Unusual cellular fatty acids and distinctive ultrastructure in a new spiral bacterium (Campylobacter pyloridis) from the human gastric mucosa

Abstract

Spiral bacteria, named Campylobacter pyloridis, were obtained from endoscopic biopsies of the gastric antrum of 14 patients with active chronic gastritis. Methyl esters of their cellular fatty acids were prepared by acid-catalysed transmethylation of whole cells. Their major fatty acids were tetradecanoic acid (14:0) and cis-9,10-methyleneoctadecanoic acid (19:0 delta), with a very small amount of hexadecanoic acid (16:0). This is markedly different from the fatty acids of other Campylobacter sp. whose major fatty acids are hexadecanoic, octadecenoic (18:1) and hexadecenoic acids (16:1). This is also different from other enterobacteria. Thin-section electronmicroscopy of gastric mucosal biopsies, and negative staining of cultured C. pyloridis, revealed features that differ from those of other campylobacters so far studied. C. pyloridis has a smooth not a rugose surface and multiple unipolar flagella of the sheathed type, each with a terminal bulb. Flagellar sheaths were in continuity with the unit membrane of the outer cell wall. The proposed species C. pyloridis does not belong among the spirochaetes and its DNA composition is incompatible with membership of the genera Spirillum or Vibrio but is compatible with Campylobacter. Thus C. pyloridis is either an atypical member of the genus Campylobacter, the limits of which may have to be redefined to accommodate the new species, or a representative of a new genus.