Which phylum includes Helicobacter pylori?
Helicobacter pylori represents microaerophilic curved Gram-negative bacterium classified within class Epsilonproteobacteria of phylum Proteobacteria based on 16S rRNA phylogeny, unipolar flagellation, and microaerophilic physiology. It colonizes human gastric mucosa using urease producing ammonia to neutralize gastric acid, adhesins and cytotoxins CagA and VacA triggering inflammation. Strong association with chronic gastritis, peptic ulcers, and gastric adenocarcinoma established it as type species of Helicobacter. Its proteobacterial affiliation contrasts with Spirochaetes, Firmicutes, and Actinobacteria, clustering near Campylobacter within epsilon subgroup recognized in molecular taxonomy.
Ref: Tortora Microbiology 12th ed., Chapter 11 Epsilonproteobacteria Helicobacter; Bergey's Manual Volume 2 Proteobacteria Helicobacter pylori gastric