 26695, and H. pylori J99, respectively, were studied by means of a multiplex reverse-transcription PCR assay and Southern blot analysis of the RT-PCR-amplified products. Nonrandom fragmentation of 23S rRNA was assessed by a recently described assay. Virulence-gene-derived mRNA transcripts were visualized in DNase I-treated RNA preparations. All three strains revealed the presence of different mRNA patterns in bacillary and coccoid forms. Putative promoter sequences similar to the consensus Escherichia coli -10 hexamer TATAAA box were present in all six virulence genes analyzed. Moreover, the decrease seen in mRNA levels during conversion into the coccoid form appeared to correlate with the 23S rRNA nonrandom fragmentation pattern. The present data indicate that modulation of virulence-gene expression is differently regulated in bacillary and coccoid H. pylori.