Host-Specific larval lepidopteran mortality to pathogenic Serratia mediated by poor diet

Area of Science:

• Insect microbiology
• Host-pathogen interactions
• Nutritional ecology

Background:

• Insect guts host numerous bacteria, some commensal, others opportunistic pathogens.
• Host stress can trigger a shift from commensalism to pathogenicity in gut microbes.

Purpose of the Study:

• To investigate how dietary nutrient concentration influences the commensal-pathogen balance in insect guts.
• To determine if host species affects the interaction between gut bacteria and the host.

Main Methods:

• Three lepidopteran species (fall armyworm, beet armyworm, corn earworm) were used as hosts.
• Dietary nutrient concentration was reduced using cellulose dilution.
• Hosts were orally inoculated with a Serratia strain.

Main Results:

• Low nutrient diets increased mortality in beet armyworm and corn earworm infected with Serratia.
• Fall armyworm showed low mortality across all diet conditions.
• Antimicrobial peptide expression remained unchanged in fall and beet armyworms, suggesting alternative mortality mechanisms.

Conclusions:

• Dietary nutrition is a critical factor in the commensal-to-pathogen switch for insect gut bacteria.
• Host species-specific responses are crucial in determining pathogen success.
• Opportunistic enteric pathogens' persistence is influenced by host physiology and environmental conditions.