Summary auto-generated
This study identified and characterized a previously unculturable spiral bacterium from pig stomachs, provisionally named 'Gastrospirillum suis'. Researchers collected stomach samples from five slaughterhouse pigs and used immunohistochemistry, electron microscopy, and molecular techniques to investigate the organism. Using PCR amplification and sequencing of 16S rRNA genes, they obtained five nearly identical sequences (>97.7% similarity), indicating a single bacterial species. Phylogenetic analysis placed this organism within the genus Helicobacter, forming a distinct subgroup with other gastrospirillum-like bacteria. The porcine sequence showed 99.5% similarity to 'Helicobacter heilmannii' type 1 but only 96.6% similarity to its closest validly named relative, H. salomonis. Researchers developed species-specific PCR primers and a probe that distinguished this organism from all known Helicobacter species. In situ hybridization confirmed the molecular sequences corresponded to the observed spiral bacteria in gastric tissue. The authors propose the provisional name 'Candidatus Helicobacter suis' for this novel gastric helicobacter from pigs, using the Candidatus category for unculturable microorganisms identified through genomic data.
Key findings
- The porcine gastrospirillum organism forms a distinct phylogenetic subgroup within Helicobacter alongside H. felis, H. bizzozeronii, H. salomonis, and 'H. heilmannii' types 1 and 2
- Five 16S rRNA sequences from different pig stomachs showed >97.7% similarity, indicating they represent a single bacterial species
- The organism shares 96.6% 16S rRNA similarity with H. salomonis (its closest validly named relative), supporting classification as a novel species
- Species-specific PCR primers and probe were successfully developed to differentiate this organism from all known Helicobacter species
- In situ hybridization confirmed the molecular sequences matched the tightly coiled spiral bacteria observed in pig gastric crypts
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Abstract
'Gastrospirillum suis' is an uncultured, tightly spiral micro-organism that has been associated with ulcer disease in the stomachs of pigs. It was the purpose of this study to determine the phylogenetic position of 'G. suis'. Stomachs of five slaughterhouse pigs, originating from different Belgian and Dutch farms, were selected on the basis of the presence of 'G. suis'-like bacteria, as demonstrated by biochemical, immunohistochemical and electron microscopical data. Bacterial 16S rDNA was amplified by PCR using broad-range primers and five helicobacter-like sequences were determined either by direct or indirect sequence analysis. An inter-sequence homology of 99.7% was observed, suggesting that the sequences originated from strains belonging to a single species. Phylogenetic analysis of the consensus sequence placed the organism within the genus Helicobacter, where it formed a distinct sub-group together with other gastrospirillum-like bacteria (Helicobacter felis, Helicobacter bizzozeronii, Helicobacter salomonis and 'Helicobacter heilmannii' types 1 and 2). Diagnostic PCR primers and a probe were developed that differentiated the porcine sequences from all known helicobacters. These results indicate that the porcine sequences represent a single taxon within the genus Helicobacter. The low similarity level towards H. salomonis (96.6%), its closest validly named neighbour, strongly suggests that this taxon is a novel Helicobacter species. In situ hybridization experiments linked the reference sequence to the 'G. suis'-like bacteria. On the basis of these results, we propose the name 'Candidatus Helicobacter suis' for this gastric helicobacter from pigs.