Streptococcus mitis induces conversion of Helicobacter pylori to coccoid cells during co-culture in vitro

Area of Science:

• Microbiology
• Gastroenterology
• Human Microbiome Research

Background:

• Helicobacter pylori (H. pylori) is a significant gastric pathogen linked to various diseases like ulcers and cancers.
• The role of the gastric microbiota in H. pylori pathogenesis was historically underestimated due to the perceived hostility of the stomach environment.
• Interactions between H. pylori and resident gastric bacteria are crucial but poorly understood in human gastric disease.

Purpose of the Study:

• To investigate the interactions between H. pylori and common gastric bacteria, Streptococcus mitis and Lactobacillus fermentum.
• To determine how these interactions influence H. pylori physiology and survival within the gastric environment.
• To explore the impact of gastric microbiota on H. pylori-associated diseases.

Main Methods:

• Co-culture experiments analyzing the effects of H. pylori, S. mitis, and L. fermentum on each other's growth and morphology.
• Metabolomics analysis to identify specific compounds mediating bacterial interactions.
• Comparative analysis in the context of both healthy and diseased human gastric conditions.

Main Results:

• Streptococcus mitis secretes diffusible factors that inhibit H. pylori growth and induce its conversion to a non-infectious coccoid form.
• H. pylori and Lactobacillus fermentum produce factors that enhance the survival of S. mitis during stationary growth phase.
• Metabolomics identified potential compounds responsible for H. pylori coccoid conversion.

Conclusions:

• Gastric commensal bacteria significantly influence H. pylori physiology, including its growth and morphology.
• These microbial interactions within the stomach may play a critical role in the development and progression of H. pylori-related gastric diseases.
• The findings highlight the importance of considering the gastric microbiota in understanding H. pylori pathogenesis.