Microbiome Structure Influences Infection by the Parasite Crithidia bombi in Bumble Bees

Area of Science:

• Ecology
• Microbiology
• Conservation Biology

Background:

• Bumble bee populations are declining, raising concerns about pathogen impacts.
• The gut microbiota may play a role in host resistance to infections.
• Previous studies showed gut microbiota protection against Crithidia bombi in Bombus terrestris.

Purpose of the Study:

• To identify factors within the gut microbiome that confer protection against Crithidia parasites in Bombus impatiens.
• To investigate the role of microbiome diversity, bacterial load, and specific bacterial taxa in bee resilience.
• To determine if microbiome-mediated resistance is conserved across bumble bee species.

Main Methods:

• Cross-wise microbiota transplants were performed between wild and commercially sourced Bombus impatiens.
• Naive hosts received microbiota from different backgrounds.
• Recipients were challenged with Crithidia parasites to assess infection loads.

Main Results:

• Microbiota-dependent protection against Crithidia was observed in Bombus impatiens.
• Lower infection loads correlated with higher microbiome diversity and bacterial abundance.
• Presence of Apibacter, Lactobacillus Firm-5, and Gilliamella spp. was associated with reduced parasite loads.
• Bee origin (genetic background) influenced susceptibility.

Conclusions:

• Gut microbiome structure significantly impacts bumble bee defense against Crithidia parasites.
• Microbiome diversity and specific bacterial groups are key factors in host resilience.
• Microbiome-mediated resistance to Crithidia is conserved across bumble bee species, highlighting its ecological importance.