The Dual-Functioning Fumarate Reductase: A Critical Enzyme in Campylobacter Jejuni Colonization

Research from the United States has revealed that Campylobacter jejuni, a leading cause of foodborne illness, relies on amino acids as its exclusive source of reduced carbon, incorporated into central carbon metabolism. The oxidation of succinate to fumarate is a crucial step in the oxidative tricarboxylic acid (TCA) cycle, and a new study has identified the dual-functioning fumarate reductase as the sole succinate:quinone reductase in C. jejuni. This enzyme is essential for full host colonization, as demonstrated by colonization trials that showed the frdA::cat(+) strain colonized chickens at significantly lower levels than the wild type.

Key Takeaways:

• Campylobacter jejuni relies exclusively on amino acids as the source of reduced carbon, incorporated into central carbon metabolism.
• The oxidation of succinate to fumarate is a key step in the oxidative TCA cycle.
• The dual-functioning fumarate reductase is the sole succinate:quinone reductase in Campylobacter jejuni.
• The frdA::cat(+) strain was completely deficient in succinate dehydrogenase activity in vitro and was unable to perform whole-cell succinate-dependent respiration.
• The sdhA::cat(+) strain exhibited wild-type levels of succinate dehydrogenase activity both in vivo and in vitro.
• The frdA::cat(+) strain was unable to grow with the characteristic wild-type biphasic growth pattern and exhibited only the first growth phase.
• Substrates consumed in the second growth phase were not catabolized by the frdA::cat(+) strain, indicating that the oxidation of succinate is a crucial step in metabolism.
• Campylobacter colonization trials confirmed the in vivo importance of succinate oxidation, as the frdA::cat(+) strain colonized chickens at significantly lower levels than the wild type.

Statistics:

• Campylobacter jejuni causes approximately 1.3 million illnesses, 12,000 hospitalizations, and 120 deaths in the United States each year (Centers for Disease Control and Prevention).
• The dual-functioning fumarate reductase is essential for the oxidation of succinate, which is a key step in the TCA cycle.
• The frdA::cat(+) strain colonized chickens at significantly lower levels than the wild type in colonization trials (Weingarten et al., 2009).

Sources:

• Weingarten, R.A., et al. (2009). The dual-functioning fumarate reductase is the sole succinate:quinone reductase in Campylobacter jejuni and is required for full host colonization. Journal of Bacteriology, 191(16), 5293-300.
• Centers for Disease Control and Prevention. (n.d.). Campylobacter. Retrieved from