Effects of a freeze substitution method and chemical fixation techniques on the ultrastructure of campylobacter pylori

Abstract

Campylobacter pylori is a newly recognized microaerophilic, gram-negative spiral bacterium. The role of this organism in the pathogenesis of human gastritis and ulceration is currently being widely investigated. Published reports of the ultrastructure of C. pylori exhibit poor preservation of subcellular detail indicating that certain conventional fixation procedures may not be appropriate for optimal results. Consequently, we utilized freeze substitution and conventional methods to examine the influence of fixation technique on the preservation of ultrastructural detail.C. pylori strain NCTC 11638 was grown for 24 h in liquid media. Conventional fixation was performed with (1) the Ryter-Kellenberger procedure, (2) to 3% glutaraldehyde with secondary fixation in 2% OsO4 (3) combinations of formaldehyde (F) and glutaraldehyde (G) ranging from 10% F/0.5% G to 2% F/1% G with secondary fixation in 2% OsO4 and (4) fixation at 0°C. For all fixatives, pH was 7.2-7.4; osmolarity varied between 300 and 2000 mOsM depending on the fixative.